Photo: 90-minute ride, one-hour run, 8:00 a.m., 28 degrees, Linn County, Iowa

Weekly activity log:
Swim: 5,100 yds (ytd 44,200 yds.)
Bike: 58 miles (ytd 617 mi.)
Run: 28 miles (ytd 253 mi.)

Photo: one-mile run, one-hour ride, 9:00 a.m., 32 degrees, Marion, Iowa

Weekly activity log:
Swim: 5,100 yds (ytd 39,100 yds.)
Bike: 59 miles (ytd 559 mi.)
Run: 26 miles (ytd 225 mi.)

The experiment begins.

Photo: one-hour run, one-hour ride, 9:00 a.m., 39 degrees, Marion, Iowa

Weekly activity log:
Swim: 5,100 yds (ytd 34,000 yds.)
Bike: 54 miles (ytd 500 mi.)
Run: 27 miles (ytd 199 mi.)

Drear, the fifth season.

Photo: 7-mile run, 8:00 a.m., 55 degrees, Scottsdale, Arizona

Weekly activity log:
Swim: 3,500 yds (ytd 28,900 yds.)
Bike: 49 miles (ytd 446 mi.)
Run: 24 miles (ytd 172 mi.)