EFFECTS OF DIFFERENT SIMULATED GRAVITY CONDITIONS ON NEUROMUSCULAR CONTROL IN DROP JUMP EXERCISES

The neuromuscular characteristics of the triceps surae muscle were inv estigated during the various types of stretch-shortening cycle (SSC) m uscle loading. The analysis concentrated on the preactivation and the contact phases of SSC. Muscle loading was changed unconventionally by artificially changing the condition of the gravity in drop jumps. This was accomplished by using a special lifting block system where the gr avity could be modified to control loading and unloading effects of th e triceps surae muscle. The normal gravity condition showed an advanta ge over the other gravity drop jump conditions for the measured parame ters. The same tendency could be seen in the activation characteristic s of the investigated muscles in the preactivation and eccentric phase s. Further, the preactivation EMG was related to the eccentric peak an gular velocity of the ankle joint. The correlation coefficients were 0 .37 (p < 0.05) and 0.48 (p < 0.01) for the gastrocnemius and the soleu s muscles, respectively. All the results emphasized considerable adapt ation of the neuromuscular system to the normal gravity condition. How ever, the overall control of landing may also depend on the vestibular and visual inputs, which might modify even the earlier learned centra l programs.