Please see Bibliography of References for a list of abstracts, manuscripts and posters.
Snyder AC, Parmenter MA. Med Sci Sports Exerc. 2002;34(5, Supplement 1):S23.
A valuable exercise intensity for developing an aerobic base is maximal steady state (MSS) velocity as determined by blood lactate (MLSS). Increasing workload above MSS results in a rate of lactate production that exceeds the rate of clearance of lactate; therefore, blood lactate levels increase and exercise generally lasts less than 30 minutes before fatigue occurs. While MSS can be determined from the blood lactate levels obtained during an incremental exercise test, this method is less than optimal for both logistic and public health reasons.
Purpose: To determine whether near-infrared spectroscopy technology could be used to detect a breakpoint in percent oxygen saturation of the muscle (StO2), and whether the breakpoint exercise intensity could be used to determine MSS exercise intensity. A change in linearity when plotting StO2versus exercise intensity was defined as the breakpoint.
Methods: Sixteen distance runners and triathletes (males = 9, females = 7) completed an incremental exercise test (6-min stages per workload) to near-maximal effort. During this test, StO2, blood lactate (HLa), oxygen consumption (VO2), heart rate (HR), and rating of perceived exertion (RPE) were measured to assist in determining breakpoint speeds. The runners then completed two to three 30-minute constant speed runs to determine MLSS. Criteria for bouts above MLSS were: 1) HLa values above 4mM at the conclusion of the 30-min run and 2) HLa increase of >1mM from min 10 to min 30.
Results: Mean (+ SD) 30-min HLa values for runs determined to be at or below MLSS were 2.86 ± 0.55mM; 30-min HLa values for runs determined to be above MLSS were 5.17 ± 0.73mM (p<0.01). In 13 subjects, breakpoints were identified for both HLa and StO2values from the incremental test. Predicted MLSS velocities from HLa breakpoint (7.93 ± 1.01mph), StO2breakpoint (7.98 ± 0.98mph), and 4mM HLa methods (8.38 ± 1.06mph;) from the incremental test did not differ from MLSS velocities (8.10±1.26).
Conclusions: Near-infrared spectroscopy determination of StO2appears to be a non-invasive technique that is comparable to HLa in determining MSS intensity and, therefore, appropriate for use in determining exercise training intensity.
Supported by Hutchinson Technology Incorporated, Hutchinson, Minnesota