Introduction: The use of oral appliances to enhance sports performance has been advocated by some authors, however, studies addressing the effectiveness of these strategies are inconclusive. Methods: Here we investigate the effects of dental occlusions on shoulder strength. Fourteen healthy male subjects (age ¼ 21.67 ± 0.86 years) without temporomandibular joint (TMJ) disorder participated in this study. Isokinetic strength was evaluated in shoulder abduction/adduction and arm external/internal rotation tests. Three randomised conditions were assessed: (1) occlusal splint (OS), which repositioned the TMJ in centric relation; (2) placebo splint (PS); and (3) no-splint (N). The strength tests were performed at a speed of 60 /sec in concentric mode. Muscle activity was measured by surface electromyography (EMG) in the main muscles engaged in the movements. Results: Significant differences in peak torque between OS and both of the other experimental conditions were found in some of the analyzed variables. Moreover, there was significantly higher muscular EMG activation in the OS condition when compared to the other conditions for some of the tested muscles. These data suggest that splints may have a positive ergogenic effect on shoulder muscular strength in healthy male subjects. Conclusion: OS may provide an advantage for healthy subjects engaged in sports whereby shoulder and arm strength are important for performance. KEY MESSAGES Occlusal splints in centric relation position have an ergogenic effect, by increasing strength and muscle activation on shoulder in healthy subjects. These results could have implications for sports or other physical activities were arm and shoulder strength are important.

Occlusal splints, to some extent, have been related to reduced body sway in a static position and increased muscle activity in the upper limbs. However, how dental occlusion status affects sports performance remains unclear. Here, we investigated whether occlusal splints that reposition the temporomandibular joint (TMJ) influenced body posture, muscle activity, and performance in 10-meter pistol shooters. Thirteen national-level male shooters (age = 38.8 ± 10.9 yrs) were recruited for this study, and cleared of any cervical pathology. An occlusal splint (OS) and a placebo splint (PS) were fabricated for each of the subjects, with the mandibular and maxillary position verified by an expert dentist, with the aid of an adjustable articulator. Surface electromyography (EMG) was assessed in the upper limb that holds the pistol while the subjects were standing on a force platform. Subjects performed two series of 10 shots for each of the three experimental conditions (OS, PS, N (no splint)) in randomized order, with the mandible in a rest position. Results revealed similar centre of pressure (COP) parameters in all conditions, despite a reduction in the average oscillation area caused by the OS. There were also no significant differences in EMG activity between conditions in the five upper limb muscles monitored. Consistent with this, shooting performance was similar in all conditions, despite a reduction in shot dispersion in subjects using OS. Thus, changes in dental occlusion status induced by OS do not affect body posture, upper limb EMG muscle activity, or shot performance in healthy male pistol shooters.

a b s t r a c tBackground: Balance training is often employed for the prevention of ankle injuries. However, until now, most of the studies have focused on the prevention of a recurrent injury. The objective of this study was to look into the effects of balance training on the onset of peroneal muscle activity in healthy subjects. Methods: 34 participants (mean age ¼ 19.5 years AE 1.5; height ¼ 1.70 m AE 0.12; weight ¼ 62.06 kg AE 11.24), physically active, with no history of injuries took part in this study. The participants underwent a 4-week balance training program using an ankle disk. Onset of peroneal muscles activation was measured using surface electromyography and a trap-door. Findings: Parametric and non-parametric tests showed no significant differences between the control group and the experimental group (P > 0.05). Interpretation:The results indicate that the use of balance training, for a 4-week period with two training sessions per week, on physically active subjects with no history of injuries in the ankle joint, does not cause noteworthy changes on the onset of peroneal muscles activity.

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Hamstring strain injuries (HSI) are the most common injury in male professional football and are potentially a primary risk factor to re-injury. Although the isokinetic strength ratios have often been used to identify strength imbalances that can augment the risk of injury in football players, the rate of torque development hamstring to quadriceps ratio (RTD H/Q) has rarely been considered in previous reports. Furthermore, little consideration has been given to selective hamstring lengths (30°of knee flexion) and its influence on torque production. The aim of this study was to investigate the RTD H/ Q at long hamstring lengths, conventional (concentric/concentric) and functional (eccentric/concentric) H/Q ratios in football players with and without previous HSI. Twenty-four professional male football players (12 and 12 without previous HSI) performed maximal voluntary isometric contractions at long hamstring lengths (knee and hip flexed at 30°a nd 85°, respectively) and isokinetic concentric and eccentric contractions at 180°.s −1 and 60°.s −1 . Conventional and functional H/Q ratios based on peak torque throughout the entire isokinetic range of motion and at long hamstring lengths were calculated. The RTD H/Q was extracted at long hamstring lengths in incrementing time periods of 50 milliseconds (ms) from the onset of contraction (50-250 ms). No significant differences were found between groups in any H/Q ratios studied. However, small effects (d = 0.4) were found in previously injured hamstrings to lower RTD H/Q at 50 ms and flexor eccentric torque. Previous HSI group showed small to moderate (0.4 > d < 0.6) higher RTD H/Q in late time intervals (>100 ms).

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The extent of occlusal splints' impact on muscle strength is presently unknown. At this stage, there is no general agreement as to whether occlusal splints can be used as ergogenic aids. The number of studies on this specific topic and their different experimental designs precludes drawing more definite conclusions. Further research is warranted to elucidate possible changes resulting from occlusal splints during exercise.

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