Short Term Detraining Notes

Detraining: Loss of Training-Induced Adaptations

Definition
  • Detraining is the partial or complete loss of training-induced adaptations due to an insufficient training stimulus.
  • The principle of training reversibility states that stopping or reducing training reverses adaptations, compromising performance.
Terminology
  • Training Cessation: Temporary discontinuation of physical conditioning.
  • Reduced Training: Nonprogressive reduction in training quantity.
  • Taper: Progressive nonlinear reduction of training load to reduce stress and optimize performance.
  • Detraining Syndrome: Clinical entity after athletes abandon regular training, characterized by dizziness, cardiac disturbances, and psychological symptoms.
Time Frame
  • Short Term Detraining: Less than 4 weeks of insufficient training stimulus.
  • Long Term Detraining: More than 4 weeks of insufficient training stimulus.

Short Term Cardiorespiratory Detraining

Maximal Oxygen Uptake (V.O2max)
  • Highly trained individuals experience a 4-14% decline.
  • Recently trained individuals show a smaller decline (3.6-6%).
  • V.O2maxV.O_{2max} decline depends on the trained state.
Blood Volume
  • Endurance-trained athletes experience a 5-12% decline in blood and plasma volume.
  • Plasma volume may decline within the first 2 days of inactivity.
  • Recently trained individuals also experience decreased blood volume.
Heart Rate
  • Exercise heart rate increases by 5-10% at submaximal and maximal intensities due to reduced blood volume.
  • Maximal heart rate stabilizes after 2-3 weeks without training.
  • Resting heart rate may not change.
Stroke Volume
  • Stroke volume decreases by 10-17% after 12-21 days of training cessation.
Cardiac Output
  • Maximal cardiac output is reduced by 8% after 21 days without training.
Cardiac Dimensions
  • Possible decrease in left ventricular wall thickness and mass.
  • Blood pressure may increase during exercise.
Ventilatory Function
  • Decline in maximal ventilatory volume.
  • Reduced O2O_2 pulse and increased ventilatory equivalent.
Endurance Performance
  • Performance declines rapidly.

Short Term Metabolic Detraining

Substrate Availability and Utilization
  • Increased respiratory exchange ratio (RER) indicates higher reliance on carbohydrate metabolism.
  • Decreased insulin sensitivity.
  • Reduced muscle GLUT-4 transporter protein content (17-33%).
  • Decreased muscle lipoprotein lipase activity.
Blood Lactate Kinetics
  • Increased blood lactate levels after training cessation.
Muscle Glycogen
  • Muscle glycogen level decreases (20% in 1 week).

Short Term Muscular Detraining

Muscle Capillarization
  • Capillary density may decline or remain unchanged.
Arterial-Venous Oxygen Difference
  • No change reported.
Myoglobin Level
  • No effect observed.
Enzymatic Activities
  • Decreased skeletal muscle citrate synthase activity (25-45%).
  • Reduced β-hydroxyacil-CoA dehydrogenase, malate dehydrogenase, and succinate dehydrogenase.
  • Decreased glycogen synthase activity (42% after 5 days).
Mitochondrial ATP Production
  • Decreases in sedentary individuals.
Muscle Fibre Characteristics
  • No change in muscle fibre distribution.
  • Mean fibre cross-sectional area may decrease.
Strength Performance
  • Slight, non-significant reductions in strength.
  • Decline in eccentric force and sport-specific power.

Short Term Hormonal Detraining

Hormonal Changes
  • Reduced insulin sensitivity.
  • Anabolic hormones may increase in strength athletes.
  • Fluid-electrolyte regulating hormones normalize to pretraining levels.