Electromyographic Activity of Lower Limb Muscles during Ankle Destabilizing Tests

Ankle destabilizing devices were developed to improve the recruitment of the evertor muscles. Nevertheless, the activity of lower-leg muscles has never been compared to each other during functional tests performed with destabilization. The objectives were i) to compare the electromyographic activity between the lower-leg muscles during four functional tests performed with ankle destabilization, and ii) to determine sex-related differences in neuromuscular activation. Twenty-six healthy volunteers (13 males, 13 females) performed the modified Star Excursion Balance Test (mSEBT), unipedal balance and weight-bearing inversion and eversion tests with a destabilizing device, while recording electromyographic activity of the peroneus longus and brevis, tibialis anterior, gastrocnemius lateralis and gluteus medius. The activity of peroneal muscles was significantly greater than other muscles during all functional tests. Furthermore, the anterior direction of the mSEBT was the one implying the greatest activity of the peroneus longus muscle compared to the posteromedial (p=0.003) or posterolateral (p<0.001) directions. Finally, no significant sex-related differences in neuromuscular activity were reported. This study highlights the effectiveness of the destabilizing device to involve specifically the peroneal muscles when performing various functional tests. This device should be used by clinicians to be more specific to the stabilizers of the ankle joint during functional exercises.

Acute Neuromuscular Alterations of Ankle Evertors Induced by Short Trail Running: Sex-Related Considerations

Ravier, G, Dury, J, Grevillot, J, Girard, B, Bouzigon, R, and Michel, F. Acute neuromuscular alterations of ankle evertors induced by short trail running: sex-related considerations. J Strength Cond Res 37(10): 2008–2015, 2023—This study investigated the exercise-induced effects on the neuromuscular function of ankle evertors, balance control associated with trail running, and sex-related interactions. Fourteen male and 14 female medium-level runners completed a 16-km (400 D+) course. At rest and immediately after running, maximal voluntary isometric contraction (MVC) and rate of force development (RFD) for knee extension and ankle eversion, electromyographic (EMG) activity of peroneus muscles during MVC plateau (EMG) and the first 200 ms (EMG200), ankle angular velocity ( INV) during 20 weight-bearing inversion movements, and balance control during destabilizing single-leg task were evaluated. Repeated measures ANOVA-revealed changes in knee and ankle MVC (ankle: P = 0.0004, −12%) and RFD (ankle: P < 0.0001, −19%), EMG (P < 0.0001, −17%), EMG200 (P < 0.0001, −19%), and ankle INV (P < 0.0001, +35%) in response to trail running. Single-leg balance was not impaired. Sex-related differences were observed in EMG and EMG200 with higher values in men than in women. MVC and RFD were greater in men when expressed in absolute values, but not different relative to body mass. Single-leg balance and ankle INV did not differ between men and women. Finally, none of these variables showed any sex-related difference when considering pre-exercise to postexercise changes. This study demonstrated impairment in neuromuscular function of evertor muscles and ability in braking inversion in response to trail running. Sex-related differences were observed in neuromuscular activity but not in fatigability. These data suggest that coaches might implement strength exercises specifically designed for ankle lateral stability into their training program.

Hip Abductor Muscle Fatigue Induces Different Strategies During Disrupted Postural Control

Background

Ankle sprain is one of the most common injuries in sport, and hip abductor muscle weakness has recently been reported as a predisposing factor. Currently, the influence of hip abductor muscle fatigue on ankle joint control has not been elucidated during an ankle disturbed balance exercise. This study aimed to determine the influence of hip abductor muscle fatigue on ankle joint control during a disturbed balance task, and to consider inter-individual variability in the kinematic and neuromuscular reorganizations implemented.

Methods

Twenty-six healthy subjects (13 males; 13 females) performed a unipedal postural balance task with eyes closed before and after a fatiguing exercise (up to a 50% decrease in strength) of the hip abductor muscles. Subjects completed balance task while equipped with an ankle destabilization device that allows inversion/eversion movements. Electromyographic (EMG) activity of the gastrocnemius lateralis (GastL), peroneus longus (PL) and brevis, tibialis anterior, and gluteus medius were recorded during task. Kinematics (e.g., frontal foot angulation) of the ankle complex were determined using inertial measurement units.

Results

In the overall group, no significant time, sex or interaction effect was observed for kinematic and EMG variables. However, when considering individual responses to hip fatigue, 14 subjects decreased the standard deviation of frontal angulation (−30%) suggesting enhancement of ankle joint control, while 12 subjects increased it (+46%). Normalized EMG for PL and GastL muscles changed with fatigue for both these groups. However, variations were significantly different between groups (p = 0.027 for PL and p = 0.006 for GastL). Indeed, the contribution of ankle muscles increased for the enhanced-stability group while no change for the impaired-stability group.

Conclusion

These results highlight that subject adopt different neuromuscular and kinematic ankle strategies to control ankle destabilization in response to hip abductor muscle fatigue. Frontal foot angulation variability seemed to be a valuable marker to detect the type of strategy employed. The strategy adopted by the impaired-stability group might have important implications when analyzing risk factors for ankle sprains. Further studies should consider individual responses to fatigue, to understand which factor could predispose athletes to use of one or other strategy.

Fatigue of hip abductor muscles implies neuromuscular and kinematic adaptations of the ankle during dynamic balance

OBJECTIVE

Determine whether hip abductor muscle fatigue influenced ankle kinematic and muscle activity during ankle-destabilized tasks.

DESIGN

Cross-sectional study.

METHODS

Twenty-six healthy, active participants performed two tests (Star Excursion Balance Test, SEBT; Weight Bearing Inversion Test, WBIT) for assessment of dynamic balance and ability to control inversion. Participants were equipped with an ankle-destabilizing sandal in inversion and eversion to perform both tests, which were completed before and after a fatiguing exercise of hip abductor muscles (up to 50% reduction in strength). Electromyographic activity of peroneus longus (PL) and brevis (PB), tibialis anterior, gastrocnemius lateralis (GastL) and gluteus medius (GlutM) muscles were recorded. In addition, ankle kinematics were recorded using an inertial measurement unit.

RESULTS

Hip abductor fatigue induced a significant decrease in SEBT scores in three directions (p < 0.01). During SEBT, ankle supination decreased by 3.2° in the anterior and posteromedial directions (p < 0.01). Muscle activity of GastL increased during achievement of three directions (p < 0.05) in response to hip abductor fatigue. In posteromedial direction, PL (p < 0.001) and GlutM (p < 0.01) activity increased with fatigue. During WBIT, inversion angular velocity was not impacted by fatigue while, PB and GastL activity increased after fatiguing exercise (p < 0.005).

CONCLUSION

A decrease in SEBT performance and EMG adaptations with proximal fatigue attest to the importance of the hip abductor muscle in dynamic postural control. This could have important implications in building injury prevention programs. Changes in ankle supination may reflect a protective strategy of the joint in response to hip fatigue.

Post-Exercise Hyperbaric Oxygenation Improves Recovery for Subsequent Performance

Background: The improvement of athletes' recovery seems crucial to maintaining a high-performance level. Since hyperbaric oxygenation (HBO) could be a valuable recovery method, this study aimed at determining the effects of post-exercise HBO at modest pressure (97% O₂; 1.3 ATA) on physiological response and subsequent cycling performance compared to passive recovery (PR; 21% O₂; 1 ATA). Methods: Twelve trained cyclists completed two testing sessions in a random crossover design. Both sessions consisted of one fatiguing exercise immediately followed by either HBO or PR recovery intervention (75 minutes), then a 5-minute maximal cycling effort. Cycling power output, heart rate variability (HRV) during recovery, blood lactate, and the rating of perceived exertion (RPE) were analyzed and compared between conditions. Results: Compared with PR, the cycling power output was significantly higher after HBO (307.5 ± 19.0 W vs 314.5 ± 19.3 W; p = .005; ES = 0.11 [-0.70-0.90]). Moreover, several HRV indices revealed an improvement in HRV recovery in HBO condition. Blood lactate was not significantly different between conditions, neither following the fatiguing exercise nor the maximal effort. HBO decreased RPE after maximal cycling effort and improved the perceived recovery the day after testing sessions (p < .001). Conclusion: This study suggests that HBO is an efficient strategy to improve cardiac parasympathetic reactivation and is beneficial for subsequent performance.

Psychophysiological responses of firefighters to day and night rescue interventions

This study aimed 1) to assess the psychophysiological responses throughout a rescue intervention performed during the day and at night and 2) to determine if a vibrating alarm influences these psychophysiological responses at night. Sixteen male firefighters completed a simulated intervention under three different conditions: 1) during the day with a sound alarm signal (Day_SA), 2) during the night with a sound alarm signal (Night_SA), 3) during the night with a vibrating alarm signal (Night_VA). Cardiovascular and psychological stress were recorded throughout the interventions. During the alarm signal, HR reactivity was greater in Night_SA than in Day_SA (p < 0.01). Parasympathetic reactivation and self-confidence were significantly lower in Night_SA than in Day_SA (p < 0.05). HR reactivity was decreased in Night_VA in comparison to Night_SA (p < 0.05). Overall, the rescue intervention had a greater impact on the psychophysiological variables during the night than during the day, and the type of alarm had a minor effect.

The type of visual biofeedback influences maximal handgrip strength and activation strategies

PURPOSE

This study investigated the effects of force and electromyographic (EMG) feedbacks on forearm muscle activations and handgrip maximal isometric voluntary contraction (MIVC).

METHODS

Sixteen males performed a set of MIVC in four different feedback conditions: (1) NO-FB: no feedback is given to the participant; (2) FORCE-FB: participants received a visual feedback of the produced force; (3) AGO-FB: participants received a visual feedback of the EMG activity of two agonist grip muscles; (4) ANTAGO-FB: participants received a visual feedback of the EMG activity of two hand extensors muscles. Each feedback was displayed by monitoring the signal of either force or electrical activity of the corresponding muscles.

RESULTS

Compared to NO-FB, FORCE-FB was associated with a higher MIVC force (+ 11%, P < 0.05), a higher EMG activity of agonist and antagonist muscles (+ 8.7% and + 9.2%, respectively, P < 0.05) and a better MIVC/EMG ratio with the agonist muscles (P < 0.05). AGO-FB was associated with a higher EMG activity of agonist muscles (P < 0.05) and ANTAGO-FB was associated with a higher EMG activity of antagonist muscles (P < 0.05). MIVC force was higher in the agonist feedback condition than in the antagonist feedback condition (+ 5.9%, P < 0.05).

CONCLUSION

Our results showed that the MIVC force can be influenced by different visuals feedback, such as force or EMG feedbacks. Moreover, these results suggested that the type of feedback employed could modify the EMG-to-force relationships. Finally, EMG biofeedback could represent an interesting tool to optimize motor strategies. But in the purpose of performing the highest strength independently of the strategy, the force feedback should be recommended.

Does firefighters' physical fitness influence their cardiac parasympathetic reactivation? Analysis with post-exercise heart rate variability and ultra-short-term measures

Purpose. This study assessed the influence of firefighters' physical fitness on performances and parasympathetic reactivation in rescue interventions, and tested the validity of post-exercise ultra-short-term heart rate variability. Methods. Twenty-four firefighters were assigned to two groups based on their fitness and performed three simulated interventions. The mean completion time was recorded. The post-exercise root mean square of successive differences of R-R intervals (LnRMSSD) was determined from both criterion (between 5 and 10 min) and ultra-short-term (every 1-min segment from minutes 0-6) analyses. Results. Completion time was better for the highest fitness group in the three simulated interventions while post-exercise LnRMSSD was not influenced by the firefighters' fitness. Reliability between ultra-short-term and criterion analyses differed between the segments tested; minute 5-6 revealed the highest intra-class correlations (0.86-0.97). Concerning sensitivity of both analyses, the criterion analysis revealed differences between the three rescue interventions and the fitness test, but these results were not observed with ultra-short-term measures. Conclusions. Fitness was associated with firefighters' performances but not with parasympathetic reactivation in the firefighting intervention. The ultra-short-term measures do not seem to be a suitable post-exercise LnRMSSD analysis because of the low sensitivity to reveal differences among exercise conditions.

Benefits of Compression Garments Worn During Handball-Specific Circuit on Short-Term Fatigue in Professional Players

Ravier, G, Bouzigon, R, Beliard, S, Tordi, N, and Grappe, F. Benefits of compression garments worn during handball-specific circuit on short-term fatigue in professional players. J Strength Cond Res 32(12): 3528-3536, 2018-The purpose of this study was to investigate the benefits of full-leg length compression garments (CGs) worn during a handball-specific circuit exercises on athletic performance and acute fatigue-induced changes in strength and muscle soreness in professional handball players. Eighteen men (mean ± SD: age 23.22 ± 4.97 years; body mass: 82.06 ± 9.69 kg; height: 184.61 ± 4.78 cm) completed 2 identical sessions either wearing regular gym short or CGs in a randomized crossover design. Exercise circuits of explosive activities included 3 periods of 12 minutes of sprints, jumps, and agility drills every 25 seconds. Before, immediately after and 24 hours postexercise, maximal voluntary knee extension (maximal voluntary contraction, MVC), rate of force development (RFD), and muscle soreness were assessed. During the handball-specific circuit sprint and jump performances were unchanged in both conditions. Immediately after performing the circuit exercises MVC, RFD, and PPT decreased significantly compared with preexercise with CGs and noncompression clothes. Decrement was similar in both conditions for RFD (effect size, ES = 0.40) and PPT for the soleus (ES = 0.86). However, wearing CGs attenuated decrement in MVC (p < 0.001) with a smaller decrease (ES = 1.53) in CGs compared with regular gym shorts condition (-5.4 vs. -18.7%, respectively). Full recovery was observed 24 hours postexercise in both conditions for muscle soreness, MVC, and RFD. These findings suggest that wearing CGs during a handball-specific circuit provides benefits on the impairment of the maximal muscle force characteristics and is likely to be worthwhile for handball players involved in activities such as tackles.

Thermal Sensations during a Partial-Body Cryostimulation Exposure in Elite Basketball Players

Partial-body cryostimulation is used to improve recovery after exercise, especially during competitions or heavy training; however, a limited number of studies have been conducted with international-level athletes in situ during competitions. This study was undertaken to assess the thermal sensation ratings during 3 min of cold exposure (at –130°C) in 24 international-level athletes during the European Basketball Championship. The mean thermal sensation score, measured using a perceptive scale, increased significantly (p < 0.05) during partial-body cryostimulation exposure in athletes from 3.0 ± 1.7 at 30 s to 5.7 ± 2.3 at 3 min (maximal observed value = 10.0). The mean value of 5.7 is considered a “cold” sensation on the scale (ranging from 0 = neutral sensation to 10 = very cold). However, we observed a large inter-individual variation in the perceived thermal sensations. The body mass index was significantly and negatively correlated with the thermal sensation value after 2 min 30 s and 3 min of exposure in females (r = –0.61, n = 13, p < 0.05; r = –0.56, n = 13, p = 0.054, respectively). Three participants reported high perceived thermal sensation after 30 s of exposure and their cold-induced discomfort worsened as the exposure continued. In conclusion, a 3-min exposure is globally well tolerated by athletes and can be used during a heavy competition period and/or during a training period. However, special attention should be given to female athletes with a low body mass index as they seem to be much more sensitive to cold.

Reproducibility of heart rate and perceptual demands of game-based training drills in handball players

Game-based training are popular in team-sports; however there is a lack of research specific to team handball. The aim of this study was to assess i) the test-retest reliability of heart rate (HR), time spent in HR zone intensities and rating of perceived exertion of a novel small-sided game, ii) and whether it is comparable to that of generic intermittent shuttle running and match play with team handball players. Fourteen elite male handball players completed each exercise comprising two periods of 10min interspersed with 2min recovery in separate occasions and repeated them one week apart. Exercises consisted of intermittent 30s-30s shuttle running (ISR), intermittent 30s-30s small-sided game (with 3-a-side field players, 3vs3) and match play (with 6-a-side field players, 6vs6). Mean HR demonstrated high level of reproducibility for the three drills (r = 0.86-0.89, TEM = 2.21-2.63 bpm, CV = 1.23-1.55%). For time spent in heart rate zones TEMs reached up 1.12, 1.40 and 2.48 min for ISR, 6vs6 and 3vs3, respectively. Specifically for HR zone higher than 90% of HRmax, CVs showed wide extent of scores with 9.73 (ISR), 27.39 (6vs6) and 108.29% (3vs3). Mean HR results suggest that physiological response was consistent between sessions. Because of the poor reproducibility for time spent in the target zone higher than 90% of HRmax, the efficiency of both 3vs3 and 6vs6 in improving aerobic power should be analysed with caution. The present results suggest that reproducibility of physiological demand of ball-drills should be considered before prescribing them as conditioning training.

Changes in femoral artery blood flow during thermoneutral, cold, and contrast-water therapy

AIM

The purpose of this study was to examine the changes in femoral artery blood flow during cold water immersion (CWI), contrast water therapy (CWT) and thermoneutral water immersion (TWI).

METHODS

Ten athletes came to the laboratory three times, to complete a 20-min procedure in upright position: 4 min in air (baseline), then 16-min full leg TWI (~35 °C), CWI (~12 °C) or CWT (2:2 ~12 °C to ~35 °C) min ratio, in a random order. Blood flow was measured every 2 min: baseline (i.e. min 3 and 1) and throughout water immersion (i.e. min 1, 3, 5, 7, 9, 11, 13 and 15), using Doppler ultrasound in the superficial femoral artery, distal to the common bifurcation (~3 cm), above the water and stocking.

RESULTS

Compared with baseline, blood flow was significantly higher throughout TWI (min 1 to 15: P<0.001; +74.6%), significantly lower during CWI (from min 7 to 15: P<0.05; -16.2%) and did not change during CWT (min 1 to 15). No changes in blood flow occurred between the hot and cold transitions of CWT.

CONCLUSION

This study shows that external hydrostatic pressure (TWI ~35 °C) significantly increases femoral artery blood flow. We also show that associating hydrostatic pressure with cooling (CWI ~12 °C) decreases femoral artery blood flow after a sufficient duration, whereas associating hydrostatic pressure with alternating brief exposures to contrasted temperatures does not change femoral artery blood flow under resting conditions.

Impressive anaerobic adaptations in elite karate athletes due to few intensive intermittent sessions added to regular karate training

The aim of this study was to investigate the effects of adding a high-intensity intermittent session twice a week during a 7-week karate training (KT) on markers of aerobic and anaerobic metabolisms in elite class karate athletes. Two groups were studied: a KT group (n=8, age 20.1+/-0.9 years, 70.0+/-8.8 kg) that followed traditional KT, and a group that followed combined traditional karate and a high-intensity intermittent training (HIT group, n=9, age 24.4+/-3.1 years, 67.0+/-7.8 kg). The subjects undertook a supramaximal exercise and a maximal oxygen uptake test before and after the training. Blood lactate, pH and plasma ammonia were determined at rest, immediately at the end of the supramaximal exercise and during the recovery period at 2, 4, 6, 8, 10 and 15 min. After the training period, no changes occurred in the KT group. However, in the HIT group, the time to exhaustion, MAOD and in the maximal oxygen uptake test were significantly improved by 23.6%, 10.3% and 4.6%, respectively. A clear-cut discrepancy was observed in the time course of lactate and pH in the supramaximal test after the training in the HIT group. We observed a significantly higher peak for lactate and a lower extreme value for pH with a shorter delay of appearance. At the end of the test, the lactate concentration increased significantly (+53.7%) and pH declined significantly, when compared with the values obtained after the same test before the training period. Ammonia was not influenced. The addition of high-intensity intermittent sessions twice per week during the period of KT induced beneficial physiological adaptations in athletes, allowing improvement in the duration of intense physical exercise before a state of fatigue is reached.

Maximal Accumulated Oxygen Deficit and Blood Responses of Ammonia, Lactate and pH after Anaerobic Test: a Comparison between International and National Elite Karate Athletes

The purpose of this study was to compare maximal accumulated oxygen deficit (MAOD) and the time course of blood markers of the anaerobic metabolism in response to exhaustive supramaximal test in two elite (international vs. national) class karate athletes. Ten male international competitors from the French national team (Int, age 21.2 +/- 3.1 years, 71.9 +/- 11.4 kg) and eight national class (Nat, 23.7 +/- 2.4 years, 70.7 +/- 12.2 kg) athletes with a similar maximal oxygen uptake of 57.6 and 59.4 ml . kg (-1) . min (-1), respectively, were involved in this study. The MAOD was determined after an exhaustive supramaximal exercise (2 - 3 min at 140 % of their VO2max velocity) on a treadmill ergometer. Blood lactate, pH and plasma ammonia were determined at rest, immediately at the end of exercise and during the recovery period at 2, 4, 6, 8, 10 and 15 min. After the supramaximal exercise, a dramatic higher increase in the blood concentration of ammonia until its peak was observed in the Nat compared with the Int. Time course of [NH4+] and [La] reveals significant (p < 0.01) differences between the two groups. Peak values for [H+] (89.2 +/- 6.7 vs. 75.9 +/- 8.8 nmol . l (-1); p < 0.01), [NH4+] (180 +/- 67.9 vs. 118.7 +/- 22.7 micromol . l (-1); p < 0.05) and [La] (20.7 +/- 2.7 vs. 17.9 +/- 1.1 mmol.l (-1); p < 0.05) were higher in Nat compared with Int group, respectively. However, the MAOD was similar in both groups (67.8 +/- 8 ml . kg (-1) and 64.5 +/- 6.4 for Int and Nat groups, respectively). These data suggest that ammonia and lactate accumulation are sensitive to the level of performance in karate. Higher concentrations of these metabolites in blood after supramaximal exhaustive exercise may be related to either higher anaerobic contribution to energy supply in Nat or higher removal ability in the Int group.

Application of force-velocity cycle ergometer test and vertical jump tests in the functional assessment of karate competitor

AIM

The aim of this study was to analyze the links between tests performances (vertical jump and force-velocity sprint on cycle ergometer) and 2 different karate level groups in order to propose a test battery adjusted to karate.

METHODS

Twenty-two karate competitors (10 national junior team (IJ) and 12 national competition level (NL)) performed 4 maximal squat jumps (SJ), 4 maximal counter movement jumps (CMJ) on an ergojump and 3 8-s sprints on a friction braked cycle ergometer (friction loads of 0.5, 0.7, 0.9 N x kg(-1)). The maximal theoretical force (F(0)) and velocity (V(0)), the maximal power output (P(max)) and the optimal pedalling velocity (V(opt)) were derived from both the force -- velocity and the power -- velocity relationships plotted from all the 3 friction loads data. V(0), F(0), V(opt), P(max) and the best SJ and CMJ, were compared between IJ and NL groups.

RESULTS

The IJ group was characterised by significantly higher values of V(0) (+13%) and SJ (+14.3%) compared to NL group, whereas no significant difference was observed between groups for F(0). Thus, karate performance would depend on maximal velocity and explosive strength. In addition, V(opt) was significantly higher in IJ group compared to NL group (135.4 rpm vs 119.2 rpm, p<0.001). Although based upon indirect evidence, these results accounted for mechanical functional capabilities of experts which could be particularly valuable when monitoring training of karate competitor.

CONCLUSIONS

A force-velocity and a vertical jump tests may be applied in the functional assessment of karate competitor.

[Sensitivity test to antifungal agents: results relative to 150 strains of yeasts]

In vitro sensitivity of 150 yeast strains has been evaluated with diffusion method in solid medium. In order to 9 antifungal agents available at present in disk for the in vitro sensitivity test has been utilized. The authors emphasize the importance to perform methodically in vitro sensitivity underlined, so that specific therapy carry out.