Effects of Collagen Peptides on Recovery Following Eccentric Exercise in Resistance-Trained Males-A Pilot Study.

The authors sought to determine whether consuming collagen peptides (CP) enhances musculoskeletal recovery of connective tissues following a damaging exercise bout. Resistance-trained males consumed 15 g/day of CP (n = 7) or placebo (n = 8), and after 7 days, maximal voluntary isometric contraction (MVIC), countermovement jump height, soreness, and collagen turnover were examined. Five sets of 20 drop jumps were performed and outcome measures were collected 24, 48, and 120 hr postexercise. Countermovement jump height was maintained in the CP group at 24 hr (PRE = 39.9 ± 8.8 cm vs. 24 hr = 37.9 ± 8.9 cm, p = .102), whereas the CP group experienced a significant decline at 24 hr (PRE = 40.4 ± 7.9 cm vs. 24 hr = 35.5 ± 6.4 cm, p = .001; d = 0.32). In both groups, muscle soreness was significantly higher than PRE at 24 hr (p = .001) and 48 hr (p = .018) but not at 120 hr (p > .05). MVIC in both legs showed a significant time effect (left: p = .007; right: p = .010) over the 5-day postexercise period. Neither collagen biomarker changed significantly at any time point. CP supplementation attenuated performance decline 24 hr following muscle damage. Acute consumption of CP may provide a performance benefit the day following a bout of damaging exercise in resistance-trained males.

Estimation of critical end-test torque using neuromuscular electrical stimulation of the quadriceps in humans.

Characterization of critical power/torque (CP/CT) during voluntary exercise requires maximal effort, making difficult for those with neuromuscular impairments. To address this issue we sought to determine if electrically stimulated intermittent isometric exercise resulted in a critical end-test torque (ETT) that behaved similar to voluntary CT. In the first experiment participants (n = 9) completed four bouts of stimulated exercise at a 3:2 duty cycle, at frequencies of 100, 50, 25 Hz, and a low frequency below ETT (Sub-ETT; ≤ 15 Hz). The second experiment (n = 20) consisted of four bouts at a 2:2 duty cycle-two bouts at 100 Hz, one at an intermediate frequency (15-30 Hz), and one at Sub-ETT. The third experiment (n = 12) consisted of two bouts at 50 Hz at a 3:2 duty* cycle with proximal blood flow occlusion during one of the bouts. ETT torque was similar (p ≥ 0.43) within and among stimulation frequencies in experiment 1. No fatigue was observed during the Sub-ETT bouts (p > 0.05). For experiment 2, ETT was similar at 100 Hz and at the intermediate frequency (p ≥ 0.29). Again, Sub-ETT stimulation did not result in fatigue (p > 0.05). Altering oxygen delivery by altering the duty cycle (3:2 vs. 2:2; p = 0.02) and by occlusion (p < 0.001) resulted in lower ETT values. Stimulated exercise resulted in an ETT that was consistent from day-to-day and similar regardless of initial torque, as long as that torque exceeded ETT, and was sensitive to oxygen delivery. As such we propose it represents a parameter similar to voluntary CT.

The effects of exercise-induced muscle damage on critical torque.

OBJECTIVE: Exercise-induced muscle damage (EIMD) has been shown to reduce endurance exercise performance. This study examined the effects of EIMD on critical torque (CT) and the sum of the torque integral above CT during (∫ T total) during a 5-min all-out, intermittent isometric knee extension exercise. METHODS: CT was determined in eight participants prior to and 48-h following EIMD. EIMD was induced using electrically stimulated eccentric knee extensions until maximal voluntary strength (MVC) was reduced by 40%. EIMD was assessed by changes in MVC and ratings of muscle soreness using a VAS scale. EMG and near-infrared spectroscopy (NIRS) were collected from the vastus lateralis and vastus medialis, respectively, during the CT test to assess neuromuscular electrical activity and microvascular circulation. RESULTS: MVC decreased 22% (p = 0.006) and soreness increased from 2.1 ± 1.9 to 50.4 ± 31.5 mm (p = 0.002) 48-h following eccentric exercise. CT declined from 61.6 ± 17.8 to 52.0 ± 14.1 Nm (-14%; p = 0.005) post-EIMD. ∫ T total declined 33% (p = 0.0006) post-EIMD. No changes were observed in neuromuscular electrical activity (p = 0.95 for EMG RMS and p = 0.57 for EMG median frequency) or any parameter of microvascular circulation (p = 0.60 for tissue saturation index, p = 0.27 for total hemoglobin and myoglobin, p = 0.51 for oxyhemoglobin, and p = 0.26 for deoxyhemoglobin) between conditions. CONCLUSIONS: Our finding that EIMD-reduced CT may explain the decrements in endurance performance following EIMD observed in the previous studies. The disproportionate reduction in ∫ T total compared to MVC and CT is suggestive of a more rapid depletion of anaerobic energy stores and/or accumulation of metabolic by-products leading to fatigue following EIMD.