Blog 4 (Endurance part 1)
by Steve Dunning
Posted: 4th Jun 2011
Introduction to Endurance Training
What is Endurance?
Endurance is the ability to endure sub maximal climbing. At one end of the spectrum it encompasses a sub 2 minute redpoint of a 10m sport route, at the other end a 50m trad onsight which could easily take an hour or more. The type of endurance needed for these 2 ascents is very different and consequently will need a different training approach.
Endurance is typically measured by the length of a climb, or by how many moves it has, but a more accurate measure for climbing is time: a 20m route will have the same number of moves whether you climb it in 4mins on a well rehearsed redpoint or >20mins on an onsight, the type of endurance needed will be very different however, in particular the energy sources the muscles utilise.
Energy for muscle contraction comes from Adenosine Tri-Phosphate (ATP) which is stored in small amounts in the muscle. ATP stores provide energy for only a few seconds of effort, for continued effort ATP must be re synthesised by one of three methods:
- The ATP-PCr System.
This relies on Phospho-Creatine, which is stored in the muscle. This can provide energy for a few seconds of intense effort.
Once depleted it takes ~30seconds to return to 50% of resting levels, with full restoration taking up to 2 minutes.
- The Anaerobic Glycolytic System.
For simplicity we will refer to this as the Anaerobic System as in this context it re synthesises ATP from Glycogen (a form of stored glucose in the muscle) in the absence of Oxygen (anaerobic = without oxygen, aerobic = with oxygen). This system provides energy for only a couple of minutes of intense effort, and has the side effects of creating waste products, and making the blood acidic which as well as being uncomfortable impairs muscle function and the production of ATP.
Half the amount of waste is cleared from the muscle in 15-25 minutes, with full clearance taking ~ 1 hour. In these articles the combination of waste, metabolic by-products and acidosis will be referred to for convenience as Lactic Acid (LA), although the actual role of LA is actually more complicated as it is also a fuel.
- The Oxidative Glycolytic System.
This is also known as the Aerobic System as ATP production takes place in the presence of oxygen. In this system ATP is produced within special cell organelles within the muscle called mitochondria from glycogen, fats, and proteins. The Aerobic System can provide muscle energy for hours, until ultimately muscle and liver glycogen stores are depleted.
In climbing all 3 systems contribute in different proportions depending on the nature of the route. A short sport redpoint will rely heavily on anaerobic energy production, a long trad onsight will be mostly aerobic. Things are complicated further because routes are often not uniform in difficulty; there may be short hard sections where the emphasis is anaerobic, separated by rests or easier climbing where having a well trained aerobic system is key.
Aerobic Vs Anaerobic Training.
When a muscle contracts it starts to squeeze shut the capillaries (the tiny blood vessels) that supply blood to the muscle and carry waste products away. Blood, as well as carrying various nutrients, supplies the muscle with oxygen. The harder the contraction, the more the capillaries will be occluded (squeezed shut) and the greater the reliance on anaerobic energy production with all its undesirable side effects.
Training the aerobic system will result in increases of: the size and number of capillaries, the number, size and efficiency of mitochondria, myoglobin content (ability to store oxygen in the muscle), the size of SO fibres, and oxidative enzyme activity.
Anaerobic training will increase: tolerance to acidosis, acid buffering capacity, and ATP-PCr and glycolytic enzyme activity.
Because training is unlikely to be 100% aerobic or anaerobic the actual adaptations will be a mixture of both, depending on how aerobic/anaerobic the training is.
The more the training resembles the anaerobic/aerobic profile of the type of climbing you do the more beneficial it will be. The more time you have available to train, or the more varied the climbing you?re training for, the more you will benefit from training aerobic and anaerobic adaptations separately.