# The role of starting knee angle in squat jump force-velocity profiles: interactions with subjects’ strength levels and imputed push-off distance

## TL;DR

This study examines how starting knee angle and push-off distance affect force-velocity profiles during squat jumps, and how these factors interact with strength levels.

## Contribution

The study introduces insights on standardizing push-off distance and knee angle to improve consistency in force-velocity profile assessments.

## Key findings

- Starting knee angle significantly affects maximum force and force-velocity slope during squat jumps.
- Standardizing push-off distance at 90° improves consistency in force-velocity profile measurements.
- Subject strength levels do not influence the observed differences in force-velocity profiles.

## Abstract

This study investigated whether differences in the force-velocity (F-v) profile obtained using Samozino’s method during squat jumps (SJ) performed at varying knee angles are influenced by subjects’ strength levels and the push-off distance (HpO) used in the analysis.

Twenty-one resistance-trained men were classified as stronger (n = 10) or weaker (n = 11) based on the external load required to achieve a 10 cm SJ height. F-v profiles were randomly assessed over three sessions, with SJs performed at starting knee angles of 70° (SJ70), 90° (SJ90), and 110° (SJ110), using either the actual HpO specific to each condition or a standardized HpO corresponding to SJ90.

Significant differences between SJ types were observed for maximum force (F
0) and the F-v slope (SJ110 > SJ90 > SJ70). These differences were never influenced by subjects’ strength levels. The standardized HpO produced similar outcomes for maximum power (Pmax) and maximum velocity (v
0), and more consistent results for F
0 and the F-v slope compared to the actual HpO.

Regardless of strength levels, standardizing HpO at 90° and allowing subjects to select a starting knee angle between 70° and 90° could simplify the evaluation process and improve the comparability of F-v profiles across subjects when using Samozino’s method.