Effects of Hip Flexion Angle on Quadriceps Muscle hypertrophy in the Leg Extension Exercise
Comparing the effects of 90° vs 40° of hip flexion during leg extensions.
The study "The effects of hip flexion angle on quadriceps femoris muscle hypertrophy in the leg extension exercise" investigated how different hip flexion angles during leg extension exercises affect muscle hypertrophy in the quadriceps, specifically the rectus femoris and vastus lateralis muscles.
Key Points
Aim
The study aimed to compare the hypertrophic effects of performing leg extensions at two different hip flexion angles: 40° (recumbent) and 90° (upright). The hypothesis posited that training at 40° would yield greater hypertrophy in the rectus femoris compared to 90°, while no significant difference would be observed in the vastus lateralis.
Methods
Participants: The study involved 30 untrained men aged between 18 and 50 years. After exclusions for non-compliance, 22 participants (average age: 33 years, body mass: 84.1 kg, height: 179.2 cm) completed the intervention.
Design: A within-participant design was employed, with each participant's legs randomly assigned to either the 40° or 90° hip flexion condition.
Training Protocol: Participants underwent a ten-week training program consisting of two sessions per week. Each session involved unilateral leg extensions performed to momentary concentric failure, with an increase in sets from three to four after five weeks.
Measurement: Muscle thickness of the rectus femoris and vastus lateralis was assessed using ultrasound imaging before and after the intervention. The analysis utilised Bayesian mixed-effect models to evaluate differences in hypertrophy.
Results
The findings supported the initial hypothesis:
Rectus Femoris: There was "extreme" evidence (Bayes Factor >100) indicating greater hypertrophic response at the 40° hip flexion angle compared to 90°. The average treatment effect (ATE) for distal and proximal measurements was significantly positive.
Vastus Lateralis: There was "strong" evidence (Bayes Factor = 0.07) showing no significant difference in hypertrophy between the two conditions, suggesting that hip flexion angle does not influence vastus lateralis growth as it does for rectus femoris.
Related
Key Takeaways
Training at a reduced hip flexion angle (40°) is more effective for increasing rectus femoris hypertrophy compared to a higher angle (90°).
The vastus lateralis does not exhibit significant differences in hypertrophic response based on hip flexion angle during leg extensions.
These findings highlight the importance of exercise selection and technique in resistance training aimed at muscle or portion-specific muscle growth.
The study concluded that for trainees aiming to enhance quadriceps hypertrophy, particularly targeting the rectus femoris, performing leg extensions at a lower hip flexion angle is advantageous.
Reference
Larsen, S., Kristiansen, B.S., Swinton, P.A., Wolf, M., Fredriksen, A.B., Falch, H.N., van den Tillaar, R., Sandberg, N.Ø. (2024). The effects of hip flexion angle on quadriceps femoris muscle hypertrophy in the leg extension exerciseSportRχiv.