This study aimed to characterize neuromuscular, perceptual, and cardiorespiratory responses to high-intensity interval training (HIIT) with superimposed blood flow restriction in males and females. Twenty-four, healthy individuals (n=12 females) completed two cycling HIIT protocols to task failure (1-min work phases at 90% of peak power output interspersed by 1-min rest phases). The blood flow restriction (BFR) and control (CON) protocols were identical except for the presence and absence of BFR during rest phases, respectively. The interpolated twitch technique, including maximal voluntary isometric knee extension (MVC) and femoral nerve electrical stimuli, was performed at baseline, every six intervals, and task failure. Perceptual and cardiorespiratory responses were recorded every three intervals and continuously during exercise, respectively. Bayesian inference was used to obtain the joint posterior distribution for all parameters and evidence of an effect was determined via the marginal posterior probability (PP). The BFR shortened task duration by 57.3% compared to CON (PP>0.99), without a sex difference. The application of BFR exacerbated the rate of decline in neuromuscular measures (MVC and twitch force output), increase of perceptual responses (perceived effort, pain, dyspnea, fatigue), and development of cardiorespiratory parameters (minute ventilation and heart rate), compared to CON (PP>0.95). Additionally, BFR exacerbated the neuromuscular, perceptual, and cardiorespiratory responses to a greater extent in females than males (PP>0.99). Our results suggest that superimposition of blood flow restriction exacerbates psychophysiological responses to a HIIT protocol to a greater extent in females than males.
IntroductionThe intensity, duration, and distribution of work and recovery phases during high-intensity interval training (HIIT) modulate metabolic perturbations during exercise and subsequently influence the development of performance fatigability and exercise tolerance. This study aimed to characterize neuromuscular, perceptual, and cardiorespiratory responses to work-to-rest ratio-matched HIIT protocols differing in work and rest interval duration.MethodsTwelve healthy individuals (six women) first completed a ramp incremental test to determine 90% of peak power output, and then in three randomized visits, they completed three cycling protocols to task failure at 90% of peak power output: (i) 3- to 3-min work-to-passive rest ratio HIIT (HIIT3min), (ii) 1- to 1-min work-to-passive rest ratio HIIT (HIIT1min), and (iii) constant load (CL). Interpolated twitch technique, including maximal voluntary isometric knee extensions and femoral nerve electrical stimuli, was performed at baseline, every 6 min of work, and task failure. Perceptual and cardiorespiratory responses were recorded every 3 min and continuously across the exercises, respectively.ResultsThe work completed during HIIT1min (8447 ± 5124 kJ) was considerably greater than HIIT3min (1930 ± 712 kJ) and CL (1076 ± 356) (P < 0.001). At work-matched, HIIT1min resulted in a lesser decline in maximal voluntary contraction and twitch force compared with HIIT3min and CL (P < 0.001). Perceived effort, pain, and dyspnea were least in HIIT1min and HIIT3min compared with CL (P < 0.001). At task failure, HIIT1min resulted in less voluntary activation than HIIT3min (P = 0.010) and CL (P = 0.043), and engendered less twitch force decline than CL (P = 0.021).ConclusionsOverall, the mitigated physiological and perceptual responses during shorter work periods (HIIT1min) enhance exercise tolerance in comparison to longer work intervals at the same intensity (HIIT3min, CL).
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