Relationship of sex, exercise, and growth rate of life span in the Wistar rat: a multivariate correlational approach.

Measures of body weight change were calculated and examined in relation to the life span of 68 male and 71 female Wistar rats that were maintained either in wheel-cage units of cages without wheels. The analysis revealed the following: (a) sex and wheel exercise accounted for nearly one third of the obtained variation in life span; (b) growth rate, defined as the ratio of peak body weight to growth duration, accounted for over 15% of the variance in life span unattributable to sex and exercise; (c) measures of body weight gain early in the developmental span were virtually unrelated to life span; (d) beyond 9 months of age, measures of body weight gain showed a significant positive relationship with life span. Thus, there was no evidence of a negative relationship between life span and body weight gain during early life.