Muscle activation during aquatic and land treadmill running /by W. Matthew Silvers.

Purpose. Lower extremity muscle activation during land (TM) and aquatic (ATM) treadmill running was compared to gain insight on the specificity of ATM running. Methods. Twelve male runners performed land treadmill (TM) and ATM (xiphoid depth) running at 174.4, 201.2, and 228.0 m{middot}min{esc}p-1{esc}s while metabolic (VO{esc}b2{esc}s) and surface electromyographic (EMG) data were recorded from the tibialis anterior (TA), gastrocnemius (GAS), biceps femoris (BF), vastus medialis (VM), and rectus femoris (RF). The final ten strides at each speed were selected for EMG data analyses. Relative timing and duration were normalized to the stride cycle. Muscle activation was normalized to maximal voluntary contractions (%MVC), performed prior to, and after, TM and ATM trials. In addition, ATM muscle activation was expressed as a percentage of TM (%TM) at each speed. Results. Swing and stride duration were extended for ATM (p=0.00). The order of muscle recruitment was similar between modalities, except for earlier VM onset during ATM. ATM relative durations for VM and RF1 were extended, reduced for GAS and RF2, and similar for TA and BF compared to TM. ATM %MVC was lower for GAS and VM (p0.19) compared to TM %MVC. ATM %TM was lower for GAS and RF2, but higher for TA, RF1, VM and BF. ATM and TM VO{esc}b2{esc}s were comparable (p>0.180). In general, ATM and TM demonstrated earlier muscle onsets, extended relative durations, and greater %MVC and VO{esc}b2{esc}s with speed. Conclusion. The cumulative effect of buoyancy and drag during ATM may have reduced the need for muscular support during stance and increased emphasis on forward propulsion. Notable differences in muscle activation may negatively or positively affect muscular adaptations during chronic ATM run training. Despite similarities in VO{esc}b2{esc}s, the observations for muscle activation remain inconclusive in regard to implications for training specificity as they pertain to land-based running. Ultimately, an individual's specific needs and goals for training still must be considered when prescribing ATM exercise.Thesis (Ph. D., Education)--University of Idaho, December 2007