• The effects of repeated bouts of muscle damaging exercise on the physiological and perceptual responses during single-leg cycling: Evidence for cross-transfer during endurance exercise

      Twist, Craig; Lamb, Kevin L.; Wade, Laura (University of Chester, 2013-09)
      Unaccustomed eccentric exercise commonly induces the immediate and prolonged symptoms of exercise-induced muscle damage (EIMD). Whilst an initial bout impairs sub maximal endurance performance, a repeated bout of the same eccentric exercise attenuates symptoms of EIMD. This is known as the repeated bout effect (RBE). Furthermore, it is claimed that training the unilateral limb, increases the strength of the contralateral homologous limb. This is manifested through neural adaptations and is known as cross-transfer. Accordingly, this study investigated if an initial bout of eccentric exercise in the unilateral leg would provide protection from the detrimental effects of EIMD on endurance performance after a second bout of eccentric exercise in the contralateral leg. After institutional ethical approval, 12 healthy, recreational participants were randomly assigned to two groups (ipsilateral, n = 6 both bouts performed in the same leg; contralateral, n = 6 one bout performed in each leg) who performed 10 x 10 eccentric contractions. Strength, perceived soreness and sub maximal cycling exercise was measured at baseline, 24 h and 48 h. Two weeks later, when symptoms of EIMD had dissipated, all procedures were repeated. Results revealed that perceived muscle soreness and isometric strength (P < 0.05) were significantly altered following the eccentric exercise at 24-48 h after an initial bout of EIMD. However, after a repeated bout, the symptoms of EIMD were attenuated in both the ipsilateral and contralateral groups. Furthermore, this had no significant effect on sub maximal endurance cycling. EMG data provided evidence for RBE after decreases in MF and increases in peak amplitude. This data further supports the evidence for a RBE, and supports observations that protective adaptations transfer to the untrained limb. EMG data supports this neural adaptation.