Effect of four jumping endurance trainings on metabolic fatigue and on indirect symptoms of skeletal muscle damage

The aim was to analyze the effect of four trainings on the neuromuscular adaptation of the knee extensors muscles, and particularly the connection with neuromuscular fatigue and exercise-induced muscle damage (EIMD). The subjects were healthy untrained men (age 20.8 1.2 years, n=11). The four jumping endurance trainings (JETs) were repeated every 3 days and each consisted of five series of 20 jumps performed with maximal intensity with 10 s intervals between the series. The maximal voluntary contraction force (MVCF) and electrically evoked muscle contraction force at high and low frequencies, jump height (JH), muscle pain, creatine kinaze (CK) activity and lactate concentration were measured before and after first and fourth JET. The main findings in this study are that four JETs, caused: 1) no changes in decrease both of JH and MVCF 3 min after JET and no changes in their recovery rate (up to 60 min) either; 2) smaller low frequency fatigue (LFF) 3 min after JET; 3) smaller secondary decrease in electrically induced muscle force at high stimulation frequencies from 3 min until 60 min after JET; 4) smaller manifestation of indirect symptoms of EIMD 24 h after JET. Our study showed that four JETs caused no changes in jumping performance but increased resistance of skeletal muscle to LFF and EIMD. It is evident that brief training effect manifest itself rather in electrically induced muscle performance than in voluntary muscle performance