Neuromuscular Adaptations are Specific to the Training Stimulus

The SAID (Specific Adaptations to Imposed Demands) Principle dictates that the training response or effect will be specific to the nature of training performed. For example; training the squat will likely result in improvements in lower body performance in tasks like sprinting and jumping. However, it will likely not improve performance in tasks limited to the upper body as these muscles are stimulated to a much lesser degree during squatting. In untrained and novice athletes, getting stronger in the main compound exercises (squat, bench, deadlift, pull up, press, dips, rows, etc.) will likely carry over to improved performance in most athletic tasks. More advanced athletes however, require more specific stimuli to further improve performance in more specific tasks. For example; improving squat strength will improve vertical jumping ability to a point where further strength improvements will likely yield no further gains. To continue progressing, the training stimulus must be made more specific to the task. Squat jumps or hang cleans are exercise that train a similar pattern to the vertical jump and emphasize explosiveness, a key element in the task of jumping for maximal height. Therefore, those exercise may provide the specific stimulus required to make further improvements in jump height.

A recent study published this month in the European Journal of Applied Physiology demonstrates the significance of specificity in training and the resulting neuromuscular adaptations. Tillin and Folland (2013) set out to determine the differences in functional neural changes following a 4 week period of explosive strength training (n=9) or maximal strength training (n=10) in male subjects. Pre and post testing of the quadriceps muscles included maximal voluntary contractions and explosive force in 50-ms intervals from explosive contractions. Electromyography was used to assess neuromuscular activation at 0-50, 0-100 and 0-150-ms during the explosive contractions. Maximal voluntary force improvements were significantly greater in the maximal strength training group (21 ± 12% vs. 11 ± 7%). Explosive force improved only in the explosive strength training group by an average of 16% which was attributed to increased EMG activity during the first 50-ms of the explosive contraction.

Essentially, the results demonstrated that training explosively will make you more explosive while training for maximal strength will improve maximal force production. A study by McBride et al. (1999) showed how athletic performance markers varied between powerlifters (PL), weightlifters (OL), sprinters (S) and a control group (C), also demonstrating the importance of specificity:

“The PL group was as strong as the OL and S groups but scored significantly lower in tests for power and explosive performance. This included lower peak power outputs, peak velocities, and jump heights. In some instances, the PL group even performed worse than the C group in relation to these variables. The OL group was comparable in strength to the PL group, was stronger than the S group, and was also the most powerful of all the groups. The OL group also scored well in physical performance as determined by vertical jump height. The S group was not as powerful as expected but was able to generate high peak velocities and some of the highest recorded jump heights”

There are distinct neuromuscular adaptations to training that are specific to the chosen exercise. This includes velocity of movement, percentage of 1 rep max, amount of repetitions performed and so forth. To elicit specific changes in performance, the training stimulus must meet certain criteria. This serves as a great reminder to also emphasize explosiveness in training as opposed to only maximal strength.

References:

McBride, J. M., Tiplett-McBride, T.D.A., & Newton, R.U. (1999). A comparison of strength and power characteristics between power lifters, Olympic lifters, and sprinters. The Journal of Strength & Conditioning Research, 13(1), 58-66.

Tillin, N. A., & Folland, J. P. (2013). Maximal and explosive strength training elicit distinct neuromuscular adaptations, specific to the training stimulus. European Journal of Applied Physiology, 1-10.