Relationship between leg and back strength with inter-joint coordination of females during lifting

- Individual strength characteristics are one of the factors that can influence movement patterns of a lifting technique.
- Isometric lifting capacity and strength plays a role in affecting the inter-joint coordination of the hip-back segments.
- Results are pertinent when the initial adopted posture is semi-squat or squat, and this posture was assumed by most females.
- Females should be considered separately in lifting-related studies.

The role of strength and fatigue in the lifting technique is not very clear, especially with regards to inter-joint coordination. We examined the relationships between muscle strength and endurance with inter-joint coordination of the knee-hip (KH) and hip-back (HB) during a lifting task performed until exhaustion. Thirteen healthy females were recruited to participate in the study. Significant negative correlations were found between HB maximum relative phase angle and leg lifting strength (r = −0.805), knee extensor strength (r = −0.705), knee flexor strength (r = −0.633), back extensor strength (r = −0.593) and back flexor strength (r = −0.596). The greater the strength of these muscles, the more synchronized the hip-back inter-joint coordination. However, no significant relationships were found with endurance test performance. Moreover, although the lifting task induced muscle fatigue, there were no significant fatigue-induced changes in lifting coordination.