# A comparison of spinal and lower extremity biomechanics during maximal and sub-maximal deadlifts among strength-trained women

## TL;DR

This study examines how spinal and lower body biomechanics change in women during deadlifts at different weight loads.

## Contribution

The study provides new insights into biomechanical changes during maximal and sub-maximal deadlifts in strength-trained women.

## Key findings

- Maximal loads increased lower thoracic flexion angles and erector spinae muscle activity compared to sub-maximal loads.
- Hip joint moments were significantly lower at 70% load compared to 90% and 100% loads.
- Lifting beyond 90% of 3RM may involve increased spinal flexion to compensate for hip extensor strength limits.

## Abstract

Previous studies have examined changes in biomechanical variables in response to different deadlift loads, yet, the effect of sub-maximal and maximal loads on potential deviation in lifting technique remain inadequately understood.

Therefore, this study compared barbell and joint kinematics, net joint moments (NJMs), and surface electromyography (sEMG) amplitude during 70%, 90%, and 100% of three-repetition maximum (3RM) load using statistical parametric mapping. Twelve strength-trained women (age: 23.18 ± 3.46 years, height: 166.72 ± 2.90 cm, body mass: 68.18 ± 7.67 kg) lifted 72.5 ± 9.3 kg, 93.9 ± 16.6 kg, and 102.9 ± 17.6 kg s at 70%, 90%, and 100% of 3RM deadlifts, respectively.

The main findings revealed that the maximal load resulted in a significant increase in lower thoracic flexion angles and erector spinae sEMG amplitudes compared to the sub-maximal loads. Additionally, significantly lower hip NJMs were observed with a 70% load compared to 90% and 100% loads.

Therefore, increasing loads beyond 90% of 3RM might not be necessary if the goal is to train hip extensor strength through deadlifting. Deadlifting loads beyond 90% of 3RM may be achieved by increasing spinal flexion. This posture may allow strength-trained women to lift beyond the strength capacity of their hip extensors during the final repetition of a 3RM deadlift.