There are certain immutable truths concerning the performance of the human body as it ages, particularly as the athlete reaches age 40. The physical peak for most humans, in most sports, is between 25 and 35 years of age; during this peak period, the well-conditioned athlete can create a confluence of muscular strength, peak cardiovascular and oxygen transport, speed and reaction time, and mental capabilities (including the ability to deal with competitive pressures), all bound together by a desire to succeed.
The heart, as with every other human muscle, will gradually lose efficiency and power over time. A typical rule-of-thumb calculation to confirm the physiological fact of reduced heart capacity is that utilized by the American College of Sport Medicine: in males, 220—age = maximum heart rate (beats/minute); in females, 226—age = maximum heart rate.
Athletes cannot train at a maximum heart rate for extended periods; the usual target training rate for a fit, healthy athlete will be approximately 80% of the maximum rate. It is for this reason that, as an athlete ages, the heart's ability to work is reduced. The rule of thumb is not an accurate predictor in every case; extensive research in the triathlon and distance sports communities demonstrates that maximum heart rate may vary significantly between athletes of equal abilities.
In sports such as tennis, golf, and baseball, or at specific team sport positions, such as ice hockey goaltender or the American football quarterback, the mental training and experience components are of greater importance to athletic performance. With more training and experience, an athlete can remain competitive for a longer period. The competitions sanctioned by both the Professional Golfers Association (PGA) and its European counterpart are evidence of ability of older athletes to compete, as the so-called seniors tour in each organization has a minimum age limit of 50 years or older. Jack Nicklaus won the prestigious Masters championship in 1986 at age 46; there are individual tournament winners on the PGA tour each season who are over 40 years of age.
However, for sports in which strength (both muscular strength and bone density), oxygen uptake, and cardiovascular efficiency are vital to success, the aging process may be slowed, though never halted or reversed. Since 1950, the average age of world champion distance runners in the 3-mi (5,000 m) races through to the 26-mi marathons (42.2 km) ranges between 28 and 32 years of age. From this peak of ability, runners will continue to perform at levels close to their personal best into their late 30s and early 40s; performance then declines at a rate of approximately 2% per year through age 80. Swimming, which like running places a premium on cardiovascular strength, shows a similar regression from best performance times as an athlete ages. The success of female swimmers at early ages (there have been numerous Olympic gold medals and world records set by female swimmers under the age of 20) is related to both the earlier physical maturation of female athletes, as well as the physical dynamics of the female swimmer in the water; the progressive decline in the performance of female swimmers due to age is similar to that of male swimmers.
Consistent with these physiological constants, the oldest gold medalist in the history of all Olympic track and field events was Patrick McDonald, an American hammer thrower, who won the 1920 competition at age 42. The oldest Olympic track champion in the 1,500-m race was 31-year-old Albert Hill of Kenya, in 1988. Female competitors have the added variables of prospective pregnancy and child-rearing, which will remove the athlete from intense training and competition for an often-significant period. Childbirth may also change the physical shape of a female athlete, particularly in a widening of the pelvis, which may impact subsequent athletic performance.
In addition to the generalized impact that age presents on injury and the body's ability to recover, age is a significant reducing factor in the assessment of reaction time in athletes. "Reaction time" is the expression used to describe a complex sequence of related actions when the body is called upon to respond to a stimulus. Every competitive sport involves a reaction time; examples include the cricket batsman deciding whether to swing at a particular ball, an ice hockey goalie moving to stop a shot, or a sprinter exploding from the starters' block. The speed with which the athlete reacts is a combination of their ability to recognize the required response, the choices available to them, the type of reaction required, practice in responding to this situation, fatigue, and the age of the athlete.