This was a research project that was conducted by a visiting scholar and his time for departure came earlier than the study completion.

The purpose of this study to determine if older adults who are healthy and physically active (i.e., Masters athletes) demonstrate slower rates of recovery from unaccustomed strenuous exercise of downhill running than younger peers.

There is a well-conceived notion that the recovery from strenuous exercise gets slower as individuals get older in age. Studies using animal models have demonstrated that stretching of electrically-activated skeletal muscle to mimic eccentric muscle contractions results in a greater decline and slower recovery in muscular force in old mice than in young mice. Similarly, in human studies using sedentary adults, age has been associated with a slower rate of recovery from a series of eccentric contractions. However, the process of aging is often confounded by coexisting diseases and gradual sedentary lifestyles that progress with advancing aging. Could older adults who are apparently healthy and habitually exercising demonstrate slower rates of recovery from strenuous exercise? In a small-scale study, recreationally-active middle-aged adults did not display a slower recovery from unaccustomed eccentric exercise than young adults. Masters athletes are an effective experimental model to address this question as extrinsic factors (e.g., deconditioning, chronic degenerative diseases) that often confound the intrinsic aging process can be minimized in this population. As no study has been conducted in Masters athletes, it is unknown if Masters athletes would experience slower rates of recovery similar to their sedentary peers.

With this information as background, the general aim of the proposed study is to determine if older adults who are healthy and physically active demonstrate slower rates of recovery from unaccustomed strenuous exercise of downhill running than younger peers. In an attempt to properly determine the influence of aging and regular physical activity, 4 groups of apparently healthy adults, including young sedentary, young trained, older sedentary, and older trained adults, will be studied.

A total of 60 apparently healthy men and women will serve as subjects. Half will be young [18-40-year-old (n=30)] and the other half older [50-80-year-old (n=30)]. After the screening and familiarization, investigators will ask participants to visit the laboratory four times (four consecutive days) to perform downhill running and to test physiological measurements (muscular strength, pain scale, range of motion, arterial stiffness and blood pressure and blood creatinine and myoglobin concentrations).

Inclusion Criteria:

• Sedentary (exercise < 1 time/week) or well-trained individuals (exercise ≧ 2 times/week)
• Ages 18-39 and 50-80 years
• Individuals who can safely exercise

Exclusion Criteria:

• Individuals who reports "Symptoms or Signs Suggestive of Disease" on the Health Research Questionnaire (heart and respiratory problems, dizziness and ankle edema).
• Individuals who report substance abuse within the last 6 months (elicit drugs, alcohol)
• Smokers

We were not able to recruit older sedentary partcipants so this group was dropped from the data analyses.

Each participant was followed for a span of 4 days. After the downhill running protocol, various markers of muscle damage and muscular strength were obtained 24 hours post (the third visit), 48 hours post (the forth visit) and 72 hours post (the fifth visit).

This is an acute exercise study. No adverse events were reported.