# An Analysis of Hip and Knee Joint Movement Characteristics in Overweight Individuals During Sit-to-Stand Transfers—Based on Statistical Parametric Mapping: An Exploratory Study

## TL;DR

This study examines how overweight individuals move their hips and knees when standing up from a seated position, finding they use different strategies to maintain balance.

## Contribution

The study introduces the use of statistical parametric mapping to analyze joint movement differences in overweight individuals during sit-to-stand transfers.

## Key findings

- Overweight individuals showed smaller hip flexion angles but greater abduction and external rotation angles during sit-to-stand transfers.
- Hip abduction amplitude was significantly greater in the overweight group during the early phase of the movement.
- Overweight individuals exhibited higher hip joint torque, indicating a compensatory strategy for stability.

## Abstract

Objective: The objective of this study was to explore the motion characteristics and movement strategies of the hip and knee joints in overweight individuals during sit-to-stand (STS) transfers using statistical parametric mapping (SPM). Methods: Twenty subjects were divided into an overweight group (n = 10) and a normal-weight group (n = 10) based on body mass index (BMI). The Qualisys infrared motion capture system and Kistler three-dimensional force platform were used for motion data collection, and Visual 3D and Matlab were used to calculate the angles and torque indicators of the lower limb hip and knee joints. Results: During the STS process, the maximum hip flexion angle of the overweight group was smaller than that of the control group (Z = −1.83, p = 0.043, r = 0.39), while the maximum abduction and external rotation angles were greater than those of the control group (Z = −2.15, p = 0.022, r = 0.46; Z = −2.02, p = 0.028, r = 0.48). SPM analysis showed that during the 0–52% phase of the hip joint in the frontal plane, the abduction amplitude of the overweight population was greater than that of the normal population (p < 0.05). The minimum external rotation angle of the knee joint was less than that of the control group (F(1,18) = 9.135, p = 0.043). The peak internal adduction and abduction torque of the hip joint in the overweight group was greater than that of the control group (Z = 2.37, p = 0.017, r = 0.54). Conclusions: Compared with the normal-weight population, the overweight population exhibited distinct motion characteristics of the hip and knee joints during the STS, with particularly pronounced differences in the hip joint. To maintain stability during STS, the overweight population adopts a compensatory movement strategy featuring a wider base of support via hip abduction and increased muscular torque to control frontal plane stability, which imposes greater functional loads on the hip joint. BMI-related movement characteristics should be studied in young adults under controlled experimental conditions, and future studies are needed to verify whether similar patterns exist in older adults.