Reliability Of Vastus Lateralis Oxygenation Measured By Near Infrared Spectroscopy During Resistance Exercise

Abstract

Near infrared spectroscopy (NIRS) is a non-invasive optical technique that has been extensively used to monitor muscle oxygenation (Mox) during various tasks in different populations. However, its use during exercise has been restricted to aerobic or isometric activities, with very few attempts to investigate Mox during dynamic resistance exercise. PURPOSE To determine the reliability of vastus lateralis (VL) Mox measured by NIRS during isotonic knee extensions. METHODS Informed consent was obtained from 9 healthy volunteers (37.2 ± 10.2 yr; 74.1 ± 16.7 kg; 170.5 ± 9.6 cm) who randomly completed 4 sessions of 1 set of maximum repetitions (REPS) of the dominant leg on a knee extension machine with 80% 1RM at slow (SS: ∼25°·s−1) and fast (FS: ∼80°·s−1) speeds. A repetition was considered valid if range of motion was at least 60°. Test/ retest measurements were undertaken within a two-week period. The NIRS probe was positioned over VL (∼16 cm above knee joint) and Mox was continuously monitored during 2 min rest, REPS, and 3 min recovery. Variables considered for analysis after adjustment for baseline were: minimum during REPS plus recovery (MIN), range from MIN to maximum during recovery (RANGE), and time for half-recovery after REPS (T1/2). RESULTS Bland-Altman analysis revealed an outlier on FS REPS and one on SS Mox whose data were discarded. Mox data was further discarded for one subject in each speed due to probe displacement. Number of REPS were 6.1 ± 0.8 and 6.3 ± 0.9 for test and retest, respectively, for SS (n = 9; intraclass correlation coefficient, ICC = .674; p = .016); and 9.3 ± 1.9 and 9.9 ± 1.6, respectively, for FS (n = 8; ICC = .560; p = .046). For SS (n = 7), MIN (ICC = .730; p = .014), RANGE (ICC = .795; p = .006) and T1/2 (ICC = .780; p = .007) showed significant reliability, but only MIN (ICC = .854; p = .002) and RANGE (ICC = .973; p = .000) were reliable for FS (n = 7), with ICC = .309 for T1/2 (p = .773). CONCLUSIONS Reproducibility of Mox measurements of VL was moderately high at 80% 1RM during dynamic knee extensions to voluntary fatigue. NIRS is a suitable technique for evaluating Mox changes during resistance exercise. Partly supported by CAPES/Ministry of Education, FAPERJ (E-26/170.774/2003), and Righetto Fitness Equipment, Brazil.