Variability of neural activation during walking in humans: short heels and big calves

Ahn, Anna; Kang, J K; Quitt, M.; Davidson, Brooke; Nguyen, C T

doi:10.1098/rsbl.2010.1169

Cited by 20 publications

(31 citation statements)

References 14 publications

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“…Finally, among the triceps surae (plantarflexors), only GM was affected by the use of independent cranks. This further confirms that GM and GL, although belonging to the same muscle group, may receive a different neural activation (Ahn et al, 2011). …”

Section: Discussionsupporting

confidence: 73%

Altered muscle coordination when pedaling with independent cranks

Hug¹,

Boumier²,

Dorel³

2013

Front. Physiol.

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Pedaling with independent cranks ensures each leg cycles independently of the other, and thus eliminates the contribution of the contralateral leg during the upstroke phase. Consequently the subject is required to actively pull-up the pedal to complete the cycle. The present study aimed to determine the acute effect of the use of independent cranks on muscle coordination during a submaximal pedaling exercise. Ten healthy males were asked to perform submaximal pedaling exercises at 100 Watts with normal fixed cranks (control condition) or independent cranks. Both 2-D pedal forces and electromyographic (EMG) SIGNALS of 10 lower limb muscles were recorded. When the mean EMG activity across the cycle was considered, the use of independent cranks significantly increased the activity level compared to control for Tibialis anterior (TA) (P = 0.0017; +336 ± 302%), Gastrocnemius medialis (GM) (P = 0.0005; +47 ± 25%), Rectus femoris (RF) (P = 0.005; +123 ± 153%), Biceps femoris (BF)—long head (P = 0.0001; +162 ± 97%), Semimembranosus (SM) (P = 0.0001; +304 ± 192%), and Tensor fascia latae (P = 0.0001; +586 ± 262%). The analysis of the four pedaling sectors revealed that the increased activity of hip and knee flexors mainly occurred during the top dead center and the upstroke phase. In addition, a high inter-individual variability was found in the way the participants adapted to pedaling with independent cranks. The present results showed that the enforced pull-up action required when using independent cranks was achieved by increasing the activation of hip and knee flexors. Further studies are needed to determine whether training with independent cranks has the potential to induce long-term changes in muscle coordination, and, if so, whether these changes are beneficial for cycling performance.

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Section: Discussionsupporting

confidence: 73%

Altered muscle coordination when pedaling with independent cranks

Hug¹,

Boumier²,

Dorel³

2013

Front. Physiol.

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“…For example, during walking greater EMG amplitude is observed in the medial than the lateral gastrocnemius in %50% of participants, whereas the other half has similar EMG amplitude of both muscles [9]. Similarly, during a wide range of tasks, some [10,11], but not all [12], studies report greater EMG amplitude of the lateral (vastus lateralis, VL) than the medial (vastus medialis, VM) head of the quadriceps with a large difference between individuals (e.g.…”

Section: Introductionmentioning

confidence: 99%

Nature of the coupling between neural drive and force-generating capacity in the human quadriceps muscle

et al. 2015

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The force produced by a muscle depends on both the neural drive it receives and several biomechanical factors. When multiple muscles act on a single joint, the nature of the relationship between the neural drive and forcegenerating capacity of the synergistic muscles is largely unknown. This study aimed to determine the relationship between the ratio of neural drive and the ratio of muscle force-generating capacity between two synergist muscles (vastus lateralis (VL) and vastus medialis (VM)) in humans. Twenty-one participants performed isometric knee extensions at 20 and 50% of maximal voluntary contractions (MVC). Myoelectric activity (surface electromyography (EMG)) provided an index of neural drive. Physiological cross-sectional area (PCSA) was estimated from measurements of muscle volume (magnetic resonance imaging) and muscle fascicle length (threedimensional ultrasound imaging) to represent the muscles' force-generating capacities. Neither PCSA nor neural drive was balanced between VL and VM. There was a large (r ¼ 0.68) and moderate (r ¼ 0.43) correlation between the ratio of VL/VM EMG amplitude and the ratio of VL/VM PCSA at 20 and 50% of MVC, respectively. This study provides evidence that neural drive is biased by muscle force-generating capacity, the greater the force-generating capacity of VL compared with VM, the stronger bias of drive to the VL.

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“…In addition to r, thickness of the triceps surae muscles varies among individuals due to training type or differences in muscle activation patterns in sedentary individuals (Abe et al, 2000;Komi, 1986;Ahn et al, 2011;Baxter and Piazza, 2013). As a group, sedentary individuals have the same triceps surae muscle thickness as distance runners (Abe et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

“…In healthy young men, plantarflexor moment arm correlates with plantarflexor muscle volume and torque (Baxter and Piazza, 2013). However, sedentary individuals divide into two sub-groups depending on their muscle activation pattern during walking: 'MG-biased' individuals activate their medial gastrocnemius muscle (MG) more strongly than their lateral gastrocnemius (LG) and 'unbiased' individuals activate both MG and LG muscles equally (Ahn et al, 2011). MG-biased individuals have larger MG muscles than unbiased individuals (Ahn et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

“…However, sedentary individuals divide into two sub-groups depending on their muscle activation pattern during walking: 'MG-biased' individuals activate their medial gastrocnemius muscle (MG) more strongly than their lateral gastrocnemius (LG) and 'unbiased' individuals activate both MG and LG muscles equally (Ahn et al, 2011). MG-biased individuals have larger MG muscles than unbiased individuals (Ahn et al, 2011). As sedentary subjects walk faster, activation of their MG and LG muscles become less biased (Ahn et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

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Lower leg morphology in runners: forefoot strikers have longer heels but not bigger muscles than rearfoot strikers

Wessbecher

Ahn

2019

Journal of Experimental Biology

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Foot strike pattern used during running may relate to lower leg morphology. We tested the hypotheses that forefoot strike (FFS) runners have longer plantarflexor moment arms (r) and larger plantarflexor muscles than rearfoot strike (RFS) runners. FFS runners had 17% longer r than RFS runners, but all runners had similarly sized medial and lateral gastrocnemius (MG and LG) muscles. Because muscle size also depends on activation pattern (Ahn et al., 2011), we compared MG:LG activation bias during walking in 24 runners and 23 sedentary subjects. Half of all subjects activated their MG and LG muscles equally ('unbiased') while walking, while the other half activated their MG more strongly than their LG muscles ('MG-biased'). Unbiased sedentary subjects had 16-23% smaller MG muscles compared with MG-biased sedentary subjects, unbiased runners and MG-biased runners. Muscle contraction dynamics during FFS running may balance the effects of longer plantarflexor moment arms in determining MG and LG muscle size.

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Variability of neural activation during walking in humans: short heels and big calves

Cited by 20 publications

References 14 publications

Altered muscle coordination when pedaling with independent cranks

Altered muscle coordination when pedaling with independent cranks

Nature of the coupling between neural drive and force-generating capacity in the human quadriceps muscle

Lower leg morphology in runners: forefoot strikers have longer heels but not bigger muscles than rearfoot strikers

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