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The learning effects on lower limb kinetics during single-leg forward and backward hopping
Gu, Yu Malik, Nawfal Nguyen, Thanh Anne, Jordan Song, Yu
Gu, Yu
Malik, Nawfal
Nguyen, Thanh
Anne, Jordan
Song, Yu
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Abstract
Introduction: Single-leg forward hopping for distance is the most popular task to evaluate knee function in patients following anterior cruciate ligament (ACL) injuries. However, a similar forward hopping distance cannot ensure that knee function is fully restored in the involved leg [1]. This is likely due to inconsistent task execution in clinical settings and compensatory movements at the hip and/or ankle joints. On the one hand, inconsistent practice trials were employed in clinics, which may mislead the data interpretation and comparisons. On the other hand, single-leg backward hopping for distance has been suggested to be more appropriate for assessing knee function, as it places greater knee demands compared to forward hopping [2]. Therefore, this study aimed to quantify the learning effects on lower limb (hip, knee, and ankle) mechanics during single-leg forward and backward hopping. Methods: Forty-five injury-free participants (age: 21.0 ± 0.7 years old, height: 1.7 ± 0.1 m, body mass: 68.9 ± 11.9 kg) performed 10 single-leg forward and backward hops on one leg while motion and force data were collected [2]. Hopping performance, peak power, and work of hip, knee, and ankle joints during jumping were calculated for each trial. To quantify learning effects, the 10 trials for each hopping direction were grouped as one practice trial, Block 1 (average of trials 2-4), Block 2 (average of trials 5-7), and Block 3 (average practice at the beginning of the testing [3]. Two-by-three repeated-measures ANOVAs were applied to all dependent variables. of trials 8-10). Such arrangements were based on previous studies, which commonly reported an average of three trials with a single Results & Discussion: For the learning effect (Table 1), hopping performance and peak hip power significantly increased across three Blocks, with the greatest hip work observed in Block 3, regardless of hopping direction. No significant differences were found in peak knee power and knee work across all Blocks for both hopping directions. Although hopping performance increased, knee measurements (peak knee power and knee work) remained consistent. As such, the increased performance might be achieved through greater hip power and work rather than greater knee involvement. For the hopping directions (Table 1), single-leg backward hopping demonstrated smaller hopping distance, smaller peak power and work of hip and ankle joints, but greater peak knee power and work compared to forward hopping, regardless of Blocks. The results were consistent with a previous study [2], which showed that single-leg backward hopping requires greater knee demands compared to forward hopping. Significance: Single-leg backward hopping imposes greater knee demands than forward hopping, suggesting its potential as a more appropriate task to assess knee function in patients following ACL injury. Additionally, one practice trial might be appropriate when using performance to evaluate knee function during single-leg forward and backward hopping. Future studies need to investigate the relationships between hopping performance and knee metrics in patients following ACL injuries to extend the current findings to the clinical population.
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This is the paper from a presentation given at the American Society of Biomechanics held in Pittsburgh, Pennsylvania on 8/15/2025.
Date
2025-08-15
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University of Kansas
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GuY_2025.pdf
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Keywords
Anterior cruciate ligament, ACL injury, Knee, Rehabilitation