The focus is on increasing the duration of exercise and introducing intervals to improve aerobic efficiency, improve the client's ability to utilize fat as a fuel source, and add variety to the exercise program.
The heart and lungs become stronger and better able to deliver oxygen to muscles.
There is a growth of more capillaries around the recruited muscle fibers, which enhances the delivery of oxygenated blood to the muscle fibers.
Muscles are better equipped to use oxygen because their cells contain more and larger mitochondria.
Above 55% VO2max, hormones slow glucose release from the liver and speed up the use of fat instead:
Lipolysis is modulated by catecholamines, the release of which increases with exercise intensity.
Determine HR at T1.
Increase workload at T1, then introduce low zone 2 intervals just above T1.
Progress low zone 2 intervals by increasing the time of the work interval and later decreasing the recovery interval time.
As client progresses, introduce intervals in the upper end of zone 2.
Many clients will stay in this phase for many years.
If a client has event-specific goals or is a fitness enthusiast looking for increased challenges and fitness gains, progress to phase 3.
The focus is on designing programs to help clients perform physical work at or near T2 for an extended period, which will result in improved endurance, speed, and power to meet primary performance goals.
Exercise at 60% to 65% VO2max helps in eliciting the maximal rate of fat oxidation.
Above T1 (65% VO2max), there is a shift toward the recruitment of more fast-twitch muscles which have metabolic characteristics that are geared toward glycolysis:
Fat oxidation decreases significantly due to carbohydrate utilization or lactic acid accumulation, or both.
Sustained exercise above T1 results in a reduction of glycogen stores, triggering the release of glucagon, cortisol and growth hormones, which function to stimulate the breakdown of lipid.
Determine HR at T2.
Programs will have the majority of cardiovascular training time in zone 1 (70-80%).
Interval and higher-intensity sessions will be very focused in zones 2 and 3, but will make up only a small amount of the total training time to allow for adaptation to the total training load (10-20%).
Many clients will never train in phase 3, as all of their non-competitive fitness goals can be achieved through phase 2 training.
Only clients who have very specific goals for increasing speed for short bursts at near-maximal efforts during endurance or athletic competitions will move on to phase 4.
The focus is on improving anaerobic power to improve phosphagen energy pathways and buffer large accumulations of blood lactate in order to improve speed for short bursts at near-maximal efforts during endurance or athletic competitions.
Increases muscular strength and non-aerobic power output (force-speed patterns that affect muscle activation and recruitment).
Increases glycolic enzyme activity (phosphagen, glucose and glycogen liberation of ATP).
Increases ATP-CP output (phosphocreatine recovery) to improve high-speed bursts of effort and high-resistance movements.
Improves lactate tolerance (hydrogen ion buffering).
Programs will have a similar distribution to phase 3 training times in zones 1, 2, and 3.
Phase 4 training will include very intense anaerobic-power intervals.
Clients will generally only work in phase 4 during specific training cycles prior to competition.
"Cardiorespiratory Training: Programming and Progressions." ACE Personal Trainer Manual: The Ultimate Resource for Fitness Professionals. San Diego, CA: American Council on Exercise, 2003. N. pag. Print.