The decrease in electrically evoked force production is delayed by a previous bout of stretch-shortening cycle...

Area of Science:

• Exercise physiology
• Muscle biology
• Sports science

Background:

• Unaccustomed eccentric exercise causes muscle damage and reduced function, particularly at low frequencies.
• Repeated bouts of eccentric exercise lead to reduced damage and faster recovery.
• The protective effects of prior exercise on muscle function are not fully understood.

Purpose of the Study:

• To test if prior stretch-shortening cycle (SSC) exercise protects against muscle function impairment during a subsequent SSC bout.
• To determine if this protection is transient and diminishes as exercise progresses.

Main Methods:

• Seven healthy untrained men performed 100 maximal drop jumps (SSC exercise) at 30-second intervals.
• The same exercise protocol was repeated four weeks later.
• Quadriceps muscle force (P15, P50) was measured pre-exercise, during exercise (10, 25, 50, 100 jumps), and 1, 24 hours post-exercise.

Main Results:

• Peak muscle forces (P15, P50) were higher during the initial phase of the repeated bout compared to the first bout.
• No significant difference in force was observed between bouts at the end of exercise.
• Forces were again higher 24 hours after the repeated bout; the P15/P50 ratio was higher post-repeated bout.

Conclusions:

• Prior SSC exercise provides temporary protection against impaired muscle contractile function during a repeated bout.
• This protection is observable during exercise and also post-exercise, suggesting potentially different underlying mechanisms.