Roles of metabolites in muscle fatigue

OBJECTIVES• Methodology:

• Experimental approach• Temperature

• Are the changes in metabolites responsible for the decrease in force during fatigue at the level of the sarcomere

INTRODUCTION

ATP PRODUCTION – METABOLIC PATHWAYS

ATP HYDROLYSIS

CREATINE PHOSPHATE

PURINE CYCLE

ADENYLATE KINASE

ATP + H2O ADP + Pi + H+ + WORK

PCr + ADP ATP + Cr

2 ADP ATP + AMP

AMP + H2O + H+ IMP + NH4+

IMP + ASPARTATE + GTP ADENYLSUCCINATE + GDP +Pi

ADENYLSUCCINATE AMP + FUMARATE

ATP PRODUCTION – METABOLIC PATHWAYS

GLYCOGENOLYSIS AND GLYCOLYSIS

KREB’S CYCLE & OXYDATIVE PHOSPHORYLATION

GLUCOSE + 2 ADP + 2 Pi 2 ATP + 2 PYRUVATE

GLUCOSE + 6 O2 + 36 ADP + 36 Pi 36 ATP + 6 CO2

NO O2

2 LACTATE O2

-OXIDATION

FATTY ACID ACYL-CoA KREB’S CYCLE & OXYDATIVE PHOSPHORYLATION

GLUCOSYL + 3 ADP + 3 Pi 3 ATP + 3 PYRUVATE

FATIGUE: FAST & GLYCOLYTIC TWITCH MUSCLE

FATIGUE: SLOW & OXIDATIVE TWITCH MUSCLE

ATP EFFECT ON MAXIMUM SHORTENING VELOCITY

ATP EFFECT ON MAXIMUM FORCE

DISCUSSION

CONTROL EARLY FATIGUE FATIGUE

Mg2+ 1 1 1

MgATP 6.18 4.7 4.7

ADPtotal 0.05 0.7 0.7

AMPtotal 0.0002 0.062 0.062

Pitotal 0.88 17.38 17.38

PCr 14.16 1.42 1.42

Creatine 11.46 21.14 47.3

pH 7.00 7.00 6.65

ALL CONCENTRATION IN mM

Δ DURING FATIGUE FMAX Ca50

H+ ↑↑ ↓↓ ↓↓Pi ↑↑ ↓↓ ↓↓ATP ↓ ↑ ↓ADP ↑ ↑ ↑AMP ↑ ↑ ↑IMP ↑↑ ↑PCr ↓↓ ↑ ↑Creatine ↑↑ ↓ ↑Lactate ↑↑ → →

0% CO2

WATER

15% CO2

30% CO2