# Eight weeks equivalent-volume RT and HIIT performed within same session or alternated weekly: comparative effects on physiological adaptations in young adult males

PMID: 41366794
Journal: BMC Sports Science, Medicine and Rehabilitation
Published: 2025-12-09
Authors: Cheng Y, Ma J, Ye R, Bo S, Li Q

## 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.

## Population

- Healthy young adult males recruited from Beijing universities.
- Sample size: 23
- Age: Group A 22.73 +/- 2.83 years; Group B 24.08 +/- 2.39 years
- Sex: 23 male completers
- Fitness level: Young healthy adults with baseline VO2max around 47 ml/kg/min
- Health status: Healthy; exclusions included chronic disease, obesity, injuries, surgery, and medications affecting metabolism or performance

## Methodology

- Randomized two-group concurrent-training study
- 8 weeks
- University/training setting with treadmill and resistance training
- Randomized and controlled study design.

## Protocol

- Same-session RT plus HIIT.
- Modality: Resistance training followed by treadmill HIIT.
- Work intervals: Treadmill HIIT: 1 minute at 85% VO2max intensity.
- Recovery: 1 minute at 35% VO2max intensity.
- Sets or repetitions: RT: 2 sets each of squat, bench press, and bent-over row at 70% 1RM for 8-10 reps; HIIT: 5 cycles.
- Intensity: RT at 70% 1RM; HIIT work at intensity corresponding to 85% VO2max.
- Session duration: About 40 minutes.
- Frequency: 3 sessions per week.
- Program length: 8 weeks.
- Progression: Training intensity recalibrated at week 5 using updated 1RM and VO2max measures.
- Weekly alternating RT and HIIT.
- Modality: Resistance training weeks alternating with treadmill HIIT weeks.
- Work intervals: During HIIT weeks: 1 minute at 85% VO2max intensity.
- Recovery: 1 minute at 35% VO2max intensity.
- Sets or repetitions: During RT weeks: 4 sets each of squat, bench press, and bent-over row; during HIIT weeks: 10 cycles.
- Intensity: RT at 70% 1RM; HIIT work at intensity corresponding to 85% VO2max.
- Session duration: About 40 minutes.
- Frequency: 3 sessions per week.
- Program length: 8 weeks.
- Progression: Training intensity recalibrated at week 5.

## Outcomes

### Body composition and muscle thickness
Status: improved
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
Status: improved
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
Status: improved
Squat, bench press, and row 1RM improved over time in both groups.

Significant time effects; no group or interaction effects.

### Strength endurance
Status: mixed
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
Status: no clear change
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.

## Practical 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 And Adherence

- 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.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/41366794/) (pubmed)
- [DOI](https://doi.org/10.1186/s13102-025-01464-0) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12801475/) (full text)

## Agent Guidance

Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.