Twenty well-trained runners (˙VO2max 4.6 ± 0.5 L·min-1) were age and ability matched and assigned to either a cross training (CT) or run only group (RT). All subjects maintained normal running distance and intensity for 6 wk and reported for three additional training sessions per week. These workouts were performed outdoors on a 400-m track or measured road course (RT) or on a bicycle ergometer (CT). The sessions were as follows: (work·rest-1 ratio = 1): 5 × 5 min at >95% ˙VO2max/peak (Monday), 50-60 min at 70%˙VO2max/peak (Wednesday), and 3 × 2.5 min at >105%˙VO2max/peak, plus 6 × 1.25 min at >115%˙VO2max/peak (Friday). Subjects were tested before (PRE), after 3 wk (MID), and after 6 wk (POST) of intensified training. Blood samples were obtained from RT, CT, and ten controls (CON) at each time point (0600 h). Runners also completed a 10-min submaximal run at the same absolute intensity(velocity to elicit 75% of initial ˙VO2max) during which heart rate, RPE, and ˙VO2 were measured. Each runner then completed a simulated 5-km race (time trial) on a treadmill. Total testosterone (TT), free testosterone (FT), cortisol (C), and creatine kinase activity (CK) were determined. Running economy was similar between RT and CT; however, RPE decreased significantly at MID and POST compared with that at PRE (P< 0.05; time effect). There were no significant differences among groups for TT, FT, or CK, but C was significantly lower in CON than in RT and CT. Performance was significantly faster (P < 0.05; time effect) in the 5-km race at MID (1076.1 ± 81.4 s) and POST (1068.6 ± 83.9) compared with PRE (1096.6 ± 79.5) but was not different between CT and RT. In conclusion, RT and CT responded similarly to 6 wk of increased training, and both groups improved 5-km performance to a similar extent.
Wastl Human Performance Laboratory, Purdue University, West Lafayette, IN 47907; Exercise Physiology Laboratories, University of Toledo; and Northwest Ohio Center for Sports Medicine, The Toledo Hospital, Toledo OH 43606
Submitted for publication April 1997.
Accepted for publication August 1997.
The authors would like to acknowledge the assistance of Cindy Hodgson, James Fritz, and Laura Lewis. We would also like to thank our subjects for their dedication to this investigation. This study funded in part by a United States Olympic Committee Sports Science grant.
Address for correspondence: Michael G. Flynn, Ph.D., Purdue University, Wastl Human Performance Laboratory, Department of HKLS, Lambert 107C, West Lafayette, IN 47907. E-mail: firstname.lastname@example.org.