title: Effect of sex on the acute skeletal muscle response to sprint interval exercise.
abstract: What is the central question of this study? Are there sex-based differences in the acute skeletal muscle response to sprint interval training (SIT)? What is the main finding and its importance? In response to a SIT protocol that involved three 20 s bouts of 'all-out' cycling, the expression of multiple genes associated with mitochondrial biogenesis, metabolic control and structural remodelling was largely similar between men and women matched for fitness. Our findings cannot explain previous reports of sex-based differences in the adaptive response to SIT and suggest that the mechanistic basis for these differences remains to be elucidated. A few studies have reported sex-based differences in response to several weeks of sprint interval training (SIT). These findings may relate to sex-specific responses to an acute session of SIT. We tested the hypothesis that the acute skeletal muscle response to SIT differs between sexes. Sedentary but healthy men (n = 10) and women (n = 9) were matched for age (22 ± 3 versus 22 ± 3 years old) and cardiorespiratory fitness [45 ± 7 versus 43 ± 10 ml O2(kg fat-free mass)-1min-1], with women tested in the mid-follicular phase of their menstrual cycles. Subjects performed three 20 s 'all-out' cycling efforts against a resistance of 5% of body mass, interspersed with 2 min of recovery. Relative mean power outputs [7.6 ± 0.5 versus 7.5 ± 0.9 W (kg fat-free mass)-1] were similar between men and women (P > 0.05). Furthermore, there were no differences in the exercise-induced changes in mRNA expression of PGC-1α, PRC, PPARD, SIRT1, RIP140, HSL, HKII, PDK4, PDP1, FOXO3, MURF-1, Myf5, MyoD and VEGFA at 3 h of recovery versus rest (P < 0.05, main effect of time). The only sex-specific responses to exercise were an increase in the mRNA expression of GLUT4 and LPL in women only and Atrogin-1 in men only (P < 0.05). Women also had higher expression of HKII and lower expression of FOXO3 compared with men (P < 0.05, main effect of sex). We conclude that the acute skeletal muscle response to SIT is largely similar in young men and women. The mechanistic basis for sex-based differences in response to several weeks of SIT that has been previously reported remains to be elucidated.
authors.affiliation: Department of Kinesiology, Ivor Wynne Centre, Room 210, McMaster University, Hamilton, ON, Canada, L8S 4K1.
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Skelly
authors.affiliation: Department of Kinesiology, Ivor Wynne Centre, Room 210, McMaster University, Hamilton, ON, Canada, L8S 4K1.
authors.forename: Jenna B
authors.initials: JB
authors.lastname: Gillen
authors.affiliation: Department of Kinesiology, Ivor Wynne Centre, Room 210, McMaster University, Hamilton, ON, Canada, L8S 4K1.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: MacInnis
authors.affiliation: Department of Kinesiology, Ivor Wynne Centre, Room 210, McMaster University, Hamilton, ON, Canada, L8S 4K1.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Martin
authors.affiliation: Department of Pediatrics and Medicine, McMaster University, Hamilton, ON, Canada, L8N 3Z5.
authors.forename: Adeel
authors.initials: A
authors.lastname: Safdar
authors.affiliation: Department of Pediatrics and Medicine, McMaster University, Hamilton, ON, Canada, L8N 3Z5.
authors.forename: Mahmood
authors.initials: M
authors.lastname: Akhtar
authors.affiliation: Department of Kinesiology, Ivor Wynne Centre, Room 210, McMaster University, Hamilton, ON, Canada, L8S 4K1.
authors.forename: Maureen J
authors.initials: MJ
authors.lastname: MacDonald
authors.affiliation: Department of Pediatrics and Medicine, McMaster University, Hamilton, ON, Canada, L8N 3Z5.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Tarnopolsky
authors.affiliation: Department of Kinesiology, Ivor Wynne Centre, Room 210, McMaster University, Hamilton, ON, Canada, L8S 4K1.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Gibala
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology; D012727:Sex Characteristics; D014157:Transcription Factors; D055815:Young Adult
chemical_list: D014157:Transcription Factors
keywords: gene expression; metabolism; sex-based differences