Inspiratory muscles pre-activation in young swimmers submitted to a tethered swimming test: effects on mechanical, physiological, and skin temperature parameters

Inspiratory muscles pre-activation (IMPA) has been studied to improve subsequent performance in swimming. However, the effects of IMPA on various parameters in swimmers are still unknown. Therefore, this study aimed to investigate the effects of IMPA on the mechanical parameters, physiological responses, and their possible correlations with swimming performance. A total of 14 young swimmers (aged 16 ± 0 years) underwent a 30-s all-out tethered swimming test, preceded or not by IMPA, a load of 40% of the maximal inspiratory pressure (MIP), and with a volume of 2 sets of 15 repetitions. The mechanical (strength, impulse, and fatigue index) and physiological parameters (skin temperature and lactatemia) and the assessment of perceived exertion and dyspnea were monitored in both protocols. The IMPA used did not increase the swimming force, and skin temperature, decrease blood lactate concentration, or subjective perception of exertion and dyspnea after the high-intensity tethered swimming exercises. Positive correlations were found between mean force and blood lactate (without IMPA: r = 0.62, P = 0.02; with IMPA: r = 0.65, P = 0.01). The impulse was positively correlated with blood lactate (without IMPA: r = 0.71, P < 0.01; with IMPA: r = 0.56, P = 0.03). Our results suggest that new IMPA protocols, possibly with increased volume, should be developed in order to improve the performance of young swimmers.

Response of skin temperature, blood ammonia and lactate during incremental exercise until exhaustion in elite athletes

The study aimed to evaluate the lower limb skin temperature (Tsk) and blood concentrations of lactate (LA) and ammonia (NH3) during exercise and recovery. Eleven elite sprint athletes (25 ± 3.4 yrs) and 11 elite endurance athletes (24.45 ± 5.4 yrs) performed an incremental running test until exhaustion. Body composition was estimated using the DXA method. Thermograms of the anterior and posterior surfaces of the lower limbs were recorded at rest, before each test stage (every 3 min, starting from 10 km h-1 and increasing by 2 km h-1), and in the 5th, 10th, 15th, 20th, and 30th minute of recovery. Endurance athletes had a higher maximum oxygen uptake than sprint athletes (5.0 ± 0.7 vs 4.3 ± 0.4 l·kg-1, p = 0.018), lower percentage of lean content (79 ± 2 vs 83 ± 2%, p < 0.001), and a higher percentage of fat content in the lower limbs (17 ± 2 vs 12 ± 2%, p < 0.001). In both groups, a significant decrease in Tsk was observed compared to resting value (endurance athletes-31.5 ± 0.6 °C; sprint athletes-32.3 ± 0.6 °C), during exercise (p < 0.001) and rewarming during recovery (p < 0.001). However, endurance athletes had a lower Tsk than sprint athletes at the exhaustion point (30.0 ± 1.1 vs 31.6 ± 0.8 °C, p < 0.05) and the pattern of change in Tsk differed between groups (p < 0.001). Tsk in the endurance athletes group decreased throughout the exercise protocol and returned more rapidly to initial values during recovery, while Tsk in the sprint group stabilised between moderate intensity and exhaustion, recovering more slowly after exercise. Both LA (endurance athletes-max 10.2 ± 1.5; sprint athletes-max 10.1 ± 1.4 mmol⋅L-1, p < 0.001) and NH3 (endurance athletes-max 75.6 ± 11.5; sprint athletes-max 76.7 ± 9.0 mmol⋅L-1, p < 0.001) increased during exercise and decreased during recovery (p < 0.001). During exercise, lower levels and slower increases in LA were observed during exercise in the endurance athletes' group (p < 0.05). A negative correlation was revealed between Tsk and fat percentage (r = -0.43 to -0.71, p < 0.05). Tsk was positively correlated with LA during recovery (r = 0.43 to 0.48, p < 0.05), and negatively during recovery (r = -0.45 to -0.54, p < 0.05). Differences between groups in maximum aerobic capacity, the pattern of change in Tsk, and the correlation between Tsk and LA suggest that individuals who decrease less Tsk during exercise and higher Tsk during recovery are those with better aerobic capacity. In addition, athletes with less body fat dissipate heat from their tissues more efficiently.

Effects of Resistance Training on Skin Temperature and Its Relationship with Central Nervous System (CNS) Activation

The aim of this work was to relate the activation of the sympathetic and parasympathetic nervous systems with the skin temperature (Tsk) of the lower limbs after a resistance training exercise. Under controlled conditions, the average Tsk in the areas of the anterior and posterior thighs, knees and legs was obtained with a thermal imager and the parasympathetic and sympathetic activation was registered with an Omegawave^® device on 20 healthy and trained male volunteers (25.39 ± 8.21 years) before exercise, immediately after standard resistance training (3 exercises (2 quadriceps + 1 hamstrings) × 4 sets × 10 repetitions (70% 1RM), 90-sec recovery) and after 20 min of recovery. The results showed a significant effect of exercise and recovery on Tsk in all regions of interest (ROIs) considered (p < 0.05) and strong inverse relationships between sympathetic and parasympathetic activation values. Significant results were found for the total variation of Tsk (p < 0.05) with highly positive values for subjects with lower sympathetic activation and almost null or even negative values for those with higher sympathetic activation. Sympathetic activity was a significant predictor of total Tsk variation in the anterior thigh, posterior thigh and anterior knee but not in the posterior knee, anterior leg, and posterior leg. Baseline Tsk was a significant predictor of total Tsk variation the all ROIs except in the posterior knee. Tsk measured by thermography could be used to estimate the level of participation of muscle areas in exercise and registering the level of sympathetic activation before exercise could be interesting in predicting the athlete’s physiological response to strength training.

Regions of interest selection and thermal imaging data analysis in sports and exercise science: a narrative review

OBJECTIVE

Infrared thermography (IRT) is a non-invasive, contactless and low-cost technology that allows recording of the radiating energy that is released from a body, providing an estimate of its superficial temperature. Thanks to the improvement of infrared thermal detectors, this technique is widely used in the biomedical field to monitor the skin temperature for different purposes (e.g. assessing circulatory diseases, psychophysiological state, affective computing). Particularly, in sports and exercise science, thermography is extensively used to assess sports performance, to investigate superficial vascular changes induced by physical exercise, and to monitor injuries. However, the methods of analysis employed to treat IRT data are not standardized, and hence introduce variability in the results.

APPROACH

This review focuses on the methods of analysis currently used for thermal imaging in sports and exercise science.

MAIN RESULTS

Firstly, the procedures employed for the selection of regions of interest (ROIs) from anatomical body districts are reviewed, paying attention also to the potentialities of morphing algorithms to increase the reproducibility of thermal results. Secondly, the statistical approaches utilized to characterize the temperature frequency and spatial distributions within ROIs are investigated, showing their strengths and weaknesses. Moreover, the importance of employing tracking methods to analyze the temporal thermal oscillations within ROIs is discussed. Thirdly, the capability of employing procedures of investigation based on machine learning frameworks on thermal imaging in sports science is examined.

SIGNIFICANCE

Finally, some proposals to improve the standardization and the reproducibility of IRT data analysis are provided, in order to facilitate the development of a common database of thermal images and to improve the effectiveness of IRT in sports science.

Physically active men with high brown adipose tissue activity showed increased energy expenditure after caffeine supplementation

This study measured the effect of caffeine on brown adipose tissue (BAT) activity and the energy expenditure (EE) of subjects with high (HBAT) or low (LBAT) activation. We performed a quasi-experimental double-blind protocol in which 24 physically active healthy men were measured (age: 24.1 ± 6.0 yrs; BM: 75.3 ± 14.4 kg; HT: 171.8 ± 5.9 cm; BMI: 25.5 ± 4.9 kg/m²). Infrared thermography (IRT) protocol was used to separate the participants into the groups according to the BAT activation: high (HBAT; n = 11) and low (LBAT; n = 13). All participants ingested a single supplement caffeine capsule (CAF) of 375 mg (~5 mg/kg BM) or placebo (PLA). Our experimental protocol measured two groups (HBAT and LBAT) under two conditions (CAF and PLA), with intake 30-min before the data collection. BAT activity lasted 60-min (0, 10, 20, 30, 40, 50, 60 min) and was estimated by IRT in subclavicular (Δ SCV) and external (Δ EXT) regions of interest (ROI) and EE by indirect calorimetry. The main results indicated that HBAT at 40-min showed an increased EE versus the other groups and conditions (p = 0.009). There was a significant difference for BAT activation at the 30 (p = 0.019), 40 (p = 0.009), 50 (p = 0.007) and 60 min (p = 0.012) between HBAT-CAF vs. LBAT-CAF. There was also a significant difference at the 20 (p = 0.024), 30 (p = 0.036), 50 (p = 0.05) and 60 min (p = 0.011) between HBAT-CAF vs. HBAT-PLA. In conclusion CAF intake (≈5 mg) increases the thermogenic activity of BAT in healthy young men and increases EE in HBAT subjects.

Differences in the Bodyweight, Hydration Levels, Lean Mass, and Fat Mass in Spanish Junior Elite Judokas

Combat sports have a great interest in society and among professional sports. They are an important group of sports in the Olympic Games, but the strategies carried out by athletes to reduce body weight for weighing day, is famously known, suffering the adverse physical and psychological effects of rapid weight loss. This could compromise not only the performance, but the health and development of young athletes. A total of 22 elite male judokas (18.05 ± 1.05 years old) were evaluated during four different competitions in one season; the variables of body weight, water levels, and lean and fat mass were measured by bioimpedance (BIA), (Tanita BC545N) during one season. Using the linear mixed model test, we found significant differences in bodyweight variable during the competitions 3-4. The water level variable showed significant differences in all competitions, except for 2-4. Body mass index was significantly different in all competitions, being higher in the later competitions, except between competitions 1-2 and 2-3. Judokas participate in weight loss methods for their weigh-in days. Furthermore, the age at which the athletes reduced their water levels are worrisome. These results could be used to create healthy programs, especially in elite judokas, in order to carry out strategies before, during, and after competitions with weight loss and controlled water levels increasing future performance and health.