Effect of Lower Limb Muscle Fatigue on Ground Reaction Force Components During Landing in People With Non-Specific Chronic Low Back Pain.

CONTEXT: The link between landing parameters and lower limb muscle fatigue in association with chronic low back pain (CLBP) is not well understood.

OBJECTIVE: The purpose of this study was to examine the effects of fatigue on the ground reaction force (GRF) components during landing in people with non-specific CLBP.

DESIGN: Quasi- Experimental study.

SETTING: Clinical Biomechanics Laboratory.

PARTICIPANTS: Forty-four subjects were equally divided into a healthy group and a group with CLBP.

MAIN OUTCOME MEASURES: The GRF along anterior-posterior(y), and medial-lateral (x) and vertical (z) axes, time to peak (TTP), the rate of force development (RFD), impulses for all axes were calculated. A repeated-measures ANOVA (group x fatigue) was used to compare the data among groups.

RESULTS: In the unfatigued conditions, the amplitudes of Fy3, Fz2, and TTP of Fy1, Fy2, Fz1, Fz2, Fz3, Fz4, RFD in Y in the CLBP subjects are significantly different than those in the healthy subjects (P<0.05). In the fatigued conditions, the amplitudes of Fz2, Fz3, F4, and TTP of Fy2, Fy3, Fy4, Fz2, Impulses of X2, Z in the CLBP group were significantly different than those in the healthy subjects(P<0.05). Within-group comparisons of measured Fx1, Fy1, Fy2, Fz2, Fz4, and TTP of Fx1, Fy1, Fy2, Fz2, Fz3, Fz4, Impulses of X2, z were significantly different from pre- to post-fatigue in the healthy group(P<0.05). Within-group comparisons of measured Fx1, Fy1, Fz1, Fz2, and TTP of Fx5, Fz1, Impulses of X2 significantly differed from pre-to post-fatigue in the CLBP group(P<0.05).

CONCLUSIONS: It seems that TTP of GRF variables in CLBP may have clinical values for rehabilitation. Muscle fatigue altered landing performance. While CLBP patients will respond differently to lower extremity fatigue. These altered variables in LBP patients are the cause of future injuries or lower extremity injuries need to be addressed in further studies.