# Sprint interval exercise versus continuous moderate intensity exercise: acute effects on tissue oxygenation, blood pressure and enjoyment in 18-30 year old inactive men PMID: 31211019 Journal: PeerJ Published: 2019-06-07 Authors: Kriel Y, Askew CD, Solomon C ## Question In young inactive men, does a work-matched session of sprint interval exercise produce greater local tissue oxygen utilization, lower post-exercise blood pressure, and lower enjoyment than continuous moderate intensity exercise? ## Summary Eleven inactive young men completed an acute sprint interval cycling session and a work-matched continuous moderate cycling session on separate days. The sprint session produced higher systemic oxygen consumption, heart rate, mechanical power, and higher deoxygenated hemoglobin in the prefrontal cortex and gastrocnemius, but not in vastus lateralis sites. Sprint exercise also produced lower post-exercise diastolic blood pressure, lower enjoyment, and symptoms such as dizziness, nausea, or leg discomfort in several participants. ## Population - Eleven inactive men aged 18-30 years with no reported cardiovascular or metabolic disease and no medications. - Sample size: 11 - Age: 23 +/- 4 years; eligible range 18-30 years. - Sex: Male only. - Fitness level: Inactive; less than recommended weekly physical activity and no HIIT in previous 3 months. - Health status: Apparently healthy, without reported cardiovascular or metabolic disease. ## Methodology - Acute within-participant comparison of two cycling exercise conditions after a maximal ramp-incremental exercise test; SIT was performed before work-matched CMIE with sessions separated by 3 to 7 days. - Single acute SIT session and single acute work-matched CMIE session, separated by 3 to 7 days. - Laboratory cycle ergometer testing at the University of the Sunshine Coast. - Controlled study design. ## Protocol - SIT. - Modality: Cycle ergometer sprint intervals. - Work intervals: 30 s all-out sprint. - Recovery: 2 min passive recovery between bouts. - Sets or repetitions: 4 bouts. - Intensity: Maximal effort against 0.075 kg per kg body weight flywheel resistance. - Session duration: Approximately 16 min including baseline and recovery; 2 min total sprint work. - Program length: Single acute session. - Progression: None. - CMIE. - Modality: Cycle ergometer continuous exercise. - Work intervals: Continuous cycling. - Sets or repetitions: One continuous bout. - Intensity: 50% of peak power output from maximal test. - Session duration: Exercise duration 5:33-7:38 min, matched to SIT mechanical work, plus the same 4 min warm-up and 6 min passive recovery. - Program length: Single acute session. - Progression: None. ## Outcomes ### Prefrontal cortex and gastrocnemius delta HHb Status: improved Delta HHb was higher during SIT than CMIE at the prefrontal cortex and gastrocnemius. Prefrontal cortex p = 0.016, F = 8.783, partial eta squared = 0.494; gastrocnemius p = 0.001, F = 18.76, partial eta squared = 0.652. ### Vastus lateralis delta HHb Status: no clear change No significant differences were found between SIT and CMIE for left or right vastus lateralis delta HHb. ### VO2, heart rate, and mechanical power Status: improved SIT produced higher VO2, heart rate, and mechanical power than CMIE. VO2 t(9) = 11.243, p < 0.001; HR t(10) = 9.718, p < 0.001; mechanical power t(10) = 21.811, p < 0.001. ### Systolic blood pressure Status: no clear change Systolic blood pressure increased after exercise and returned toward baseline in both conditions, with no significant difference between conditions. Main effect for time p < 0.001, F = 78.564, partial eta squared = 0.940. ### Diastolic blood pressure Status: mixed Post-exercise diastolic blood pressure was lower during SIT than CMIE at 2, 4, and 6 min recovery. Condition p = 0.043; condition by time p = 0.042; Rec 2 p = 0.038, Rec 4 p = 0.017, Rec 6 p = 0.031. ### Enjoyment Status: worse/safety concern PACES enjoyment was lower after SIT than CMIE. t(10) = -2.482, p = 0.032, partial eta squared = 0.381. ## Practical Insights - All-out 4 x 30 s cycling SIT can produce high acute physiological stress with only 2 min of hard work. - In inactive young men, all-out SIT may be less enjoyable than a work-matched moderate bout. - Dizziness, nausea, and lower post-exercise DBP are practical reasons to include conservative recovery monitoring after all-out intervals. - Work-matched moderate exercise may be shorter than guideline-based CMIE, so practical comparisons should distinguish work matching from normal exercise prescriptions. ## Limitations - Small sample. - Male-only young inactive participants. - Acute-only outcomes. - SIT and CMIE differed in intermittent versus continuous structure, so intensity was not isolated from format. - CMIE bout was shorter than routine moderate-intensity health prescriptions. - Only one SIT protocol was tested. - Fixed condition order. - Laboratory cycling protocol may not generalize to bodyweight or home workouts. ## Safety And Adherence - Seven participants reported dizziness and/or nausea during SIT recovery. - Three participants reported leg muscle discomfort or cramping during SIT recovery. - All participants felt well when leaving the laboratory within 30 min after exercise. - Lower DBP after SIT coincided with pre-syncopal symptoms in some participants. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/31211019/) (pubmed) - [DOI](https://doi.org/10.7717/peerj.7077) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6557258/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.