EFFECT OF POST-EXERCISE COLD WATER IMMERSION ON MOLECULAR RESPONSES TO HIGH-INTENSITY INTERMITTENT EXERCISE

The balance between the stress of training and competition and sufficient recovery is critical within the development of athletic performance. This stems from the need to recover between successive intense periods of exercise and provide sufficient time through which to adapt to the prescribed training stimulus. Cold water immersion (CWI) is now widely used by athletes to enhance the rate of recovery following training and competition. However, little information currently exists with respect to its influence on skeletal muscle adaptation. Therefore, the aim of this thesis was to investigate the impact of CWI on acute markers of adaptation in human skeletal muscle following low-damaging high-intensity intermittent exercise.The aim of study 1 (Chapter 4) was to devise a low-damaging high-intensity intermittent running protocol which would be used as the criterion mode of exercise in future studies within the thesis. The exercise was comprised of 60-min of high-intensity intermittent exercise (8 × 3-min bouts at 90% V ̇O2max interspersed with 3-min recovery) on a motorised treadmill. No significant reduction in maximal voluntary contraction of the quadriceps was observed immediately following completion of the exercise protocol or during the subsequent 7 d period compared to pre-exercise values (P = 0.59). Creatine Kinase (CK) concentrations remained similar to baseline following exercise (P = 0.96). Myoglobin (Mb) content increased following exercise (P = 0.01). However, values returned to baseline after 24 h (P = 0.32). These results suggest the high-intensity intermittent running protocol induced changes in physiological and subjective indices consistent with the effects of low muscle damaging as opposed to those changes normally associated with exercise-induced severe muscle damage.The purpose of the second study (Chapter 5) was to examine the effects of CWI (2 × 5-min (8oC)) on acute markers of skeletal muscle adaptation at rest. Rectal temperature remained similar throughout the CWI protocol (P = 0.36). However, significant reductions in skin (thigh and calf) and muscle temperature were observed immediately post-immersion and the post-immersion period (P 0.05), however, skin (thigh and calf) and muscle temperature were reduced in the CWI condition compared to Cont (P 0.05). These results indicate that increasing the repeated post-exercise CWI does not further increases the expression of upstream signalling pathways associated with mitochondrial biogenesis and angiogenesis in human skeletal muscle.This thesis provides novel findings concerning the influence of high-intensity intermittent exercise and post-exercise CWI on cellular and molecular adaptations in human skeletal muscle. These findings may offer important insights for athletes wishing to maximize training adaptations