Week 2 Notes- Endurance Training Adaptations PDF

Endurance training adaptations Powers & Howley Ch13  Learning Outcomes 1. Review the basic principles of training: overload and specificity. 2. State the formula for VO2max using heart rate, stroke volume, and the a-vO2 difference; understand and discuss which of the variables is mos...

Endurance training adaptations Powers & Howley Ch13  Learning Outcomes 1. Review the basic principles of training: overload and specificity. 2. State the formula for VO2max using heart rate, stroke volume, and the a-vO2 difference; understand and discuss which of the variables is most important in explaining the wide range of VO2max values in the population (and indicate typical values). 3. Discuss, using the variables identified in outcome 2, how the increase in VO2max comes about for the sedentary subject who participates in an endurance training program. 4. Describe the changes in muscle structure that are responsible for the increase in the maximal a-vO2 difference with endurance training.  Learning Outcomes 5. Describe how capillary and mitochondrial characteristics change in muscle as a result of an endurance training program 6. Outline the relationship between volume of endurance training and immune function.  Training Principles Overload – a greater than normal stress or load is required for training adaptation to take place Body adapts to stimulus Intensity Duration Frequency  Training Principles Specificity Specific Adaptation to Imposed Demands (SAID) Principle -Training effect is specific to: Muscle fibres involved (Type I, IIa, Iib, Iix) Energy system involved (aerobic vs. anaerobic) Velocity of contraction (heavy squat vs plyometrics Type of contraction (eccentric, concentric, isometric) Reversibility - Gains are lost when overload is removed Adaptations to Aerobic Training Cardiovascular Heart size Cardiac output – HR and SV Blood volume Muscle Fibre type Capillary density Mitochondria – number, size, efficiency Metabolic CHO utilisation and fat oxidation Lactate threshold Adaptations to Aerobic Training Cardiorespiratory Adaptations Specific Aerobic Training Training to increase VO2 max Large muscle groups, dynamic activity 20–60 min, 3–5 times/week, 50–85% VO2 max Expected increases in VO2 max Average = 15% 2–3% in those with high initial VO2 max Requires intensity of 95–100% VO2 max 30–50% in those with low initial VO2 max Training intensity of 40–70% VO2 max Genetic predisposition Accounts for 40%–66% VO2 max Prerequisite for VO2 max of 60–80 ml kg–1 min–1 Heart Size ↑25% Heart Size  Heart Size The left ventricle changes the most in response to endurance training The internal dimensions of the left ventricle increase mostly due to an increase in ventricular filling Left ventricle wall thickness increases, allowing a more forceful contraction of the left ventricle J Am Coll Cardiol, 2002; 40:1856-1863  Stroke Volume ↑ in SV with endurance training ↓ HR = ↑diastolic filling time Frank-Starling Mechanism: strength of ventricular contraction ↑ when the ventricle is stretched prior to contraction + relationship between SV & EDV SV ↑ in response to ↑ volume of blood in LV before contraction (EDV) Occurs as a result of length- tension relationship in cardiac muscle  Stroke Volume SV = EDV (volume of blood in ventricle at END of loading) – ESV (volume of blood in ventricle at END of contraction) EF = (SV/EDV) x 100 Trained for 60min/day, 4/wk, 60-90% VO2max At end contraction  Stroke Volume Endurance training ↑ SV at rest and during submaximal and maximal exercise. End diastolic volume ↑, caused by an ↑ in blood plasma and greater diastolic filling time, contributing to ↑ SV. The ↑ size of the heart allows the left ventricle to stretch more and fill with more blood; wall thickness ↑ enhance contractility. Reduced systemic blood pressure lowers the resistance to the flow of blood pumped from the left ventricle. Stroke Volume (↑compliance) Stroke Volume: Trained vs Untrained Untrained Trained Small increase in SV occurs during transition Larger SV during rest and exercise from rest to exercise Increase in Q due to acceleration in HR as a Endurance trained athletes= HR and SV is result of SV increase increased to increase CO Maximum SV occurs between 40-50% of Frank-Starling Mechanism VO2max (~110-120 bpm) Upright exercises elicits greater SV’s regardless of training status Stroke Volume ↑ Pre-load ↑ stroke volume https://www.cvphysiology.com/Cardiac%20Function/CF024  Heart Rate Submaximal: ↓ in HR at same intensity = ↑ parasympathetic tone, ↑ SV Maximal: no change or slight decrease to allow for filling ↑Q What about resting conditions?  Cardiac Output (Q) ↑ at max Untrained: 14-20 L/min Trained: 25-35 L/min Highly trained: ≥ 40 L/min  Mitochondria – Oxidative Enzymes Mitochondrial enzymes increase in muscle in response to 7-10 days of cycle exercise. Spina RJ, Chi MM, Hopkins MG, Nemeth PM, Lowry OH, Holloszy JO. 2h/day at 60-70% of peak VO2 Enzymatic ↑ succinate dehydrogenase (SDH) – Krebs cycle & ETC ↑ citrate synthase (CS) – 1st step in Krebs cycle ↑ carnitine acetyltransferase – buffers acetyl-CoA Morphological ↑ in fibre size Mitochondria – Oxidative Enzymes 20 min / day → 25% ↑ in leg muscle SDH 60-90 min / day → 2.6 fold ↑ in SDH  Mitochondria – Oxidative Enzymes Training volume is related to changes in CS activity (mitochondrial volume) Citrate synthase= initial enzyme of the Kreb’s Cycle David J Bishop http://buff.ly/1MiKO8D @BlueSpotScience Mitochondria – Increase in Number ATP broken down to ADP and Pi ↑ [ADP] stimulus for ATP production to meet demands of cross bridge cycling Few mitochondria = high [ADP] to stimulate mitochondrial O2 consumption Training: ↑ enzymes, O2 delivery, size = shared ATP production Adaptations to Aerobic Training Oxygen kinetics and modelling of time to exhaustion whilst running at various velocities. Billat et al 2000 t VO depended on a balance between the time lim 2max to attain VO and the time to exhaustion t. 2max lim  Capillary Density Learning Outcome 4 + 5 Red Staining = Capillaries ↓diffusion distance, > opening of existing capillaries, slow rate of blood flow Endurance Trained Physically Active 10 vs 3  Blood Volume BV increases in response to regular exercise (