Differences in joint power distribution in high and low lactate threshold cyclists
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ORIGINAL ARTICLE
Differences in joint power distribution in high and low lactate threshold cyclists Brian K. Leary1 · Heath M. Burton1 · Emre Vardarli1 · Anthony S. Wolfe1 · Charles K. Crawford1 · John D. Akins1 · Edward F. Coyle1 Received: 1 June 2020 / Accepted: 21 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Purpose The biomechanical differences between cyclists with a high compared with a low blood lactate threshold (HLT; 80% VO2max vs LLT, 70% VO2max) have yet to be completely described. We hypothesize that HLT cyclists reduce the stress placed on the knee extensor muscles by increasing the relative contribution from the hip joint during high-intensity cycling. Method Sixteen well-trained endurance athletes, with equally high VO2max while cycling and running completed submaximal tests during incremental exercise to identify lactate threshold ( LTVO2 ) while running and cycling. Subjects were separated into two groups based on % VO2max at LT during cycling (high; HLT: 80.2 ± 2.1% VO2max; n = 8) and (LLT: 70.3 ± 2.9% VO2max; n = 8; p 0.05) while running. While cycling in LLT, knee joint absolute power increased with work rate (p 0.05). The HLT generated significantly greater relative hip power compared with the LLT group at 90% VO2max (p 1.1, maximal heart rate ± 10 bpm of predicted max heart rate (HRmax), plateau of ≤ 150 mL/min VO2, and a rating of perceived exertion (RPE) > 17. Heart rate was measured continuously by a monitor worn around the chest (Suunto, Vantaa, Finland). Respiratory analyses were determined using oxygen and carbon dioxide analyzers (Applied Electrochemistry, Models S-3A/I and CD-3A, respectively) while the participants breathed through a one-way valve (Hans Rudolph, Kansas City, MO, USA). Ventilation was measured via an inspiratory pneumotachometer (Hans Rudolph, Kansas City, MO, USA). VO2, VCO2, and RER were continuously monitored throughout the exercise test. The highest 30 s average of VO2 was used as the measurement of VO2max.
Lactate threshold testing This protocol required 30 min of continuous exercise at submaximal intensities (5 min at each stage of approximately 40, 50, 60, 70, 80, 90% of VO2max). During the cycling test, cadence was maintained at 80–100 RPM. During treadmill testing subjects ran at a constant 10% grade and speed was increased. A catheter (BD Instye™ Autoguard™ BC Shield IV, BD, Sandy, UT, USA) was inserted into an antecubital vein of the arm and flushed regularly with saline solution to remain patent (BD PosiFlush, BD, Sandy, UT, USA). Lactate threshold was determined from a series of venous blood samples obtained between minutes 4 and 5 in each stage. Blood samples were immediately deproteinized in 10% perchloric acid and were measured on the supernatant using enzymatic analysis. (Coyle et al. 1988, 1991; Farrell et al. 1979). The lactate threshold was defined as the exercise intensity that elicits a 1-mM increase above baseline in blood lactate concentration (Coyle et al. 1983). VO2, VCO2, RER, and HR (Suunto,
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