# Comparative effects of high-intensity interval training at low and moderate altitudes on 5000-m performance and perceptual responses: A randomized controlled trial

## TL;DR

This study found that high-intensity interval training at low altitude improved 5000-m race performance and reduced perceived exertion more than training at moderate altitude.

## Contribution

The study provides novel evidence that low-altitude HIIT yields greater performance and perceptual benefits than moderate-altitude HIIT for distance runners.

## Key findings

- HIIT at low altitude improved 5000-m time more than at moderate altitude.
- Low-altitude HIIT resulted in lower perceived exertion and better pacing regulation.
- Both altitude-based HIIT groups outperformed the control group in race performance.

## Abstract

Hypoxia compromises training quality, yet high-intensity interval training (HIIT) performed under hypoxia may elicit greater benefits than does normoxic HIIT. However, its effects on pacing and perceived exertion remain underexplored, particularly in moderate-altitude distance runners. This study aimed to compare the efficacy of HIIT performed at low (∼1220 m) versus moderate (∼2850 m) altitudes on pacing and rated perceived exertion (RPE) during a 5000 m race.

Forty-two moderate-altitude inhabitant runners (men/women, 23/19) were randomly allocated into the HIIT groups at ∼2850 m (HIIT2850m, n = 14) and at ∼1220 m (HIIT1220m, n = 14), and the control group at ∼2850 m (CG2850m, n = 14). The HIIT intervention was completed by the HIIT2850m group at moderate altitude and the HIIT1220m group, which travelled to low altitude for 8 weeks with 2 sessions.wk−1. Each session consisted of 4 × 4 min intervals at 100% velocity at maximum oxygen consumption (vVO2 max, determined at their respective training sites), with 3 min recovery at 70% vVO2 max intensity. Before and after the intervention, 5000 m races were performed in a matched group on a 400 m track at ∼2850 m and every km speed and RPE were recorded.

The results indicated that the participants used a similar parabolic reversed-J shaped strategy, with significant 5000-m time improvements observed in both the HIIT1220m (Δ: 20.1 ± 23.7 s, p = 0.007) and the HIIT2850m (Δ: 16.7 ± 25.9 s, p = 0.003) groups. A significant main effect of time (except at the 2nd km, p = 0.693) and a main effect of group (at the 1st km, p = 0.034 and 5th km, p = 0.044) were observed in pace, along with a significant group-by-time interaction in all km segments. Compared with the CG2850m, both interventions demonstrated significantly greater speeds at the 1st and 5th km and lower RPE, with greater changes in the HIIT1220m group.

The results suggest that HIIT at both altitudes improved performance and RPE, with quality training at low altitudes producing greater benefits, offering strategic insights for athletes and coaches.

•High-intensity interval training (HIIT) improved 5,000 m time, pacing speed, and reduced perceived exertion.•Lower perceived exertion reflected better intensity tolerance and pacing regulation, resulting in faster 5,000 m times.•HIIT performed at low altitude elicited greater benefits in pacing and perceptual responses than did at moderate altitude.

High-intensity interval training (HIIT) improved 5,000 m time, pacing speed, and reduced perceived exertion.

Lower perceived exertion reflected better intensity tolerance and pacing regulation, resulting in faster 5,000 m times.

HIIT performed at low altitude elicited greater benefits in pacing and perceptual responses than did at moderate altitude.