Relationship between muscle oxygenation by NIRS and blood lactate

A Wireless Multi-Layered EMG/MMG/NIRS Sensor for Muscular Activity Evaluation

A wireless multi-layered sensor that allows electromyography (EMG), mechanomyography (MMG) and near-infrared spectroscopy (NIRS) measurements to be carried out simultaneously is presented. The multi-layered sensor comprises a thin silver electrode, transparent piezo-film and photosensor. EMG and MMG measurements are performed using the electrode and piezo-film, respectively. NIRS measurements are performed using the photosensor. Muscular activity is then analyzed in detail using the three types of data obtained. In experiments, the EMG, MMG and NIRS signals were measured for isometric ramp contraction at the forearm and cycling exercise of the lateral vastus muscle with stepped increments of the load using the layered sensor. The results showed that it was possible to perform simultaneous EMG, MMG and NIRS measurements at a local position using the proposed sensor. It is suggested that the proposed sensor has the potential to evaluate muscular activity during exercise, although the detection of the anaerobic threshold has not been clearly addressed.

Lower-limb Dynamics of Muscle Oxygen Saturation During the Back-squat Exercise: Effects of Training Load and Effort Level

Gómez-Carmona, CD, Bastida-Castillo, A, Rojas-Valverde, D, de la Cruz Sánchez, E, García-Rubio, J, Ibáñez, SJ, and Pino-Ortega, J. Lower-limb dynamics of muscle oxygen saturation during the back-squat exercise: effects of training load and effort level. J Strength Cond Res 34(5): 1227-1236, 2020-The aim of this study was to analyze the effect of strength training on lower limb muscle oxygenation. The sample consisted of 12 male subjects (22.4 ± 1.73 years; 1.81 ± 0.08 cm height and 77.76 ± 8.77 kg body mass). Six different strength training stimuli were analyzed, based on the training variables: load (60-75% 1 repetition maximum [1RM]) and level of effort (LE) (E1: 4 × 8 [20RM], E2: 4 × 12 [20RM], E3: 4 × 16 [20RM], E4: 4 × 4 [10RM], E5: 4 × 6 [10RM], and E6: 4 × 8 [10RM]) in the squat exercise up to 90° with a 2-second stop between repetitions to avoid the myotatic reflex. Oxygen saturation at the beginning of the series (SmO2start), oxygen saturation at the end of the series (SmO2stop), percentage of oxygen saturation loss (▽%SmO2), and reoxygenation time (SmO2recT) were assessed using a near-infrared spectroscopy device. In addition, the percentage of mean propulsive velocity loss (%MPVL) was recorded using a linear transducer. The results suggested an influence of LE and training load on muscle oxygenation. A greater LE was directly associated with SmO2recT (r = 0.864), ▽%SmO2 (r = 0.873), and %MPVL (r = 0.883) and inversely with SmO2stop (r = -0.871). When the same LE was used (E1 vs. E4, E2 vs. E5, and E3 vs. E6), it was found that the stimuli with a higher load had a lower SmO2recT, ▽%SmO2, and %MPVL and a higher SmO2stop. Muscle oxygen saturation was found to be minimal (%SmO2 = 0) in stimuli with a LE greater than 60% (E3 and E6). The SmO2 variables studied in the present research could be considered as an easier and more useful method for understanding skeletal muscle fatigue during resistance training.

Using an Inertial Device (WIMU PRO) to Quantify Neuromuscular Load in Running: Reliability, Convergent Validity, and Influence of Type of Surface and Device Location

Gómez-Carmona, CD, Bastida-Castillo, A, González-Custodio, A, Olcina, G, and Pino-Ortega, J. Using an inertial device (WIMU PRO) to quantify neuromuscular load in running: reliability, convergent validity, and influence of type of surface and device location. J Strength Cond Res 34(2): 365-373, 2020-Currently, the use of accelerometers in sport is increasing, and thus, the devices are required to be valid and reliable. This study tested (a) the reliability and validity of WIMU PRO accelerometers to measure PlayerLoad (PL) and (b) the influence of speed, inertial device location, and type of surface where the incremental test is performed. Twenty resistance-trained men (age: 27.32 ± 6.65 years; height: 1.74 ± 0.03 m; body mass: 68.96 ± 4.37 kg; and body mass index: 22.76 ± 1.11 kg·m) volunteered to participate in the study that lasted 5 weeks. Four progressive incremental tests were performed in treadmill and athletic track conditions. External load variable (PL) and physiological variables (heart rate [HR] and SmO2) were recorded by 4 WIMU PRO inertial devices (scapulae, center of mass, knee, and ankle), a GARMIN HR band, and a MOXY near-infrared spectroscopy device, respectively. High reliability was found on both types of surface, showing the best values at the ankle (treadmill: intraclass correlation coefficient [ICC] = 0.99, coefficient of variation [CV] = 4.65%; track: ICC = 0.96, CV = 6.54%). A nearly perfect convergent validity was shown with HRAVG (r = 0.99) and a moderate one with SmO2 (r = -0.69). Significant differences in the PL variable between surfaces were reported in all locations except the scapulae (p = 0.173), and the higher values were found on the track. In the analysis per location, the ankle location reported the highest values at all speeds and on the 2 surfaces analyzed. Assessment needs to be individualized, due to the great variability of gait biomechanics among subjects. The accelerometer location should be chosen according to the purpose of the measurement, with the ankle location being recommended for neuromuscular load analysis in running.

Dose-Response Matters! - A Perspective on the Exercise Prescription in Exercise-Cognition Research

In general, it is well recognized that both acute physical exercises and regular physical training influence brain plasticity and cognitive functions positively. However, growing evidence shows that the same physical exercises induce very heterogeneous outcomes across individuals. In an attempt to better understand this interindividual heterogeneity in response to acute and regular physical exercising, most research, so far, has focused on non-modifiable factors such as sex and different genotypes, while relatively little attention has been paid to exercise prescription as a modifiable factor. With an adapted exercise prescription, dosage can be made comparable across individuals, a procedure that is necessary to better understand the dose-response relationship in exercise-cognition research. This improved understanding of dose-response relationships could help to design more efficient physical training approaches against, for instance, cognitive decline.