There was a high drop-out rate and we were unable to recruit new subjects.

Muscle power is one of the most important parameters in almost every athletic action, and expresses the ability of the human muscle to produce great amounts of force with the greatest possible speed. Thus, muscle power is critical for high performance in athletic actions such as jumping, throwing, change of direction and sprinting. For enhancing their muscle power, athletes comprise several resistance training programs as part of their training. Muscle power training comprises of eccentric muscle actions, and the magnitude of these actions depend on the emphasis that is given on the concentric or eccentric action, respectively, of the muscles during the exercises. However, eccentric muscle action, especially when unaccustomed, can lead to exercise-induced muscle damage (EIMD), and deterioration of muscle performance.

Despite the fact that muscle power training comprises eccentric muscle actions, and consequently can lead to muscle injury and muscle performance reduction during the following days, the recovery kinetics after acute muscle power training have not been adequately studied. However, information regarding the recovery of the muscles after a power training protocol, is critical for the correct design of a training microcycle, and the reduction of injury risk.

The aim of the present study is to investigate the muscle injury provoked after acute muscle power training using three different power training exercise protocols. Additionally, we will examine the effect of these protocols on muscle performance and neuromuscular fatigue indices.

Muscle power is one of the most important parameters in almost every athletic action, and expresses the ability of the human muscle to produce great amounts of force with the greatest possible speed. Thus, muscle power is critical for high performance in athletic actions such as jumping, throwing, change of direction and sprinting.

For enhancing their muscle power, athletes comprise several resistance training programs as part of their training. Core exercises as long as Olympic lifting has been used in muscle power training. The loads that are applied regarding the accomplishment of the most favorable power production are varying. Training load of 0% 1RM favored power production at the countermovement squat jump, while loads of 56% 1rm and 80% 1RM, favored the power production at squat and hang clean, respectively. Additionally, In the recent years, accentuated eccentric training has been proposed as a new training method for the enhancement of muscle power. This method emphasizes the eccentric component of the muscle contraction, and there is evidence supporting the greater production of muscle force after accentuated eccentric training compared with the typical resistance exercise training method.

Taking the above into consideration, muscle power training comprises of eccentric muscle actions, and the magnitude of the eccentric component depends on the emphasis that is given on the concentric or eccentric action, respectively, of the muscles during the exercises. However, eccentric muscle action, especially when unaccustomed, can lead to exercise-induced muscle damage (EIMD). Although concentric and isometric exercise may also lead to muscle injury, the amount of damage after eccentric muscle contractions is greater. EIMD, amongst others, is accompanied by increased levels of creatine kinase (CK) into the circulation, increased delayed onset of muscle soreness (DOMS), reduction of force production, reduction of flexibility speed.

Despite the fact that muscle power training comprises eccentric muscle actions, and consequently can lead to muscle injury and muscle performance reduction during the following days, the recovery kinetics after acute muscle power training protocols have not been adequately studied. However, information regarding the recovery of the muscles after a power training protocol, is critical for the correct design of a training microcycle, and the reduction of injury risk.

The aim of the present study is to investigate the muscle injury provoked after muscle acute power training using three different power training exercise protocols. Additionally, the effect of these protocols on muscle performance and neuromuscular fatigue indices will be examined.

Inclusion Criteria:

• No recent history of musculoskeletal injury
• No use of ergogenic supplements and drugs
• No use of anti-inflammatory and antioxidant supplements (> 6 months)
• No participation at intense eccentric exercise for at least 3 days before protocols

Exclusion Criteria:

• Recent history of musculoskeletal injury
• Use of ergogenic supplements and drugs
• Use of anti-inflammatory and antioxidant supplements (< 6 months)
• Participation at intense eccentric exercise for at least 3 days before protocols