THE PHYSIOLOGY OF ALTITUDE SIMULATION
The benefits of altitude training are derived from the body's adaptive physiological responses to altitude acclimatization. As altitude increases, the partial pressure of oxygen decreases in proportion to the reduction in the atmospheric barometric pressure and the rate of oxygen transfer from the lungs to the blood falls. This results in proportionately less oxygen being delivered to the tissues of the body. In response to reduced tissue oxygenation, a variety of physiological adaptations occur that collectively result in facilitated oxygen delivery to the tissues. Altitude acclimatization results in the following physiological adaptations:
Increased respiratory efficiency via:
- increased alveolar ventilation rates increased rate of oxygen uptake in lungs
- increased tidal volume resulting in increased capacity for oxygen exchange in lungs
- increased V02max increased oxygen consumption resulting in improved aerobic power output
- increased respiratory muscle strength improved respiratory efficiency
Increased respiratory efficiency via:
- increased circulating red blood cell mass increased oxygen transport capacity
- increased concentration of 2,3-DPG in red blood cells facilitates release of oxygen from the red blood cells to the skeletal muscles
- rightward shift in the oxy hemoglobin dissociation curve increased affinity for hemoglobin to release oxygen to the skeletal muscles
- increased capillary density in skeletal muscles allowed greater propensity for oxygen delivery to muscles and transport of lactate away from muscles
- improved theological (de formability) properties of red blood cells improved blood flow through micro-capillary beds in muscles
- increased oxidative enzyme capacity in the muscles improved aerobic capacity and higher anaerobic threshold
Improved aerobic power and endurance as a result of:
- increased V02max
- change in substrate utilization from muscle glycogen to fat and carbohydrate metabolism prolonged aerobic energy cycles
- increased blood buffering capacity resulted in lower lactate levels and higher aerobic thresholds
- decreased lactate formation due to reduced glycogen substrate utilization
- increased mitochondria concentration of skeletal muscle increased aerobic capacity
- increased oxidative enzyme capacity of skeletal muscle prolonged aerobic capacity and higher anaerobic thresholds
Improved cardiovascular fitness through:
- lowered peak exertional heart rates allows for greater cardiac reserves
- improved diastolic filling of heart chambers allows for greater cardiac efficiency
- increased stroke volume and total cardiac output allows for greater cardiac efficiency
- improved myocardial energy utilization allows for greater cardiac efficiency and endurance
- greater cardiac reserve allows for improved endurance
Faster and more complete recovery after high intensity exercise
- more efficient training reduced number of prep days
- faster recovery following high intensity workouts
- shorter prep times
- lower incidence of fatigue-related training injuries because of more effective training and fewer number of training cycles
When combined with targeted conditioning programs the cumulative effect of these physiological adaptations to altitude are that acclimatized horses are able to perform at maximum aerobic power outputs for longer periods of time, and are able to recover from these intense efforts more quickly. This translates into more efficient training with reduced likelihood of incurring stress related injuries associated with pre-race training.
Jan. 2008 Willie Mullins , Ireland's leading National Hunt and Steeplechase Trainer, Adopts Altitude Training.
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