Acute Responses Of A 90 K Cycle To Substrate Utilization, Muscle Deoxygenation, GET, And Performance

Abstract

PURPOSE: To observe the acute responses of a 90 k cycle on VO2max, gas exchange threshold (GET), critical power (CP), substrate use, blood lactate, and muscle deoxygenation during ramp (RAMP) and CP testing. METHODS: 12 male cyclists (28±6y; VO2max 4.2±0.5 L/min) performed RAMP and CP tests on a cycle ergometer, pre and post 90 k moderate intensity cycle on the open road. The RAMP test (30 W/min) was used to determine VO2max and GET whereas the CP test demonstrated peak power and CP. Breath-by-breath pulmonary VO2 and muscle deoxygenation (HHb) was measured during both RAMP and CP tests. Blood lactate concentration was collected pre and post, both tests. RESULTS: RAMP: Decreased VCO2/VO2 (RER) and carbohydrate oxidation at CP (pre 1.08 ± 0.08, post 1.03 ± 0.06; pre 5.8 g/min, post 5.07 g/min; P<0.05; P<0.05) demonstrating increased activation of glycolytic oxidative phosphorylation and reduced substrate glycolytic phosphorylation was observed. VO2 at GET was unchanged, whereas work rate decreased (pre 2.5 ± 0.43 L/min, post 2.38 ± 0.4 L/min; pre 209 ± 33 W, post 188±29 W; P>0.05; P<0.05) implicating increased oxidative phosphorylation from fat. Post ride, post RAMP test blood lactate, peak work rate and VO2max were lower (pre 12.08 ± 2.28 mmol/L, post 9.16 ± 3.3 mmol/L; pre 392 ± 29 W, post 361 ± 28 W; pre 4.2 ± 0.46 L/min, post 3.85 ± 0.45 L/min; P<0.05). Increased HHb from 175-310 s post cycle, with no change in VO2 suggests reduced blood flow distribution (BFD) (P<0.05; P>0.05). CP: CP and associated VO2 were similar pre to post-ride (pre 300 ± 35 W, post 306 ± 39 W; pre 3.92 ± 0.32 L/min, post 3.76 ± 0.43 L/min; P>0.05). Whereas RER decreased pre- to post-ride at CP (pre 1.15 ± 0.07, post 1.08 ± 0.07; P<0.05) suggesting lower substrate glycolytic phosphorylation. Reduced HHb from 10-75 s post cycle, with no change in VO2 suggests improved BFD (P<0.05; P>0.05). Decreased power output from 10-95 s (P<0.05) post ride, coupled with the lower blood lactate (pre 15.38 ± 2.75 mmol/L, post 10.62 ± 2.18 mmol/L; P<0.05) suggests lower anaerobic glycolytic phosphorylation. CONCLUSION: The acute response to a long duration cycle enables cyclists to perform at CP and GET with lower glycogen utilization due to up regulation of glycolytic oxidative phosphorylation. Chronic long duration training sessions (90 k) may increase aerobic power from carbohydrates.