Cortisol and insulin behaviors during an ultramarathon event: are they real markers of extreme exertion?

BACKGROUND: The current work aimed to describe and compare the cortisol and insulin concentrations behavior and rate of perceived exertion (RPE) during a 115 km ultramarathon race. METHODS: Nine ultrarunners (eight males) were evaluated six times (0, 37, 60, 76, 89 and 115 km). At each moment, saliva samples (for cortisol and insulin assessment) and RPE (CR10 scale) were collected. Statistical analysis included correlation, one-way repeated measure ANOVA, and Statistical Parametric Mapping to define discrete and continues changes and compare cortisol, insulin and RPE profiles. RESULTS: Our main findings revealed an early peak in cortisol and RPE, accompanied by a decline in insulin responses (402±49 min of the race, P<0.05). Cortisol and insulin only showed magnitude differences with inverse behaviors until ~6% (7 km) of the ultramarathon duration. Cortisol and RPE presented similar behaviors, rising from the beginning of the race and remaining elevated throughout the race (η2=0.91 and η2=1.0, P<0.001). Insulin levels decreased when the race started, remaining below 60% of baseline values from the midpoint to the end of the race (P=0.04). CONCLUSIONS: The study showed an imbalance in the catabolic/anabolic hormone profile during an ultramarathon race, with a prominence in catabolic state. It should be considered in the ultramarathon races preparation and participation due to its possible detrimental effect on the athlete's health.

Swimming Velocity Analysis Using Wearable Inertial Sensors and Speedometer: A Comparative Study.

The speedometer is widely used to evaluate swimming velocity but has some constraints. With the constant development of inertial units (IMUs), it is expected that they will become a good alternative to the speedometer. This study aimed to compare the data retrieved by an IMU and a speedometer when breaststroke is performed at maximum speed. Sixteen swimmers, nine males and seven females (20.3 ± 3.3 vs. 18.7 ± 1.1 years old, 65.8 ± 11.2 vs. 57.7 ± 9.1 kg of body mass and 1.75 ± 0.07 vs. 1.61 ± 0.10 m of height, respectively), performed 4 × 25 m of breaststroke sprint. They were equipped with an IMU fixed to the sacrum and with the line of an electromechanical speedometer (acquisition frequency of 50 Hz) fixed at the central point in the lumbar region. Statistical parametric mapping was used to compare the velocity curves, IBM SPSS was used for descriptive statistics and Bland-Altman plots were used for agreement of measurements. The results show that the IMU and speedometer do not show similar patterns, and the velocity values measured by the IMU are lower (p < 0.001). Bland-Altman plots presented a larger bias in terms of coefficient of variation and intracycle velocity variation. It can be concluded that IMUs and speedometers are not substitutes for each other as methods for evaluating intracycle velocity variations.

How to Work with Electromyography Decomposition in Practical Classes of Exercise Physiology and Biomechanics.

Concepts about motor unit recruitment are important learning contents in exercise physiology and biomechanics classes that are usually taught theoretically. In the last few years, great advances have occurred in the decomposition of surface electromyography, allowing the learning of theoretical contents in an experimental way. In this tutorial paper, we have described the decomposition of surface electromyography methodological aspects and examples to teach motor unit recruitment concepts in exercise physiology and biomechanics practical lessons. This work has the aim to facilitate physiology and biomechanics academics to introduce this technique in practical classes.

Aerobic exercise ameliorates survival, clinical score, lung inflammation, DNA and protein damage in septic mice.

BACKGROUND AND OBJECTIVE: Sepsis is a potentially deadly organic dysfunction, and one of the main causes of mortality in intensive care units (ICU). Aerobic exercise (AE) is a preventive intervention in the establishment of inflammatory conditions, such as chronic lung diseases, but its effects on sepsis remain unclear. Therefore, this study aimed to evaluate the effects of AE on health condition, mortality, inflammation, and oxidative damage in an experimental model of pneumosepsis induced by Klebsiella pneumoniae (K.p). METHODS: Animals were randomly allocated to Control; Exercise (EXE); Pneumosepsis (PS) or Exercise + Pneumosepsis (EPS) groups. Exercised animals were submitted to treadmill exercise for 2 weeks, 30 min/day, prior to pneumosepsis induced by K.p tracheal instillation. RESULTS: PS produced a striking decrease in the health condition leading to massive death (85%). AE protected mice, as evidenced by better clinical scores and increased survival (70%). AE alleviated sickness behavior in EPS mice as evaluated in the open field test, and inflammation (nitrite + nitrate, TNF-α and IL-1ß levels) in broncoalveolar fluid. Catalase activity, oxidative damage to proteins and DNA was increased by sepsis and prevented by exercise. CONCLUSION: Overall, the beneficial effects of exercise in septic animals encompassed a markedly improved clinical score and decreased mortality, along with lower inflammation markers, less DNA and protein damage, as well as preserved antioxidant enzyme activity. Neural network risk analysis revealed exercise had a considerable effect on the overall health condition of septic mice.

A global view on how local muscular fatigue affects human performance.

There is a growing interest in scientific literature on identifying how and to what extent interventions applied to a specific body region influence the responses and functions of other seemingly unrelated body regions. To investigate such a construct, it is necessary to have a global multivariate model that considers the interaction among several variables that are involved in a specific task and how a local and acute impairment affects the behavior of the output of such a model. We developed an artificial neural network (ANN)-based multivariate model by using parameters of motor skills obtained from kinematic, postural control, joint torque, and proprioception variables to assess the local fatigue effects of the abductor hip muscles on the functional profile during a single-leg drop landing and a squatting task. Findings suggest that hip abductor muscles' local fatigue produces a significant effect on a general functional profile, built on different control systems. We propose that expanded and global approaches, such as the one used in this study, have great applicability and have the potential to serve as a tool that guarantees ecological validity of future investigations.

Kinesio Taping effects on knee extension force among soccer players

Background : Kinesio Taping (KT) is widely used, however the effects of KT on muscle activation and force are contradictory. Objective : To evaluate the effects of KT on knee extension force in soccer players. Method: This is a clinical trial study design. Thirty-four subjects performed two maximal isometric voluntary contractions of the lower limbs pre, immediately post, and 24 hours after tape application on the lower limbs. Both lower limbs were taped, using K-Tape and 3M Micropore tape randomly on the right and left thighs of the participants. Isometric knee extension force was measured for dominant side using a strain gauge. The following variables were assessed: peak force, time to peak force, rate of force development until peak force, time to peak rate of force development, and 200 ms pulse. Results : There were no statistically significant differences in the variables assessed between KT and Micropore conditions (F=0.645, p=0.666) or among testing sessions (pre, post, and 24h after) (F=0.528, p=0.868), and there was no statistical significance (F=0.271, p=0.986) for interaction between tape conditions and testing session. Conclusion: KT did not affect the force-related measures assessed immediately and 24 hours after the KT application compared with Micropore application, during maximal isometric voluntary knee extension. .

Kinesio Taping effects on knee extension force among soccer players.

BACKGROUND: Kinesio Taping (KT) is widely used, however the effects of KT on muscle activation and force are contradictory. OBJECTIVE: To evaluate the effects of KT on knee extension force in soccer players. METHOD: This is a clinical trial study design. Thirty-four subjects performed two maximal isometric voluntary contractions of the lower limbs pre, immediately post, and 24 hours after tape application on the lower limbs. Both lower limbs were taped, using K-Tape and 3M Micropore tape randomly on the right and left thighs of the participants. Isometric knee extension force was measured for dominant side using a strain gauge. The following variables were assessed: peak force, time to peak force, rate of force development until peak force, time to peak rate of force development, and 200 ms pulse. RESULTS: There were no statistically significant differences in the variables assessed between KT and Micropore conditions (F=0.645, p=0.666) or among testing sessions (pre, post, and 24h after) (F=0.528, p=0.868), and there was no statistical significance (F=0.271, p=0.986) for interaction between tape conditions and testing session. CONCLUSION: KT did not affect the force-related measures assessed immediately and 24 hours after the KT application compared with Micropore application, during maximal isometric voluntary knee extension.