Evidence for restricted muscle blood flow during speed skating

Introduction: We have previously hypothesized restricted muscle blood flaw during speed skating, secondary to the high intramuscular forces intrinsic to the unique posture assumed by speed skaters and to the prolonged duty cy cle of the skating stroke, Methods: To test this hypothesis, we studied spe ed skaters (N = 10) during submaximal and maximal cycling and in-line skati ng, in both low (knee angle = 107 degrees) and high (knee angle = 112 degre es) skating positions (CE vs SkL vs SkH). Supportive experiments evaluated muscle desaturation and lactate accumulation during on-ice speed skating an d muscle desaturation during static exercise at different joint positions. Results: Consistent with the hypothesis were reductions during skating in ( V) over dotO(2peak) (4.28 vs 3.83 vs 4.26 L.min(-1)), the (V) over dotO(2) at 4 mmol.L-1 blood lactate (3.38 vs 1.93 vs 3.31 L.min(-1)), and cardiac o utput during maximal exercise (33.2 vs 25.3 vs 25.6 L.min(-1)). The reducti on in maximal cardiac output was not attributable to differences in HRmax ( 197 vs 192 vs 193 b.min(-1)) but to a reduction in SVmax (172 vs 135 vs 134 mL.beat(-1)). The reduction in SV appeared to be related to an increased c alculated systemic vascular resistance (354 vs 483 vs 453 dynes.s(-1).cm(-1 )). During maximal skating there was also a greater % O-2 desaturation of t he vastus lateralis based on near infrared spectrophotometry (50.3 vs 74.9 vs 60.4% of maximal desaturation during cuff ischemia). The results were su pported by greater desaturation with smaller knee angles during static exer cise and by greater desaturation and accelerated blood lactate accumulation during on-ice speed skating in the low vs high position. The results of th is study support the hypothesis that physiological responses during speed s kating are dominated by restriction of blood flow, attributable either to h igh intramuscular forces, the long duty cycle of the skating stroke; or bot h.