PHYSIOLOGY AND NUTRITION

We hypothesised that experienced runners would select a stride frequency closer to the optimum (minimal energy costs) than would novice runners. In addition, we expected that optimal stride frequency could simply be determined by monitoring heart rate without measuring oxygen consumption (VO sub(2)). Ten healthy males (mean plus or minus s: 24 plus or minus 2 year) with no running training experience and 10 trained runners of similar age ran at constant treadmill speed corresponding to 80% of individual ventilatory threshold. For two days, they ran at seven different stride frequencies (self-selected stride frequency plus or minus 18%) imposed by a metronome. Optimal stride frequency was based on the minimum of a second-order polynomial equation fitted through steady state VO sub(2) at each stride frequency. Running cost (mean plus or minus s) at optimal stride frequency was higher (P < 0.05) in novice (236 plus or minus 31 ml O sub(2).kg super(-1.)km super(-1)) than trained (189 plus or minus 13 ml O sub(2).kg super(-1.)km super(-1)) runners. Self-selected stride frequency (mean plus or minus s; strides super(.)min super(-1)) for novice (77.8 plus or minus 2.8) and trained runners (84.4 plus or minus 5.3) were lower (P < 0.05) than optimal stride frequency (respectively, 84.9 plus or minus 5.0 and 87.1 plus or minus 4.8). The difference between self-selected and optimal stride frequency was smaller (P < 0.05) for trained runners. In both the groups optimal stride frequency established with heart rate was not different (P > 0.3) from optimal stride frequency based on VO sub(2). In each group and despite limited variation between participants, optimal stride frequencies derived from VO sub(2) and heart rate were related (r > 0.7; P < 0.05). In conclusion, trained runners chose a stride frequency closer to the optimum for energy expenditure than novices. Heart rate could be used to establish optimal stride frequency.