In-shoe orthotics used in the treatment of a number of running injuries (see post 12, p. 449) will increase shoe weight and therefore might influence running economy adversely. In the study of Burkett et al. (1985), the addition of an 80-g orthotic device to each running shoe increased the oxygen cost of running by about 1.4%; smaller increases (0.4 to 1.1%) were reported by Berg and Sady (1985). These studies indicate that the added weight of the orthotic device decreases running economy in direct proportion to its weight.
Work at the Nike Sport Research Laboratory has shown that the air pocket used in the midsole of different Nike Air running shoes reduces the oxygen cost of running by 1.6 to 2.8% at a running speed of 16 km/hr (Frederick etal, 1983; Stripe, 1982a). If these savings directly translate into equivalent improvements in racing performance, then they are significant, at least for the top athletes. Further research is needed to study this possibility.
Photo Gallery of Yoga Poses For Insomnia
Click to on Photo for Next Yoga Poses For Insomnia Images
Obviously, prevailing conditions such as running surface, gradient, and wind speed and direction will have considerable effect on a runner’s economy. The influence of the running surface on the oxygen cost of running was first noted by Passmore and Dumin (1955), who reported that the oxygen cost of walking across a plowed field was 35 % greater than the cost of walking at the same speed on a smooth, firm surface. Running on sand has a similar effect (Wyngand et al, 1985). More recently McMahon and Greene (1979; see also post 11) suggested that optimizing the spring constant of a running track will likely improve running performance and running economy (and reduce injury risk).
One of the first scientists to study the influence of wind speed on running performance was the great British physiologist Dr. Griffiths Pugh, whose work on the effects of altitude on athletic performance is among the classic contributions on that topic (Pugh, 1958, 1967a). Pugh performed four different studies designed to measure how wind speed and the gradient of the running surface influence the oxygen cost of running (Pugh, 1970a, 1970b). His studies showed that the extra cost of running into a facing wind increased as the square of the wind speed. Thus the oxygen cost of running into a 66-km/hr head wind increases by 30 ml/kg/min. Similarly, running up an 8% incline increases the oxygen cost of running by about 20 ml/kg/min.
Exercises 2.2 indicates that for each 1 km/hr increase in running speed, the oxygen cost increases about 4 ml/kg/min. Thus, the increased oxygen cost of 30 ml/kg/min caused by running into a 66-km/hr wind would cause a 7.5-km/hr reduction in running speed. Similarly, an 8% gradient would slow the runner by