The process to a certain degree can be slowed down, if the training is progressively increased, which is not unlimited. Other examples is where the 'design' is biased, such as a person starting exercise at later age, or a person comparing himself with relatively untrained people of lower age. Instead of many "I think that" and "in my experience", that have no foundation whatsoever and reflect a lack of understanding of how anatomy and physiology function, go find a basic exercise physiology book.
The process cannot be stopped and is irreversible, period. One of the basic principles of human life is that cells need to renewed in order to sustain life. Cells wear out, bare damaged by free radicals, bacteries, viruses, polutants, and toxines, and become dysfunctional over time. Of these cells, the brain does not have any regenerative function, and the cells do not divide unless in a brain tumor. The other cells in our body, at the DNA level require unwinding of the DNA and replication. The end strands of DNA are protected by so-called telomeres. The number of telomeres is set at birth, and by each cell division you lose telomeres, until finally you run out. They cannot be added and in the end are responsible for the fact that a human finally dies, and maximal age of humans is limited.
Genetics determine this process, which is mediated by nutrition, environment, training, and disease. The deterioration of certain physiological systems already starts after birth. Cardiovascular disease starts that early, but the efficiency of the system is compensated by growth, and the pump and supporting system becoming far larger, far more coordinated and efficient. After maximization of the system, deterioration occurs of which the steepness depends on lifestyle. Exercise can develope the system far more than in the average person, so that you start from higher, and neutralize some of the effects caused by the environment.
Bone health deteriorates because of deterioration in cardiovascular system and because a decrease in growth hormone production and androgens with age. In the male, both androgens produced by the adrenals and the tests undergo changes, as well as in amount, relationship, and in type of hormones being produced. For example, DHEA, DHEAS and Androstenedione undergo pretty sharp changes; same for dihydrotestosterone. In consequence, muscle integrity decreases as well as elasticity. The major mechanism of muscle growth after puberty is hypertrophy, though hyperplasia through formation of satellite cells can occur in those with excessive training; the latter option becomes erased with age.
In the female the process is even more abrupt with the occurrence of menopause. Menopause results in an enormous decrease of estrogens, particularly estradiol, which results in estrone becoming the leading hormone. The decrease in estradiol leads to a sharp increase in bone loss and muscle elasticity and also negatively affects the skin. It makes reproduction impossible through natural ways, although with specific treatment the potential can be extended. The decrease in estradiol neutralizes the gender-protective effect of the female with regard to her cardiovascular system; females have far less cardiovascular disease than males, but that is because of their situation before menopause. After menopause they lose the protection.
Males can retain substantial static strength, but dynamic and explosive strength deteriorate irrespective of whether your train or not, though trainining reduces the slope of the decrease.
Because of the decrease in muscle elasticity and volume, and deterioration of the cardiovascular system at the level of the capillaries, muscles become more prone to both acute and chronic injury; underlying problems such as diabetes-II or its prestage, the metabolic syndrome, also contribute. On top of that, recovery from injury decreases, both in time and in quality, as regenerative possibilities decrease, as cell division decreases. The rate of mistakes in cell division increases. This takes place at every level, even at the scalp with progressive hairloss. Sure we all know a case of a person who was past his 90's and still had a lot of hair, but even in that case he or she will have had more at a younger age ... except for on your body. The changes in DHEA, its sulphate, as well as in DHT affect body hair, with males losing hair on their scalp but often increasing hair on the back, chest and ears ...
Pigment is lost over time, resulting in skin pigmentation. In the female, the loss of estradiol also leads to a thinning of the sking particularly in the genital area, which can make intercourse more problematic over time.
It isn't much better with sexual function in the male. Enjoy your erections while you still can. Add a couple of decades, and their frequency will become a unique event rather than routine; Don't make yourself any illusions over their quality either. Blood circulation at the capillary level, nervous system, and falling androgens are responsible for it. spam will now provide a help and will appear on the nightstand of most of us after a certain age.
The nervous system's abilities decrease too. Eye sight and hearing decrease. A person loses his ability for hearing the highest frequences even pretty early in life, and children hear tones that adults don't do. Sure, this parti isn't initially very relevant for judo, but it is when it comes to injury to any of those structures. The one thing that is little affected is the 'memory of the nerves' meaning, even at very old age, people may be able to do exceptional skills. I saw Margot Fontaine, Rudolf Nurejev's partner, dance ballet in her 70s. Though she had lost explosiveness, some grace, and some flexibility, her exceptional skills still allowed her to do thngs that most young dancers can't. However, when you comparted her to herself ... the deterioration was obvious comparted to her abilities 40 years earlier.
The progression of age cannot be stopped, not by nutrition, not by training, not by drugs. The slope can be slowed down, and even reversed for some time.
If at age 40 you decided to start taking anabolic steroids and growth hormone, you may indeed temporarilly increase you volume of muscles beyond what you ever had as a youngster as a mere effect of training.