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

Foreword

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.

$10/month
 

Acute Creatine Consumption Doesn't Improve Swimming Performance


The newest edition of the Swimming Science Research Review was released yesterday. The theme of this edition is motor learning, 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. 

Order today and find the answer to the following questions:
  1. Do Elite Swimmers have Suboptimal Nutrition?
  2. Does Protein Decrease Soreness?
  3. What we Know about the Low Carb Diet?
  4. Does a Moderately Low Carb Diet Decrease Swimming Performance?
  5. Does Multivitamin Supplementation Increase Swimming Performance?
  6. Do Medium Chain Fatty Acids Enhance Performance?
  7. Does Acute Carbohydrate Consumption Improve Test Set Performance?  
  8. Does Doping Enhance Sports Performance?
  9. Does Probiotic Yogurt Decreases Illness Length?
  10. Are Youth Swimmers Mineral Deficient?
  11. Does a Carbohydrate Drink Improve Performance in those with Lower Body Mass ?
  12. Does L-carnitine Decrease Lactate Accumulation?
  13. Do Bite-Aligning Mouthpieces Improve Power?  
  14. Are Youth Swimmers Deficient in Vitamin A, Fiber, and Selenium?
  15. Does Sodium Bicarbonate Improves Repeated Sprint Performance>
  16. Does Energy Drink Consumption Increase Lactate?
  17. Does Dehydration Increase Cramps?
  18. Does High Swimming Training Intensity Alter Iron Status?
Also, remember to stay current and on top of the literature for the health and benefit of your swimmers! If you're interested in the SSRR, Order your copy today for $10!

Take Home Points on Acute Creatine Doesn't Improve Swimming Performance

  1. Acute creatine ingestion of 5.0 g/d does not improve sprint or repeated swimming performance than carbohydrate consumption. 
Creatine is a popular ergogenic aid in all spots. Physiologically, phosphocreatine can limit
short-duration, high-intensity exercise. For swimming, this potentially increases repeated sprint performance and high-intensity swimming duration.

We've written previously about the positive effects of creatine, mostly extrapolating research from other sports, as swimming does not receive the bulk of the exercise science research. This makes swimming specific research essential for prescription to swimmers.

Mendes (2004) had eighteen competitive swimmers (M=12, F=6) undergo a double-blind, placebo-controlled study. For the first week, the swimmers underwent a biochemical evaluation. After this, the group was divided randomly into two, receiving either creatine or placebo.

The creatine group (received four doses of 5.0 g creatine and carbohydrate per day). The placebo received four doses of 20.0 g carbohydrates per day.

The swimmers were tested in three types of exercise:
  1. 50-m sprint
  2. 100-m sprint
  3. 3 sets of 3x50 with :30 interval between repetitions and 2:30 between sets
There were no significant differences in any of the performance tests. Approximately 50% of the creatine consumed was excreted in the urine.

Overall, body water weight increases in this study, with a speculated increase in muscular creatine. These findings question the use of creatine, but also warrant longer investigations, as an acute increase in body weight may alter biomechanics and cancel out any potential benefits.

These results conflict some previous studies and conclusions. If using creatine, perhaps longer dosing periods are needed for body adaptations.

References

  1. Mendes RR, Pires I, Oliveira A, Tirapegui J. Effects of creatine supplementation on the performance and body composition of competitive swimmers. J Nutr Biochem. 2004 Aug;15(8):473-8.

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.

Motor Imagery Guide for Swimmers


Take Home Points on Motor Imagery Guide for Swimmers

  1. Motor imagery may enhance gains in biomechanics, injury rehabilitation, mobility, and psychology.
  2. Consider adding 15 minutes of motor imagery in your training.
The use of motor imagery (MI;the mental representation of an action without overt execution,also known as visualization) during actual training sessions is usually recommended. Most Olympians use some form of MI, but it is rarely practiced in non-elite athletes. The lack of use is not well understood, as it can range from improving race anxiety to improving mobility

Allami (2014) split ten right handed subjects (~27.5 years) into two training groups. In one group, subjects executed a reach to grasp task for 240 trials. In the second group, subjects learned the task through a combination of mental rehearsal for the initial 180 trials followed by the execution of 60 trials. Thus, one group physically executed the task for 240 trials, the other only for 60 trials.


The task has been previously described in detail. Briefly, they used a two-step task, where subjects reached for and grasped an object, and transported it to insert it in an adapted support.

In the mental rehearsal task, the subjects were instructed to follow the same sequence of events as in the physical practice, except that they were told to imagine and feel themselves (first person) doing the task as if real (i.e., grasp the object, lift it and transport it to the support).

Amplitudes and latencies of event-related potentials (ERPs) were compared across groups at different stages during learning.

Results:

ERP activity increases dramatically with training and reaches the same amplitude over the premotor regions in the two groups, despite large differences in physically executed trials.

Another study looked at motor skill acquisition. Zhang (2014) had twenty-six right hand-dominant college
students (M=12, F=14; ~22 years) undergo a resting- and task-state functional MRI scan. Overall, the protocol included a pre-rest scan, pre-task scan, a motor imagery (MI) learning period or a no-learning period, a post-rest scan and a post-test scan.
The experimental group performed finger movements coordinated with a metronome. During the learning period, 14 motor imagery practice sessions were performed over 14 days.

Results:

Greater connectivity strengths in fusiform gyrus and precuneus of the sensory resting state networks (RSNs), LVN and SMN after learning. There was also decreased network strength induced by learning in the cognitive RSN specifically DMN. 

However, the use of motor imagery during heavy training may not be most effective, as motor imagery may be altered during fatigue. 

Di Rienzo (2012) had twelve swimmers (nine males, mean age 15.5 years) perform a 45 min physically-fatiguing protocol where they swam from 70% to 100% of their maximal aerobic speed. They were tested in motor imagery ability immediately before and after fatigue state. Participants randomly imagined performing a swim turn using internal and external visual imagery. Self-reports ratings, imagery times and electrodermal responses, an index of alertness from the autonomic nervous system, were the dependent variables.

Results:

Self-reports ratings indicated that participants did not encounter difficulty when performing motor imagery after fatigue. However, motor imagery times were significantly shortened during posttest compared to both pretest and actual turn times, thus indicating reduced timing accuracy. Looking at the selective effect of physical fatigue on external visual imagery did not reveal any difference before and after fatigue, whereas significantly shorter imagined times and electrodermal responses were observed during the posttest for internal visual imagery. A significant correlation was observed between motor imagery vividness (estimated through imagery questionnaire) and autonomic responses during motor imagery after fatigue. These data support that unlike local muscle fatigue, physical fatigue occurring during intense sport training sessions is likely to affect motor imagery accuracy.

Another possible use for motor imagery is the use of imagery during an injury. Hoyek (2014) had sixteen
participants (M=8, F=8; ~46.31 years) randomly assigned to a MI or control group.
The MI group imagined four movements using first-person perspective imagery. Each movement was imagined 10 times divided in five sets of two separated by 30-s rest periods.
Shoulder functional assessment (Constant score), range of motion, and pain were measured before and after.

Results:

Higher Constant score was observed in the MI than in the control group. The MI group had greater improvement amplitude in flexion, extension, and external rotation. The MI group also had decreased pain. 

Summary

MI has the potential of improving biomechanics through neural plasticity. It also may improve pain and function in those with shoulder impingement. Future studies must use better comparison groups for confirmation and making the most effective recommendations. 

6 Steps for Motor Imagery for Swimmers

There are several techniques for motor imagery training. For your individualized program, please consult a sports psychologist. If looking to try out motor imagery, try these 8 steps:
  1. Before the motor imagery in the pool. The physical nature of the imagery should include wearing a suit and being in the water (if weather and temperature permits). 
  2. Begin with deep breathing for 5 minutes. The purpose of instructing the participants through relaxation was to facilitate gaining control of breathing and physiological responses (e.g., heart rate); however, the focus was not on obtaining a highly relaxed state but to prepare for MI. 
  3. Follow this with 10 minutes of MI. Use an imagery script in which the participants were instructed to focus on their personal thoughts and feelings related to a performance event. A script is better than a video, since they'll ideally be in the water. 
  4. Focus on the specifics of swimming the task (i.e., reinforcing participants to focus on thoughts, feelings, and actions as during the physical performance and focusing on the kinesthetic nature of imagery), timing (i.e., same timing as race), learning (i.e., focusing on the ‘‘feel’’ of the movement), and emotion (i.e., experiencing all emotions and arousal associated with performance). With regard to the learning component, ‘‘feel’’ of the movement is more applicable for trained swimmers
  5. Don't instruct the participants on a specific perspective (internal or external) they should use during imagery. 
  6. Perform the script a total of 2 times. 
  7. Allow a few minutes (2 - 3 minutes) for individual mental rehearsal. 

References:

  1. Di Rienzo F, Collet C, Hoyek N, Guillot A. Selective effect of physical fatigue on motor imagery accuracy. PLoS One. 2012;7(10)
  2. Allami N, Brovelli A, Hamzaoui el M, Regragui F, Paulignan Y, Boussaoud D. Neurophysiological correlates of visuo-motor learning through mental and physical practice. Neuropsychologia. 2014 Mar;55:6-14. doi: 10.1016/j.neuropsychologia.2013.12.017. Epub 2014 Jan 3.
  3. Hoyek N, Di Rienzo F, Collet C, Hoyek F, Guillot A. The therapeutic role of motor imagery on the functional rehabilitation of a stage II shoulder impingement syndrome. Disabil Rehabil. 2014 Feb 28. [Epub ahead of print]
  4. Zhang H, Long Z, Ge R, Xu L, Jin Z, Yao L, Liu Y. Motor imagery learning modulates functional connectivity of multiple brain systems in resting state. PLoS One. 2014 Jan 17;9(1):e85489. doi: 10.1371/journal.pone.0085489. eCollection 2014.
The newest edition of the Swimming Science Research Review was released yesterday. The theme of this edition is motor learning, 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. 

Contents

  1. Athletes are More Coordinated | PROPRIOCEPTION   
  2. Fatigue Alters Motor Imagery Accuracy  | IMAGERY  
  3. Submaximal Speed Improves Maximal Speed in Untrained  | MOTOR LEARNING   
  4. Cortical Changes in as Quick as Five Days  | MOTOR LEARNING   
  5. Motor Imagery Improves Shoulder Pain  | IMAGERY  
  6. Mental Rehearsal Results in Similar Gains as Practice  | IMAGERY  
  7. Mental Fatigue Impairs Endurance Performance  | MENTAL FATIGUE  
  8. Aerobic Exercises Causes SICI and Neural Plasticity  | MOTOR LEARNING   
  9. Motor Imagery May Improve Motor Skill  | IMAGERY  
  10. CMJ Performance Correlates with Cortical Level  | OVERTRAINING   
  11. Individuals Learn at Different Speeds  | MOTOR LEARNING   
  12. Individualized Feedback Improves Long-Term Retention  | MOTOR LEARNING   
  13. High-Intensity Training Alters Skilled Movement  | MOTOR LEARNING   
  14. Co-Contraction Training Improves Strength  | STRENGTH
  15. Unilateral Training May Crossover Skill  | CROSS-EDUCATION   
  16. Random Practices Improves Retention  | MOTOR LEARNING   
  17. HIIT Doesn’t Decrease Enjoyment  | ENJOYMENT  
  18. Intense Training Alters Cortical Composition  | NEURAL PLASTICITY  
  19. fMRI Appears Accurate for Neural Plasticity Changes  | NEURAL PLASTICITY  


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. 




$10/month

Written by G. John Mullen received his Doctorate in Physical at University of Southern California (USC) and is a certified strength and conditioning specialist (CSCS). At USC, he was a clinical research assistant performing research on adolescent  diabetes, lung adaptations to swimming, and swimming biomechanics. G. John has been featured in Swimming World Magazine, Swimmer Magazine, and the International Society of Swim Coaches Journal. He is currently the owner of COR, providing Physical Therapy, Personal Training, and Swim Lessons to swimmers and athletes of all skills and ages. He is also the creator of the Swimmer's Shoulder SystemSwimming ScienceSwimming Science Research Review, and the Swimming Troubleshooting System.

Power and Swimming Start Performance

Take Home Points for Power and Swimming Start Performance

  1. Plyometric training is superior to no additional training in intermediately skilled adolescent swimmers.

Last week, Herbie Behm wrote a review piece on resistance training and the dive start. His take home points did not sit well with everyone, especially in light of some recent research by Bishop (2009). This is a review of the Bishop article as well as the contents of the Swimming Science Research Review for January, where every article on starts was analyzed. 

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Background 

Plyometrics are commonly given to swimmers with the hopes of improving start and turn performance. However, their effectiveness is not well known. This study analyzed the effects of plyometrics on start performance. 

What was done 

Twenty-two trained swimmers (~13.1 years; minimum of 8 hours/week; best 50-m freestyle ~35 s) were split into a plyometric training (PT) or habitual training (HT) group. The PT group was given an additional 2 hours per week of specific plyometric exercises for 8-weeks. Land and water testing was performed after the 8-weeks. 

Results 

The PT group had significantly greater change in time to 5.5 m, take-off to contact, distance to head contact, and time to head contact. No significant changes were noted in angle out of blocks and angle of entry into water. The swim time to 5.5 was improved on average by 0.59 seconds or 15%. 

Discussion 

PT seems to improve starting power, subsequently improving time to 5.5 m. 

Practical Implication 

Plyometric training is superior to no additional training in intermediately skilled adolescent swimmers. However, simply swimming or doing another dry-land activity may provide similar benefit. It seems performing dive starts during each workout with technical feedback and/or video analysis is superior for improving the start. 

On a start, maximal hip extension force is not ever achieved (as it takes time to develop maximal force). However, a more rapid extension may help with reaction time and generating a greater force in a shorter amount also will theoretically help the dive.

However, the biomechancis are obviously different, as you note, is the main issue as simply creating more force over a period of time, if not directed in the correct fashion may be wasteful.

Reference

  1. Bishop DC, Smith RJ, Smith MF, Rigby HE. Effect of plyometric training on swimming block start performance in adolescents. J Strength Cond Res. 2009 Oct;23(7):2137-43. doi: 10.1519/JSC.0b013e3181b866d0.

January Contents

  1. Foreword
  2. Practicing Starts Improves All Starting Styles
  3. Initial Stroke Speeds do Not Different Between Starting Styles
  4. Greater Streamline in International Breaststroke Starts
  5. Omega Blocks Improve Start Times
  6. Elite Swimmers with Different Feet Positions in Backstroke Start
  7. Ideal Time to Start Kicking off the Start
  8. Greater Leg Extensor Force is correlated with Greater 10 m Starting Performance in Elite Sprint Swimmers
  9. Hip Movement Indicates Backstroke Start Kinematics
  10. Plyometrics Improve Swimming Performance
  11. PAP May Improve Some Swimmer’s Starts
  12. Resistance Training Doesn’t Improve Starting Kinematics
  13. Starting Styles for Females
  14. Starting Profiles in Elite Sprinters
  15. Grab vs Track Start Efficiency
  16. Plyometrics Benefit Starts Compared to No Additional Training
  17. Omega Track Start Profiling
  18. Motor control during freestyle starts
  19. How to attack starts and undulations for performance
  20. Strength and Power Variables Predictors of Start Performance
  21. Does start aerial phase impact 15 m performance?
  22. Common features of an effective backstroke start
  23. Glossary
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Why Swimming Increases Low Back Degeneration

Take Home Points on Swimming and Low Back Degeneration

  1. Swimmers have greater disc degeneration than low load swimmers.
  2. Swimmers have one of the highest degeneration rates among athletes.
  3. While competing, swimmers do not have a higher injury rate for LBP compared to low load swimmers, but when pain is present the severity is higher.
The newest edition of the Swimming Science Research Review was released on Sunday.

Make sure you pick your copy up today to enhance your swimming and evidence-based coaching. 

$10/month

Background on Swimming and Low Back Degeneration

The shoulder is the primary site of injury in swimmers, but the low back is the second most commonly injured site. In fact, ~8% of those competing at a 2001 International competition experienced low back pain. Despite the anecdotal claims, few studies have compared low back pain and degeneration in swimmers to a control population. Also, comparing specific stroke specialists has also not been performed, limiting the stress from each swimming stroke.

Many feel butterfly and breaststroke are the most problematic strokes to the low back due to the amount of flexion cycles, but this website has already debunked the flexion cycle debate. In fact, rotation actually increases spinal stress, due to the shear stress at the joints.

Research on Low Back Degeneration in Swimmers

Kaneoka (2007) had fifty-six elite swimmers (M=35, F=21, ~19.6 years) and a control group (38 recreational swimmers; M=24, F=14; ~21.1 years) underwent a magnetic resonance image (MRI). Disc degeneration was compared between groups. Participants also completed a questionnaire about their main strokes as well as their low back pain history.



Thirty-eight (68%) elite swimmers and 11 (29%) controls had degenerated discs at various levels. Disc level L5-S1 was more frequently degenerated in the elite swimming group. However, there was no significant relationship of low back pain symptoms associated with this increase in disc degeneration. Swimmers had a lower rate of low back pain, but back pain was more debilitating.


 
Hangai (2008) analyzed 308 well-trained university athletes (baseball, basketball, kendo, runners, soccer players, and swimmer) and 71 nonathlete university students. Disc degeneration was evaluated with a T2-weighted magnetic resonance image (MRI). A questionnaire concerning low back pain was also performed.


Disc degeneration was significantly higher in baseball players and swimmers compared to the nonathletes. There was an association between low back pain and degeneration and the degree of severity of low back pain with disc degeneration. 

Conclusions on Low Back Degeneration in Swimmers

The L5-S1 segment undergoes greater degeneration in elite swimmers. However, the lack of associating symptoms brings to light the lack of correlation between defects in imaging and symptoms.


Repetitive sports such as baseball and swimming appear to increase incidence of disc degeneration. These sports also have greater rotation than the others studied, one possible mechanism of degeneration.


Disc degeneration is a higher risk in swimmers compared to nonathletes, yet injury rate was not significantly higher in swimmers. It seems low back pain and degeneration do not correlate, at least in the acute term. Longer studies must assess the degree of degeneration and injury rate later in life. Nonetheless, it seems swimmers have greater degeneration, but not injury rate. Moreover, swimmers and coaches should not be alarmed if an athlete undergoes an MRI and sees degeneration, as degeneration is greater in asymptomatic swimmers.
 
This month, the Swimming Science Research Review focused on low back pain. If you are looking for a quick and easy way to stay up-to-date with swimming research, subscribe today for only $10/month! 

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See the below December Table of Contents:
    1. Injury May Predict High Risk Individuals | PREVENTION
    2. Low Back Stabilization Prediction Rule not Validated | REHABILITATION
    3. Manipulation Responders have Higher Disc Diffusion | REHABILITATION
    4. Core Strength is Supposedly Important in Rehabilitation | REHABILITATION
    5. Multi-planar Strengthening Appears Important in Rehabilitation | REHABILITATION
    6. Core Stability Still Requires More Research for Performance Enhancement | DRY-LAND
    7. Instability Training Improves Joint Proprioception | PREVENTION
    8. Core Stability Improves Reflex Amplitude in LBP Patients | REHABILITATION
    9. Core Training Improves Throwing Accuracy | DRY-LAND
    10. Endurance Performance Improves with Addition of Core Stability Training | DRY-LAND
    11. Instability Training Improves Proprioception | DRY-LAND
    12. Dual Task Core Training Increases Core Stability | REHABILITATION
    13. Dynamic Core Strength Correlated with Ground-Based Performance | DRY-LAND
    14. Core Stability Improves Throwing Velocity | DRY-LAND
    15. Chinese Ointments may Enhance Rehabilitation with Massage | REHABILITATION
    16. Medicine Ball Throw Correlates with Core Stability | DRY-LAND
    17. Disc Degeneration Greater in Swimmers | REHABILITATION.. 29
    18. Disc Degeneration Greater, but Pain Lower in Elite Swimmers | REHABILITATION
    19. Free Weight Exercises Increase Core Muscle Activation | DRY-land
    20. Myofascial Release Systematic Review | REHABILITATION
    21. Prevention of Recurring Low Back Pain | REHABILITATION
    22. Trunk Motor Responses Increase in those with LBP| REHABILITATION
    23. Application of Stability Training to Sports Conditioning | DRY-LAND
    24. Glossary
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    Reference

    1. Kaneoka K, Shimizu K, Hangai M, Okuwaki T, Mamizuka N, Sakane M, Ochiai N. Lumbar intervertebral disk degeneration in elite competitive swimmers: a case control study. Am J Sports Med. 2007 Aug;35(8):1341-5. Epub 2007 Apr 3.
    2. Hangai M, Kaneoka K, Hinotsu S, Shimizu K, Okubo Y, Miyakawa S, Mukai N, Sakane M, Ochiai N. Lumbar intervertebral disk degeneration in athletes. Am J Sports Med. 2009 Jan;37(1):149-55. doi: 10.1177/0363546508323252. Epub 2008 Sep 17. 
    G. John Mullen received his Doctorate in Physical at University of Southern California (USC) and is a certified strength and conditioning specialist (CSCS). At USC, he was a clinical research assistant performing research on adolescent diabetes, lung adaptations to swimming, and swimming biomechanics. G. John has been featured in Swimming World Magazine, Swimmer Magazine, and the International Society of Swim Coaches Journal. He is currently the owner of COR, providing Physical Therapy, Personal Training, and Swim Lessons to swimmers and athletes of all skills and ages. He is also the creator of the Swimmer's Shoulder System, Swimming Science, Swimming Science Research Review, and the Swimming Troubleshooting System.