Module 7 (Part 1: Sex Differences in Exercise Phyisology)

6 pillars of knowledge in sex differences

1. Hormonal milieu & fluctuations

2. Substrate use & metabolic responses

3. Skeletal muscle physiology

4. Cardiovascular & respiratory function

5. Molecular & cellular mechanisms

6. Exercise prescription & study design

insulin sensitivity

how easily cells respond to insulin’s signal to take up glucose

insulin resistance

means that your cells don’t respond well to insulin, requiring more of it to do the same job

insulin mediated pathway

1. Insulin binds to receptor at sarcolemma

2. Signal cascade

3. GLUT4 translocation to sarcolemma

4. Glucose enters cell

exercise and insulin sensitivity

• exercise improves insulin sensitivity

• higher exercise intensities use more carbohydrates

glycogen and insulin sensitivity

greater glycogen use associated w improved insulin sensitivity

• post-exercise, glycogen stores are depleted

• insulin sensitivity of cells increased to replenish glycogen more easily

sex

biologically determined, assigned at birth based on reproductive organs and chromosomes

gender

socially or culturally determined

• how one identifies

SIT

sprint interval training

• high intensity

6 weeks of SIT training

after 6 weeks of SIT training

• males saw a dramatic inc in insulin sensitivity

• females saw a less dramatic inc in insulin sensitivity

6 weeks of HIIT for obese females

after 6 weeks of HIIT training

• obese females did not see a dramatic inc in insulin sensitivity

study conclusions

results of study suggests that females tend to oxidize more fats than carbs compared to males

sex differences

there are sex differences in

• skeletal muscle metabolism

• muscle fiber distribution

• capillary density

skeletal muscle metabolism sex differences

there are hormonal differences in estrogen vs testosterone and how they interact with AMPK signalling

• lower AMPK activity in females compared to males

• more AMPK signalling = more favourable for exercise adaptations

AMPK

AMP activated protein kinase

• many cellular functions

RER in females

females typically have lower RER during exercise compared to males

• (tend to use more fat)

why RER is lower in females

females have lower activities of enzymes involved in carb metabolism

• lower capacity for carb metabolism

• e.g lower LDH activity

adaptation signal attenuated

signals that force carb/glycogen use (ADP, AMP, Cr, H+ accumulation) are lower in females compared to males

muscle fiber distribution sex diffrences

females tend to have greater Type I fibers (slow-twitch, oxidative) than males who tend to have more Type IIa/IIb fibers

• more fat utilization

capillary density sex differences

females have greater capillary density in all fiber types

• greater aerobic capacity

estrogen

females have higher levels of estrogen

• studies show higher estrogen levels lead to greater fat oxidation and lower glucose oxidation

menstrual cycle

menstrual cycle can affect exercise metabolism

pre-menopause

pre-menopausal females tend to have better baseline insulin sensitivity than males

room for improvement

room for improvement in training adaptations tends to be greater in males compared to females

oral contraceptives

oral contraceptives dampen physiological adaptations to training