Jones Andrew M, Campbell Iain T, Pringle Jamie S M
Department of Exercise and Sport Science, Manchester Metropolitan University, Hassall Road, ST7 2HL, Alsager, UK.
Eur J Appl Physiol. 2004 Mar;91(2-3):238-45. doi: 10.1007/s00421-003-0971-7. Epub 2003 Oct 18.
We hypothesised that the ratio between the increase in oxygen uptake and the increase in work rate (Delta VO(2)/DeltaWR) during ramp cycle exercise would be significantly related to the percentage type II muscle fibres at work rates above the gas exchange threshold (GET) where type II fibres are presumed to be active. We further hypothesised that ramp exercise at higher pedal rates, which would be expected to increase the proportional contribution of type II fibres to the total power delivered, would increase the Delta VO(2)/DeltaWR slope at work rates above the GET. Fourteen healthy subjects [four female; mean (SD): age 25 (3) years, body mass 74.3 (15.1) kg] performed a ramp exercise test to exhaustion (25 W min(-1)) at a pedal rate of 75 rev min(-1), and consented to a muscle biopsy of the vastus lateralis. Eleven of the subjects also performed two further ramp tests at pedal rates of 35 and 115 rev min(-1). The Delta VO(2)/DeltaWR slope for exercise <GET ( S(1)) was significantly correlated with VO(2) peak in ml kg(-1) min(-1) ( r=0.60; P<0.05), whereas the Delta VO(2)/DeltaWR slope for exercise >GET ( S(2)) was significantly correlated to percentage type II fibres ( r=0.54; P=0.05). The ratio between the Delta VO(2)/DeltaWR slopes for exercise above and below the GET ( S(2)/ S(1)) was significantly greater at the pedal rate of 115 rev min(-1) [1.22 (0.09)] compared to pedal rates of 35 rev min(-1) [0.96 (0.02)] and 75 rev min(-1) [1.09 (0.05), ( P<0.05)]. The greater increase in S(2) relative to S(1) in subjects (1) with a high percentage type II fibres, and (2) at a high pedal rate, suggests that a greater recruitment of type II fibres contributes in some manner to the "xs" VO(2) observed during ramp exercise.
我们假设，在递增式周期运动中，摄氧量增加与功率增加的比值（ΔVO₂/ΔWR）在高于气体交换阈值（GET）的功率水平时，会与II型肌纤维的百分比显著相关，因为在此功率水平下II型纤维被认为处于活跃状态。我们还进一步假设，较高踏频的递增式运动，预计会增加II型纤维对总输出功率的比例贡献，这将使高于GET的功率水平下的ΔVO₂/ΔWR斜率增加。14名健康受试者[4名女性；平均（标准差）：年龄25（3）岁，体重74.3（15.1）kg]以75转/分钟的踏频进行递增式运动测试直至力竭（25瓦/分钟），并同意对股外侧肌进行肌肉活检。其中11名受试者还分别以35转/分钟和115转/分钟的踏频进行了另外两次递增式测试。运动<GET时的ΔVO₂/ΔWR斜率（S₁）与以毫升·千克⁻¹·分钟⁻¹为单位的VO₂峰值显著相关（r = 0.60；P<0.05），而运动>GET时的ΔVO₂/ΔWR斜率（S₂）与II型纤维百分比显著相关（r = 0.54；P = 0.05）。与35转/分钟[0.96（0.02）]和75转/分钟[1.09（0.05）]的踏频相比，115转/分钟踏频下高于和低于GET的运动的ΔVO₂/ΔWR斜率之比（S₂/S₁）显著更大[1.22（0.09）]（P<0.05）。在（1）II型纤维百分比高和（2）踏频高的受试者中，S₂相对于S₁的更大增加表明，II型纤维的更大募集在某种程度上导致了递增式运动中观察到的“额外”VO₂。
