The Physiology of Training Performance Effect on VO 2max and Strength Chapter 13.

Principles of Training Overload –Training effect occurs when a system is exercised at a level beyond which it is normally accustomed Specificity –Training effect is specific to the muscle fibers involved –Type of exercise Reversibility –Gains are lost when overload is removed

Moffit’s corollary to Principles of Training Consistency –Once in a while is better than nothing….. but just barely –Even if just a little overload, as long as there is consistency there will be positive changes

Result of Endurance Training Structural and biochemical changes in muscle –  Mitochondrial number  Enzyme activity –  Capillary density

Result of Endurance Training Ability to perform repeated sub maximal muscle contractions Ability to support aerobic energy production –For longer periods (duration) –At higher intensities (work capacity) Higher maximal oxygen consumption (VO 2max ).

What is VO 2max ? Maximum capacity to use oxygen in the recycling of ATP Factors Affecting: –Delivery of oxygen Blood circulation –Extraction of oxygen Unloading –Use in metabolism Mitochondria.

Calculation of VO 2max Product of maximal cardiac output (Q) and arteriovenous difference (a-vO 2 ) a-vO 2 difference –Represents amount of oxygen taken into muscle tissue –Known from PO 2 in arterial and venous blood –Greater difference = more O 2 extracted VO 2max = HR max x SV max x (a-vO 2 ) max...

Questions: Can VO 2max be improved? How much can it be improved? What change influences it the most?.

Answers: Yes, it can be improved It can be increased by up to 15% Improvements in VO 2max from: –50% due to  a-vO 2 difference –50% due to  SV Differences in VO 2max in untrained –Due to differences in SV max..

a-vO 2 Difference and Increased VO 2max Improved ability of the muscle to extract oxygen from the blood: –1.  Muscle blood flow (delivery)  Capillary density (delivery) –2.  Mitochondial number.

Stroke Volume and Increased VO 2max Increased SV max –  Preload (EDV)  Plasma volume  Venous return  Ventricular volume –  Afterload (TPR)  Arterial constriction  Maximal muscle blood flow with no change in mean arterial pressure –  Contractility.

Structural and Biochemical Adaptations to Endurance Training  Mitochondrial number   Oxidative enzymes –Krebs cycle (citrate synthase) –Fatty acid availability (  -oxidation) –Electron transport chain (cytochromes)  NADH (shuttling system) Change in type of LDH (pyruvate unchanged) Adaptations quickly lost with detraining

Influence of Mitochondrial Number on ADP Concentration and VO 2 [ADP] stimulates mitochondrial ATP production Increased mitochondrial number following training –Lower [ADP] needed to increase ATP production and VO 2 –More ATP available sooner when trained..

Effect of Exercise Intensity and Duration on Mitochondrial Enzymes Citrate synthase (CS) –Marker of mitochondrial oxidative capacity Light to moderate endurance training –Increased CS in high oxidative fibers (Type I and IIa) Strenuous endurance training –Increased CS in low oxidative fibers (Type IIb)

Biochemical Changes and FFA Oxidation Increased mitochondrial number and capillary density –Increased capacity to transport FFA from plasma to cytoplasm to mitochondria Increased enzymes of  -oxidation –Increased rate of acetyl CoA formation Increased FFA oxidation –Spares muscle glycogen and blood glucose

Blood *Lactate Concentration Lactate production during exercise Endurance training  production –FFA use instead of glycolysis –H isoform of LDH = low affinity for pyruvate  removal –Malate-aspartate shuttle = NADH to mitochondria pyruvate + NADHlactate + NAD LDH

Detraining and VO 2max Decrease in VO 2max with cessation of training –  SV max –  maximal a-vO 2 difference (Opposite of training effect)..

Detraining: Time Course of Changes in Mitochondrial Number: Study Results About 50% of the increase in mitochondrial content was lost after one week of detraining All of the adaptations were lost after five weeks of detraining It took four weeks of retraining to regain the adaptations lost in the first week of detraining

Time-course of Training/Detraining Mitochondrial Changes

Time Course of Changes Associated With Detraining

Physiological Effects of Strength Training Neural factors –Increased ability to activate motor units - recruitment –Strength gains in initial 8-20 weeks Muscular enlargement –Mainly due enlargement of fibers (hypertrophy) More sarcomeres in parallel More fluid within the cell –Long-term strength training

Neural and Muscular Adaptations to Resistance Training

Questions?

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