# A 12-Week Pilot Study Comparing High-Intensity Interval Training and Peripheral Heart Action Training on ISAK-Based Anthropometric Outcomes and Perceived Psychophysical Well-Being in Young Adults

## TL;DR

This 12-week study compared two exercise methods, HIIT and PHA, on body composition and well-being in young adults, finding distinct effects for each.

## Contribution

The study provides new longitudinal data comparing HIIT and PHA using standardized ISAK anthropometry in a non-randomized pilot design.

## Key findings

- Both HIIT and PHA led to significant improvements in body composition over 12 weeks.
- HIIT resulted in greater reductions in skinfolds and perceived performance improvement.
- PHA showed greater increases in arm circumference and mesomorphy.

## Abstract

Background: High-Intensity Interval Training (HIIT) and Peripheral Heart Action (PHA) are widely used training modalities, but comparative longitudinal data using standardized anthropometric methods remain limited. Purpose: To compare within-group changes over 12 weeks of HIIT and PHA training on body composition and perceived psychophysical well-being in moderately active young adults. Methods: Twenty-four adults (12 males, 12 females; age 30.9 ± 3.5 years) were allocated to either HIIT or PHA in a non-randomized pilot study, based on training schedule availability and previous training routine, which may introduce selection bias. Training was performed three times per week for 12 weeks. Body composition was assessed using standardized ISAK anthropometry. Data were analyzed using linear mixed-effects models. Results: Significant effects of Time were found for body mass, BMI, sum of skinfolds, waist circumference, and endomorphy (all p < 0.05). Significant Time × Group interactions were observed for BMI, sum of skinfolds, waist circumference, and endomorphy (p < 0.05), indicating different adaptation patterns. HIIT showed greater reductions in selected skinfolds and higher perceived performance improvement (p < 0.001), whereas PHA showed greater increases in arm circumferences and mesomorphy (p < 0.01). Conclusions: Within-group improvements were observed in anthropometric/body composition indicators over time, with distinct longitudinal adaptation patterns between HIIT and PHA.