Ankle plantar flexion exercise has been incorporated as part of rehabilitation programs and an exercise to promote hypertrophy, increase power and strength of the plantar flexors. Various populations such as sprinters, jumpers, older adults and individuals recovering from Achilles tendinopathy are interested in benefits from training the plantar flexors for maintaining function and performance of daily activities.
PURPOSE: The purpose of this study was to compare electrical activity of lower leg muscles during heel raise exercise with three different foot positions. Subjects were performing heel raise exercise with neutral, internally-rotated and externally-rotated foot positions.
METHODS: Nineteen subjects cooperated in this study (8 male, 11 female; 20,7 ± 2,4 yrs; 176 ± 10,6 cm; 67,6 ± 12,5 kg). Subjects were instructed how to perform each exercise properly, prior to collecting data. The surface electromyography (EMG) was used to assess muscle activity from the soleus, lateral and medial head of gastrocnemius, tibialis anterior and extensor digitorum longus muscle. After warm up protocol, maximal voluntary isometric contractions have been measured followed by 1 RM measurement and 80%-1RM calculations. Subjects were performing heel raise exercise with three different foot positions in random order. The surface of the heel raise exercise has been adjusted so that metatarsal bones were aligned with the line of the boards. In each foot position they performed 1 series of 5 repetitions. After each exercise there was a 5 minute rest. The EMG data were normalized with maximum voluntary muscle contractions and assessed with repeated-measures ANOVA.
RESULTS: One statistical difference has been found in this research. The difference has been found comparing the internally-rotated and externally-rotated foot positionat the musculus gastrocnemius medialis (p=0,043). There has been no statistical differences with other muscles in amplitude of EMG.
CONCLUSION: The position of feet at heel raise execise on adjusted surface does not affect the activation of calf muscles. Performing heel raises with internally-rotated and externally-rotated foot positions on adjusted surface is senseless due to the same activation of both heads of gastrocnemius muscle with neutral feet position.