Exploration Of Muscle Activity Patterns During Deep Water Running

Abstract

Deep water running (DWR) simulates running while submerged in the water up to neck level and unable to touch the bottom of the pool. It is not known which aspects of DWR are critical to provide a cross-training stimulus for on land running. We sought to understand the coordination between select lower extremity muscles. PURPOSE: To compare the magnitude of co-contraction between select muscles during DWR and treadmill running (TMR). METHODS: Subjects (n=7, 26.3±4.3 yrs, 158±9.9 cm, 61±6.6 kg) were instrumented to record electromyography (EMG) of the Rectus Femoris (RF), Biceps Femoris (BF), Gastrocnemius (GA), and Tibialis Anterior (TA). Subjects first completed three exercise conditions during DWR at Rating of Perceived Exertion (RPE) levels of 11 (fairly light), 13 (somewhat hard), and 15 (hard). Subjects then completed the same RPE levels during TMR. EMG data were recorded (1500 Hz) and a 25-s data set extracted for analysis. EMG data were smoothed (500 Hz), zero-offset removed, rectified and normalized to maximal voluntary contraction. A co-contraction index (CCI) was calculated for RF-BF and GA-TA muscle combinations using the formula: CCI(i) = (M1(i)/M2(i) × (M1(i) + M2(i)))/2 for i=0-25s, M1 is the lower and M2 the higher EMG at each time. Average CCI for RF-TF and GA-TA was calculated across the 25-s data set and compared across Mode (DWR, TMR) and RPE (11, 13, 15) using a 2 x 3 repeated measures ANOVA. Planned comparisons were conducted using paired t-tests to compare CCI between DWR and TMR at each RPE level. RESULTS: RF-BF CCI was influenced by the interaction of Mode and RPE (p=0.036) whereas GA-TA CCI only tended to be different between modes (p=0.069). It was determined that RF-BF CCI was lower (p<0.05) during DWR then TMR at RPE 11 (DWR 1.94±0.64%, TMR 7.65±6.1%) and RPE 13 (DWR 2.76±1.4%, TMR 7.49±5.2%) but not at RPE 15 (DWR 4.46±2.34, TMR 9.59±7.4%, p>0.05). GA-TA CCI was lower (p<0.05) during DWR than TMR at RPE 11 (DWR 1.65±1.2%, TMR 8.89±3.7%) and RPE 13 (DWR 1.99±2.2%, TMR 8.61±3.7%) and tended to be lower at RPE 15 (DWR 3.20±3.8%, TMR 8.07±6.43, p=0.08). CONCLUSION: There was less co-contraction for flexor/extensor pairs of muscles during DWR then TMR at lower intensities. It appears that higher intensity DWR is needed to achieve similar co-contraction magnitudes of lower intensity TMR.