Increased cortisol levels caused by acute resistance physical exercise impair memory and learning ability.

Acute physical exercise works as an activator of the responses of the human organism to stress. This is based on the activation of the hypothalamic-pituitary-adrenal (HPA) axis, affecting physical, physiological and psychological levels. This study aimed to analyse the effects of a single bout of high-intensity resistance exercise on cognitive-behavioural responses: visuo-spatial path learning and memory, as well as physiological responses (salivary cortisol levels). Nineteen healthy male military-trained powerlifting subjects were tested in a within-subject design on two experimental days with an interval of 48 h. The stress and cognitive variables were measured by cortisol levels and Ruff-Light trail-learning test (RULIT) test scores, respectively. The results showed the immediate influence of acute exercise on cortisol, with significantly higher cortisol levels found in subjects after completion of the acute resistance exercise. In addition, this study found a significant deterioration of memory and learning ability after a dose of intense resistance exercise. In conclusion, the study highlights the relative effects of resistance exercise on cortisol and cognitive performance depending on the intensity and type of the exercise, the moment of measurement and the cerebral areas implicated.

The effect of match fatigue in elite badminton players using plantar pressure measurements and the implications to injury mechanisms.

The purpose of this study was to investigate the differences in plantar pressure under the lead and trail foot between two lunge tasks to the net in the dominant (LD) and non-dominant (LND) directions, and to explore how fatigue affects the plantar pressure patterns whilst performing movements before and after a competitive match. Peak and mean pressure were measured with the Biofoot-IBV in-shoe system from five repetitions of each task, with sensors positioned under the calcaneus, midfoot and phalanges on the lead and trail foot. Data were collected pre and immediately post-playing an official first national league competition match. The study was conducted with a sample of thirteen first league badminton players. A 2 × 2 repeated ANOVA found significant differences between the two tasks and between pre- and post-match (fatigued state). Players also had different foot pressure distributions for the LD and LND tasks, which indicated a difference in loading strategy. In a fatigued state, the plantar pressure shifted to the medial aspect of the midfoot in the trail limb, indicating a reduction in control and a higher injury risk during non-dominant lunge tasks.

Players' On-Court Movements and Contextual Variables in Badminton World Championship.

This study aimed to analyze the elite badminton players' on-court movements related to contextual variables (game, round, and match status). A total of 18 matches of the Jakarta 2015 World Championship (1,273 points and 5,710 play actions) were examined by univariate and bivariate analyses. Significant differences were found when comparing the players' on-court movements related to game, round, and match status (p < 0.05). All movements were executed more frequently in game 2, with the exception of diagonal large backward left (DLBL), diagonal short backward left (DSBL), diagonal short backward right (DSBR), and longitudinal short backward (LSB). The results obtained related to the round showed that longitudinal large backward (LLB) was the most frequent footwork in R1/16 and R1/2, diagonal short forward left (DSFL) was the most frequent one for R1/4, and transversal short right (TSR) was the most used movement for the final round. According to match status, no movement (NM) was the most common situation before hitting the shuttlecock at any moment during the match. This study shows how contextual variables modulate the elite players' on-court movements. This information could be valuable for coaches and players, allowing them to better understand the players' behavior in a competition, which could be used to design more specific training tasks and prepare match strategies in order to improve the players' performance in competitions.

An exploration of the differences in hip strength, gluteus medius activity, and trunk, pelvis, and lower-limb biomechanics during different functional tasks.

The purpose of the study was to explore differences in the coronal biomechanics of the trunk, pelvis, hip, and knee joints, and gluteus medius muscle activity (GMed) during walking and step down from two riser heights. Joint kinematics and kinetics from 20 healthy participants were recorded using a 10-camera Qualisys system and force plates, and GMed EMG was recorded using a Delsys Trigno system. Hip abductor strength was measured using a hand-held dynamometer. Pelvic obliquity and lateral trunk bending excursions were significantly higher in walking than in step-down tasks. Significantly greater knee adduction moments were seen during both step-down tasks compared to level walking with significantly greater GMed activity. However, a significant interaction between side and task was seen for hip adduction moment, with step-down tasks showing lower hip moments than during walking, with greater peak hip moments being more apparent in the dominant limb. This suggests the GMed has a greater stabilizing role during the step-down tasks, although walking required a greater mechanical demand. Health professionals should expect to find less excursion of lateral trunk bending in step-down tasks compared to level walking and consider that GMed has different roles in these two tasks.

Effect of vibration vs non-vibration foam rolling techniques on flexibility, dynamic balance and perceived joint stability after fatigue.

BACKGROUND: Foam roller and vibration techniques are currently used to assist in recovery after fatigue. The main purpose of this study was to determine the effects of the use of a foam roller with and without vibration on dynamic balance, ankle dorsiflexion, hamstring and lumbar spine flexibility and perceived knee and ankle stability after an induced fatigue protocol. METHODS: A total of 24 healthy recreationally active participants (17 males and seven females) were recruited to a randomized cross over trial consisting of; no treatment (NT), foam roller treatment (FR) and vibration foam roller treatment (VFR). The assessments included; the Sit & Reach test, Y balance test and post-treatment perceived knee and ankle stability. Measurements were taken after a standardized warm up (baseline) and repeated following an exercise-induced muscle fatigue protocol consisting of repeated lunges until volitional fatigue. The three treatment conditions were assessed on three separate days in a randomized order. A 3 × 3 repeated measures ANOVA was used to investigate differences between the three treatments over the three time points and a one factor repeated measures ANOVA was used to determine any differences between treatments using the Global Rate of Change scale when considering perceived stability. RESULTS: FR and VFR conditions both showed a greater ankle dorsiflexion range of motion (ROM) (p < 0.001), greater posteromedial and posterolateral reach distances (p < 0.001) and a better knee and ankle perceived stability (p < 0.001) when compared to the NT condition. A trend toward significance was observed in the hamstring and lumbar spine flexibility (p = 0.074) in both treatment conditions when compared to the NT condition. However, no differences were seen between the FR and VFR conditions. CONCLUSIONS: Both FR conditions seem to assist in exercise-induced muscle fatigue recovery with improvements in ROM, balance and perceived stability.

An exploration of the effect of proprioceptive knee bracing on biomechanics during a badminton lunge to the net, and the implications to injury mechanisms.

The aim of this study was to determine changes in knee biomechanics during badminton lunges due to fatigue, lunge strategy and knee bracing. Kinetic and kinematic data were collected from 16 experienced right-handed badminton players. Three factor repeated measures ANOVAs (lunge direction-fatigue-brace) were performed with Least Significant Difference pairwise comparisons. In addition, clinical assessments including; Y-balance test, one leg hop distance and ankle dorsiflexion range of motion were performed pre- and postfatigue. The knee showed significantly greater flexion during the forehand lunge compared to backhand. In contrast, the internal rotation velocity and the knee extension moment were greater during backhand. Knee angular velocity in the sagittal plane, peak knee moment and range of moment in the coronal plane and stance time showed significantly lower values postfatigue. In addition, the peak knee adduction moment showed significantly lower values in the braced condition in both the fatigued and nonfatigues states, and no significant differences were seen for peak vertical force, loading rate, approach velocity, or in any of the clinical assessment scores. There appears to be greater risk factors when performing a backhand lunge to the net compared to a forehand lunge, and proprioceptive bracing appears to reduce the loading at the knee.