# Lower extremity bilateral explosive strength asymmetry predicts non-contact low back injuries in mine rescue workers: a prospective cohort study

## TL;DR

This study found that uneven explosive strength in the legs of mine rescue workers increases their risk of non-contact low back injuries.

## Contribution

The study introduces a new method to predict low back injuries in mine rescue workers using lower extremity asymmetry metrics.

## Key findings

- Bilateral takeoff peak force asymmetry significantly increases the risk of non-contact low back injuries.
- Each 1% increase in asymmetry raises injury risk by 18.5%.
- A 7.05% asymmetry threshold identifies high-risk workers with 3.6 times higher injury risk.

## Abstract

The purpose of this study was to investigate the relationship between bilateral lower extremity explosive strength asymmetry and non-contact low back injuries in mine rescue workers, a specialized occupational group.

A single-leg countermovement jump (SLCMJ) test was performed on 101 rescue members who had participated in frontline rescue missions, using a force platform. The collected force platform data were used to calculate lower limb asymmetry. Injury incidence was measured by recording all non-contact low back injuries occurring during routine training or rescue operations over a 12-month follow-up period. Jump metrics (including eccentric peak force, vertical velocity at takeoff, peak takeoff acceleration, and takeoff peak force) associated with non-contact low back injuries were identified through Poisson regression analysis, and the optimal threshold for predicting injuries was determined using the receiver operating characteristic (ROC) curve.

Bilateral takeoff peak force asymmetry significantly increased the risk of non-contact low back injury. Each 1% increase in asymmetry raised the injury risk by 18.5% (RR = 1.185, 95% CI: 1.091–1.288, p < 0.001), equivalent to an absolute increase of 3.2% (RD = 0.032, 95% CI: 0.009–0.056). Using the optimal threshold of 7.05% for risk stratification, rescue workers in the high-risk group had a 3.6 times higher injury risk than the low-risk group (RR = 3.64, 95% CI: 1.353–9.832, p = 0.011), corresponding to an absolute risk difference of 24.1% (RD = 0.241, 95% CI: 0.073–0.409).

The interlimb asymmetry measured during the single-leg countermovement jump can be used to predict the risk of non-contact low back injuries in mine rescue workers over a 12-month follow-up period. Particular emphasis should be placed on the interlimb asymmetry of takeoff peak force.