Physiological Responses to Low-Volume Interval Training in Women

Abstract

Interval training is a form of exercise that involves intermittent bouts of relatively intense effort interspersed with periods of rest or lower-intensity exercise for recovery. Low-volume high-intensity interval training (HIIT) and sprint interval training (SIT) induce physiological and health-related adaptations comparable to traditional moderate-intensity continuous training (MICT) in healthy adults and those with chronic disease despite a lower time commitment. However, most studies within the field have been conducted in men, with a relatively limited number of studies conducted in women cohorts across the lifespan. This review summarizes our understanding of physiological responses to low-volume interval training in women, including those with overweight/obesity or type 2 diabetes, with a focus on cardiorespiratory fitness, glycemic control, and skeletal muscle mitochondrial content. We also describe emerging evidence demonstrating similarities and differences in the adaptive response between women and men. Collectively, HIIT and SIT have consistently been demonstrated to improve cardiorespiratory fitness in women, and most sex-based comparisons demonstrate similar improvements in men and women. However, research examining insulin sensitivity and skeletal muscle mitochondrial responses to HIIT and SIT in women is limited and conflicting, with some evidence of blunted improvements in women relative to men. There is a need for additional research that examines physiological adaptations to low-volume interval training in women across the lifespan, including studies that directly compare responses to MICT, evaluate potential mechanisms, and/or assess the influence of sex on the adaptive response. Future work in this area will strengthen the evidence-base for physical activity recommendations in women.

Sprint Interval Training Attenuates Neuromuscular Function and Vagal Reactivity Compared With High-Intensity Functional Training in Real-World Circumstances

“…In a recent meta-analysis summarizing studies performed in healthy and unhealthy adults, Sultana et al (35) demonstrated that the completion of low-volume interval training induces greater improvements in maximum oxygen consumption (V Ȯ2 max) than MICT. More recent studies show that extremely low-volume interval training applied in laboratory or outdoor setting (,20 minutes per session) is sufficient for improving redox status, and insulin sensitivity and reducing blood pressure, and body fat in young adults (4,18,32). Furthermore, SIT protocols requiring few repetitions of very short sprints (#10 seconds) significantly enhance V Ȯ2 max and anaerobic power (6), likely because of the high-power generation characteristic of these bouts.…”

The Effect of a Sprint Interval and Resistance Training Program on Body Composition, Aerobic Fitness, and Self-regulation in Young Women

“…It has been proposed that activating and building muscle, while participating in high intensity cardiovascular training improves metabolic system components (MacDougall et al, 1998;MacInnis & Gibala, 2017). These improvements allow total energy expenditure increases, beneficing the reduction of body fat content (Atakan et al, 2021;Skelly et al, 2021).…”

Skeletal muscle mechanisms contributing to improved glycemic control following intense interval exercise and training

“…In response to training, many markers of skeletal muscle remodelling linked to insulin sensitivity are reportedly similar between males and females, including glycogen synthase and hexokinase protein expression 85 and mitochondrial content 93 ; although, one study has observed greater increases in GLUT4 protein content with training in males compared to females. 93 However, as has been noted previously, 20 studies simultaneously measuring sex differences in insulin sensitivity and associated muscle mechanisms with interval training are scarce. Taken together, while the available literature demonstrates greater improvements in insulin sensitivity following intense interval exercise in males compared to females (particularly with low-volume SIT), additional research is needed to elucidate potential mechanisms.…”

“…Importantly, future studies should involve larger sample sizes and control for factors that may confound sex-based comparisons including proper matching between males and females, menstrual cycle phase, and oral contraceptive use. Given the greater proportion of male-only cohorts in muscle physiology research 115 including amongst studies within the HIIT/SIT literature, 20 , 116 more research involving exclusively females is also warranted to enhance our basic understanding of how exercise influences muscle insulin sensitivity in females.…”

“…Specifically, we highlight acute changes in exercised skeletal muscle that enhance glucose uptake in the hours to days following a single session of HIIT and SIT and evaluate the relationship between chronic changes in skeletal muscle phenotype and insulin sensitivity after training. For this review – and consistent with the terminology used in the literature 6 , 18 , 19 , 20 – we broadly define HIIT and SIT as short, repeated bouts of intense submaximal and supramaximal exercise, respectively, that are separated by periods of rest or active recovery. MICT was used to describe protocols involving prolonged (≥ 30 min) continuous exercise performed at a submaximal intensity that typically elicit ∼65%–75% of maximum heart rate (HRmax) or ∼55%–75% of peak oxygen uptake ( O 2 peak).…”