Loaded Inter-Set Stretch During Calf Raises
Is it the key to calf muscle hypertrophy hyperdrive?
This study investigated whether incorporating a loaded inter-set stretch during calf raise resistance training enhances muscle thickness (MT) and strength of the plantar flexors compared to traditional resistance training (RT) with passive rest.
PMID: 36048793
Key Points
Aim
The primary aim was to compare changes in muscle strength and muscle thickness of the plantar flexors between traditional RT (with passive rest) and RT combined with a 20-second loaded inter-set stretch during calf raises. A secondary aim was to determine if the stretch had differential effects on individual muscles of the plantar flexors: lateral gastrocnemius (LG), medial gastrocnemius (MG), and soleus (SOL).
Methods
Participants: 21 healthy, untrained young men.
Design: Within-subject; one leg randomly assigned to traditional RT (TRAD) and the other to RT with inter-set stretch (STRETCH).
Training: Twice weekly for 8 weeks, performing seated and straight-leg calf raises.
Intervention: STRETCH leg performed a 20-second loaded stretch immediately after each set using the same load as the exercise; TRAD leg rested passively.
Measurements: Ultrasound assessed muscle thickness of LG, MG, and SOL; isometric plantar flexor strength was measured pre-and post-intervention.
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Results
Muscle Thickness:
The soleus muscle showed a potential hypertrophic benefit from the inter-set stretch with an increase of 0.7 mm (90% confidence interval [CI] = 0 to 1.6 mm).
The lateral gastrocnemius showed ambiguous effects (0.4 mm increase, CI = -0.4 to 1.3 mm).
The medial gastrocnemius showed no clear effect (0 mm change, CI = -0.6 to 0.7 mm).
Overall, the LG exhibited greater standardised growth compared to MG and SOL.
Strength:
Isometric plantar flexor strength showed a modest advantage in the STRETCH condition compared to TRAD.
Practical Takeaways
Adding a 20-second loaded stretch between sets during calf raise exercises may enhance muscle thickness, specifically in the soleus muscle.
The gastrocnemius muscles (LG and MG) may not benefit significantly in terms of hypertrophy from this inter-set stretch protocol.
Plantar flexor strength can be modestly improved by incorporating loaded inter-set stretching.
This method can be integrated into calf training routines without increasing total workout time since the stretch replaces passive rest.
