Why physical fitness
To achieve a good physical performance we need to develop optimal interaction between, and strengthening of, these systems: lungs, heart, muscles.
LUNGS
Their job is to oxygenate the blood.
During exertion we greatly increase ventilation, that is, the number of breaths and the volumes of air breathed in. In truth it has been shown that the blood circulating around the alveoli is oxygenated very quickly; this means that the consumption of the oxygen in the blood is not in fact the limiting factor responsible for so-called breathlessness.
HEART
It is the heart that decides what level of exertion we will reach. It receives oxygenated blood from the lungs and pumps it to the muscles all over the body.
The amount of blood pumped over time, which is what really distinguishes the sportsperson from the sedentary person, is called cardiac output. It is determined by the heart rate and by how much blood is ejected in one beat (stroke volume). The theoretical maximum heart rate (220 - age) is fixed; during exertion we raise our heart rate up to a certain limit. The real aim of training is to increase the stroke volume. With training the heart, for biochemical reasons, becomes more used to higher performance: it grows larger and thicker (curiously, this is the same thing that happens in heart patients, but after years of doubts and hypotheses cardiologists have finally become convinced that, although not on the surface, the hypertrophy of the heart patient is profoundly different from that of the so-called “athlete's heart”).
If we press the accelerator of our sporting activity we reach a point called the “anaerobic threshold”, at which we reach about 95% of the theoretical maximum heart rate, where our heart can no longer keep up with us. The output of pumped blood stays constant, but the muscle no longer receives oxygenated blood, so to produce energy it turns to an anaerobic metabolism (without oxygen): lactic acid is formed, which is the substance that brings on the feeling of fatigue.
The mountaineer is not a runner or a cyclist who must know how to get just under the threshold and never go over it; it is enough to know that if we climb too fast in the mountains we risk going over that threshold, which then inevitably leads to muscular exhaustion. In our training we must know that cardiac effort is necessary. Trainers, in fact, talk about “training heart rate” precisely to indicate the rate that must be reached and maintained during a training session, and which varies according to the results we set out to achieve; in short, a fast heartbeat during training is normal, indeed it has to be there.
MUSCLES
Muscle changes its composition during training.
For mountaineering you need red fibres (suited to endurance), which are fibres rich in myoglobin (red), a molecule that greedily consumes oxygen, taking it from the blood. Trained muscle, apart from the myriad biochemical adjustments, is muscle that becomes richer in mitochondria, the power stations of the cell. A trained muscle is richer in myoglobin and mitochondria, and so is more efficient at receiving oxygen and getting energy from it for the contraction of the fibres.
LENGTH OF TRAINING
At the start of a training session the muscle uses the circulating energy stores such as (phosphocreatine). As the exertion continues the muscle starts to use its internal glucose (up to 15 min). Beyond a certain time the muscle starts to depend entirely on components such as glucose produced by the metabolism of carbohydrates and proteins inside the liver, etc. To train the heart it is, therefore, advisable to go beyond a certain number of minutes: over 20 minutes if you want to train the heart, over 40 if you want to lose a substantial amount of fat.
N.B.: it is true that fats are burned together with sugars by the muscle all the time, but after 40' the circulating sugars drop (the liver's stores run out) and the muscles throw themselves into burning fats only. These are metabolic changes, when we get our second wind (presumably in the switch from using intramuscular glucose to glucose from the bloodstream) or if we feel steps when we run.
Good training, in the end, must be:
- fairly hard but not above 120-150 heartbeats per minute
- longer than 30 and at least 45 minutes for the mountaineer
- and, something that can never be stressed enough, consistent. Consistency (2-3 times a week minimum) is the winning weapon.
Must our heart get used to working at high revs for many hours, or not? And learn to perfuse with oxygen, absorbed from the thin air of high altitude, our muscles, which, contracting rhythmically and continuously, try to carry us to the summit?
The basics are explained in the first part of the physiology of exertion.