Effects of task and hip-abductor fatigue on lower limb alignment and muscle activation

Abstract

Purpose Fatigue-induced hip-abductor weakness may exacerbate lower-limb misalignments during different dynamic single-leg tasks. We sought to evaluate the effects of fatigue and task on lower limb kinematics and muscle activation and to find associations between measurements obtained in two tasks. Methods One-group pretest–posttest design. Seventeen healthy adults (9 W) performed the single-leg squat (SLSQUAT) and the single-leg hop (SLHOP) before and after a hip-abduction fatigue protocol. Hip adduction, knee frontal plane projection angle (knee FPPA) and heel inversion displacement were measured during the eccentric phase of the SLSQUAT and the SLHOP, as well as activation of the gluteus medius (GMed), tensor fascia latae (TFL), peroneus longus (PER) and tibialis anterior (TA). Moments and tasks were compared using a repeated-measures two-way ANOVA. Correlation between tasks was evaluated using Spearman’s correlation. Results No differences in kinematics or activation were found between moments. Hip-adduction displacement (P = 0.005), GMed (P = 0.008) and PER (P = 0.037) activation were higher during SLSQUAT, while TA activation was higher during SLHOP (P < 0.001). No differences were found between tasks in knee FPPA and heel inversion. Hip-adduction and knee FPPA were not correlated between tasks, while ankle inversion displacement was positively correlated (rs = 0.524–0.746). Conclusion Different characteristics of SLSQUAT (slower and deeper) seem to have led to increased hip adduction displacement, GMed, and PER activation and decreased TA activation, likely due to higher balance requirements. However, hip-abductor fatigue didn’t influence lower-limb alignment during the tasks. Finally, evaluations should be performed with different single-leg tasks since they don’t give the same lower-limb alignment information.

Females Present Different Single-Leg Squat Kinematics and Muscle Activation Strategies than Males Even after Hip Abductor Fatigue

“…The EMG data were processed using a band-pass digital filter (5th order Butterworth) with the cut-off frequencies set at 20-500 Hz. Additionally, the signals were smoothed using the 150 ms moving window root mean square (RMS) method [25]. To determine the median frequency (MDF), spectral analysis was conducted using Fast Fourier Transformation.…”

“…For the EMG amplitude analysis, the RMS values were standardized against the values recorded during the MVICs and presented as a percentage of the maximal activation [24]. All the data were assessed by a single experienced evaluator using Miotec Suite software (version 1.0, Miotec-Biomedical Equipment, Porto Alegre, Brazil) [24,25].…”

“…The participants were directed to maintain both feet grounded until instructed by the researcher. Upon receiving the command, they were to shift their weight onto their dominant side and flex the knee on the opposite side [25], crossing their arms in front of the chest. Prior to initiating the test, the participants completed three repetitions to familiarize themselves with the procedure.…”

“…The pace of the movements was regulated by a metronome (2 beats for the eccentric phase and 2 beats for the concentric phase). Following this, the participants performed five consecutive single-leg squats with a self-selected degree of knee flexion [25].…”

“…For example, if a participant was able to perform 10 repetitions with 15 kg, the estimated 1RM would be 20.4 kg, corresponding to 15 kg (load) × 1.36 (coefficient). In this test, the participants used ankle weights equivalent to 20% of their body mass, based on previous studies with a similar sample that performed a 10-repetition maximum (10 RM) of the side-lying hip abduction exercise [25]. A metronome was set at 60 beats per minute to ensure the exercise was executed at a controlled speed, with 2 beats for each phase.…”