Acute Changes in Gastrocnemius Muscle Stiffness

This randomized, three-period crossover study examined the acute effects of different work-to-rest configurations during a standardized bilateral calf-raise exercise on medial gastrocnemius stiffness in trained volleyball athletes.

Thirty participants, comprising 15 women and 15 men, completed three experimental sessions in a computer-generated randomized order. Sessions were separated by at least 48 hours and were conducted at approximately the same time of day for each participant to reduce the effects of fatigue, carryover, and daily variation. Before data collection, participants completed a familiarization session.

Each experimental session lasted five minutes and included one of the following work-to-rest configurations:

30 seconds of calf raises followed by 30 seconds of rest; 15 seconds of calf raises followed by 45 seconds of rest; or 45 seconds of calf raises followed by 15 seconds of rest.

The exercise cadence was standardized at one repetition per second using a metronome. Participants performed the calf raises barefoot, with their feet approximately shoulder-width apart and their hands placed on their hips. The total session duration was the same for all conditions, while the amount and distribution of exercise and rest differed between protocols.

Medial gastrocnemius stiffness was assessed bilaterally using shear-wave elastography. Measurements were obtained before exercise, immediately after completion of the calf-raise protocol, and after a standardized five-minute recovery period involving percussive therapy. Three elastography acquisitions were recorded for each leg at each assessment and were averaged for analysis.

Percussive therapy was applied to both medial gastrocnemius muscles using a Theragun PRO device with a spherical attachment at approximately 1,750 percussions per minute. Each leg received two 60-second applications separated by 30 seconds of rest. The same experienced researcher administered the intervention and performed the measurements during all sessions.

The primary analysis evaluated changes in shear-wave velocity across the three measurement times and compared those changes among the three exercise protocols. Limb side and participant sex were also examined as exploratory factors.

The primary hypothesis was that the protocol containing 45 seconds of exercise and 15 seconds of rest would produce the greatest immediate increase in gastrocnemius stiffness because it had the highest work density. A secondary objective was to examine whether stiffness decreased toward baseline during the subsequent percussive therapy recovery period.

No sham percussive therapy or passive recovery condition was included. Therefore, changes between the immediate post-exercise and final assessments were interpreted as recovery occurring during the percussive therapy period and not as definitive evidence of an isolated treatment effect