Spring-mass behavior and electromyographic activity evolution during a cycle-run test to exhaustion in triathletes

PURPOSE: To evaluate spring-mass (SM) behavior and associated electromyographic (EMG) activity during a run to exhaustion following a cycle exercise in trained triathletes. METHODS: Ten triathletes completed four tests: a cycling test to determine V˙O(2max); a running test to determine the lactate threshold (LT); a 5 min control run at LT (C-Run) followed after a total recovery period by a cycle-to-run session to exhaustion [30 min of cycling at ∼80% V˙O(2max) followed by a run until exhaustion at LT (T-Run)]. SM behavior and EMG signals in nine lower limb muscles were recorded throughout the running sessions. RESULTS: Immediately after cycling, leg stiffness was 12.1% higher than its C-Run value and a concomitant increase of EMG activity of knee extensors was observed during pre-contact. Throughout T-Run, leg stiffness decreased by 7.3%, while knee extensors and ankle flexors activities decreased during pre-contact and braking phases. No significant variations in SM parameters and no significant increase of muscle activity were reported between C-Run and the end of T-Run. CONCLUSION: SM behavior during the cycle-run test was consistent with EMG activity changes. Cessation of exercise was not associated with significant alterations of stiffness values and EMG activity.