FISIOLOGI OLAHRAGA

Rahmatina B. HermanBagian Fisiologi

Fakultas Kedokteran Universitas Andalas

Introduction

No other normal stresses that nearly approach the extreme stresses of heavy exercise

If some of extremes of exercise were continued for even slightly prolonged periods, they might easily be lethal

Therefore, Sports Physiology, in the main, is a discussion of the ultimate limits to which most of the bodily mechanisms can be stressed

Comparison:- Extremely high fever approaching the level of lethality, body metabolism increases to about 100%- During marathon race, body metabolism increases to 2000 % above normal

Strength of Muscles in Exercise

Determined mainly by its size

Maximum contractile force: 3-4 kg/cm2 of muscle cross-sectional area

The holding strength is ± 40% greater than contractile strength

Power of Muscles in Exercise

Power:- a measure of the total amount of work that the muscle performs in a unit of time:- determined by:

> strength of muscle contraction> distance of contraction> number of times it contracts each minute

- measured in kg-m/ minute - power of 1 kg-m/minute, that is a muscle

> that can lift 1 kg weight to a height of 1 m in 1 min, or

> that can move object laterally against a force of 1 kg for a distance of 1 m in 1 min

Endurance

Final measures of muscle performance

The efficiency for translation of muscle power output into athletic performance is often much less during rapid activity than during less rapid but sustained activity

Depends on nutritive support for muscle, more than anything else on the amount of glycogen that has been stored in muscle before the period of exercise

A person on a high-carbohydrate diet stores far more glycogen in muscles than a person on mixed diet or high-fat diet → endurance is greatly enhanced by a high-carbohydrate diet

…..Endurance

Type of Diet Glycogen stored (gm/ kg muscles)

Complete exhaustion(minutes)

High-carbohydrate 40 240

Mixed 20 120

High-fat 6 85

Muscle Metabolic System in Exercise

The same basic metabolic systems are present in muscle as in all other parts of body

However, the activities of 3 metabolic systems are exceedingly important in understanding the limits of physical activity:1. Phosphagen system2. Glycogen-lactic acid system (anaerobic)3. Aerobic system

The amount of ATP present in the muscles, even in well-trained athlete , is sufficient to sustain maximal muscle power for only ± 3 seconds/ one half of a 50-m dash

…..Muscle Metabolic System in Exercise

Phosphocreatine

Glycogen

GlucoseFatty acidAmino acids

Creatine + PO3

Lactic acid

CO2 + H2O+ O2

+ Urea

ATP

ADP

AMP

EnergyForMusclecontraction

…..Muscle Metabolic System in Exercise

Metabolic system M of ATP/ min Time

Phosphagen system 4 8 – 10 secGlycogen-lactic acid system 2.5 1.3 – 1.6 min

Aerobic system 1Unlimited time

(as long as nutrients last)

Recovery of Metabolic System After Exercise

1. Repaid of oxygen debt: ± 11.5 LBody normally contains ± 2 L of stored O2:- 0.5 L in lungs- 0.25 L dissolved in body fluids- 1 L combined with Hb- 0.3 L combined with myoglobinIn heavy exercise , almost all O2 is used After exercise over, the stored oxygen must be replenished by breathing ± 9 L more to provide for reconstituting phosphagen and lactic acid system

....Recovery of Metabolic System After Exercise

2. Recovery of muscle glycogenNot a simple matterOften requires days- A high carbohydrate diet: full recovery in ± 2 days- A high -fat/ high-protein diet: little recovery even

after 5 days

- Important for athlete to have a high carbohydrate diet before a grueling athletic event

- not to participate in exhaustive exercise during the 48 hours preceding the event

Effect of Training on Muscles

Muscles that function under no load, even if they are exercised for hours on end, increase little in strength

Muscle that contract at > 50% maximal force of contraction will develop strength rapidly even if the contractions are performed only a few times each day

Experiments on muscle building: maximal muscle contractions performed in three sets 3 days a week give approximately optimal increase in muscle strength and without producing chronic muscle fatigue

Fast-twitch and Slow-twitch Muscle Fibers

Fast-twitch:- twice as large in diameter- the enzymes that promote rapid release of energy

are 2-3 times as active in fast-twitch as in slow-twitchSlow-twitch:- mainly organized for endurance especially for generation of aerobic energy- contain more myoglobin- the enzymes of aerobic metabolic system more active than fast-twitch- the number of capillaries per mass of fibers is greater than in fast-twitch

Cardio-respiratory Function in Exercise

Oxygen consumption and total pulmonary ventilation increase ± 20-fold between the resting state and maximum intensity of exercise in the well-trained athleteO2 diffusing capacity, that is the rate at which O2 can diffuse from alveoli into the blood: 3-fold increaseRespiration is stimulated mainly by neurogenic mechanismsVenous return and COP ↑Hypertrophy of myocardium

Effect of Training on VO2 Max

VO2 max is abbreviation for the rate of oxygen usage under maximal aerobic metabolismExperiments:- Athletic training for 7-13 weeks: VO2 max

increased only ±10 %, and the frequency of training had little effect on the increase in

VO2 max- Marathon training: VO2 max increased > 10 %

Body Heat in Exercise

During endurance athletics, body temperature often rises to 40°C even under normal environmental conditionsWith very hot and humid conditions or excess clothing, the body temperature can easily rise to 42°C → heat stroke → destructive to tissue cells, especially to brain cells:- extreme weakness- exhaustion- headache, dizziness, nausea- profuse sweating- confusing, staggering gait, collapse, unconsciousness

Body Fluids in Exercise

5-10 pound weight loss has been recorded in athletes in a period of 1 hour during endurance athletic events under hot and humid conditionsEssentially results from loss of sweatLoss of sweat to decrease body weight - 3%: can significantly diminish performance- 5-10% rapid decrease can often be serious, leading to muscle cramps, nausea and other effectsTherefore it is essential to replace fluid as it is lost including replacement of salt and potassium

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