Hip Flexion Angle and Leg Extensions
Effects on longitudinal muscle activity of the rectus femoris during leg extensions.
The study "Hip flexion angle affects longitudinal muscle activity of the rectus femoris in leg extension exercise" investigates how varying hip flexion angles (HFA) influence the activity of the rectus femoris (RF) muscle during leg extension exercises (LEE).
PMID: 36795130
Key Points
Aim: The primary aim of the study was to determine the effect of different hip flexion angles on the longitudinal muscle activity of the rectus femoris during isotonic leg extension exercises.
Methods
Participants: Nine male bodybuilders were recruited for this acute study.
Exercise Protocol: Participants performed isotonic LEE using a leg extension machine at three different hip flexion angles: 0°, 40°, and 80°. Each participant executed four sets of ten repetitions at 70% of their one-repetition maximum (1RM), extending their knees from 90° to 0°.
Measurements: The transverse relaxation time (T2) of the RF was measured before and after the exercise using magnetic resonance imaging (MRI). The study analysed changes in T2 values across the proximal, middle, and distal regions of the RF. Additionally, subjective sensations of muscle contraction were assessed using a numerical rating scale (NRS) and compared to T2 values.
Results
At a hip flexion angle of 80°, the T2 value in the middle RF was significantly lower than that in the distal RF (p < 0.05).
The T2 values at 0° and 40° HFA were higher than those at 80° HFA in both proximal (p < 0.05 for 0°, p < 0.01 for 40°) and middle RF regions (p < 0.01 for both).
The subjective NRS scores did not align consistently with the objective T2 measurements, indicating discrepancies between perceived muscle contraction and actual muscle activity.
