Kinetic and electromyographic analysis of single repetition constant and variable resistance leg press actions

Walker, Simon; Peltonen, Heikki; Avela, Janne; Häkkinen, Keijo

doi:10.1016/j.jelekin.2010.12.004

Cited by 26 publications

(36 citation statements)

References 29 publications

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“…Previous studies investigating the impact of variable resistance in the squat have demonstrated an increased EMG activity with increasing stress throughout the ROM (1,9,15,19,31), although this is not a universal finding (10). However, these studies examined leg muscles only and not the trunk muscles.…”

Section: Discussionmentioning

confidence: 99%

“…This variable resistance should, in theory, provide a greater neuromuscular stimulus than should constant resistance across the whole range of motion (ROM) (14,19), and especially in the upper part of the movement. Previous studies have used weights in combination with elastic bands to examine quadriceps electromyography (EMG) activity during squat and leg extension exercise (1,9,31,33). However, to the best of our knowledge, no study has investigated core muscle activation during free-weight squats with and without external load from elastic bands.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Replacing Free Weights With Elastic Band Resistance in Squats on Trunk Muscle Activation

Sæterbakken

Andersen

Kolnes

et al. 2014

Journal of Strength and Conditioning Research

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The purpose of this study was to assess the effects of adding elastic bands to free-weight squats on the neuromuscular activation of core muscles. Twenty-five resistance trained women with 4.6 ± 2.1 years of resistance training experience participated in the study. In randomized order, the participants performed 6 repetition maximum in free-weight squats, with and without elastic bands (i.e., matched relative intensity between exercises). During free-weight squats with elastic bands, some of the free weights were replaced with 2 elastic bands attached to the lowest part of the squat rack. Surface electromyography (EMG) activity was measured from the erector spinae, external oblique, and rectus abdominis, whereas a linear encoder measured the vertical displacement. The EMG activities were compared between the 2 lifting modalities for the whole repetition and separately for the eccentric, concentric, and upper and lower eccentric and concentric phases. In the upper (greatest stretch of the elastic band), middle, and lower positions in squats with elastic bands, the resistance values were approximately 117, 105, and 93% of the free weight-only trial. Similar EMG activities were observed for the 2 lifting modalities for the erector spinae (p = 0.112-0.782), external oblique (p = 0.225-0.977), and rectus abdominis (p = 0.315-0.729) in all analyzed phases. In conclusion, there were no effects on the muscle activity of trunk muscles of substituting some resistance from free weights with elastic bands in the free-weight squat.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of Replacing Free Weights With Elastic Band Resistance in Squats on Trunk Muscle Activation

Sæterbakken

Andersen

Kolnes

et al. 2014

Journal of Strength and Conditioning Research

View full text Add to dashboard Cite

show abstract

“…[20] The Teager-Kaiser Energy Operator (TKEO) was applied to the filtered EMG signal. The TKEO combines the amplitude and instantaneous frequency[21] of the EMG signal and is recommended for use when determining timing in data with a low signal-to-noise ratio.…”

Section: Methodsmentioning

confidence: 99%

Quadriceps/hamstrings co-activation increases early after total knee arthroplasty

Thomas¹,

Judd²,

Davidson

et al. 2014

The Knee

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Quadriceps and hamstrings weakness and co-activation present following total knee arthroplasty (TKA) and may impair functional performance. How surgery and post-operative rehabilitation influence muscle activation during walking early after surgery is unclear. Purpose Examine muscle strength and activation during walking before and one and 6-months post-TKA. Methods Ten patients (n=6 female; age:64.7±7.9years; body mass index[BMI]:29.2±2.5kg/m2) and 10 healthy adults (n=6 female; age:60.6±7.4years; BMI:25.5±4.0kg/m2) participated. The patients underwent bilateral quadriceps and hamstrings strength assessment and assessment of quadriceps/hamstrings co-activation and on/off timing using surface electromyography during a six-minute walk test (6MW). Groups, limbs, and changes with TKA surgery were compared. Results Patients reported greater 6MW knee pain pre- versus post-TKA and compared to controls (P<0.05). Patients had weaker surgical limb hamstrings (P<0.05) and bilateral quadriceps (P<0.05) than controls pre- and post-TKA. Before and 1-month post-TKA, patients had side-to-side differences in quadriceps and hamstrings strength (P<0.05). Controls walked farther than patients (P<0.01). Patients demonstrated greater surgical limb co-activation pre-operatively than controls (P<0.05). Co-activation was higher bilaterally one-month post-TKA compared to controls (P<0.05). Patients turned off their quadriceps later during stance than controls before and 1-month post-TKA (P<0.05). Conclusions Muscle strength, co-activation, and timing differed between patients and controls before and early after surgery. Rehabilitation to improve strength and muscle activation seems imperative to restore proper muscle firing patterns early after surgery.

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“…Concentric rms EMG amplitude was normalized to maximum isometric leg extension values. Concentric EMG median frequency was obtained by fast fourier transformation from 60°to 120°knee angles ($2410 ms MAX, $1198 ms HYP), as this has been shown to produce the highest knee extensor EMG amplitudes during leg press (Walker et al, 2011a) in accordance with the procedures of Gonzalez-Izal et al (2010). Neuromuscular efficiency was calculated as maximum isometric force/ EMG amplitude (Deschenes et al, 2008).…”

Section: Acute Loading Protocol Measurementsmentioning

confidence: 99%

Neuromuscular fatigue during dynamic maximal strength and hypertrophic resistance loadings

Walker¹,

Davis²,

Avela³

et al. 2012

Journal of Electromyography and Kinesiology

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Kinetic and electromyographic analysis of single repetition constant and variable resistance leg press actions

Cited by 26 publications

References 29 publications

Effects of Replacing Free Weights With Elastic Band Resistance in Squats on Trunk Muscle Activation

Effects of Replacing Free Weights With Elastic Band Resistance in Squats on Trunk Muscle Activation

Quadriceps/hamstrings co-activation increases early after total knee arthroplasty

Neuromuscular fatigue during dynamic maximal strength and hypertrophic resistance loadings

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