7 - Domains of Exercise

Power vs Duration

1. Opposite to MLSS (low to high intensity)

2. Higher to lower power output

3. Reach power where athlete can go on indefinitely

4. Asymptote curve

Critical Power

Highest power output that can be maintained over time

1. Homeostasis - Steady state in:

• VO2

• BLa concentration

• HR

• Muscle cell physiology

• Fatigue products

W’ (W’ Prime)

1. W’ can be increased if supplemented with creatine

2. Fuels anaerobic battery with more glycogen as creatine breaks down more PCr

W’ and CP

1. 100m sprinters - anaerobic metabolism (W’)

2. Cycling - maintain effort over time (CP)

CP: Practical Applications

1. Characterisation of Athletes - highest sustainable power, fittest athlete?

2. Power Zones - training prescription, steady state training level

3. Athlete tracking over season/training cycle

Domains of Exercise

1. Low intensity domain

2. Moderate domain

3. Severe domain (Interval)

Low Intensity Domain

Below the LT

1. BLa < ~2 mmol/L;

2. < 70% VO2max

3. Steady state in < 3min

Moderate domain

Between the LT and MLSS/CP

1. BLa elevated but stable at 2-8 mmol/L

2. 70-90& VO2max

3. Steady state delayed

Severe Domain (Interval)

Above the MLSS/CP

1. BLa > 2-8 mmol/L

2. 70-90% VO2max

3. Steady state not attainable

Exercising at/above CP

O2 Uptake Kinetics

How much o2 per breath

1. Breath by breath analysis of o2 uptake

2. Oxygen uptake kinetics differ across the exercise intensity range and can help to define domains of exercise

O2 Uptake Kinetics: 3 Distinct Phases

Procedure

1. track o2 uptake

Findings

1. O2 uptake goes up

2. Steep increase before levelling off

3. Slight increase of o2 uptake

o2 Uptake Kinetics Continued

• high demand for o2 in muscles when starting exercise but bit of a lag

• smooth rise, quick o2 rise to meet demands

1. Phase 1 - cardiodynamic component

2. Phase 2 - Primary component

3. Phase 3 - Slow component

Phase 1: cardiodynamic component (20s)

Transmit time of blood between the exercising muscle and lungs

Phase 2: Primary Component (2-3 min)

Pulmonary V O2 rises in a mono-exponential fashion to meet the muscle oxygen demand

Phase 3: Slow Component (>3 min)

Slow rise in VO2

1. Only observed at high power outputs, as a growing number of fast motor units (Type II fibres) have to be recruited

• More force can be generated

• Not as efficient and fatigue resistant as Type I fibres - more o2 needed per unit of force

2. Reached strenuous watts so activate T2 - not efficient, fatigue, require more o2 than T2

Moderate Exercise (Below LT)

1. Mainly T1

2. Below/At CP = Steady state

3. Phase 2 - mono-exponential increase in VO2

4. Phase 3 - none

Heavy Exercise (between LT and CP)

1. Delayed steady state due to T2

2. Phase 2 - mono-exponential increase in VO2

3. Phase 3 - slow component

Severe Exercise (Above CP)

• Doesn’t stabilise - reach VO2 max

1. Phase II - mono-exponential increase in VO2

2. Phase III - “slow component” never stabilises and continues until exercise has to be terminated or V is attained

Practical Implications in the Lab

1. Steady state exercise above LT (slow component)

2. Check douglas bag over time

Summary