Last week we looked at energy systems as a whole and aimed to explain how the body produces energy to meet the demands of a particular environment… (like running a red light and being chased by police.)
This week we are taking a closer look at the Alactic Phosphocreatine energy system or ATP-PC and the activities that depend on it. A little off topic but very relative, the sympathetic nervous system will use this as its prime energy source during ‘fight or flight’. The ATP-PC system provides short explosive explosive bursts of power that are most activated by a survival instinct.
The ATP-PC system does not require oxygen therefore it is anaerobic, its responsible for providing energy to the highest threshold muscle fibres, capable of producing the greates amount of force. Although trainable or energy systems are genetic the ATP-PC system seems to be the least adaptable.
As we now know the high power output of the ATP-PC system cannot be maintained for long periods of time, anywhere between 6-15s. The high energy demands and shorter work times indicate how quickly Adenosine Triphosphate (ATP) depletes in the muscles. Because of this longer rest periods are required to allow for repeated efforts. We can observe this in sports like Olympic weightlifting where athletes will take anywhere from 5 minutes between lifts, the nervous system as well as the muscular system needs time to recover.
Energy Production :
(Phosphocreatine + ADP) ⇒ (Creatine Phosphokinase) ⇒ (Creatine + ATP)
To make ATP, phosphocreatine transfers a phosphate molecule to ADP. The newly-formed ATP is now available to be used for muscle contraction. This is part of a process known as Glycolysis.
Approximately ATP stores last in the muscle for 2-4s. The resynthesis of ATP from Creatine Phosphate will continue for approximately 4-6 until CP stores in the muscle are depleted. This gives us anywhere between 4-10 of ATP production.
Training the ATP-PC system:
Can be achieved by using short duration high power demand activities followed by longer rest periods. E.g 3-10s Work with 1-3+ minutes rest. The longer rest periods is to allow stores to recover and the nervous system time to recharge.
Recovery time is vital, a study by Holmyard et al. 1994 took a group of subjects who performed 6s sprints with recovery intervals between 15-180 seconds. The study found that there is an 81% recovery in peak power output with a 1 minute rest period compared to a 92% recovery of peak power output with a 3 minute rest period.
The ATP-PC system does not produce lactate, however the anaerobic lactic system is at work at the same time. The ATP-PC system is one that leads to the highest rate of fatigue due to its effects on the nervous system, therefore it should be used wisely in a training programme.To increase the levels of ATP-PC fitness one must increase the size and contractile ability of these muscle fibres.
Example Sessions to Train ATP-PC system:
Assault Bike: 15 x 10s Max Effort Every 2 Minutes.
Running: 15 × 60 metres with 60 seconds recovery.