Strength after bouts of eccentric or concentric actions

Area of Science:

• Exercise Physiology
• Muscle Physiology
• Biomechanics

Background:

• Understanding the effects of different exercise types on muscular strength is crucial for training.
• Eccentric and concentric muscle actions have distinct physiological impacts.
• Investigating the influence of repeated exercise bouts on strength recovery is important for exercise programming.

Purpose of the Study:

• To examine how initial eccentric or concentric exercise bouts affect subsequent eccentric exercise performance.
• To determine the impact of repeated eccentric exercise bouts on muscular strength and speed-torque relationships.
• To compare the effects of different exercise protocols on quadriceps femoris strength recovery.

Main Methods:

• Twenty-four healthy males were divided into eccentric/eccentric, concentric/eccentric, and control groups.
• Participants performed unilateral quadriceps femoris actions (10 sets of 10 reps) at 85% of their one repetition maximum (1 RM).
• Eccentric and concentric 1 RM, and speed-torque relations were measured before and at various time points after exercise bouts.

Main Results:

• The eccentric/eccentric group showed a 32% decrease in 1 RM and a 38% downshift in the speed-torque relation after the first bout.
• Eccentric strength and torque recovered within 6 days, but concentric strength remained impaired at day 10.
• A second eccentric bout further reduced concentric 1 RM and speed-torque relations in the eccentric/eccentric group.

Conclusions:

• Initial eccentric exercise causes significant, but transient, reductions in muscular strength and torque.
• Repeated eccentric exercise bouts can lead to persistent deficits in concentric strength and altered muscle function.
• These findings highlight the importance of considering exercise modality and recovery in training programs to optimize muscle adaptation.