Selective Recruitment of the Triceps Surae Muscles With Changes in Knee Angle

Abstract

The muscles of the triceps surae group are important for performance in most sports and in the performance of activities of daily life. In addition, hypertrophy and balance among these muscles are integral to success in bodybuilding. The purpose of this study was to compare the muscle utilization patterns of the 2 major muscles of the triceps surae group, the soleus (SOL) and gastrocnemius (lateral head = LG and medial head = MG), and the tibialis anterior (TA) as an antagonist muscle to the group. Their electromyographic (EMG) signals were compared during 50 constant external resistance contractions at a level established before the testing session. Eleven experienced subjects contributed data during plantar flexion at 3 different knee angles (90, 135, and 180 degrees ). Both root mean square amplitude and integrated signal analyses of the EMGs revealed that the MG produced significantly greater activity than either the SOL or TA at 180 degrees, whereas the LG was not different from the SOL at any knee angle measured. Data also revealed that the SOL produced less electrical activity at 180 degrees than at the other knee angles, whereas the MG produced greater electrical activity. As would be expected, the TA produced lower EMG values than any of the triceps surae muscles at all angles tested. These data indicate that selective targeting of the SOL and MG is possible through the manipulation of knee angle. This targeting appears to be controlled by the biarticular and monoarticular structures of the MG and SOL, respectively. The LG appears less affected by knee position than the MG. Results suggest that the SOL can be targeted most effectively with the knee flexed at 90 degrees and the MG with the leg fully extended. The LG appears to also be more active at 180 degrees; however, it is not as affected as the MG or SOL by knee angle.

Integrated Electromyography and Performance Outcomes to Inertial Resistance Exercise

“…Triceps surae REX as the knee maintains full extension, as done in the current study, note similar results (17,(23)(24)(25). Plantar flexion at three angles (0, 30, and 60Њ) and velocities (6,30, and 60Њ·s Ϫ1 ) showed peak MG IEMG values were significantly greater with full (0Њ) knee extension (24).…”

“…At loads 5-10% of the subject's maximal voluntary contraction, the same study showed significantly higher peak MG IEMG values occurred at a shortening velocity of 60Њ vs. 6Њ·s Ϫ1 as full knee extension was maintained (24). Triceps surae activity during isotonic plantar flexion with full knee extension noted MG IEMG activity was significantly greater than for the SOL (23). MG activity from a 60-second jump test led to greater IEMG and fatigue during concentric, eccentric, and pre-activation phases vs. the SOL (17).…”

“…Electrode placement, done by the same investigator, was held constant across workouts. A 5-second baseline signal was recorded before workouts to ensure no visible artifacts appeared on any collection channel (23).…”

“…Thus the inertial device has broad exercise/rehabilitation applications for various populations. In addition, although prior studies assessed triceps surae IEMG activity, none examined the impact of inertia-based REX to this muscle group, which shows selective recruitment during various tasks (17,23,24). The current study examines IEMG and performance outcomes from calf presses done on the inertial device.…”

Concurrent Exercise on a Gravity-Independent Device during Simulated Microgravity

“…The knee angle utilized for each mode of testing was different with the knee angle being 0 rad for the 3RM and 2.09 rad for isokinetic testing. It is known that selective recruitment of the triceps surae muscles can occur through the manipulation of knee angles (23, 40). Additionally, isolation of the plantar flexors during isokinetic testing has previously been known to be difficult.…”