# Characteristics of Force Development and Muscle Excitation in Resisted and Assisted Jumps in Comparison with the Isometric Mid-Shin Pull

## TL;DR

This study compares force development and muscle activity in different jump exercises and an isometric test, finding that jumps better enhance power and muscle excitation.

## Contribution

The study provides new insights into how different jump conditions affect force and muscle activity compared to isometric holds.

## Key findings

- MSP produced higher peak force than all CMJ variations.
- CMJs showed greater peak rate of force development and vastus lateralis activation than MSP.
- Regular CMJ at body mass is most effective for power development.

## Abstract

Background: The purpose of this study was to examine the relationships between the characteristics of force development and electromyographic activity of the quadriceps muscles in the isometric mid-shin pull (MSP) and the countermovement jump (CMJ) performed under different conditions. Methods: Fifteen resistance-trained individuals (age = 25.9 ± 4.0 y; body mass = 73.2 ± 11.7 Kg; stature = 172.3 ± 9.5 cm) were tested for MSP and for the following CMJs: regular CMJ (CMJ); elastic band-assisted CMJ (CMJAB); elastic band-resisted CMJ (CMJRB); weighted vest CMJ (CMJV) in random order, using a force plate. Peak force (PF) and peak rate of force development (PRFD) were calculated in all the assessments, while peak velocity and power were calculated only in the CMJs. In addition, during all the tests, electromyographic activity of the vastus lateralis (EMGVL) and of vastus medialis (EMGVM) was detected. Results: Higher PF was registered in MSP compared to the CMJs (p < 0.001). PRFD and EMGVL were significantly more elevated in the CMJs compared to the MSP (p < 0.05). No significant correlations were noted between the PRFD measured in MSP and in CMJs, while the PRFD in MSP was largely correlated with PP in CMJs (r = 0.68/0.83). Conclusions: Results of the present study showed that CMJs promote PRFD and the excitation of the vastus lateralis, to a greater extent compared to MSP. Regular CMJ performed at body mass may represent the best option for power development, and small variations in loads allowed by weighted vests or elastic bands do not seem to alter the characteristics of force development.