• Affect is positive at low to moderate exercise intensities yet is more aversive at intensities above the lactate threshold. • Women and men differ in regards to muscle fiber type and muscle mass. • This study examined if sex alters the affective response to interval based exercise. • Data show lower affective valence and higher blood lactate concentration in men versus women. • Clinicians may need to consider sex of their clientele when prescribing interval based exercise. High intensity interval exercise (HIIE) is identified as an alternative to moderate intensity continuous exercise (MICE) due to its similar effects on outcomes including maximal oxygen uptake and glycemic control. Nevertheless, its widespread implementation in adults is questioned because acute HIIE elicits more aversive responses (negative affective valence) than MICE which may make it impractical to perform long-term. Differences in muscle mass, fiber type, and substrate utilization exist between men and women that alter physiological responses which may cause differences in affective valence, yet the effect of sex on this outcome is unresolved. This study compared changes in affective valence between active men and women (mean age = 24.0 ± 4.8 yr) performing HIIE and sprint interval exercise (SIE) on a cycle ergometer. Affect (+5 to -5), rating of perceived exertion (RPE 1-10), and blood lactate concentration (BLa) were measured before and throughout exercise, and enjoyment was assessed post-exercise. Results showed that women exhibit more positive affect (p < .05) during HIIE and SIE than men (0.6-1.8 units higher values). In addition, women exhibited lower BLa (p = .003) than men during SIE (11.8 ± 2.4 mM vs. 14.9 ± 3.1 mM). In contrast, there was no effect of sex on RPE (p = .32 and p = .54) or enjoyment (p = .24 and p = .37) in response to HIIE or SIE. Practitioners should consider the sex of their clients when assessing change in affective valence induced by interval-based exercise.
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