# Effects of high-intensity interval training on lean mass, strength, and power of the lower limbs in healthy old and young people

PMID: 37829114
Journal: Frontiers in physiology
Published: 2023
Authors: Caparrós-Manosalva C, Garrido-Muñoz N, Alvear-Constanzo B, Sanzana-Laurié S, Artigas-Arias M, Alegría-Molina A, Vidal-Seguel N, Espinoza-Araneda J, Huard N, Pagnussat AS, Sapunar J, Salazar LA, Marzuca-Nassr GN

## Question

Does 12 weeks of stationary-bike HIIT improve lower-limb lean mass, maximal strength, rate of force development, and muscle power in healthy young and older men?

## Summary

This small uncontrolled study tested 12 weeks of stationary-bike HIIT in physically inactive healthy young and older men. Both age groups completed all 36 sessions, and the authors reported increases in lower-limb lean mass, knee-extension strength, early rate of force development, and sit-to-stand power. Because there was no non-exercising control group and only 9 men per age group, results should be treated as suggestive rather than definitive.

## Population

- Healthy physically inactive young and older men with BMI 18.5-30 kg/m2.
- Sample size: 18
- Age: Young 21 +/- 1 years; older 66 +/- 6 years.
- Sex: All male.
- Fitness level: Physically inactive; did not perform programmed exercise more than twice per week.
- Health status: Healthy; excluded diabetes, uncontrolled hypertension, smoking, recent surgery, and exercise-limiting cardiorespiratory or musculoskeletal conditions.

## Methodology

- Two-group pre-post intervention study nested in a larger HIIT project; no non-training control group.
- 12 weeks with pre-testing 48 hours before the first session and post-testing 48 hours after the last session.
- University of La Frontera laboratory and supervised stationary-bike training in Chile.

## Protocol

- Stationary-bike 10 x 1-minute HIIT.
- Modality: Stationary bicycle.
- Work intervals: 1 minute at 90% HRmax.
- Recovery: 2 minutes inactive rest.
- Sets or repetitions: 10 repetitions.
- Intensity: 90% of maximum HR from reference testing.
- Session duration: 30-minute interval block; training warm-up/cool-down not reported.
- Frequency: 3 sessions/week.
- Program length: 12 weeks.
- Progression: No progression reported.

## Outcomes

### Lower-limb lean mass
Status: improved
Non-dominant limb lean mass increased over time in both groups, without a time-by-group interaction.

NDL time effect p=0.014; DL interaction p=0.335, NDL interaction p=0.294.

### Maximal strength
Status: improved
Dominant-limb maximal strength increased over time, with no time-by-group interaction.

DL time effect p=0.022; interactions were not significant.

### Rate of force development
Status: mixed
RFD 0-50 ms improved in the non-dominant limb; other RFD intervals did not show broad improvement.

NDL RFD 0-50 ms time effect p=0.021; all time-by-group interactions p>0.05.

### Sit-to-stand power
Status: improved
Sit-to-stand power increased in both groups, with a larger relative increase in older adults.

Time effect p=0.02; no time-by-group interaction p=0.425; young +12.1%, older +34.7% described in discussion.

## Practical Insights

- Stationary-bike HIIT may be a tolerable supervised option for inactive older men who pass screening.
- Muscle-power outcomes can improve alongside cycling HIIT, but causal claims are weak without a control group.
- Lower-limb asymmetry may persist after bilateral cycling and deserves monitoring in older users.

## Limitations

- Small sample size.
- No randomization or control group.
- All participants were men.
- Order of strength testing was not randomized.
- Adverse events were not reported in detail.

## Safety And Adherence

- Participants were screened for cardiorespiratory and musculoskeletal contraindications.
- All sessions were supervised with continuous HR monitoring.
- The article did not report adverse events.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/37829114/) (pubmed)
- [DOI](https://doi.org/10.3389/fphys.2023.1223069) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10565117/) (full text)

## Agent Guidance

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