Stuart Goodall

The influence of cold water immersions on adaptation following a single bout of damaging exercise.

The aim of this investigation was to elucidate the effects of cold water immersions (CWIs) following damaging exercise on the repeated bout effect (RBE). Sixteen males performed two bouts of drop jump exercise separated by 14–21xa0days. Participants were equally, but randomly assigned to either a CWI (12-min CWI at 15°C) or control group (12-min seated rest). Treatments were given immediately after the first exercise bout, 24, 48 and 72xa0h post-exercise. No interventions were given following the second bout. Maximum voluntary contraction (MIVC), soreness (DOMS), creatine kinase (CK), thigh girth and range of motion (ROM) were recorded before and for 96xa0h following the initial and repeated bouts of damaging exercise. All variables, except ROM, showed a significant time effect (Pxa0<xa00.01) indicating the presence of muscle damage following the initial bout; there were no differences between the CWI and control groups after the initial bout. Following the repeated bout of exercise there was a significant attenuation in the reduction of MIVC (Pxa0=xa00.002) and a reduction in DOMS (Pxa0<xa00.001), which is indicative of the RBE. There were no significant differences between groups following the repeated bout of damaging exercise. These data show that CWI had no effect following damaging exercise and did not inhibit the RBE. Despite CWI being used routinely, its efficacy remains unclear and there is a need to elucidate the benefits of this intervention on recovery and adaptation to provide practitioners with evidence based practice.

Supraspinal fatigue after normoxic and hypoxic exercise in humans

•u2002 Processes leading to fatigue occur within the exercising muscle (peripheral fatigue) and the nervous system (central fatigue). •u2002 We asked whether central processes of fatigue would be increased after strenuous exercise in environments where oxygen availability is reduced (hypoxia) compared to the same absolute exercise intensity at sea‐level. •u2002 Our main finding was that the contribution of central processes to fatigue was increased after exercise in hypoxia (equivalent to ∼3800 m above sea‐level). •u2002 The greater amount of central fatigue in hypoxia was due to suboptimal neural output from the brain and was associated with reductions in oxygen availability. •u2002 The findings provide a plausible mechanism for why exercise performance is impaired at high altitude, and might help our understanding of exercise limitation in patients with reduced oxygen delivery to the brain.

Voluntary activation of human knee extensors measured using transcranial magnetic stimulation

The aim of this study was to determine the applicability and reliability of a transcranial magnetic stimulation twitch interpolation technique for measuring voluntary activation of a lower limb muscle group. Cortical voluntary activation of the knee extensors was determined in nine healthy men on two separate visits by measuring superimposed twitch torques evoked by transcranial magnetic stimulation during isometric knee extensions of varying intensity. Superimposed twitch amplitude decreased linearly with increasing voluntary torque between 50 and 100% of mean maximal torque, allowing estimation of resting twitch amplitude and subsequent calculation of voluntary activation. There were no systematic differences for maximal voluntary activation within day (mean ±s.d. 90.9 ± 6.2 versus 90.7 ± 5.9%; P= 0.98) or between days (90.8 ± 6.0 versus 91.2 ± 5.7%; P= 0.92). Systematic bias and random error components of the 95% limits of agreement were 0.23 and 9.3% within day versus−0.38 and 7.5% between days. Voluntary activation was also determined immediately after a 2 min maximal voluntary isometric contraction; in four of these subjects, voluntary activation was determined 30 min after the sustained contraction. Immediately after the sustained isometric contraction, maximal voluntary activation was reduced from 91.2 ± 5.7 to 74.2 ± 12.0% (P < 0.001), indicating supraspinal fatigue. After 30 min, voluntary activation had recovered to 85.4 ± 8.8% (P= 0.39 versus baseline). These results demonstrate that transcranial magnetic stimulation enables reliable measurement of maximal voluntary activation and assessment of supraspinal fatigue of the knee extensors.