For some geneticists, aging is a genetically predetermined process; for others aging is caused by DNA duplication errors, which increase exponentially over time. Other scholars, on the other hand, believe that the aging process is linked to the responsiveness and efficiency of the immune system.
With the passage of time it has also been noticed how people age in different ways, coming to determine the concept of biological age and chronological age (registry). Based on this concept, two types of aging can be distinguished:
- Natural aging, due to gradual and physiological variations that progressively reduce the adaptability of the elderly (in this case biological age and chronological age coincide)
- Premature aging, due to genetic factors, unfavorable living conditions, strenuous jobs, food errors, alcohol abuse, etc. (in this case the biological age exceeds the chronological one).
Histological examinations have highlighted this degeneration to a set of involutional actions recognized as:
- Decreased weight and brain volume
- Variation of neurons
- Loss of dendrites
- Increased sulci and ventricles
- Presence of senile plaques
- Amyloid deposit
- Capillary alterations
- Presence of neurofibrillar degeneration.
Aging highlights this characteristic, mainly due to the hypotonicity of the muscles with consequent postural, joint and bone matrix density problems.
The respiratory system also suffers from muscular hypotonia due to a lower thoracic expansion with consequent reduction in respiratory volume, to the detriment of all tissues that require oxygen for their metabolic activity.
like strength, power and speed.Aging and strength
Grimby and Saltin showed that muscle strength, both static and dynamic, decreases slightly up to the age of 45 and from this period onwards it decreases by 5% for each decade so that, at age 65, the reduction in strength is about 25%. But be careful, these data concern only those who do not train; the same is not true for sportsmen and athletes.
The main cause of muscle decay in the elderly was determined by a quantitative and non-qualitative reduction in muscle mass. Other scholars have confirmed this theory by analyzing the number of fibers of the vastus lateralis in cadavers. They showed that over the course of life, from 20 to 80 years, there is a reduction of the muscle area of 40%.
Aging and speed
Regarding speed, in 1990 Klitgaard and collaborators demonstrated greater speed of movement in elderly people who practiced regular strength training with weights compared to sedentary subjects of the same age and compared to elderly swimmers and runners.
The authors related this reduction in speed to differences in distribution in various types of fibers and to the composition of myosin heavy chains. A higher content of slow myosin and tropomyosin was observed in a group of non-exercising elderly people, swimmers and runners, compared to those who had performed strength training. This cross-sectional study shows how regular strength training during aging can contribute to the maintenance of the morpho-functional characteristics of the fast muscle fibers.
In 1992 Skelton and collaborators showed how in the period of time ranging from 65 to 84 years, both in men and women, there is a decline in potency of about 3.5% for each year of age. The same authors in a more recent study showed that after 12 weeks of training there was an average increase of 13-30% in isometric strength of the quadriceps, hamstring and lower limb power.
The decrease in power is more evident after the age of 50 and affects men more than women: this is not due to changes in ATP or the cross section of the muscle, but rather to the alteration of other functions such as the maximum recruitment of motor units. and the degeneration of alpha-motor neurons.
: greater resistance due to increased mineralization and greater development in thickness. This process is favored by the tractions exerted during movements, which positively influence the relationship between osteocytes and osteoblasts;Cardio-circulatory system
Positive effects have been recorded regarding the increase in systolic output, the increase in cardiac output, the increase in cardiac and muscle capillaries, the reduction in resting heart rate and the reduction in recovery time after exertion.
Respiratory system
Strengthening of the diaphragm and other respiratory muscles, decrease in respiratory rate (breaths are deeper), increase in vital capacity.
Nervous system
Greater sensitivity on central and peripheral neurons with consequent improvement of the position of the body in space; increase in the conduction speed of the nerve impulse on the motor plate; decrease in reaction times; greater synchronization of muscle fibers.
