Estimation of Lactate Thresholds, Aerobic Capacity and Recovery Rate from Muscle Oxygen Saturation in Highly Trained Speed Skaters and Healthy Untrained Individuals

Objective: The main objective of this study was to compare lactate thresholds and aerobic capacity from a graded-intensity exercise test (GXT) for near-infrared spectroscopy measurements in healthy, untrained individuals and highly trained athletes. Methods: This study included 29 untrained students (13 females) and 27 highly trained speed skaters (13 females). A maximal effort GXT was performed on a cycloergometer. The lactate-based aerobic and anaerobic thresholds, and the corresponding thresholds for muscle oxygen saturation (SmO2), were determined. Results: The power values determined for all thresholds were significantly higher in female and male speed skaters compared to male and female college students. SmO2 at anaerobic thresholds was significantly lower in female speed skaters than in female students. Both female and male skaters showed greater changes in SmO2 after the GXT compared to students. The recovery did not significantly differ between groups within gender. There was a significant positive correlation in females between the rate of muscle reoxygenation and VO2max power (r = 0.610). In speed skaters, the rate of muscle reoxygenation was not significantly higher than students and correlated positively with VO2max (r = 0.449). Conclusions: The SmO2 at the exercise thresholds, during and after maximal exercise, depends on the training status of the individual. The participants with a higher physical fitness level showed greater decreases in ΔSmO2 at the AT level, as well as after maximal exercise. SmO2 corresponding to the well-established exercise thresholds may be applied to guide training prescription. The rate of muscle reoxygenation after a GXT was also dependent on the aerobic capacity of the participants.

Do freedivers and spearfishermen differ in local muscle oxygen saturation and anaerobic power?

BACKGROUND

Freediving is defined as an activity where athletes repetitively dive and are exposed to long efforts with limited oxygen consumption. Therefore, anaerobic features are expected to be an important facet of diving performance. This study aimed to investigate differences in anaerobic capacity and local muscle oxygenation in spearfisherman and freedivers.

METHODS

The sample of participants included 17 male athletes (nine freedivers, and eight spearfishermen), with an average age of 37.0±8.8 years, training experience of 10.6±9.5 years, body mass of 82.5±9.5 kg and height of 184.2±5.7 cm. Anthropometric characteristics included: body mass, body height, seated height, and body fat percentage. Wingate anaerobic test was conducted, during which local muscle oxygenation was measured with a NIRS device (Moxy monitor). Wingate power outputs were measured (peak power [W/kg] and average power [W/kg]), together with muscle oxygenation variables (baseline oxygen saturation [%], desaturation slope [%/s], minimum oxygen saturation [%], half time recovery [s], and maximum oxygen saturation [%]).

RESULTS

The differences were not obtained between freedivers and spearfisherman in power outputs (peak power (9.24±2.08 spearfisherman; 10.68±1.04 freedivers; P=0.14); average power (6.85±0.95 spearfisherman; 7.44±0.60 freedivers; P=0.15) and muscle oxygenation parameters. However, analysis of effect size showed a moderate effect in training experience (0.71), PP (0.89), AP (0.75), Desat slope mVLR (0.66), half time recovery mVLR (0.90).

CONCLUSIONS

The non-existence of differences between freedivers and spearfishermen indicates similar training adaptations to the anaerobic demands. However, the results show relatively low anaerobic capacities of our divers that could serve as an incentive for the further development of these mechanisms.

Comparing the effects of dynamic and holding isometric contractions on cardiovascular, perceptual, and near-infrared spectroscopy parameters: A pilot study

The aim of this pilot study was to assess the effect of muscle contraction type on SmO2 during a dynamic contraction protocol (DYN) and a holding isometric contraction protocol (ISO) in the back squat exercise. Ten voluntary participants (age: 26.6 ± 5.0 years, height: 176.8 ± 8.0 cm, body mass: 76.7 ± 8.1 kg, and one-repetition maximum (1RM): 112.0 ± 33.1 kg) with back squat experience were recruited. The DYN consisted of 3 sets of 16 repetitions at 50% of 1RM (56.0 ± 17.4 kg), with a 120-second rest interval between sets and 2 seconds per movement cycle. The ISO consisted of 3 sets of 1 isometric contraction with the same weight and duration as the DYN (32 seconds). Through near-infrared spectroscopy (NIRS) in the vastus lateralis (VL), soleus (SL), longissimus (LG), and semitendinosus (ST) muscles, the minimum SmO2 (SmO2 min), mean SmO2 (SmO2 avg), percent change from baseline (SmO2 Δdeoxy) and time to recovery 50% of baseline value (t SmO2 50%reoxy) were determined. No changes in SmO2 avg were found in the VL, LG, and ST muscles, however the SL muscle had lower values in DYN, in the 1st set (p = 0.002) and in the 2nd set (p = 0.044). In terms of SmO2 min and ΔSmO2 deoxy, only the SL muscle showed differences (p≤0.05) and lower values in the DYN compared to ISO regardless of the set. The t SmO2 50%reoxy was higher in the VL muscle after ISO, only in the 3rd set. These preliminary data suggested that varying the type of muscle contraction in back squat with the same load and exercise time resulted in a lower SmO2 min in the SL muscle in DYN, most likely because of a higher demand for specialized muscle activation, indicating a larger oxygen supply-consumption gap.

Muscle Oxygenation Measured with Near-Infrared Spectroscopy Following Different Intermittent Training Protocols in a World-Class Kayaker-A Case Study

Training elite kayakers at a distance of 1000 m is associated with aerobic and anaerobic metabolism, while intermittent training, in a variety of forms, is one of the effective ways to improve cardiorespiratory and metabolic function. Thus, this study aimed to investigate muscle oxygenation responses during repetition training (RT), interval training (IT), and sprint interval training (SIT). Near-infrared spectroscopy (NIRS) monitors were placed on the latissimus dorsi (LD), pectoralis major (PM), and vastus lateralis (VL) of a world-class kayaker during their preparatory period. The intensity of work, relief, and recovery intervals were the independent variables that were manipulated using three different training protocols. The inferential analysis between intermittent training protocols showed significant differences for all variables except total the hemoglobin (tHb) index in LD during bout 2 (F = 2.83, p = 0.1, ηp2 = 0.205); bout 3 (F = 2.7, p = 0.125, ηp2 = 0.193); bout 4 (F = 1.8, p = 0.202, ηp2 = 0.141); and bout 6 (F = 1.1, p = 0.327, ηp2 = 0.092). During the rest bouts, all training protocols showed significant differences for all variables except muscle oxygen saturation (SmO2) in the VL during bout 5 (F = 4.4, p = 0.053, ηp2 = 0.286) and tHb in VL during bout 1 (F = 2.28, p = 0.132, ηp2 = 0.172); bout 2 (F = 0.564, p = 0.561, ηp2 = 0.049); bout 3 (F = 1.752, p = 0.205, ηp2 = 0.137); bout 4 (F = 1.216, p = 0.301, ηp2 = 0.1); and bout 6 (F = 4.146, p = 0.053, ηp2 = 0.274). The comparison between IT protocols RT and SIT presented similar results. All variables presented higher values during SIT, except HR results. Finally, the comparison between IT and SIT showed significant differences in several variables, and a clear trend was identified. The results of this study suggest that the application of different intermittent exercise protocols promotes distinct and significant changes in the peripheral effect of muscle oxygenation in response to training stimuli and may be internal predictors of hemodynamic and metabolic changes.

Usefulness of Portable Device to Establish Differences in Muscle Oxygenation Between the Wingate Test and Graded Exercise Test: Effect of Gender on Anaerobic and Aerobic Capacity in Speed Skaters

The aim of this study was to compare the oxygenation response in the vastus lateralis muscle (SmO₂) in two types of tests: supramaximal and maximal. Furthermore, gender differences in SmO₂ response to test exercise were assessed and the usefulness of muscle oxygenation measurements in the assessment of anaerobic and aerobic capacity was determined. The Wingate test (WAnT) and the graded exercise test (GXT) to exhaustion were performed on a cycle ergometer to examine 13 female and 14 male speed skaters from the junior and U23 national teams. During both tests, SmO₂ of the vastus lateralis muscle was recorded by near-infrared spectroscopy at baseline (at rest or post warm-up), at exercise, and during recovery. The most significant SmO₂ indices (differences between baseline and post-exercise indices and half time for SmO₂ to reach the maximal post-exercise value) were not significantly different between the tests. Gender was also not a differentiating factor in muscle oxygenation regardless of test type. In the GXT test, half time required for SmO₂ to reach the maximal value correlated negatively with VO_2max and test duration, thus confirming the usefulness of SmO₂ measurements in the assessment of the aerobic capacity of speed skaters. In contrast, the WAnT test showed no significant correlations between exercise indices and muscle oxygenation indices. From the standpoint of the assessment of anaerobic capacity, SmO₂ measurements showed little diagnostic value.

Subclinical Inflammation Is Associated With Reductions in Muscle Oxygenation, Exercise Capacity and Quality of Life in Adults With Type 2 Diabetes

OBJECTIVES

Exercise capacity is related to both morbidity and mortality in patients with type 2 diabetes (T2DM). The aim of this study was to investigate the relationship between subclinical inflammation level, exercise capacity, muscle oxygenation and quality of life in T2DM.

METHODS

This study includes 28 patients with T2DM (mean age, 51.5±5.0 years; male-to-female ratio, 6:22). Exercise capacity was evaluated using an incremental symptom-limited maximal exercise test on a bicycle ergometer. Muscle oxygenation was investigated using a wearable lactate-measuring device. Diabetes-specific quality of life was assessed using the Diabetes Quality of Life Questionnaire (DQOL). Subclinical inflammation was assessed using C-reactive protein (CRP) levels.

RESULTS

CRP level was negatively correlated with peak workload during the test (r=-0.588, p=0.002), muscle oxygenation (r=-0.465, p=0.019) and the psychological impact of treatment subscale of the DQOL (r=-0.540, p=0.017), and positively correlated with body mass index (r=0.519, p=0.008), waist circumference (r=0.426, p=0.038) and fat percentage (r=0.573, p=0.004). There was no correlation between CRP and fasting blood glucose or glycated hemoglobin level (p>0.05). Peak workload was inversely related to fat percentage (r=-0.467, p=0.016) and the DQOL worry about the future impact of diabetes subscale (r=-0.501, p=0.021).

CONCLUSIONS

In our study, subclinical inflammation negatively affected muscle oxygenation, exercise capacity and quality of life independently of glycemic indicators. Our findings suggest that the degree of glycemic control is insufficient to explain lower exercise capacity. Further studies are needed to investigate subclinical inflammation-reducing interventions in T2DM.

Underwater near-infrared spectroscopy can measure training adaptations in adolescent swimmers

The development of an underwater near-infrared spectroscopy (uNIRS) device has enabled previously unattainable measurements of peripheral muscle hemodynamics and oxygenation to be taken within the natural aquatic environment. The purposes of this study were (i) to trial the use of uNIRS, in a real world training study, and (ii) to monitor the effects of a swim training program upon muscle oxygenation status in short distance swimming. A total of 14 junior club level swimmers completed a repeated swim sprint test before and after an eight week endurance training program. A waterproof, portable Near-Infrared Spectroscopy device was attached to the vastus lateralis. uNIRS successfully measured changes in muscle oxygenation and blood volume in all individuals; rapid sub-second time resolution of the device was able to demonstrate muscle oxygenation changes during the characteristic swim movements. Post training heart rate recovery and swim performance time were significantly improved. uNIRS data also showed significant changes. A larger rise in deoxyhemoglobin during individual sprints suggested training induced an increase in muscle oxygen extraction; a faster recovery time for muscle oxygenation suggested positive training induced changes and significant changes in muscle blood flow also occur. As a strong correlation was seen between an increased reoxygenation rate and an improved swim performance time, these findings support the use of uNIRS as a new performance analysis tool in swimming.