# Efficacy of different biomechanical strategies for modulating force–time parameters of high-velocity low-amplitude manipulation of the thoracic spine: a randomized crossover experimental study

## TL;DR

This study tested how different biomechanical strategies affect the force applied during spinal manipulation, finding that some strategies help increase peak force more effectively.

## Contribution

The study introduces and evaluates six biomechanical strategies to improve force modulation during high-velocity low-amplitude spinal manipulation.

## Key findings

- Peak force increased progressively from strategy S1 to S5 with moderate effect sizes.
- No significant difference in peak force or load rate was found between strategies S5 and S6.
- The strategy with the highest peak force (S6) had the lowest preload force.

## Abstract

Manual therapy, including high-velocity low-amplitude spinal manipulation (HVLA-SM), is a complex motor task performed by trained individuals. The ability to modulate the magnitude of applied forces is an attribute of proficiency that is challenging for providers and students. Adopting different biomechanical strategies may facilitate force modulation by practitioners performing HVLA-SM. This study evaluated the efficacy of different biomechanical strategies on force–time characteristics of prone thoracic HVLA-SM.

A randomized crossover experimental design was used. Data were collected between October 2022 and May 2023 from chiropractic students at the Canadian Memorial Chiropractic College who performed HVLA-SM targeted to the thoracic spine of a prone-lying manikin using as much force as possible in each of six different strategies. Strategies (S1 to S6) were specifically developed to successively increase a person’s ability to produce force while performing HVLA-SM. Force–time parameters for the HVLA-SM trials were recorded. Peak force was the primary outcome of interest while preload force, load rate, and time to peak force were analyzed as secondary measures.

Data were collected from 97 participants (51 female). Peak force increased successively from S1 to S5 with moderate effects (− 0.45 ≤ effect size ≤ −0.72). There was no statistical difference in either peak force or load rate between S5 and S6. Load rate also did not statistically increase between S3 and S4 where different muscle groups were targeted to produce force. The strategy with the highest peak force (S6) also demonstrated the lowest preload force.

Strategies used in this study effectively facilitated modulation of force–time characteristics of prone thoracic HVLA-SM. Thus, training approaches may consider introducing people to different biomechanical strategies to enhance HVLA-SM force modulation.

The online version contains supplementary material available at 10.1186/s12998-025-00585-0.