Eight weeks equivalent-volume RT and HIIT performed within same session or alternated weekly: comparative effects on physiological adaptations in young adult males
Question
Do equivalent-volume resistance training and HIIT produce different adaptations when performed in the same session versus in weekly alternating blocks?
Summary
In 23 healthy young adult men, 8 weeks of combined resistance training and treadmill HIIT improved body composition, aerobic fitness, muscle thickness, and strength whether the resistance and HIIT work were done in the same session or alternated by week. No clear between-group differences were detected, but the equivalence tests were underpowered and did not prove the two schedules were statistically equivalent.
Methodology
- Healthy young adult males recruited from Beijing universities.
- 23 participants.
- Resistance training followed by treadmill HIIT.
- Work intervals: Treadmill HIIT: 1 minute at 85% VO2max intensity.
- Recovery: 1 minute at 35% VO2max intensity.
- Intensity: RT at 70% 1RM; HIIT work at intensity corresponding to 85% VO2max.
- About 40 minutes.
- 3 sessions per week.
- 8 weeks.
- Randomized two-group concurrent-training study
- Body composition, Muscle thickness, Aerobic fitness, and Maximal strength were tracked.
Outcomes
Body composition and muscle thickness
Both concurrent-training schedules reduced body fat percentage and increased skeletal muscle mass and muscle thickness over time.
Significant time effects; no group or interaction effects.
Aerobic fitness
Wmax improved by week 5 and week 9, while VO2max, METs, and VEmax improved by week 9.
Significant time effects; no group or interaction effects.
Maximal strength
Squat, bench press, and row 1RM improved over time in both groups.
Significant time effects; no group or interaction effects.
Strength endurance
Squat repetitions improved at week 5 then trended down or plateaued by week 9; other endurance outcomes were less clear.
Squat reps showed a significant time effect; composite strength-endurance improvement was not statistically significant.
Schedule comparison/equivalence
No significant group differences or group-by-time interactions were detected, but statistical equivalence was not established.
Equivalence tests had wide confidence intervals and were likely underpowered.
Insights
- Concurrent resistance and HIIT programming may be arranged flexibly in young men when total volume is similar.
- A short 10-minute interval block after resistance training can coexist with strength and aerobic gains.
- For app design, this supports offering schedule flexibility rather than insisting on a single concurrent-training layout.
Limitations
- Small sample of young men only.
- No RT-only or HIIT-only control group.
- Hydration status for body composition testing was not objectively verified.
- Internal load and time-in-zone were not quantified beyond HR monitoring.
- Equivalence was not statistically proven despite similar observed responses.
Safety
- One participant withdrew for reasons reported as unrelated to the intervention.
- Real-time Polar H10 heart-rate monitoring was used for intensity and safety.
- No major adverse events were described in the read full text.