Effects of detraining on responses to submaximal exercise

Area of Science:

• Exercise Physiology
• Sports Science
• Skeletal Muscle Adaptations

Background:

• Endurance training induces significant physiological adaptations.
• The duration of these adaptations after training cessation is not fully understood.
• Lactate threshold is a key indicator of endurance performance.

Purpose of the Study:

• To investigate the persistence of endurance training adaptations.
• To examine changes in physiological responses and skeletal muscle enzyme activity during detraining.
• To determine the long-term effects on blood lactate threshold.

Main Methods:

• Seven endurance-trained subjects were studied at multiple time points (12, 21, 56, 84 days) post-detraining.
• Measurements included heart rate, ventilation, respiratory exchange ratio, and blood lactate concentration during submaximal exercise.
• Skeletal muscle biopsies assessed mitochondrial enzyme activity and lactate dehydrogenase (LDH) levels.

Main Results:

• Submaximal exercise revealed increased heart rate, ventilation, and blood lactate during the first 56 days of detraining.
• Skeletal muscle showed a 40% decline in mitochondrial enzyme activity and a 21% increase in LDH activity.
• After 84 days, detrained subjects maintained a higher blood lactate threshold compared to untrained controls.

Conclusions:

• Physiological detraining effects stabilize after 56 days.
• Skeletal muscle adaptations, particularly related to lactate metabolism, persist long-term.
• A significant portion of endurance training adaptations, including an elevated lactate threshold, remains for over 85 days post-training.