The present study aimed to compare muscle coordination strategies of the upper and lower limb mus... more The present study aimed to compare muscle coordination strategies of the upper and lower limb muscles between beginners and elite breaststroke swimmers. Surface electromyography (EMG) of eight muscles was recorded in 16 swimmers (8 elite, 8 beginners) during a 25 m swimming breaststroke at 100% of maximal effort. A decomposition algorithm was used to identify the muscle synergies that represent the temporal and spatial organisation of muscle coordination. Between-groups indices of similarity and lag times were calculated. Individual muscle patterns were moderately to highly similar between groups (between-group indices range: 0.61 to 0.84). Significant differences were found in terms of lag time for pectoralis major (P < 0.05), biceps brachii, rectus femoris and tibialis anterior (P < 0.01), indicating an earlier activation for these muscles in beginners compared to elites (range: -13.2 to -3.8% of the swimming cycle). Three muscle synergies were identified for both beginners and elites. Although their composition was similar between populations, the third synergy exhibited a high within-group variability. Moderate to high indices of similarity were found for the shape of synergy activation coefficients (range: 0.63 to 0.88) but there was a significant backward shift (-8.4% of the swimming cycle) in synergy #2 for beginners compared to elites. This time shift suggested differences in the global arm-to-leg coordination. These results indicate that the synergistic organisation of muscle coordination during breaststroke swimming is not profoundly affected by expertise. However, specific timing adjustments were observed between lower and upper limbs.
Peripheral nerves are exposed to mechanical stress during movement. However the in vivo mechanica... more Peripheral nerves are exposed to mechanical stress during movement. However the in vivo mechanical properties of nerves remain largely unexplored. The primary aim of this study was to characterize the effect of passive dorsiflexion on sciatic nerve shear wave velocity (an index of stiffness) when the knee was in 90° flexion (knee 90°) or extended (knee 180°). The secondary aim was to determine the effect of five repeated dorsiflexions on the nerve shear wave velocity. Nine healthy participants were tested. The repeatability of sciatic nerve shear wave velocity was good for both knee 90° and knee 180° (ICCs≥0.92, CVs≤8.1%). The shear wave velocity of the sciatic nerve significantly increased (p<0.0001) during dorsiflexion when the knee was extended (knee 180°), but no changes were observed when the knee was flexed (90°). The shear wave velocity-angle relationship displayed a hysteresis for knee 180°. Although there was a tendency for the nerve shear wave velocity to decrease throu...
PURPOSE: Cadavers and in vivo studies have shown that cervical and thoracic movements cause chang... more PURPOSE: Cadavers and in vivo studies have shown that cervical and thoracic movements cause changes in position and tension of peripheral nerves. However, it is not clear if the head, trunk, and foot position affects torque-angle response of knee joint. The aim of this study was to compare the knee passive extension torque-angle response at different combinations of foot, trunk, and head testing position.METHODS: Ten male subjects (28.8±5.7years, 78.4±13.1kg, 1.76±0.03m) performed one repetition of a knee passive extension test with a velocity of 2°/s in four randomized experimental conditions: neutral position (N); maximal active ankle dorsiflexion (AD); maximal active cervical and thoracic flexion (CTF); and cervical and thoracic maximal flexion with ankle on maximal active dorsiflexion (CTFAD). Subjects were instructed to perform the maximum range of motion (ROM) without feeling pain or discomfort. The visual analog scale (VAS) was used to access subject’s stretching intensity pe...
The aim of this study was to describe and compare the EMG patterns of select lower limb muscles t... more The aim of this study was to describe and compare the EMG patterns of select lower limb muscles throughout the golf swing, performed with three different clubs, in non-elite middle-aged players. Fourteen golfers performed eight swings each using, in random order, a pitching wedge, 7-iron and 4-iron. Surface electromyography (EMG) was recorded bilaterally from lower limb muscles: tibialis anterior, peroneus longus, gastrocnemius medialis, gastrocnemius lateralis, biceps femoris, semitendinosus, gluteus maximus, vastus medialis, rectus femoris and vastus lateralis. Three-dimensional high-speed video analysis was used to determine the golf swing phases. Results showed that, in average handicap golfers, the highest muscle activation levels occurred during the Forward Swing Phase, with the right semitendinosus and the right biceps femoris muscles producing the highest mean activation levels relative to maximal electromyography (70-76% and 68-73% EMGMAX, respectively). Significant differences between the pitching wedge and the 4-iron club were found in the activation level of the left semitendinosus, right tibialis anterior, right peroneus longus, right vastus medialis, right rectus femuris and right gastrocnemius muscles. The lower limb muscles showed, in most cases and phases, higher mean values of activation on electromyography when golfers performed shots with a 4-iron club.
ABSTRACT Objetive. The use of music and video in exercise domain might act in parallel over other... more ABSTRACT Objetive. The use of music and video in exercise domain might act in parallel over other physiological signals and its central interpretation may change the rate of perceived exertion and subsequently the final performance. The purpose of this study was to examine the effects of sensorial modulation in an isometric muscular endurance task. Method. Ten volunteers have performed three tests, in which they had to keep the dominant arm abduction until exhaustion whilst the following variables: total time, rate of perceived exertion (RPE),median frequency (MF) and root mean square (RMS) were monitored. Each subject has performed a control (CO), deprivation (DP) and stimuli (SC) condition. Analysis of variance (ANOVA) one-way was applied followed by post-hoc Scheffé test. The smallest worthwhile change was used to provide a qualitative analysis of performance. Results. No significant differences were found in muscular activity between conditions and performance (p &gt; 0.05). The slope of RPE was significant higher to DP compared to SC (4.3 + 0.77 a.u. vs 3.53 + 0.46 a.u., p &lt; 0.05; respectively). Furthermore, a higher probability of improvement for time to exhaustion was found to SC compared to DP (97 %) and CO (92 %), conversely the opposite outcome was demonstrated to DP compared to CO (59 %). Conclusion. It was concluded that a sensory strategy was capable to modulate RPE and performance
There is a lack of studies regarding EMG temporal analysis during dynamic and complex motor tasks... more There is a lack of studies regarding EMG temporal analysis during dynamic and complex motor tasks, such as golf swing. The aim of this study is to analyze the EMG onset during the golf swing, by comparing two different threshold methods. Method A threshold was determined using the baseline activity recorded between two maximum voluntary contraction (MVC). Method B threshold was calculated using the mean EMG activity for 1000ms before the 500ms prior to the start of the Backswing. Two different clubs were also studied. Three-way repeated measures ANOVA was used to compare methods, muscles and clubs. Two-way mixed Intraclass Correlation Coefficient (ICC) with absolute agreement was used to determine the methods reliability. Club type usage showed no influence in onset detection. Rectus abdominis (RA) showed the higher agreement between methods. Erector spinae (ES), on the other hand, showed a very low agreement, that might be related to postural activity before the swing. External oblique (EO) is the first being activated, at 1295ms prior impact. There is a similar activation time between right and left muscles sides, although the right EO showed better agreement between methods than left side. Therefore, the algorithms usage is task- and muscle-dependent.
The present study aimed to compare muscle coordination strategies of the upper and lower limb mus... more The present study aimed to compare muscle coordination strategies of the upper and lower limb muscles between beginners and elite breaststroke swimmers. Surface electromyography (EMG) of eight muscles was recorded in 16 swimmers (8 elite, 8 beginners) during a 25 m swimming breaststroke at 100% of maximal effort. A decomposition algorithm was used to identify the muscle synergies that represent the temporal and spatial organisation of muscle coordination. Between-groups indices of similarity and lag times were calculated. Individual muscle patterns were moderately to highly similar between groups (between-group indices range: 0.61 to 0.84). Significant differences were found in terms of lag time for pectoralis major (P &lt; 0.05), biceps brachii, rectus femoris and tibialis anterior (P &lt; 0.01), indicating an earlier activation for these muscles in beginners compared to elites (range: -13.2 to -3.8% of the swimming cycle). Three muscle synergies were identified for both beginners and elites. Although their composition was similar between populations, the third synergy exhibited a high within-group variability. Moderate to high indices of similarity were found for the shape of synergy activation coefficients (range: 0.63 to 0.88) but there was a significant backward shift (-8.4% of the swimming cycle) in synergy #2 for beginners compared to elites. This time shift suggested differences in the global arm-to-leg coordination. These results indicate that the synergistic organisation of muscle coordination during breaststroke swimming is not profoundly affected by expertise. However, specific timing adjustments were observed between lower and upper limbs.
Peripheral nerves are exposed to mechanical stress during movement. However the in vivo mechanica... more Peripheral nerves are exposed to mechanical stress during movement. However the in vivo mechanical properties of nerves remain largely unexplored. The primary aim of this study was to characterize the effect of passive dorsiflexion on sciatic nerve shear wave velocity (an index of stiffness) when the knee was in 90° flexion (knee 90°) or extended (knee 180°). The secondary aim was to determine the effect of five repeated dorsiflexions on the nerve shear wave velocity. Nine healthy participants were tested. The repeatability of sciatic nerve shear wave velocity was good for both knee 90° and knee 180° (ICCs≥0.92, CVs≤8.1%). The shear wave velocity of the sciatic nerve significantly increased (p<0.0001) during dorsiflexion when the knee was extended (knee 180°), but no changes were observed when the knee was flexed (90°). The shear wave velocity-angle relationship displayed a hysteresis for knee 180°. Although there was a tendency for the nerve shear wave velocity to decrease throu...
PURPOSE: Cadavers and in vivo studies have shown that cervical and thoracic movements cause chang... more PURPOSE: Cadavers and in vivo studies have shown that cervical and thoracic movements cause changes in position and tension of peripheral nerves. However, it is not clear if the head, trunk, and foot position affects torque-angle response of knee joint. The aim of this study was to compare the knee passive extension torque-angle response at different combinations of foot, trunk, and head testing position.METHODS: Ten male subjects (28.8±5.7years, 78.4±13.1kg, 1.76±0.03m) performed one repetition of a knee passive extension test with a velocity of 2°/s in four randomized experimental conditions: neutral position (N); maximal active ankle dorsiflexion (AD); maximal active cervical and thoracic flexion (CTF); and cervical and thoracic maximal flexion with ankle on maximal active dorsiflexion (CTFAD). Subjects were instructed to perform the maximum range of motion (ROM) without feeling pain or discomfort. The visual analog scale (VAS) was used to access subject’s stretching intensity pe...
The aim of this study was to describe and compare the EMG patterns of select lower limb muscles t... more The aim of this study was to describe and compare the EMG patterns of select lower limb muscles throughout the golf swing, performed with three different clubs, in non-elite middle-aged players. Fourteen golfers performed eight swings each using, in random order, a pitching wedge, 7-iron and 4-iron. Surface electromyography (EMG) was recorded bilaterally from lower limb muscles: tibialis anterior, peroneus longus, gastrocnemius medialis, gastrocnemius lateralis, biceps femoris, semitendinosus, gluteus maximus, vastus medialis, rectus femoris and vastus lateralis. Three-dimensional high-speed video analysis was used to determine the golf swing phases. Results showed that, in average handicap golfers, the highest muscle activation levels occurred during the Forward Swing Phase, with the right semitendinosus and the right biceps femoris muscles producing the highest mean activation levels relative to maximal electromyography (70-76% and 68-73% EMGMAX, respectively). Significant differences between the pitching wedge and the 4-iron club were found in the activation level of the left semitendinosus, right tibialis anterior, right peroneus longus, right vastus medialis, right rectus femuris and right gastrocnemius muscles. The lower limb muscles showed, in most cases and phases, higher mean values of activation on electromyography when golfers performed shots with a 4-iron club.
ABSTRACT Objetive. The use of music and video in exercise domain might act in parallel over other... more ABSTRACT Objetive. The use of music and video in exercise domain might act in parallel over other physiological signals and its central interpretation may change the rate of perceived exertion and subsequently the final performance. The purpose of this study was to examine the effects of sensorial modulation in an isometric muscular endurance task. Method. Ten volunteers have performed three tests, in which they had to keep the dominant arm abduction until exhaustion whilst the following variables: total time, rate of perceived exertion (RPE),median frequency (MF) and root mean square (RMS) were monitored. Each subject has performed a control (CO), deprivation (DP) and stimuli (SC) condition. Analysis of variance (ANOVA) one-way was applied followed by post-hoc Scheffé test. The smallest worthwhile change was used to provide a qualitative analysis of performance. Results. No significant differences were found in muscular activity between conditions and performance (p &gt; 0.05). The slope of RPE was significant higher to DP compared to SC (4.3 + 0.77 a.u. vs 3.53 + 0.46 a.u., p &lt; 0.05; respectively). Furthermore, a higher probability of improvement for time to exhaustion was found to SC compared to DP (97 %) and CO (92 %), conversely the opposite outcome was demonstrated to DP compared to CO (59 %). Conclusion. It was concluded that a sensory strategy was capable to modulate RPE and performance
There is a lack of studies regarding EMG temporal analysis during dynamic and complex motor tasks... more There is a lack of studies regarding EMG temporal analysis during dynamic and complex motor tasks, such as golf swing. The aim of this study is to analyze the EMG onset during the golf swing, by comparing two different threshold methods. Method A threshold was determined using the baseline activity recorded between two maximum voluntary contraction (MVC). Method B threshold was calculated using the mean EMG activity for 1000ms before the 500ms prior to the start of the Backswing. Two different clubs were also studied. Three-way repeated measures ANOVA was used to compare methods, muscles and clubs. Two-way mixed Intraclass Correlation Coefficient (ICC) with absolute agreement was used to determine the methods reliability. Club type usage showed no influence in onset detection. Rectus abdominis (RA) showed the higher agreement between methods. Erector spinae (ES), on the other hand, showed a very low agreement, that might be related to postural activity before the swing. External oblique (EO) is the first being activated, at 1295ms prior impact. There is a similar activation time between right and left muscles sides, although the right EO showed better agreement between methods than left side. Therefore, the algorithms usage is task- and muscle-dependent.
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