Table 1.
Descriptive statistics for weight and body composition at different ages and in response to exercise
| Trait | Whole Population |
Females Only |
Males Only |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| n | Mean | SD | Range | n | Mean | SD | Range | n | Mean | SD | Range | |
| ∼4 wk of age | ||||||||||||
| Body mass, g | 796 | 20.6 | 2.9 | 12.2–29.0 | 395 | 18.7 | 1.8 | 13.6–23.9 | 401 | 22.4 | 2.6 | 12.2–29.0 |
| % Fat | 796 | 14.2 | 3.6 | 7.2–29.8 | 395 | 16.3 | 3.4 | 9.4–29.8 | 401 | 12.1 | 2.4 | 7.2–22.4 |
| % Lean | 796 | 82.5 | 3.9 | 66.8–91.1 | 395 | 80.7 | 3.9 | 66.8–91.1 | 401 | 84.3 | 2.9 | 68.4–90.6 |
| ∼6 wk of age | ||||||||||||
| Body mass, g | 793 | 24.1 | 3.9 | 15.0–35.4 | 395 | 21.1 | 2.1 | 15.6–27.0 | 398 | 27.2 | 2.7 | 15.0–35.4 |
| % Fat | 793 | 14.4 | 4.4 | 4.0–30.4 | 395 | 15.8 | 4.8 | 5.6–30.4 | 398 | 12.9 | 3.4 | 4.0–29.2 |
| % Lean | 792 | 79.9 | 4.3 | 62.8–97.0 | 395 | 79.2 | 4.8 | 62.8–90.1 | 397 | 80.5 | 3.5 | 65.6–97.0 |
| ∼8 wk of age | ||||||||||||
| Body mass, g | 797 | 26.0 | 4.7 | 16.3–39.3 | 395 | 22.2 | 2.4 | 16.3–31.4 | 402 | 29.8 | 3.1 | 17.1–39.3 |
| % Fat | 797 | 14.4 | 4.4 | 4.6–34.1 | 395 | 15.1 | 4.7 | 6.0–30.0 | 402 | 13.6 | 3.9 | 4.6–34.1 |
| % Lean | 797 | 78.7 | 4.3 | 59.9–97.2 | 395 | 78.8 | 4.7 | 63.3–97.2 | 402 | 78.6 | 3.9 | 59.9–88.3 |
| Post exercise | ||||||||||||
| Body mass, g | 797 | 24.5 | 3.9 | 14.1–34.9 | 395 | 21.2 | 1.8 | 14.1–27.3 | 402 | 27.8 | 2.4 | 18.3–34.9 |
| % Fat | 797 | 9.4 | 3.0 | 3.7–23.3 | 395 | 10.3 | 3.2 | 4.4–23.3 | 402 | 8.5 | 2.5 | 3.7–22.4 |
| % Lean | 797 | 83.9 | 3.2 | 70.5–91.3 | 395 | 84.0 | 3.6 | 71.6–91.2 | 402 | 83.8 | 2.9 | 70.5–91.3 |
| % Change in body mass | 797 | −5.3 | 5.2 | −22.9–23.6 | 395 | −4.4 | 5.7 | −22.9–23.6 | 402 | −6.3 | 4.5 | −18.1–10.0 |
| % Change in % fat | 797 | −32.2 | 19.4 | −69.1–88.3 | 395 | −29.1 | 20.4 | −69.1–58.0 | 402 | −35.3 | 17.7 | −66.6–88.3 |
| % Change in % lean | 797 | 6.8 | 5.2 | −17.2–26.3 | 395 | 6.8 | 5.9 | −17.2–26.3 | 402 | 6.8 | 4.4 | −9.7–20.5 |
| Food intake, g | 798 | 23.6 | 3.6 | 11.8–35.9 | 395 | 22.6 | 3.4 | 11.8–30.3 | 403 | 24.6 | 3.6 | 15.6–35.9 |
| Food intake/mass | 795 | 1.0 | 0.2 | 0.5–1.4 | 394 | 1.1 | 0.2 | 0.6–1.4 | 401 | 0.9 | 0.1 | 0.5–1.3 |
Beginning at 8 wk of age body composition measurements were taken immediately before (Pre) and after (Post) 6 days of wheel access. Food intake was quantified as the amount eaten over the entire 6-day access to running wheels, and values are presented as raw values and per gram of body mass [(Pre wheel access + Post wheel access)/2]. Percent body fat (and lean) was calculated as (fat mass/body mass) × 100. Percent change variables were calculated as [(Post − Pre)/Pre] × 100.