Running economy of elite surf iron men and male runners, on soft dry beachsand and grass

The primary aim of this study was to measure the energetics of six elite su rf iron men (who participate in regular sand running training), performing steady-state running trials on grass in shoes at 8. 11 and 14 km(.)h(-1), a nd on sand bare foot and in shoes, at both 8 and I I km(.)h(-1). The net to tal energy cost (EC, J(.)kg(-1.)m(-1)) was determined from the net steady-s tate oxygen consumption and respiratory exchange ratio (net aerobic EC) plu s net lactate accumulation (net anaerobic EC). For the sand barefoot and sa nd in shoes running trials at 8 and 11 km(.)h(-1), net aerobic EC and total net EC (but not anaerobic EC) were significantly greater (P < 0.001) than the grass running trial values. No differences (P > 0.05) existed between t he sand barefoot and sand in shoes trials. These measures were compared wit h data obtained from eight well-trained male recreational runners who perfo rmed the same protocol in a previous study. but who were not accustomed to running on sand. Comparisons of net aerobic EC between the two groups for t he surface conditions were not significantly different (P > 0.05). For net anaerobic EC, the iron man values were significantly less (P < 0.02) than t he recreational runner Values. For net total EC. the iron man values were l ess than the recreational runner values. but the differences were only sign ificant when both groups ran on sand barefoot (P < 0.03: on grass P = 0.158 ; on sand in shoes P = 0.103). The lower lactate accumulation values record ed for the iron men on both grass and sand may indicate that running on san d potentially reduces metabolic fatigue when running on firm or soft surfac es.