NAME: Kimberly Strother
WEIGHT: 124 pounds
WORKOUT ROUTINE: Runs between five and 12 miles every day and swims a mile at least once a week.
BODY COMPOSITION: 13 percent body fat with a body mass index (BMI) of 19.4. (For women in their 20s and 30s, having between 21 and 23 percent body fat is considered normal.)
AEROBIC CAPACITY: Scored a 44 (90th percentile for 30- to 39-year-old women) on her VO2 Max test, which measures the amount of oxygen that the heart and lungs can deliver to the muscles. Generally, the more fit you are, the more oxygen you can pump through your body when you exercise and the higher your VO2 Max number is.
MUSCULAR STRENGTH: 12 crunches and 37 push-ups consecutively before hitting a wall.
POWER: 14-inch vertical jump.
FLEXIBILITY: 19.3 inches on the sit-and-reach test (which measures how far you can stretch over straight legs).
THE VERDICT: No gym? No problem! Strother's cross-country running regimen — which has produced a bod of lean muscle mass, good flexibility, and solid upper-body strength — is the perfect (and free!) workout for building cardio strength and burning calories. Supplement jogs with core-strengthening moves like crunches or planks to ensure total body conditioning.