high-intensity interval training

<title>Abstract</title> <p> To test the hypotheses that maintaining target rating of perceived exertion (RPE) with active (ACT) versus passive (PASS) recovery during high-intensity interval training (HIIT) in the heat results in 1) greater thermal and cardiovascular strain, 2) larger work rate adjustments during work intervals, and 3) larger decreases in maximal aerobic capacity (V̇O _2max ). Eight adults completed 4 cycling trials in 35°C, consisting of an 8-min warm-up at RPE 12 followed by 1 (15 _ACT , 15 _PASS ) or 5 (43 _ACT , 43 _PASS ) rounds of HIIT (1 round = 4 min at RPE 17 and 3 min recovery at RPE 12 or rest) totaling 15 or 43 min of exercise. Each trial was immediately followed by measurement of V̇O _2max . Rectal temperature was not different between conditions (43 _ACT =38.3°C, 43 _PASS =38.2°C, <italic>p</italic>  = 0.003 for interaction, post-hoc both <italic>p</italic>  > 0.09) but increased over time (both <italic>p</italic>  < 0.001). HR during work intervals was comparable between conditions ( <italic>p</italic>  = 0.50) with a 15 b·min ^‒1 increase between from interval 1 to 5 <italic>(p</italic>  = 0.001). Average HR during recovery was 14 b·min ⁻¹ higher in the fifth versus first interval across conditions ( <italic>p</italic>  = 0.003) and + 24 b·min ^‒1 during ACT versus PASS ( <italic>p</italic>  = 0.002). Percent change in work rate from first to fifth interval was larger during 43 _ACT (–14%±24%) versus 43 _PASS (–1%±16%; <italic>p</italic>  = 0.04). V̇O _2max was 0.4 L∙min ^‒1 (11.5%) lower following 43-min compared to 15-min of HIIT ( <italic>p</italic>  = 0.008) but was not different between recovery mode ( <italic>p</italic>  = 0.69). Maintaining target RPE with ACT and PASS resulted in similar physiological strain but averaged 21 W lower power output by the final work interval during ACT. Five rounds of HIIT in a hot environment resulted in small–moderate reductions in V̇O _2max . </p>

matched text: “high intensity interval training”

This study examined how transcranial direct current stimulation (tDCS) interacts with high-intensity interval training (HIIT) to shape cardiopulmonary fitness and executive function in elite endurance athletes across an 8-week protocol. Sixty-six nationally ranked athletes were stratified by training tenure, competitive level, and baseline maximal oxygen uptake, then prospectively allocated, with participant and outcome-assessor blinding, to one of three intervention arms: real-tDCS plus HIIT, sham-tDCS plus HIIT, or HIIT-only; 59 completed the programme. Both stimulation arms alternated between a left dorsolateral prefrontal montage and a bilateral motor montage, and cortical target was carried through the analysis as a within-subject factor rather than folded into a single stimulation label. Cardiopulmonary indices, executive function (Stroop, N-back, Flanker), prefrontal hemodynamics via functional near-infrared spectroscopy, and heart rate variability were measured at four assessment waves, with female athletes tested inside the early follicular window at every wave. Nonlinear mixed-effects and generalized additive mixed models resolved dynamic trajectories at the individual level, while a second-order partial derivative quantified the stimulation × load interaction. End-of-study allocation guesses did not depart from chance in either masked arm, so blinding held. Because masking held only for the two stimulation arms, the real- versus sham-tDCS comparison carries the causal weight of the trial, and the HIIT-only arm enters as a partially unblinded reference rather than a second control. Against sham, the real-tDCS arm showed a delayed but steeper rise in maximal oxygen uptake and an earlier separation in Stroop interference. A modelled cumulative exposure-response surface exhibited a non-monotone shape with an interior maximum whose geometry, but not whose coordinates, survived leave-one-subject-out cross-validation; because intensity and duration were fixed and exposure varied only with session completion, we present that surface as exploratory. Cross-system coupling between prefrontal oxygenation and ventilatory threshold strengthened under active stimulation, consistent with, though not proof of, a bidirectional central-peripheral regulation account. Adherence captured the largest share of individual response variance, with BDNF and ACTN3 variants contributing modestly. As exploratory findings, these patterns are consistent with a stratified, trajectory-aware view of neuromodulation in elite training, though claims about an optimal dose must await confirmatory trials that deliberately vary stimulation intensity.

matched text: “high intensity interval training”