# Effects of high intensity interval training (HIIT) on cardiopulmonary fitness and physical function in middle-aged and elderly women: a systematic review and meta-analysis

## TL;DR

This study finds that high-intensity interval training improves cardiorespiratory fitness in middle-aged and older women but has limited effects on physical function.

## Contribution

A systematic review and meta-analysis of randomized trials on HIIT effects in middle-aged and elderly women.

## Key findings

- HIIT significantly improves VO2max in middle-aged and older women.
- HIIT does not significantly improve VO2peak, muscle strength, or flexibility.
- Walking ability shows a borderline significant improvement with HIIT.

## Abstract

To systematically evaluate the effects of high-intensity interval training (HIIT) on cardiorespiratory fitness and physical function in middle-aged and older women.

PubMed, Web of Science, and Scopus were searched from inception to November 2025. Randomized controlled trials comparing HIIT with control interventions in middle-aged and older women were included. Random-effects meta-analyses were performed. Primary outcomes were maximal or peak oxygen uptake (VO2max/VO2peak) and physical or functional performance measures.

Nineteen randomized controlled trials were included. Meta-analysis showed that HIIT significantly improved VO2max compared with control interventions (SMD = 1.20, 95% CI 0.86–1.54, I2 = 31%), with high certainty of evidence. No significant effect was observed for VO2peak (SMD = 0.23, 95% CI −0.23 to 0.69). HIIT did not significantly improve muscle strength (SMD = −0.17, 95% CI −1.04 to 0.70), though strength assessments were not always specific to the muscle groups trained, flexibility, or sit-to-stand performance. Walking ability showed a borderline significant improvement (SMD = 0.49, 95% CI 0.00–0.97), with very low certainty of evidence. Subgroup analyses indicated consistent VO2max improvements across age groups, body mass status, and intervention durations.

HIIT significantly improves cardiorespiratory fitness in middle-aged and older women but shows limited effects on physical function. HIIT alone is insufficient to comprehensively improve functional performance.

https://www.crd.york.ac.uk/PROSPERO/view/CRD420251272861.