Physiology of Resistance Training

Training Induced Increases in Muscle Mass

• Hyperplasia - increase in muscle fibre number, limited evidence in humans.
• Hypertrophy - increase in muscle fibre cross sectional area, dominant factor in resistance training.

Physiological Variables Affected By Resistance Training

• Nervous System - increased neural drive, potential changes in agonist/antagonist activation ratio.
• Muscle Mass - increased.
• Muscle Fibre Specific Force Production - increased in type 1 fibres only.
• Muscle Fibre Type - small shift from type 2x to 2a fibres.
• Muscle Oxidative Capacity - unclear, depends on type of resistance training.
• Muscle Capillary Density - unclear, depends on type of training.
• Muscle Antioxidant Capacity - increased, 12 weeks of training increases antioxidant enzyme activity by almost 100%.
• Tendons And Ligament Strength - increased.
• Bone Mineral Content - increased, resulting in stronger bones.

Muscle Fatigue

• Fatigue is a complex process with multiple contributing factors.
• Peripheral Fatigue - accumulation of metabolites and depletion of energy stores in muscle.
• Central Fatigue - fatigue of the CNS.

Central Fatigue

• May lead to reduction in number of motor units and firing frequency.
• Research supports and contradicts CNS role in fatigue.
• Mental state and motivation can influence performance.
• Impairment of voluntary muscle contraction may stem from CNS issues.
• Overtraining (OT) can contribute to fatigue.

Critical Power (CP)

• Highest exercise intensity sustainable for prolonged periods.
• Synonymous with anaerobic, lactate and ventilatory threshold.
• Determined through time trials, not measuring VO2 or lactate.
• Requires curve fitting and mathematical analysis.
• W above critical power is W prime, representing anaerobic capacity.
• Asymptote of fitted curve represents CP.
• Tested through multiple time trials of varying durations (12-20 minutes).

Lactate Threshold (LT)

• Inflection point in lactate exercise intensity relationship.
• Beginning of non-linear increase in lactate concentration.
• Identified by a sudden increase in lactate on a graph.
• Measured using incremental exercise tests with blood samples.
• Requires careful data analysis method selection.

Anaerobic Threshold

• Determines maximum sustainable aerobic power.
• Older method compared to CP and LT2.
• Predictive of performance, potentially more useful than VO2max.
• Reflected by a change in the relationship between ventilation and oxygen consumption.
• Also known as the first ventilatory threshold (VT1).
• Identified using the V-Slope method on a graph.

Detraining Following Strength Training

• Ceasing resistance training leads to atrophy and strength loss.
• Strength losses occur slower than endurance based adaptations.
• Strength loss can be recovered quickly with resumed training.

Muscle Memory

• Controversial concept.
• Research suggests it is due to resistance training induced myonuclei.
• Myonuclei are not lost during detraining, providing an advantage for protein synthesis upon retraining.

Prolonged Inactivity and Muscle Atrophy

• 20-30 days of inactivity leads to 20-30% reduction in muscle fibre size.
• Conservation of muscle mass relies on balance between MPS and MPB.
• Increased radial production promotes muscle atrophy.

Training and Changes in VO2max

• VO2max represents the body's maximum oxygen transport and utilization during dynamic exercise.
• Determined by the Fick Equation: VO2max = Max Cardiac Output x a-vO2 difference.
• Primary difference in VO2max between people is stroke volume.

Training To Increase VO2max

• Large muscle group training.
• Endurance based activity 3+ times per week, above 50% VO2max.
• HIIT can also increase VO2max.

Responses to Increases in VO2max

• 15-20% increase in general population.
• Smaller increases in individuals with already high VO2max.
• Up to 50% increase in individuals with very low VO2max.
• Short duration adaptations likely due to increased volume.
• Long duration responses due to changes in stroke volume and a-vO2 differences.

Factors Influencing Stroke Volume

• TPR (afterload), contractility and EDV (preload).
• EDV is influenced by plasma volume, filling time, venous return and ventricular volume.
• Preload increases, afterload decreases with training.
• Detraining leads to rapid loss of mitochondrial adaptations.

Muscle Adaptations to Anaerobic Exercise

• Anaerobic training intensities are above VO2max.
• Fuelled primarily by ATP-PC and glycolysis systems.
• 10-30 second effort, recruits type 1 and 2 fibres.
• Less than 10 seconds fueled by ATP-PC system.
• 20-30 seconds effort, 80% anaerobic energy, 20% aerobic.
• Adaptations include: better buffering capacity, hypertrophy of type 2 fibres, elevated enzymes for ATP-PC and glycolysis.
• HIIT above 30 seconds promotes mitochondrial biogenesis.

Training - Muscle and Systemic Physiology

• Biochemical adaptations to training influence physiological responses.
• Peripheral feedback from muscle to CNS: training improves muscle homeostasis, reducing feedback from muscle chemoreceptors to the CV control centre.
• Central control of physiological response: endurance exercise training reduces feedforward output from higher brain centres to the CV control centre during submaximal exercise.

This quiz covers the physiological adaptations induced by resistance training, focusing on muscle mass changes, neural drive, and various muscle fiber characteristics. It also discusses the impact of training on muscle oxidative capacity, capillary density, and overall strength. Test your knowledge on these important concepts!