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RER Value Guide

Slow (0.7)
A1 band - warm-up, recovery, cool-down sets
Moderate (0.85)
A2 band - aerobic capacity sets
Intense (1.00)
A3 band - aerobic power, VO2max sets

Data Source: Zamparo P, Bonifazi M (2013). Bioenergetics of cycling sports activities in water.

Coded for Swimming Science by Cameron Yick

Freestyle data

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Dolphin Kicking

Take Home Points:
  1. Elite swimmers may not use a symmetrical dolphin kicking strategy.
The undulatory underwater sequence, dolphin kick, is one of the most important but unexplored phases in competitive swimming. Swimmers use this kick for butterfly and starts/ turns in freestyle and backstroke.

Unfortunately, we still have a lot of questions regarding the effectiveness of underwater kicking, as well the ideal kicking biomechanics.

In the past, I've written a lot about dolphin kicking. In these posts, I've discussed ideal depth, as Marinho (2009) looked at drag coefficients at different depths.

I've also discussed ideal kicking tempo, referencing great work by Coach Bob Gillett and Russell Mark, as well as Cohen (2012). Coach Gillett has analyzed elite male and female swimmers and suggests both groups should have a kicking tempo around 0.45 (Gillett 2013), where Russell Mark (2012) notes a tempo around 0.40 is utilized. Many feel this kicking tempo is extremely fast, but one study by Cohen (2012) indicates faster kicking tempo is correlated with net higher streamline force.

Russell Mark has even analyzed the amount of kicks by elite swimmers, noting the following kick number and time.

I've  also discussed the importance of dolphin kicking with Scott Colby, in his "pseduo-study" or elite youth swimmers, finding the 5-meter streamline, the range (depending on age) of the top times was 2.3-3.1 for boys and 2.7-2.8 for girls. For 15-Meter Dolphin Kick the ranges were 6.1-6.9 for boys and 7.1-7.3 for girls.

In another case, I've broken down a case study of dolphin kicks:

"Case Study #1

You have a 5"2" 16-year old female swimmer who goes :58 100 back and is known for her good underwaters. Her results from the aforementioned test were:
  • 0-5 m: 2.8 seconds
  • 0 - 15 m: 8.0 seconds
  • Kick Count: 16 kicks
  • Kick Tempo: 0.35
Intervention: This is a clear case of a swimmer who performs too many kicks to 15-m. For her, changing her tempo isn't needed, as high tempos are correlated with kicking speed, but instead decreasing her kick total by encouraging her to follow through her kick was advised. "Short kicking" and not following through prevents a full activation of her quadriceps and impairing forward propulsion. She was challenged to progressively decrease her kick total from 16 - 12 kicks over the course of several weeks, not progressing until she mastered her new kick count at the same or faster pace which would be tested at frequent underwater kicking tests.

Case Study #2

A 6'1" 15-year old male swimmer who goes a :49 in the 100 back. His results were:
  • 0-5 m: 2.7 seconds
  • 0-15 m: 8.2 seconds
  • Kick Count: 12
  • Kick Tempo: 0.75
Intervention: It is clear he has too slow of a tempo. However, simply giving him a 0.4 tempo will discourage and potentially impede progress. Instead, gradual increases in tempo is necessary during progression, increasing 0.05 after mastery during kicking trials.

Swimming Science has also had the opportunity to talk with some of the great minds in research of dolphin kicking Ryan Atkinson and Marc Epilot.

Dr. Epilot breaks down top speed from pushing off the start, 1.9 - 2.2 m/s and when to begin dolphin kicking. He also discusses three errors in dolphin kicking:
"To my point of view, there are 3 main mistakes that swimmers, even top athletes, do. First of all, many swimmers initiate or try to initiate underwater kicking way to soon. As I said a bit before, such mistake has huge consequences on swimmer’s efficiency. Moreover those swimmers don’t even know that they start kicking so early. They are sure to have a long and efficient gliding phase, while they start kicking immediately after water entry.

A second common mistake is to produce to large kicking movements. During a long time, trainers thought that swimmers had to push on the water with their feet, underwater propulsion being the result of that action on the water (Action-reaction Newton law). An increasing number of studies, made on different mechanical simulations, on fish swimming, or on swimmers, have shown that underwater propulsion is mostly explained by a mechanism, named the formation of a reverse Street of Karman Vortices located in the trailing edge of the swimmer. Those vortices create a backward ejection of water that leads to project the swimmer frontward. To create a coherent and propulsive street of Karman vortices, swimmers have to adjust their amplitude/Frequency ratio; usually by decreasing the amplitude and increasing the frequency.

The third mistake I would point out is the undulatory movements of the trunk and arms. In many swimmers, we can observe that their whole body is undulating, which has deleterious effects on the propulsive efficiency. The upper part of the body has to stay streamlined not to absorb the energies produce by the lower limbs. Moreover swimmer’s upper limbs have to be aligned to the orientation of his path. If the swimmer is swimming under the water straight forward, his upper limbs have to stay horizontal. If the swimmers is returning to the water surface with an angle of 30°, his upper limbs have to be at 30° regarding to the horizontal."

Ryan Atkinson mainly discussed symmetry between the downkick and upkick. He said: "Symmetry between downkick and upkick phases is highly related to high UDK velocity, and

swimmers who are more effective at the upkick phase tend to have a faster UDK velocity. Specific movements that are highly related to faster UDK are: greater peak vertical toe velocity during the upkick phase, reduced upkick duration, and less knee flexion at the end of the upkick/start of the downkick."

He also stressed the importance of "reducing the amplitude of the UDK, especially at the upper body segments (torso, head and arms) and increasing kick frequency. Particular attention should be placed on maximizing toe velocity during the upkick and limiting the duration of the upkick. Similarly with beginners, swimmers should be encouraged to recruit the muscles of the posterior chain without excessive lower back flexion or knee flexion. This can be advanced on the land by performing single leg lifts in a plank position, paying close attention to recruiting the gluteal muscles for leg lifts and keeping the hips level."

Ryan Atkinson's work feeds directly into the topic today. The results are somewhat contradictory to Ryan's statements, nonetheless a very important topic and discussion point.

The aim of this research study was to demonstrate the formation and interaction of forces near the swimmer’s body and in the swimmers wake during the dolphin kick in hopes of finding energy-saving mechanics.

What was done

A female swimmer with a 200-m butterfly time of 2:12.0 was selected. Her body was scanned with a 3D laser and subdivided into joints of the arms, torso, upper legs, lower legs, and feet. The swimmer underwater kick from a push was recorded and analyzed


Maximum thrust was generated during the down kick, and was approximately twice the maximum
thrust recorded for the up kick. Both maximum values were reached at the instant when stroke velocity was at its highest within the kick cycle. The results indicate a slight increase in propulsion of 8% over the six cycles. Maximum drag was during an active dolphin kick, 208 N (~46 lbs), and at the same speed drag was ~16 N (~3.6 lbs) during the gliding motion.

Transitioning from the gliding phase to the first kick cycle creates two vortex structures, an upstroke (upper ring) and a downstroke (lower ring). Theses vortexes are shed into the swimmers wake at the end of each cycle. These forces grow in size and strength with each cycle, with cycle 6 demonstrated larger values than cycle 2 of the underwater dolphin kick.


Optimum performance was only reached after a number of kick cycles. The dynamic drag force was ~12x higher during the kick than during the gliding phase. The mean drag and mean propulsion in cycle 6 were about 8% higher than those in cycle 2 of their dolphin kick. During the kicking cycles, the vortex created was recaptured along the body’s surface to a position where the feet would hit the vortex with the next kick

Practical Implications

Additional research is needed, but this case study shows that optimum performance was reached after 6 kick cycles, in which propulsion forces reach a constant value. This 8% increase may be explained by vortex recapturing; which may be increased with fine-tuning of body kinematics off the wall/turn.

Overall, the results are somewhat conflicting towards Ryan, but not really. Although this swimmer demonstrated a much stronger downkick, we don't know if a more symmetrical kick would improve this swimmer's dolphin kicking velocity. Looks like we need more research!


  1. Pacholak S, Hochstein S, Rudert A, Brücker C. Unsteady flow phenomena in human undulatory swimming: a numerical approach. Sports Biomech. 2014 Jun;13(2):176-94. PubMed PMID: 25123002.
  2. Marinho DA, Reis VM, Alves FB, Vilas-Boas JP, Machado L, Silva AJ, Rouboa AI. Hydrodynamic drag during gliding in swimming.J Appl Biomech. 2009 Aug;25(3):253-7.
  3. Cohen RC, Cleary PW, Mason BR. Simulations of dolphin kick swimming using smoothed particle hydrodynamics. Hum Mov Sci. 2012 Jun;31(3):604-19. doi: 10.1016/j.humov.2011.06.008. Epub 2011 Aug 12.
  4. von Loebbecke A, Mittal R, Fish F, Mark R. A comparison of the kinematics of the dolphin kick in humans and cetaceans. Hum Mov Sci. 2009 Feb;28(1):99-112. doi: 10.1016/j.humov.2008.07.005. Epub 2008 Nov 4.
  5. von Loebbecke A, Mittal R, Fish F, Mark R. Propulsive efficiency of the underwater dolphin kick in humans. J Biomech Eng. 2009 May;131(5):054504. doi: 10.1115/1.3116150. 
  6. von Loebbecke A, Mittal R, Mark R, Hahn J. A computational method for analysis of underwater dolphin kick hydrodynamics in human swimming. Sports Biomech. 2009 Mar;8(1):60-77. doi: 10.1080/14763140802629982.
  7. B. Gillett Underwater Kicking and Foil Movement Personal communication. 2013 February 24.
  8. M. Russell Dolphin Kicking. USA Swimming. 2012 April 12.
By Dr. G. John Mullen received his Doctorate in Physical Therapy from the University of Southern California and a Bachelor of Science of Health from Purdue University where he swam collegiately. He is the owner of COR, Strength Coach Consultant, Creator of the Swimmer's Shoulder System, and chief editor of the Swimming Science Research Review.

Core Muscle Activation During Swimming

Take Home Points:

  1. Core muscle activation increases correlations with faster swimming velocities. 
  2. Maximally activating the core during swimming impairs respiration.
Intra-abdominal pressure changes as a result of synchronous contraction of the abdominal muscles, diaphragm and pelvic floor muscles. Previous work suggests a positive correlation between muscle strength and intra-abdominal pressure. Other work suggests intra-abdominal pressure correlates with walking and running speed. Ogawa showed intra-abdominal pressure increases with swimming velocity during freeestyle from 0.8 - 1.4 m/s (18).

Moriyama (2014) had 7 competitive male swimmers (~19.9 years; Japanese national university championship level) undergo a intra-abdominal pressure test which involved a 1.6-mm-diameter rectal pressure transducer. Swimmers then swam in a flume at 1.0, 1.2, and 1.4 m/s with IAP being recorded.

There were significant changes in intra-abdominal pressure at varying velocity, with a positive correlation. However, the intra-abdominal pressure was significantly different in water than on land (16.6 vs. 18.9). Intra-abdominal pressure did not have a significant correlation with stroke rate or stroke length.

Despite the lack of correlation between intra-abdominal pressure and stroke length or rate, there is a positive correlation between velocity, the most important variable for swimming.

Keep these items in mind:
  1. These swimmers performed at a moderate speed, far from maximum, potentially nullifying the results.
  2. The swimmers were not tested during fatigue.
  3. There was a small sample size.
  4. This is an observational study, not proving anything.
The authors conclude: "These findings do not appear to support the effectivenss of trunk training performed by competitive swimmers aimed at increasing intra-abdominal pressure".

Swimming is unique as pulmonary function limits performance. There are many possibilities for this, some being the resistrcited oxygen, mechanical pressure against the chest, prone position, and many more. Whatever the case, total lung capacity and forced expiratory volume is greater in swimmers than other athletes.

Thirteen participants(M=8, F=5; ~22-60 years) perform two conditions, relaxed breathing while sitting and breathing with the abdominal and erector spinae muscles tensed in the seated position. During these tests ventialry function was assessed.

There was a significant difference between vital capacity, maximum voluntary ventilation, forced vital capacity over 1 second, and resting oxygen consumption between both conditions.

Overall, contracting muscles to streamline abdominal posture had negative effects on pulmonary function and caused a negative effect on pulmonary function. Therefore, abdominal musculature should not be contracted during swimming as it likely will impair swimming performance.

Personally, I feel the opposite, if you have an increase in intra-abdominal pressure as you increase in speed, then the positive correlation suggests the higher intra-abdominal pressure helps swim faster velocities. Sure, intra-abdominal pressure is going to be lower in the water than on land, but this is expected due to the instability of water! However, we still need more evidence on the effects of core training on swimming performance. This author knows of one study suggesting core training improves swimming sprint velocity, but this is far from conclusive.

Until more research occurs, core training appears helpful for swimmers, especially those going faster speeds.


  1. Moriyama S, Ogita F, Huang Z, Kurobe K, Nagira A, Tanaka T, Takahashi H, Hirano Y. Intra-abdominal pressure during swimming. Int J Sports Med. 2014 Feb;35(2):159-63. doi: 10.1055/s-0033-1349136. Epub 2013 Jul 18.
  2. Timothy W. Henrich, T. W., Robert Pankey, and Gregory Soukup. The Unintended Consequences of Tension in the Abdominal & Lumbar Musculature on Swimmers' Ventilatory Metabolic Indices. Volume 22 Spring 2014.

Dryland for Swimmers

The Dryland for Swimmers ebook and video database is the most comprehensive dryland program and guide for swimmers. It includes a detailed dryland research analysis, club programming, and individual programming.

By Dr. G. John Mullen received his Doctorate in Physical Therapy from the University of Southern California and a Bachelor of Science of Health from Purdue University where he swam collegiately. He is the owner of COR, Strength Coach Consultant, Creator of the Swimmer's Shoulder System, and chief editor of the Swimming Science Research Review.

Post-Activation Potentiation and Swimming

Take Home Points on Post-Activation Potentiation and Swimming:
  1. Highly specific post-activation potentiation improves starting distance and may improve 0 - 15 m velocity.
  2. Sprint swimming races do not benefit from post-activation potentiation compared to traditional swimming warm-up.
Starts play a vital component of every race, with increasing importance in the shorter the race. PAP improves muscle contractility, strength and speed in sporting performances by applying maximal or submaximal loads on the muscle
Warming-up the body is suggested to improve sporting performance, with post-activation potentiation (PAP) one mechanism for improvement.

prior to the performance. PAP improvements are the result of a physiologic alteration that renders actin-myosin myofibril more sensitive to Ca2+, released from the sarcoplasmic reticulum, and an increase in muscle fibre recruitment, due to an intensification of the motor-neuron’s excitation.

PAP commonly uses similar exercises to the actual event. The lunge exercise, for example, primarily
activates the hip and knee extensor muscles of the front leg and, in track starts, causes the biggest impulse. The flywheel inertial device, YoYo squat (YoYo™ Technology AB, Stockholm, Sweden), on the other hand, draws on inertial systems to induce potentiation and, as has been reported in many EMG studies, leads to very high muscular activation potential benefit of flywheel inertial devices is that the resistance is independent of gravity.

PAP and Swimming Start

Fourteen trained swimmers (M=10, F=4; 17 - 23 years old) performed an initial swimming start as a control, then two different PAP protocols before a swimming start. Eight minutes of rest were provided after the two different protocols. The initial control start followed a standard warm-up, which was varied swimming and a dynamic lower limb stretching routine. During the two PAP protocols, the participant performed a standard warm-up then 1 x 3 at 85% 1-RM for the lunge and 1 x 4 at maximal voluntary contraction for the YoYo squat flywheel.

Dive distance was significantly greater after the PAP compared to the control. The distance to entry in the water was longer for the YoYo squat flywheel (304.28 cm) and lunge (300.29 cm) compared to the control (294.2 cm). Flight time was also significantly greater after the YoYo squat flywheel compared to the control and the lunge. Swimmers were faster after the YoYo squat flywheel compared to the other protocols. Time to 5-meters was also significantly shorter after the PAP exercises. Time to 15-m was shorter after the YoYo squat flywheel, but it wasn't significant.

PAP and Swimming Performance

In another recent study, Sarramin (2014) tested 18 National level swimmers (M=10, F=9; ranked within the top 15 for their country in their age-group) on 7 occasions. The first test day aimed to provided a 3 repetition maximum (3RM) on the pull-up exercise. The second session, the participant performed a medicine ball throw 4, 8 and 12 minutes following the upper body PAP activity (1 set of 3RM of the pull-up), determining the optimal rest period for the individual. The third session involved performing a counter movement jump on a jump mat, 4, 8 and 12 minutes after the PAP stimulus (1 set of 5 jumps to the box wearing a weighted vest of 10% of their bodyweight). During sessions 4 - 7, participants swam a 50 m under race conditions preceded by one of the following:
  1. Regular swimming warm-up: 30 minutes of different speeds, drills, sprints, and cool down. 
  2. Upper body PAP
  3. Lower body PAP
  4. Combined upper and lower body PAP
All the PAP protocols first performed a 15-minute pool warm-up. The rest period after the regular warm-up was 15 minutes for each swimmer. The rest periods for the PAP were determined by the first 2 sessions. 

There were only significantly differences in time between groups for the male group. Swimming
times were significantly faster for the regular swimming warm-up and combined warm-up compared to the upper body PAP protocol for men. 

The reasons for the differences between men and women are not clear, but possibly due to muscle mass and composition.

Sarramian (2014) suggests PAP may be beneficial for swimmers when they don't adequate space or time for warm-up, which is common in swimming. However, the precise exercises for PAP are not well established for swimming due to the complex nature of the sport. 

PAP and Swimming

Overall, it seems PAP using the YoYo Flywheel provides the greatest benefit for improving the swimming start. However, it seems a traditional warm-up is just as effective as PAP for sprinters, therefore regular swimming warm-ups are likely the most beneficial mode for most swimming. Just remember, individualization is key, as some collegiate sprinters have been found to perform best after no warm-up or no warm-up (Balilionis 2012).

Another scenario for using PAP, as Sarramian (2014) suggests is its use during meets with minimal space. 


  1. Sarramian VG, Turner A, Greenhalgh AK. EFFECT OF POSTACTIVATION POTENTIATION ON FIFTY METERS FREESTYLE INNATIONAL SWIMMERS. J Strength Cond Res. 2014 Sep 25. [Epub ahead of print]
  2. Cuenca-Fernández F, López-Contreras G, Arellano R. Effect on swimming start performance of two types of activation protocols: Lunge and YoYoSquat. J Strength Cond Res. 2014 Sep 15. [Epub ahead of print]
By Dr. G. John Mullen received his Doctorate in Physical Therapy from the University of Southern California and a Bachelor of Science of Health from Purdue University where he swam collegiately. He is the owner of COR, Strength Coach Consultant, Creator of the Swimmer's Shoulder System, and chief editor of the Swimming Science Research Review.

Beetroot Juice and Swimming

Take Home Points on Beetroot Juice and Swimming: 
  1. A week of beetroot juices improves aerobic and anaerobic swimming capacity in moderately trained Masters swimmers.
Many vegetables contain inorganic nitrates (NO3-) which have a beneficial impact on body function. It is believed nitrates can reduce nitrite and in turn to nitric oxide, which influences blood dynamics and muscle metabolism. Previous research suggests beetroot juice enhances nitric oxide production in the muscle, increased blood flow and oxygen delivery.

Beetroot juice supplementation has been tested on other sports, but not in swimming, likely due to the difficulty of testing energy metabolism...typical excuse!

Pinna (2014) had fourteen trained Masters swimmers who trained an average of 6.5 hours per week performed an incremental tethered swimming test. Pretty much, the researchers tied a rope around the swimmers and had them swim against an elastic rope which measured force and when the force was impaired the test stopped. Here it is specifically:

"By means of a dynamometer, the tension applied to the elastic rope was constantly monitored on the display. Continuous vocal feedback was provided by the researcher who checked the dynamometer to an assistant who moved a pole with a coloured signal fixed at the extremity and immersed in the water forward or backward. The tested swimmer was instructed to follow the signal so that the assistant could adjust the tension applied to the rope simply by moving the pole forward or backward."

Then, the subjects performed the same test after a week of beetroot juice supplementation. Each athlete consumed 0.5 l/day organic beetroot juice containing about 5.5 mmol of inorganic nitrate. 

The results from this study demonstrate a significant increase in workload at anaerobic threshold with the beetroot juice supplementation. aerobic energy cost was also significantly reduced during the beetroot juice supplementation. Heart rate, VO2, VCO2, and pulmonary heart rate were not significantly different between groups. 
These results seem positive, but things to keep in mind:
  1. There was no control group, perhaps the swimmers were better trained in a week or were simply more familiar with the testing procedure resulting in better performance.
  2. The swimmers were moderately trained Masters swimmers, like the other research and my suggests a while back, beetroot juice seems beneficial for the moderately trained. However, the supportive research on elite athletes (especially swimmers) is lacking. 
  3. Improved anaerobic and aerobic testing is great, but what about performance? Now, this doesn't mean improving energetics is irrelevant, but does suggest energetics aren't the main test. Remember, medals aren't awarded in practice.
Like I stated previously, "It is clear, more research is needed on elite and trained athletes. Moreover, the reason for potential improvement is still muddy even in un- or moderately trained athletes. Personally, for [highly] trained populations, I don't see nitrates or beets providing any ergogenic benefit."

Luckily, consuming extra veggies and nitrates is not harmful, so give a week of beetroot juice a try, after all it is a healthy, relatively cheap ergogenic aide!

  1. Pinna M, Roberto S, Milia R, Marongiu E, Olla S, Loi A, Migliaccio GM, Padulo J, Orlandi C, Tocco F, Concu A, Crisafulli A. Effect of beetroot juice supplementation on aerobic response during swimming. Nutrients. 2014 Jan 29;6(2):605-15. doi: 10.3390/nu6020605.
By Dr. G. John Mullen received his Doctorate in Physical Therapy from the University of Southern California and a Bachelor of Science of Health from Purdue University where he swam collegiately. He is the owner of COR, Strength Coach Consultant, Creator of the Swimmer's Shoulder System, and chief editor of the Swimming Science Research Review.

Does Low Back Pain Resolve Itself?

Take Home Points for Does Low Back Pain Resolve Itself?
  1. Yes, low back pain typically resolves itself, yet underlying issues persist likely increasing the risk of re-injury.
Low back pain (LBP) is extremely common in the general and athletic population and swimmers
even have a higher risk of low back degeneration. Despite this frequency, no resolutions exist for eradicating pain. Luckily, most cases of LBP are acute and remiss over a month. This brevity in symptoms leads many not to seek treatment. However, resolution of pain, without treatment, may but a person at risk for a recurrent injury, as the recurrent rate of low back pain is extremely high.

This situation puts everyone in a bind, as everyone thinks they can wait out pain and get better. However, is waiting out the pain and having it resolve on it's own the best option? Sure, low back pain gets better in most people without any treatment, but is this passive treatment worth the risk of having a higher risk of recurrence?

Does Low Back Pain Resolve Itself?

Butler (2012) recruited fifty-four subjects without LBP and 33 people with a previous low back injury (LBI). In this study, electromyography of the core musculature and motion analysis was taken during the following task: 

“Subjects stood at a table (adjusted to standing elbow height) and performed three trials of lifting and replacing a 2.9 kg load using both hands in two reach conditions while minimizing trunk and pelvis motion. Subjects were required to move the load 4–5 cm off the table in a controlled manner and lower within a standardized 3-s count. An event marker identified lift, transition and lowering phases. Only the lift phase was examined given similar patterns were found for the two other phases. If trunk or pelvis motion was visible during the trial or upon review if the any of the three angular displacement traces exceeded 3, the trial was repeated (Butler 2012).”

The results showed a slight difference between the control and LBI, as the LBI group was slightly older and had a higher body mass index (BMI). Moreover, different movement patterns during the above tasks were noted between both groups. The LBI group also had higher muscle activation for the all the muscles except the external oblique, which showed decreased activation. 

Why is it Different?

All joints have passive structures (ie bones) and active structures (ie muscles). The higher muscular activation in the LBI group may be from a decrease in passive stability, requiring an increase in activity stability. Though high activation is assumed a good thing for stability, it may lead to increased fatigue and increased injury risk. This increases stiffness (stability) could also be a compensatory pattern for an underlying injury. A decrease in the external oblique activation may inhibit force distribution and overall core stability, as one muscle not working properly is theoretically disrupts stability according renowned spinal biomechanist Stuart McGill. 

These “scores indicates that the LBI group included individuals with inhibited as well as enhanced activation in local muscles, suggesting that there are potential subgroups. This may have implications for therapeutic interventions in that those with enhanced local activity may not benefit from therapies that focus on selectively activating deep muscles. Thus our results provide evidence of local muscle alterations although it is the first time that these impairments are reported during a functional but highly controlled task in those recovered from an episode of LBI (Butler 2012)”.

In summary, Butler concluded: “specifically, an overall increase in activity of abdominals and back extensors, increased agonist–antagonist co-activation strategy, reduced posterior oblique fiber activation and impaired local muscle responses to increased demand was found in the LBI

Practical Implications

Swimmers often have low back pain which symptoms quickly resolve. However, this study suggests underlying motor programming and impaired muscle activation exist after the resolution of symptoms. This makes it essential to seek rehabilitation or at least work on improving these imbalances, preventing a relapse. 

For some examples of core training, check out the COR Low Back Solution.

For more examples, consider purchasing Dryland for Swimmers.

  1. Butler HL, Hubley-Kozey CL, Kozey JW. Changes in electromyographic activity of trunk muscles within the sub-acute phase for individuals deemed recovered from a low back injury. J Electromyogr Kinesiol. 2012 Nov 28. doi:pii: S1050-6411(12)00195-2. 10.1016/j.jelekin.2012.10.012. [Epub ahead of print]
By Dr. G. John Mullen received his Doctorate in Physical Therapy from the University of Southern California and a Bachelor of Science of Health from Purdue University where he swam collegiately. He is the owner of COR, Strength Coach Consultant, Creator of the Swimmer's Shoulder System, and chief editor of the Swimming Science Research Review.

Thoracic Outlet Syndrome: What it is, How to Spot it, a Case Report, and Prevention!

Take Home Points on Thoracic Outlet Syndrome: What it is, How to Spot it, a Case Report, and Prevention!:
  1. Thoracic outlet syndrome is a narrowing between your collarbone and first rib, putting pressure on your neurovascular structures.
  2. There are many neurovascular impairments at the shoulder.
  3. Monitor shoulder pain, symptoms, and alter sensation closely, and adjust prevention programs and biomechanics for greatest improvement.
Though shoulder impingement is the most common form of shoulder injury in swimmers, other cases of shoulder pain exist. These other syndromes impact other tissues, typically the nerual, arterial or vascular. Although these shoulder conditions are not well known, they still occur in overhead athletes. Asymptomatic pitchers even have impaired blood flow on their throwing side, a potential risk factor for Thoracic Outlet Syndrome (TOS). Some of these issues are treated conservatively, while others require surgery.

Types of Thoracic Outlet Syndrome

Knowing what occurs and the symptoms of tissues other than the muscular system is beneficial for a coach and rehabilitation staff. Here are some examples:
  1. Nerogenic Thoracic Outlet Syndrome: Compromising the brachial plexus. Symptoms are pain, numbness, tingling, and weakness. 
  2. Vascular Thoracic Outlet Syndrome: Compromising the venous or arterial system. The typical presentation includes pain, numbness, tingling, weakness, and/or the presence of vascular compromise. Venous TOS is more common than arterial TOS and is characterized by swelling and cyanosis, pain, and a heavy feeling. 
  3. Paget-Schroetter Syndrome: A thrombosis of the subclavian vein.

Clinical Tests for Thoracic Outlet Syndrome in Swimmers

There are manual and diagnostic test for identifying vascular compromise. Sadeghi-Azandaryani (2009) notes:

"Sensitivity of clinical tests was acceptable overall (mean 72%). The EAST test showed the highest sensitivity with 98%, followed by the Adson (sensitivity: 92%) and Eden tests (sensitivity: 92%). In contrast, the sensitivity of the Hoffmann test (47%) was low. Nevertheless, a positive EAST, Eden, Adson, Green-stone or Adson test was not associated with a poorer outcome (p≥0.05).

Systolic blood pressure was measured before and after exercise. Mean systolic blood pressure of the afflicted side in the group of patients with good or fair outcome (85.9% of all patients) showed an average systolic blood pressure of 123.1 ± 12.5 mmHg before exercise and 108.9 ± 12.8 mmHg after exercise (average decrease: 16.2 ± 9.6 mmHg). A decrease in blood pressure of more than 25 mmHg could not be found in this group. In the group of patients with a poor outcome, the systolic blood pressure before exercise was 140.6 ± 24.6 mmHg and 106.7 ± 21.8 mmHg after exercise (average decrease: 35.0 ± 14.1 mmHg). Statistical analyses showed that a distinct decrease in blood pressure after exercises was associated with a poorer outcome (p = 0.0027)."

Here are some of the most common tests:
  1. Roo's test: The patient stands and abducts shoulders to 90 degrees, externally rotates the shoulders, and flexes the elbows to 90 degrees. The patient then opens and closes the hand slowly for three minutes. The test is positive if the patient is unable to complete the test or experiences heaviness, numbness, tingling or pain.
  2. Adson's test: The examiner locates the radial pulse while arm is held in extension, external rotation and slight abduction. The patient is instructed to take a deep breath and turn head toward the test arm while extending the neck. If there is compression, the radial pulse will be diminished or absent. The goal of this test is to tense the anterior and middle scalenes.
  3. Costoclavicular test: The examiner palpates the radial pulse and then draws the patient's shoulder down and back. If the pulse disappears, the test is positive. The goal of this test is to provide compression of the costoclavicular space.
  4. Halstead maneuver: The examiner palpates the radial pulse and applies downward traction on the test extremity while the patient's neck is hyperextended and rotated to the opposite side. Absence of the pulse indicates a positive test.6
  5.  Wright test (hyperabduction test): The examiner palpates the radial pulse and hyperabducts the arm so the hand is brought overhead with the elbow and arm in the coronal plane. The patient takes a deep breath and may rotate or extend the neck for additional effect.
  6. Allen maneuver: The examiner palpates the radial pulse while positioning the shoulder in external rotation and horizontal abduction. The patient then rotates the head away from the test side.
Diagnostic tests also include a Doppler arteriography testing of the vascular system. If the compromise is neurogenic, nerve stimulation is sometimes used for diagnosis.

Example Swimmer with Paget-Schroetter Syndrome

The patient was a 21-year-old male swimmer who noticed swelling and pain in his non-dominant arm. The patient was advised to ice and rest his shoulder. Then, ten days after the initial heaviness, the symptoms returned and the patient was advised to seek emergency care where a Doppler venous ultrasound could be performed. The results were negative. The patient demonstrated a cease of the radial pulse, swelling, and limb cyanosis with the Wright’s hyperabduction test. He also presented with ⅘ strength on the affected side, but 5/5 strength on the non-affected side. Despite a negative Doppler venous ultrasound, the vascular surgeon suggested a venogram, since a Doppler venous ultrasound is best used as a screening tool, not for diagnostics, since it has difficulty specifically measuring the subclavian vein due to the bony structures. The venogram showed a major block of the subclavian vein, venous stenosis, and concomitant thrombosis.

The patient was then administration heparin and a tissue plasminogen activator (tPA) over a three day period in order to achieve thrombolysis.This improved the thrombus by 70%, indicating 30% of the vein had undergone permanent thrombosis. The patient was then prescribed coumadin and Lovenox as a blood thinner. Electromyography (EMG) was also performed to rule-out a neurogenic case of TOS, which demonstrated no muscle membrane instability.

The swimmer returned to the pool with great success (winning the conference in the 100 and 200 breast), then received a resection of the first rib. After the surgery, the patient complained of pain medial to the shoulder blade and demonstrated shoulder-blade winning. Manual muscle tests were performed again and noted 5/5 strength in all muscles. Fine-wire EMG was conducted again and showed normal signs of all muscles except the serratus anterior which demonstrated signs of denervation (likely due to surgical complications to the long thoracic nerve).

Despite the findings of the serratus anterior, the patient started a physical therapy program and home program which resulted in improved EMG readings for the serratus anterior, three months postoperatively.

Thoracic Outlet Syndrome Swimming Prevention Techniques

Steady Streamline:

If the arms move excessively during streamline, the upper arm and neural structures are stressed. Maintain a stable arm position during all streamline, especially dolphin kicking.

Flatter Butterfly:

Some swimmers (like Michael Phelps) press their chest down as they enter their arms in butterfly, delaying their pull. This creates a position with the arm above the chest, stretching and stretching the brachial plexus (all the nerves and vascular areas).  Try starting the pull earlier, not allowing a position of arms higher than the chest. 

Deep catch:

Many swimmers have a "catch-up" style stroke. Unfortunately, this increases stress at the shoulder joint and vascular system. If working on less stress, have the swimmer have a deeper catch as the enter the water.

Neutral Hand Entry:

Entering without hand entry is paramount for all shoulder prevention, as excessive internal rotation increases shoulder stress.

Shallow Backstroke Catch:

Entering with a deep catch in backstroke stresses and strains the neurovascular structures in the front of the shoulder...no good! Instead, have a wider, more shallow catch, similar to Missy Franklin's technique. 

Thoracic Outlet Syndrome Dryland Techniques

Foam Roll Thoracic Spine:

SMR Scalenes:

SMR Pectoralis:

Nerve Mobility:

First Rib Mobilization: 

Anterior Neck Strengthening:

Scapular Strengthening:

Summary on Thoracic Outlet Syndrome for Swimmers

Some cases of TOS require drastic treatment, like surgery (first rib resection). Instead of dealing with potential surgery, keep a close eye on TOS symptoms and begin early with treatment and technique modifications at the first instance of symptoms. 

These are only some technique modifications and treatments, as each person is individual and different stroke biomechanics and rehabilitation/prevention programs are necessary for each person. Moreover, just because some swimmers perform with techniques which increase shoulder stress, doesn't necessarily result in TOS or injury. Therefore, if you are suffering from TOS, see a rehabilitation specialist for guidance and individualization.

If looking for more injury prevention techniques, consider purchasing the COR Swimmer's Shoulder System.

  1. Nitz AJ, Nitz JA. Vascular thoracic outlet in a competitive swimmer: a case report. Int J Sports Phys Ther. 2013 Feb;8(1):74-9. 
  2. M Sadeghi-Azandaryani, D Bürklein, A Ozimek, C Geiger, N Mendl, B Steckmeier, J Heyn Thoracic outlet syndrome: do we have clinical tests as predictors for the outcome after surgery?Eur J Med Res. 2009; 14(10): 443–446. Published online 2009 September 28. doi: 10.1186/2047-783X-14-10-443
By Dr. G. John Mullen received his Doctorate in Physical Therapy from the University of Southern California and a Bachelor of Science of Health from Purdue University where he swam collegiately. He is the owner of COR, Strength Coach Consultant, Creator of the Swimmer's Shoulder System, and chief editor of the Swimming Science Research Review.

Future of Swimming Training

Take Home Points on the Future of Swimming Training:

  1. Smart technology is on the verge of dramatically enhancing swimming performance, be ready for the revolution.
Swimming is one of the most biomechanically difficult sports. Unlike other sports, swimming works against water while in a horizontal position. The unfamiliar horizontal position makes all stroke corrections more difficult. Water also creates resistance during any motion, making improvements harder! This motion creates drag impeding performance to a greater degree than air resistance.This makes receiving feedback difficult. In fact, Stefan Szczepan beautifully described his work and the role of immediate feedback in swimming.

We reviewed Szczean and Zatoń (2014) research in the latest Swimming Science Research Review. Zatoń (2014) split sixty-four male swimmers into a control and an experimental group. The experiment consisted of 4 freestyle swimming trials of 25 meters. The first two trials were pretest and the third and fourth trials were the experimental trials. In the experimental trials, the swimmers were instructed to "reach out further". 

There was significant improvement in stroke length, stroke rate and swimming velocity.

Future of Swimming Training

Overall, there is a lack of immediate feedback in the sport of swimming despite the shown benefit. As technology decreases prices, these methods must be integrated more in swimming. Whether the feedback is through telemetry systems or visual cues, having immediate feedback will reduce errors. As technology, systems my provide automatic feedback based on performance

Biomechanics, Injury Prevention and Coaching

For example, MOOV has created a "smart watch" which provides instantaneous feedback during running. Full disclosure, I consult with MOOV, so I first hand understand the potential of this product. Imagine a device which you wear on your wrist and lets you know when your hand speed is slowing, force production is decreasing, or hand path is altering, then coaches you for improvement! This can improve biomechanics, reduce injuries, increase motivation, and other improve swimming!

Dryland and Recovery

Athos, a smart clothing, is capable of measuring muscular activity when worn! If Athos, or another company, can create waterproof clothing, then huge advancements in muscular training and recovery are possible. Imagine knowing when a muscle is completely fatigued from the resting neuromuscular activity...pretty cool! If this product isn't made waterproof, it still a beneficial product for dryland, knowing exactly which muscles are activity during each exercise. 

Sleep and Recovery

Sleep and recovery have huge potential for swimming improvement. Currently, recovery and sleep and not individualized, although everyone is unique and individual recovery patterns are needed. There are products like BioForce HRV and other smart watch technologies which track sleep and heart rate variability, a potential marker for monitoring recovery. 

Nutrient Levels

One possibility for training and monitoring is blood analysis without skin penetration. As far as I know, this technology doesn't exist. However, if someone can create a device which continuously monitors nutrient levels in the blood or via saliva, exact nutrient levels is possible. This can maximize energy, recovery, and performance!


If these products are accurate, then the world of swimming and coaching will be transformed. For example, a swimmer is held responsible throughout the main set, not allowing them to "slack" or take an unnoticed break. For the coach, the device will monitor biomechanics more accurately and continuously than the coach. For injuries, knowing when pain starts during a set and seeing the muscular activity or biomechanical deviation at this point in time will influence technique and reduce injuries. Also, knowing when and what to eat for maximal performance, as well as knowing how much sleep is needed for maximal performance has exciting potential! Once again, this will change the sport, so harnessing technology and analyzing data will become even more paramount for success. Make sure you are ready for the next phase of sports enhancement!

  1. Zatoń K, Szczepan S. The impact of immediate verbal feedback on the improvement of swimming technique. J Hum Kinet. 2014 Jul 8;41:143-54. doi: 10.2478/hukin-2014-0042. eCollection 2014 Jun 28.
By Dr. G. John Mullen received his Doctorate in Physical Therapy from the University of Southern California and a Bachelor of Science of Health from Purdue University where he swam collegiately. He is the owner of COR, Strength Coach Consultant, Creator of the Swimmer's Shoulder System, and chief editor of the Swimming Science Research Review.

Do Growth Spurts Increase Injury Risk?

Take Home Points on Do Growth Spurts Increase Injury Risk?
  1. It seems the injury rate increases during growth spurts, but research is very limited. 
Growing pains are common in children, yet the cause and treatment of growing pains are not well known. Some hypothesize growing pains occur from muscles pulling on bones creating discomfort. Others believe increase in bone size simply increases discomfort from an increase in mechanical pressure. 

Growing pains are one type of "injury" during growth spurts. Specific adolescent injuries also exists, which I commonly see for Physical Therapy

Adolescent Injuries

  1. Osgood-Schlatter's Disease: is a painful swelling of the bump on the upper part of the shinbone, just below the knee. This bump is called the anterior tibial tubercle. It is believed to occur in active children who's patella tendon pulls on the tibial tubercle. 
  2. Sever's Disease: inflammation of the growth plate in the heel of growing children, typically adolescents. The condition presents as pain in the heel and is caused by repetitive stress to the heel and is thus particularly common in active children. It usually resolves once the bone has completed growth or activity is lessened.
  3. These are just a few common musculoskeletal injuries effecting children. Many other injuries can occur during growth spurts and parents for decades believe children have a higher injury risk during a growth spurt. Combine this injury risk with chronic poor posture from computers/electronics and early sports specialization and you've got a high injury risk for child...scary!

Growth Spurts and Injuries

Now, before we jump to conclusions about the injury incidence and growth spurts, we should consult
the limited literature:

Yukutake (2014) had 654 baseball players aged 6-12 years, all male, complete an original questionnaire that included items assessing demographic data, developmental factors (increase in height and increase in weight over the preceding 12 months), and baseball related factors. Multiple regression analysis was used to identify the risk factors for elbow pain during the 12 months prior to the study.

The data collected for 392 players without omissions or blank answers were submitted to statistical analysis. The results found that 19.1% of Little League baseball players had experienced elbow pain in the 12 months leading up to the study. The analysis revealed that height and increase in height were risk factors that increased the risk of elbow pain after adjustment for demographic data, developmental data, and baseball related factors.

Wild (2012) looked at ACL injury rates in adolescent boys and girls, noting girls have a higher ACL injury rate from:
  1. The effects of changes in estrogen levels on the metabolic and mechanical properties of the ACL
  2. Changes in musculoskeletal structure and function that occur during puberty, including changes in knee laxity, and lower limb flexibility and strength. 
  3. How these hormonal and musculoskeletal changes impact upon the landing technique displayed by pubescent girls.With limited research, limited conclusions are possible. 
However, the risk of injury increases during periods of growth. Unfortunately, recommendations now are purely theoretical. Some would suggest decreasing activity during maturation, but these are the peak years of motor learning. Instead, decreasing training volume and varying activities may be the best solution. This website has brought up the idea of a "swim stroke count", similar to a pitch for baseball. However, swim stroke counts may not be effective nor practical as many other factors influence musculosketetal stress on maturing bodies. Looks like we need more research on maturing athletic children!

  1. Yukutake T, Nagai K, Yamada M, Aoyama T. Risk factors for elbow pain in Little League baseball players: a cross-sectional study focusing on anthropometric characteristics. J Sports Med Phys Fitness. 2014 Apr 9.
  2. Wild CY, Steele JR, Munro BJ. Why do girls sustain more anterior cruciate ligament injuries than boys?: a review of the changes in estrogen and musculoskeletal structure and function during puberty. Sports Med. 2012 Sep 1;42(9):733-49. doi: 10.2165/11632800-000000000-00000. Review.
By Dr. G. John Mullen received his Doctorate in Physical Therapy from the University of Southern California and a Bachelor of Science of Health from Purdue University where he swam collegiately. He is the owner of COR, Strength Coach Consultant, Creator of the Swimmer's Shoulder System, and chief editor of the Swimming Science Research Review.

Life-Long Swimming Movement

The newest edition of the Swimming Science Research Review was released today. The theme of this edition is physiology, make sure to order your copy to stay current with the latest research on dry-land. Below are the tables of contents of this edition. 

September Swimming Science Research Review Tables of Contents

  1. Apheresis PRP has Minimal Enhancements  | PRP INJECTIONS
  2. Scapular Mobility is Altered in Impingement  | SHOULDER IMPINGEMENT
  3. Consider Function when Diagnosis FAI  | HIP FAI
  4. Review of Patellofemoral Knee Pain  | PATELLOFEMORAL KNEE PAIN
  5. Push-up Plus Minimizes Pectoralis Major Activity  | REHABILITATION
  6. Clinical Tests Cannot Diagnose Sciatica  | SCIATICA
  7. Manipulation and Sham Manipulation Improve Scapular Mobility  | MANIPULATION
  8. Swimming is a Possible Exercise During Pregnancy  | PREGNANCY
  9. Corticosteroids Improve Shoulder Pain Better than NSAIDs  | THERAPEUTIC DRUGS
  10. The Slump Test Identifies those with Mechanosensitivity  | SCIATICA
  11. Aerobic Training Increases Pain Tolerance  | PAIN
  12. Elite Swimmers have Altered Pectoralis Minor Length  | MOBILITY
  13. Sympatomatic Axillopectoral Muscles  | REHABILITATION
  14. Core Strength Testing  | LOW BACK PAIN
  15. Shoulder Dryland Training Decreases Imbalances  | SHOULDER STRENGTHENING
  16. Physical Therapy and Dry Needling have Similar Results in Myofascial Pain  | REHABILITATION
  17. Pain Impairs Performance  | PAIN
  18. Core Muscle Contraction Rate Varies with Position  | LOW BACK PAIN
  19. Screening Helps Predict Injuries   | INJURY SCREENING
  20. Rotational Differences in Overhead Athletes  | PREVENTION
  21. Alarming Injury Rates in Collegiate Swimmers  | REHABILITATION
  22. Latent Myofascial Trigger Points Inhibit Strength  | PREVENTION
  23. Shoulder Adaptations to Pitching  | PREVENTION
  24. Graston Technique Improves Range of Motion  | REHABILITATION
  25. Bench Press Shoulder Pain Case Study  | PREVENTION


Injuries occur in every sport. This incidence creates acceptance in coaching, as many turn
a blind eye to aches and pains. As we’re learning, this practice is hazardous, as pain and even latent trigger points (muscle knots) impair strength and biomechanics. In swimming, biomechanics and reducing drag directly correlates with swimming success. If athletes are having pain, from either an injury, pre-injury, or training, their performance and skill will obviously suffer. As motor learning research unveils, preventing soreness, monitoring injuries, and individualizing rest/recovery requires deep consideration. Remember, few swimmers, even elite swimmers, will make a career out of swimming. With this in mind, push you swimmers, safely, and intelligently for improvement with their acute and long-term health and performance in mind. If you coach high school-aged kids, take pride in having a high percentage of them swimming at Masters meets in their life, coaching high-school, or having their children swim. This may sound silly, but building life-long ambassadors of the sport will do more for the swimming community, than building a team of disgruntled, injured, and regretful Olympic Trial qualifiers in the sport.

Re-evaluate your team, educate your parents and athletic department and join the life-long swimming movement today!

The influx of online information makes it difficult to stay up-to-date with informative, accurate research studies. The Swimming Science Research Review brings you a comprehensive research articles on swimming, biomechanics, physiology, psychology, and much more!
This monthly publication keeps busy coaches and swimming enthusiast on top of swimming research to help their programs excel, despite being extremely busy.