# Regular Cold‐Water Immersion Following HIIT Does Not Affect Intramuscular Adaptation Markers, Inflammatory Profile or Endurance Performance

## TL;DR

Cold-water immersion after high-intensity interval training does not change muscle adaptation, inflammation, or running performance in healthy males.

## Contribution

Demonstrates that cold-water immersion after HIIT does not alter intramuscular adaptation markers or endurance performance.

## Key findings

- Cold-water immersion had no effect on satellite cell pool or PGC-1α content.
- Training improved V̇O2max and running performance regardless of cold-water immersion.
- No changes in inflammatory markers were observed with cold-water immersion.

## Abstract

The study aimed to investigate the effects of 5 weeks of post‐exercise cold‐water immersion (CWI) following high‐intensity interval training (HIIT) sessions on the satellite cell pool, muscle content of inflammatory markers, muscle expression of peroxisome proliferator‐activated receptor‐γ coactivator 1‐α (PGC‐1α), maximal oxygen uptake (V̇O2max), and running performance. Sixteen healthy males completed baseline assessments, including muscle biopsies, a graded exercise test for V̇O2max determination, and a constant work‐rate (CWR) running test to assess time to task failure (TTF). Participants were ranked according to V̇O2max and randomly allocated to either a training‐only control group (n = 7) or a CWI group (n = 9), which underwent CWI (11.2°C ± 0.2°C for 15 min) following each HIIT session. The HIIT program consisted of three weekly sessions 5–8 × 2‐min bouts at 95% V̇O2max. At the end of weeks four and five, all participants repeated the same sequence of assessments. Training increased V̇O2max values, TTF at CWR, satellite cell pool, PGC‐1α content, and induced changes in muscle morphology (connective tissue), as indicated by a main effect of time (p ≤ 0.031); none of the analyzed variables showed a main effect of condition (p ≥ 0.098) or interaction (p ≥ 0.088). No significant alterations were observed in inflammatory markers over time (p ≥ 0.395) and condition (p ≥ 0.115). In conclusion, 5 weeks of post‐exercise CWI following HIIT did not influence the satellite cell pool, muscle inflammation status, muscle PGC‐1α content, muscle morphological, V̇O2max, or running performance.