This study investigated variations in electromyographic (EMG) responses of the erector spinae (ES), vastus medialis (VM), rectus femoris (RF), and vastus lateralis (VL) to different seatback angles during leg extension. Twenty men and women (10 men, 10 women; age 27.49 +/- 6.16 years) performed 8 repetitions at 70% of 8 repetition maximum at seatback angles of 1.57, 1.75, and 1.92 radius (rad). Analyses using repeated-measures analysis of variance indicated the greatest root square mean of the EMG (rmsEMG) and integrated EMG (intEMG) for the ES were at 1.92 rad, and the greatest for the VM (concentric) and VL (eccentric) were at 1.57 rad. No differences were observed among seat angles for the RF except for a higher normalized intEMG at 1.92 than 1.75 rad (concentric). Throughout all sets for all conditions and muscles, rmsEMG and intEMG significantly increased and median power frequency significantly decreased. These data indicate that a seatback angle of 1.57 rad is best for a leg extension machine, because this angle maximizes quadriceps activity while minimizing stress on the lower back muscles.
This research output has an Altmetric Attention Score of 2. This is our high-level measure of the quality and quantity of online attention that it has received. This Attention Score, as well as the ranking and number of research outputs shown below, was calculated when the research output was last mentioned on 09 May 2022.
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#23,300,432
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Outputs from Journal of Strength & Conditioning Research
#5,789
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#188,064
of 211,690 outputs
Outputs of similar age from Journal of Strength & Conditioning Research
#64
of 87 outputs
Altmetric has tracked 34,365,356 research outputs across all sources so far. This one is in the 30th percentile – i.e., 30% of other outputs scored the same or lower than it.
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