We contend that although SIT appears to be an effective exercise modality for physiological benefit, it is unlikely to be effective as a means to promote regular participation in physical activity in a largely sedentary population. We have argued that SIT is inappropriate for sedentary individuals because engaging in such training requires high levels of motivation and confidence. In addition, high intensity exercise is likely to evoke to negative affect which may lead to subsequent avoidance of further exercise. SIT programmes of exercise are also relatively complex and involve a high degree of self-regulation, which may also be a barrier to continuation in those who are uninitiated. we contend that SIT should not necessarily be considered time efficient as a session would likely last at least 30 min. We would like to see further research that addresses the motivational factors and responses of sedentary people to SIT. Specifically, we propose the following research agenda to improve knowledge of SIT in sedentary populations: (1) the acceptability of, and affective responses to, SIT programmes; (2) the social cognitive and motivational factors that may be related to participation in, and adherence to, SIT programmes; (3) the degree of adherence to SIT programmes compared to programmes of continuous aerobic exercise of moderate intensity; and (4) whether SIT programmes can be transferred to natural settings outside of the supervised laboratory environment

We assessed the short-term effects of varying the volume of high-intensity interval training (HIIT) on psychological and physiological responses of 23 healthy adult males ( M = 21 years; M peak oxygen uptake [VO2peak] = 47.2 ml·kg−1·min−1). Participants were randomly assigned to low- and very-low-volume HIIT groups and engaged in nine supervised exercise sessions over three weeks. The low-volume HIIT group performed 8-12 60-second work bouts on a cycle ergometer at the peak power output achieved during the incremental test, interspersed by 75 seconds of low-intensity active recovery. The very-low-volume HIIT performed 4-6 work bouts with the same intensity, duration, and rest intervals. During training, participants’ ratings of perceived exertion (Borg Category Ratio-10 scale) and their affective responses (Feeling Scale −5/+5) during the last 15 seconds of each work bout were recorded. Physiological data were VO2peak, endurance, and anaerobic performance before and after the intervention. Throughout training, participants in the very-low-volume group (relative to the low-volume group) reported lower ratings of perceived exertion in Week 1 ( M = 4.1 vs. M = 6.3; p < .01) and Week 3 ( M = 4.0 vs. M = 6.2; p < .01), and higher affective response in these same two weeks (Week 1: M = 1.9 vs. M = 0.3; p = .04; Week 3: M = 2.1 vs. M = 0.9; p = .06). Regarding physical fitness, Wingate peak power increased significantly after training in the very-low-volume HIIT group ( M = 1,049 W vs. M = 1,222 W; p < .05), but not in the low-volume HIIT group ( M = 1,050 W vs. M = 1,076 W). No significant change was found after training in physiological variables of peak power output, VO2peak, and endurance performance. In summary, in this short-term training period, the very-low-volume HIIT enhanced anaerobic capacity and was perceived as less strenuous and more pleasurable than low-volume HIIT.