Maximal voluntary quadriceps strength patterns in Olympic overtrained athletes

Area of Science:

• Sports Medicine
• Exercise Physiology
• Neuromuscular Function

Background:

• Overtraining syndrome (OTS) in athletes is characterized by performance decrements and physiological disturbances.
• Understanding the neuromuscular adaptations to overtraining is crucial for athlete health and performance.
• Previous research has indicated potential alterations in muscle strength and activation patterns in overtrained states.

Purpose of the Study:

• To investigate the effects of overtraining on quadriceps muscle peak torques during isokinetic and isometric contractions.
• To compare neuromuscular function between elite overtrained athletes and matched controls.
• To explore the role of central drive in overtraining-induced strength deficits.

Main Methods:

• Assessed isokinetic concentric (CON) and eccentric (ECC) maximal voluntary contractions (MVC) of the quadriceps at 60, 120, and 180 degrees.s-1 in 10 overtrained athletes and 10 controls.
• Measured sustained isometric MVCs at knee flexion angles of 10, 45, and 80 degrees.
• Superimposed 40-Hz electrical stimulation during isometric MVCs to assess the response to external activation.

Main Results:

• Overtrained athletes showed significantly lower CON peak torques at 180 degrees.s-1 (P < 0.001).
• Higher ECC/CON ratios were observed in overtrained subjects at 120 and 180 degrees.s-1 (P < 0.01, P < 0.001).
• Isometric MVCs were reduced at 10 and 45 degrees knee flexion (P < 0.01, P < 0.05) in overtrained individuals, with electrical stimulation revealing a potential increase in torque at 10 degrees (P < 0.05).

Conclusions:

• Overtraining significantly impairs quadriceps concentric strength, particularly at higher velocities.
• Altered torque-velocity characteristics and reduced isometric strength suggest neuromuscular dysfunction in overtrained athletes.
• Impaired central motor output is a likely contributor to the observed strength deficits in overtrained athletes.