Hypertrophic Effects of Single- versus Multi-Joint Exercise: A Direct Comparison between Knee Extension and Leg Press

Area of Science:

• Exercise Physiology
• Muscle Hypertrophy
• Biomechanics

Background:

• Quadriceps femoris (QF) hypertrophy is targeted by single-joint knee extension (KE) and multi-joint leg press (LP).
• Comparative effectiveness and specific muscle activation for QF hypertrophy between KE and LP are not well understood.

Purpose of the Study:

• To compare the hypertrophic effects of KE and LP on the QF and other lower-limb muscles.
• To characterize the specific muscles that undergo hypertrophy in response to LP training.

Main Methods:

• Untrained adults trained for 12 weeks, performing KE with one leg and LP with the contralateral leg.
• Training involved 70% of one-repetition maximum, 10 reps/set, 5 sets/session, twice weekly.
• Magnetic Resonance Imaging (MRI) assessed pre- and post-training muscle volumes of 17 lower-limb muscles.

Main Results:

• Both KE and LP significantly increased vasti muscles and overall QF volumes, with comparable gains between exercises.
• KE induced greater rectus femoris hypertrophy (+13.2%) compared to LP (+1.1%).
• LP significantly increased gluteus maximus (+15.4%) and adductor magnus (+6.2%) volumes, while KE did not.

Conclusions:

• LP is a time-efficient exercise for overall QF and gluteal/adductor muscle hypertrophy.
• KE is superior for targeting rectus femoris hypertrophy, which is clinically relevant for injury prevention.