Maximal Force Production for Reducing Injuries

Injuries occur in all sports. Unlike ground-based sports, nearly all swimming injuries stem from overuse. These overuse injuries commonly occur when an athlete is unable to respond during a fatigued state. During this state, the body does not respond appropriately to an unexpected stimulus.

This ability to react to an unexpected movement is dependent on many variables. One variable infrequently mentioned is spinal motor control/neural drive. This control is potentially moderated by the sympathetic nervous system (fight or flight) system and studies suggest spinal motor control/neural drive is higher in men and power trained athletes (Johnson 2012).

Spinal motor control/neural drive may also contribute to swimming success, as a recent study found a correlation between handgrip strength and 100-meter freestyle performance. Many will doubt the correlation between handgrip to predict 100-meter freestyle performance, but handgrip strength may utilize spinal motor control for a maximal contraction (Autonomic Nervous System Readiness; Handgrip Strength Predicts 100-meter Performance?). However, more research is required on this topic, assessing a broader and diverse population. Keep in mind, handgrip strength is believed to inversely correlate with overtraining. This suggests these 100-meter freestyle swimmers could have just been more rested than their peers.

One potential mechanism for improving spinal motor control/neural drive is through resistance training, as the results of a current study imply strength and endurance training result in different neural response. However, future studies must assess the response in trained athletes, before a true correlation before one can draw the conclusion that the resistance training was responsible for improvement. Moreover, the correlations with the neural adaptations are essential criteria for recommendation for the swimming community. Neural drive may also differ in a population of simultaneous resistance and endurance training (ie swimming). However, neural drive may be the avenue for improvement from resistance training in swimming (Vila-Chã 2012).


One example of this training is the rack pull:

Another area to consider is a more power training approach to dry-land after a proper foundation of training (general strengthening and injury prevention) is achieved. However, this approach must not increase the risk of injury (I suggest shortened range of motion movements), perform excessive repetitions (interferes with the principle of specificity), or result in excessive soreness (impairing motor programming).

This doesn't suggest strength training is a requirement for all swimmers, but does suggest an explanation of the consistent use of resistance training in elite swimmers. Lastly, keep in mind, resistance training (especially supra-maximal power training in shortened range of motion) must only be implemented once the swimmer has demonstrated that they have the muscle stability and timing necessary to perform the training in a safe manner, as the top priority of any dry-land program is keeping the athletes healthy, for high-intensity swimming training.

Reference:

  1. Johnson ST, Kipp K, Hoffman MA. Spinal motor control differences between the sexes. Eur J Appl Physiol. 2012 Mar 8. [Epub ahead of print]
  2. Vila-Chã C, Falla D, Correia MV, Farina D.Changes in H reflex and V wave following short-term endurance and strength training. J Appl Physiol. 2012 Jan;112(1):54-63. Epub 2011 Oct 13.

By G. John Mullen founder of the Center of Optimal Restoration, head strength coach at Santa Clara Swim Club, creator of the Swimmer's Shoulder System, and chief editor of the Swimming Science Research Review.

Autonomic Nervous System Readiness: Part II

A few weeks ago we discussed how to measure autonomic system readiness. It’s important to understand what physical state the swimmer brings to the pool each day. Is their resting state one of relaxation, indicating parasympathetic dominance? Or is their body chronically stressed, meaning the autonomic nervous system is working extra hard to just maintain the body at rest? Tools such as heart rate variability and grip strength are evidence based methods to help us answer these questions. But once we have that information, what should do with it? In this post, we’ll discuss ways to make adjustments or “call an audible” when the swimmer’s autonomic nervous system readiness requires working off the planned script for the day (see also, Friday interview with Craig Weller).

Friend of the blog Patrick Ward (now with the Nike SPARQ program in Oregon) has created guidelines on how coaches and athletes may adapt if their autonomic nervous system is not at peak readiness on any given day. Though calling an audible is as much art as science, guidelines can help us make informed adjustments based on the swimmer’s condition for the day. These guidelines can help us find a sensible middle ground between stubbornly refusing to make any adjustments versus skipping practice just because someone has a cold.

Option 1: Lower the volume but keep intensity the same:
Perform the workout as planned but with fewer reps.This works for a slight reduction in readiness, when a slight reduction is unexpected. One simple example would be doing 15 x 100 on 1:20 holding 1:10 when the original plan called for 20 x 100. You might also switch from long course to short course or shorten reps (200s become 150s or 100s). Aim for the same rep times with same rest. Offers minimal disruption to a normal lane, but it still must fit the swimmer. The same concept applies on dry land…3 x 8 pullups might become 2 x 8 or 3 x 5 as an adjustment. 

Option 2: Lower intensity but keep sets and reps the same:  
This is for a more significant reduction in readiness. Switching to shorter reps but with the same total volume is still an option here. However, you might shift to an easier interval, or if it is a hard workout planned, consider shifting to another day if possible, Pull buoy sets are also advisable if your program uses the pull buoy as a training tool

Option 3: Switch the workout to lower intensity or medicine ball circuit: 
One analogy to swimming would be a light IM kick/drill emphasis. Reduce the entire load of the entire workout. Again, it is not always possible to shift workouts during the week, but sometimes all that’s needed is to delay a workout one day. Avoid heavy lifts on these days.

Option 4: Switch the workout to low intensity cardio: 
Essentially the entire workout is like one long warmup and cooldown. If the autonomic nervous system leans heavily toward sympathetic (“fight or flight”) dominance at rest, it means the swimmer is teetering close to non-beneficial overreaching. Some overreaching is necessary for growth, but unexpected overreaching or insufficient recovery due to non-swimming factors must be dealt with accordingly. 

Option 5: Scrap the session but do light mobility work: 
For swimmers this could mean anything from extremely light swimming (double arm back), social kicking, or dryland work such as mobility drills, foam rolling, or even an appointment with a manual therapist for a regeneration type of massage. Several options are available, but if the autonomic nervous system is overstressed, most important is call an audible and minimize the damage. Sometimes its best call a run for no gain rather than throw an interception!

Summary
Have several plays in your playbook and be willing to adjust if the something unexpected occurs.  If the autonomic nervous system is not ready for the day’s planned workout, call an audible most appropriate for the situation.  Several options are available from shortening the workout but at the planned intensity to making the day one for active recovery.  

By Allan Phillips. Allan and his wife Katherine are heavily involved in the strength and conditioning community, for more information refer to Pike Athletics.

Changes in H reflex and V wave following short-term endurance and strength training

Vila-Chã C, Falla D, Correia MV, Farina D. Changes in H reflex and V wave following short-term endurance and strength training. J Appl Physiol. 2012 Jan;112(1):54-63. Epub 2011 Oct 13.

Background
The nervous system is adaptive to training. It is feasible to measure the adaptations of the nervous system via reflex responses, especially the H reflex and V wave.

“Although these evoked responses are affected by common neural mechanisms, during voluntary contractions, the H reflex is more sensitive to altered presynaptic inhibition and motoneuron excitability whereas the V wave is more sensitive to changes in supraspinal input to the motor neuron pool. Thus combined measures of the H reflex and V wave may provide a better understanding of the neural adaptations elicited by specific motor training programs (Vila-Cha 2012)”

The H reflex is expected to be higher in endurance trained athletes. The V wave is thought to increase with strength training.

The present study investigated if endurance and strength training induce parallel changes in H and V wave responses during voluntary contractions of the soleus muscle and if so whether there are associations between changes in motor performance and changes in reflex responses.

What was done
Twenty-six untrained healthy participants performed 9 training sessions over 3 weeks. The programs were progressed over the training period. The endurance training included cycling and the strength training consisted of upper and lower body exercises. Each exercise was performed for 3 rounds of 15-18 repetitions.

These two groups were compared.

Electromyography and reflexes were taken before and throughout training.

Results
The current work showed that following 3 wk of endurance training the excitability in the H-reflex pathway increased but the V-wave amplitude remained unchanged. In contrast, following strength training, the V-wave amplitude increased whereas subtle changes were observed in the H-reflex pathway. Moreover, although weakly, the improvement in time-to task-failure of the plantar flexors was associated with increased H-reflex excitability while the increase in MVC was associated with increased V-wave amplitude.

Discussion
These results suggest that elements of the H-reflex pathway are strongly involved in chronic adjustments in response to endurance training, contributing to enhanced fatigue resistance. Conversely, following strength training, it is more likely that increased descending neural drive during MVC and/or modulation in afferents other than Ia afferents contributed to increased motoneuron excitability and MVC of the plantar flexors.

Practical Implication

This study suggests that strength and endurance training result in different neural responses. However, future studies must assess the response in trained athletes, before a true correlation is appropriate. Moreover, the correlations with the neural adaptations are essential criteria for recommendation for the swimming community. However, this study opens the possibility that improved neural drive may be the chief avenue for improvement from resistance training for swimmers, as improved drive helps all athletic movements, recovery, and potentially prevents injuries.

Swimming Science Research Review 

This is a piece of the Swimming Science Research Review. Read Swimming Science Research Review October 2012 for a complete list of the articles reviewed.

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Autonomic Nervous System Readiness


The autonomic nervous system is critical to regulate our bodies.  In this post we’ll discuss ways to examine autonomic system readiness in our swimmers.  Think of these as systems checks on your “race car” (aka, swimmer’s body) before you crank up the engine.  There are several medically accepted ways to assess autonomic nervous system health, but many are not practical for the common athletic setting, let alone a pool deck.  Fortunately, there are a few reliable methods that can fit within a reasonable budget and can accommodate swim team logistics.

To review…the autonomic nervous system involves two branches: parasympathetic (“Rest and digest”) and sympathetic (“Fight or flight”).  Generally we prefer parasympathetic dominance at rest, preparing the body for a fight-or-flight response when needed.  If the body is too worked up (sympathetic) at rest, it’s a sign the body is working harder than normal just to support basic function.  The result is fewer resources in reserve when greater output is needed (race, hard workout, training camp).  Note these are guidelines, not rules, as even though we strive for parasympathetic dominance at rest, being TOO parasympathetic can signal other problems. 

The simplest way to see autonomic nervous system readiness is with basic observation…Appetite, mood, sleep patterns, (Fry 1994) skin tone, or how the athlete is moving on a particular day.  Paying attention to these factors is better than nothing, but still open to false positives and false negatives. 

A false positive is if the variable is outside the normal range, but there’s nothing actually wrong.  A false negative is if there is something wrong, but none of the relevant variables change. As an extreme example, suppressed appetite could be a sign of overtraining or it could mean you ate something disagreeable to your stomach.  Likewise, mood disturbance could mean some life event is causing stress that might resolve with physical exercise, or it could mean your body is overtraining. 


Because of these potential ambiguities, it is helpful to have quantitative measures for assessing autonomic system readiness.  Perhaps the most popular is resting heart rate (Jeukendrup 1998).  A crude way to assess resting heart rate is to take your pulse with your finger upon awakening.  More precise is to use a heart rate monitor upon awakening or sleep with a heart rate monitor on (good luck with compliance on the latter!). 

The main problem with resting heart rate is the risk of false positives. Hydration and mental stress can both spike resting heart rate temporarily, but such fluctuations are often natural and resolve quickly.  You might suggest these are signs to back off training, but this is not an absolute. Yet in other cases, there might be nothing wrong.  One way to decrease confusion is to keep a detailed log of resting heart rate and track against other variables.  If you get any readings outside the average range, it is cause to reevaluate the plan for the day.  This strategy does require interpretation, but with enough data history you can make informed decisions.

Another method is hand grip testing using a dynamometer.  Khurana (1996) noted, “Isometric hand-grip is therefore a specific, sensitive, reproducible, simple and non-invasive test of sympathetic function with relatively well-studie
d reflex pathways.”  This method is easier than resting heart rate and can simply be taken on-site right before a workout and does not need any electronics.  As with heart rate, establishing a baseline is crucial…a powerlifter on his worst day will likely have a much stronger grip than a 9-year-old swimmer on their best day.


Heart rate variability has been a hot topic in recent years in sports performance.  In studying elite swimmers, Hellard (2011) found, “HRV is a rapid and noninvasive tool to indicate autonomic function, which provides complementary information that may help to reduce the risk of infection in elite swimmers. Weekly HRV monitoring would indicate a drop in parasympathetic regulation, which increases the likelihood of pathology.”  They also found that HRV analysis could predict a shift in sympathetic dominance one week in advance, though more study is needed in that area to confirm time lags under different settings.

Of the methods commercially accessible to coaches, HRV is accepted as the most reliable.  Although commonly used for decades in medicine, many believe the Russians and Eastern Europeans in the 1970s-80s were the first to introduce heart rate variable testing for athlete readiness.  However, because these countries were tainted
by doping allegations, many valuable advances in their programs were swept aside by the rest of the world.  As other nations began revisiting these plans and sifted through the “clean” aspects, heart rate variability reemerged into the coaching toolbox. 

As with any other method, baseline measurements are mandatory before interpreting data (and yes, even baseline for mood is important, as a bad mood for a natural grouch is less alarming than an athlete with a normally sunny disposition).  Most criticisms of HRV center not in its measurement reliability but instead on how well humans can interpret the data.  Despite the need for interpretation, objective data does remove some guesswork. 

Conclusion
Measuring autonomic nervous system readiness involves both subjective and objective information.  Know your athletes subjectively and use objective data to refine your observations.  Remember, these tools are not meant as commandments but instead to serve as additional layers of security to catch problems before they occur. 

References
  1. Jeukendrup A, VanDiemen A. S91-9. Heart rate monitoring during training and competition in cyclists.J Sports Sci. 1998 Jan;16 Suppl:
  2. Baumert M, Brechtel L, Lock J, Hermsdorf M, Wolff R, Baier V, Voss A. Heart rate variability, blood pressure variability, and baroreflex sensitivity in overtrained athletes. Clin J Sport Med. 2006 Sep;16(5):412-7.
  3. Khurana RK, Setty A. The value of the isometric hand-grip test--studies in various autonomic disorders. Clin Auton Res. 1996 Aug;6(4):211-8.
  4. Hellard P, Guimaraes F, Avalos M, Houel N, Hausswirth C, Toussaint JF. Modeling the association between HR variability and illness in elite swimmers. Med Sci Sports Exerc. 2011 Jun;43(6):1063-70.
  5. Fry RW, Grove JR, Morton AR, Zeroni PM, Gaudieri S, Keast D. Psychological and immunological correlates of acute overtraining. Br J Sports Med. 1994 Dec;28(4):241-6.
By Allan Phillips. Allan and his wife Katherine are heavily involved in the strength and conditioning community, for more information refer to Pike Athletics.