An emerging body of research has explored the potential ergogenic effects of noninvasive interset recovery strategies involving the application of cold substances to the extremities distal to exercising muscles (e.g., palms of the hands or the soles of the feet). It was suggested that such strategies may acutely enhance resistance training (RT) performance by augmenting excitation and motor unit recruitment of the working muscles through enhanced stimulation of the central nervous system, resulting in greater force production and the ability to perform more repetitions to fatigue. Moreover, peripheral stimuli such as distal cooling may acutely reduce the sensation of distress during RT, allowing individuals to tolerate more exercise and achieve higher training volumes. Although there is some evidence that interset distal cooling confers an ergogenic benefit during RT, certain methodological considerations, a paucity of longitudinal research, and contrasting findings call into question its effectiveness. Thus, the purpose of this review is to assess the current evidence regarding the effects of interset palm and sole cooling on RT performance outcomes.
The physiological response to breath holding includes bradycardia and peripheral vasoconstriction, which contrasts with that of exercise which includes tachycardia and peripheral vasodilation. This raises the question as to what the physiological response is to breath holding during exercise. During low-intensity exercise, the breath holding response of bradycardia and peripheral vasoconstriction prevails over the exercise response of tachycardia and peripheral vasodilation, but nevertheless the exercise may be sustained. Due to the lack of availability of extrinsic oxygen (O 2 ) from the atmosphere during breath holding, the energy demands can be met by increased reliance on intrinsic O 2 stores (i.e., O 2 that was in the body before the breath hold) via increased O 2 extraction at the muscle compared with exercise while breathing, or increased contributions from anaerobic energy systems. During high intensity exercise of short duration, the exercise response may prevail over the breath holding response due to the increased parasympathetic withdrawal and sympathetic drive of higher intensity exercise. If breath holding during high-intensity exercise was sustained for long enough, the breath holding response may eventually overcome the exercise response, although this may be difficult due to the inverse relationship between exercise intensity and breath hold duration.