EMG coherence of foot and ankle muscles increases with a postural challenge in men.

BACKGROUND: The functional role of intrinsic foot muscles in the control of standing balance is often overlooked in rehabilitation, partly because the interactions with ankle muscles are poorly understood. RESEARCH QUESTION: How does coactivation of Flexor Digitorum Brevis (FDB) and soleus (SOL) vary across standing tasks of increasing difficulty. METHODS: Postural sway (Centre of Pressure, CoP) and the electromyographic (EMG) activity of FDB, SOL, Medial Gastrocnemius (MG) and Tibialis Anterior (TA) were measured during bipedal standing, tandem stance, one-legged balance, and standing on toes. Coherence of the rectified EMG signals for SOL and FDB in two bandwidths (0-5 and 10-20 Hz) was calculated as a coactivation index. RESULTS AND SIGNIFICANCE: The CoP sway and the EMG activity of all muscles was greater (P<0.05) for the three difficult tasks. Significant coherence between the SOL and FDB EMG activity was found in both frequency regions: 0-5 and 10-20 Hz. The coherence integral increased with the difficulty of the postural task, especially in the 10-20 Hz band. The findings underscore the important role of FDB in the control of standing balance across tasks and its coactivation with SOL. Clinical recommendations to improve balance control need to consider the interaction between the plantar flexor and intrinsic-foot muscles.

Foot-dominance does not influence force variability during ankle dorsiflexion and foot adduction.

The aim of our study was to compare the force steadiness and the discharge characteristics of motor units in the tibialis anterior (TA) during ankle dorsiflexion and foot adduction produced by submaximal isometric contractions with the dominant and non-dominant foot. Fifteen young men performed maximal and submaximal contractions at five target forces with both legs, and motor unit activity in TA was recorded using high-density electromyography. Maximal force and the fluctuations in force during submaximal contractions were similar between the two legs (p > 0.05). Motor unit activity was characterized by measures of mean discharge rate (MDR), coefficient of variation for interspike interval (CoV for ISI), and standard deviation of the filtered cumulative spike train (SD of fCST). There were no statistically significant differences in motor unit activity between legs during ankle dorsiflexion. In contrast, the MDR and the CoV for ISI but not the SD of fCST, were greater for the non-dominant foot compared with the dominant foot during foot adduction. Nonetheless, these differences in motor unit activity were not sufficient to influence the force fluctuations during the submaximal contractions. These results indicate that control of the force produced by TA during the two actions was not influenced by limb dominance.

Effects of plyometric training techniques on vertical jump performance of basketball players.

The aim of our study was to compare the effects of two different plyometric training programs (targeting knee extensors or plantar flexors) on jump height and strength of leg muscles. Twenty-nine male basketball players were assigned to the knee-flexed (KF), knee-extended (KE), or control groups. In addition to regular training, the KF group performed plyometric jumps (10 sets of 10 jumps, 3 sessions/week, 4 weeks) from 50 cm boxes with the knee flexed (90°-120°), whereas the KE group performed the jumps from 30 cm boxes with the knee much more extended (130°-170°). Jumping ability was evaluated with squat jumps (SJs), countermovement jumps (CMJs), and drop jumps from 20 cm (DJ20) and 40 cm (DJ40). Knee and ankle muscles were assessed during maximal isokinetic and isometric tests, and EMG activity was recorded from vastus lateralis and medial gastrocnemius. The KF group increased SJ (+10%, d = 0.86) and CMJ (+11%, d = 0.70) but decreased DJ40 height (-7%, d = -0.40). Conversely, the KE group increased DJ20 (+10%, d = 0.74) and DJ40 (+12%, d = 0.77) but decreased SJ height (-4%, d = -0.23). The reactivity index during DJs increased (+10% for DJ20, d = 0.47; +20% for DJ40, d = 0.91) for the KE group but decreased (-10%, d = -0.48) for the KF group during DJ40. Plantar flexor strength increased for the KE group (d = 0.72-1.00) but not for the KF group. Negative transfer across jumps is consistent with the principle of training specificity. Basketball players interested to perform fast rebounds in their training should avoid plyometric jumps with large knee flexions and long contact times.

Distal hamstrings tendons mechanical properties at rest and contraction using free-hand 3-D ultrasonography.

Tendon properties impact human locomotion, influencing sports performance, and injury prevention. Hamstrings play a crucial role in sprinting, particularly the biceps femoris long head (BFlh), which is prone to frequent injuries. It remains uncertain if BFlh exhibits distinct mechanical properties compared to other hamstring muscles. This study utilized free-hand three-dimensional ultrasound to assess morphological and mechanical properties of distal hamstrings tendons in 15 men. Scans were taken in prone position, with hip and knee extended, at rest and during 20%, 40%, 60%, and 80% of maximal voluntary isometric contraction of the knee flexors. Tendon length, volume, cross-sectional area (CSA), and anteroposterior (AP) and mediolateral (ML) widths were quantified at three locations. Longitudinal and transverse deformations, stiffness, strain, and stress were estimated. The ST had the greatest tendon strain and the lowest stiffness as well as the highest CSA and AP and ML width strain compared to other tendons. Biceps femoris short head (BFsh) exhibited the least strain, AP and ML deformation. Further, BFlh displayed the highest stiffness and stress, and BFsh had the lowest stress. Additionally, deformation varied by region, with the proximal site showing generally the lowest CSA strain. Distal tendon mechanical properties differed among the hamstring muscles during isometric knee flexions. In contrast to other bi-articular hamstrings, the BFlh high stiffness and stress may result in greater energy absorption by its muscle fascicles, rather than the distal tendon, during late swing in sprinting. This could partly account for the increased incidence of hamstring injuries in this muscle.

More Variability in Tibialis Anterior Function during the Adduction of the Foot than Dorsiflexion of the Ankle.

INTRODUCTION: The aim of the study was to compare maximal force, force steadiness, and the discharge characteristics of motor units in the tibialis anterior (TA) muscle during submaximal isometric contractions for ankle dorsiflexion and adduction of the foot. METHODS: Nineteen active young adults performed maximal and submaximal isometric dorsiflexion and adduction contractions at five target forces (5%, 10%, 20%, 40%, and 60% maximal voluntary contraction [MVC]). The activity of motor units in TA was recorded by high-density EMG. RESULTS: The maximal force was similar between dorsiflexion and adduction, despite EMG amplitude for TA being greater ( P < 0.05) during dorsiflexion than adduction. Τhe coefficient of variation (CV) for force (force steadiness) during dorsiflexion was always less ( P < 0.05) than during adduction, except of 5% MVC force. No differences were observed for mean discharge rate; however, the regression between the changes in discharge rate relative to the change of force was significant for dorsiflexion ( R2 = 0.25, P < 0.05) but not for adduction. Discharge variability, however, was usually less during dorsiflexion. The CV for interspike interval was less ( P < 0.05) at 10%, 20%, and 40% MVC but greater at 60% MVC during dorsiflexion than adduction. Similarly, the SD values of the filtered cumulative spike train of the motor units in TA were less ( P < 0.05) at 5%, 10%, 20%, and 40% MVC during dorsiflexion than adduction. CONCLUSIONS: Although the mean discharge rate of motor units in TA was similar during foot adduction and ankle dorsiflexion, discharge variability was less during dorsiflexion resulting in less accurate performance of the steady adduction contractions. The neural drive to bifunctional muscles differs during their accessory function, which must be considered for training and rehabilitation interventions.

Footedness but not dominance influences force steadiness during isometric dorsiflexion in young men.

The aim of the study was to assess the potential influence of footedness and dominance on maximal force, force fluctuations and neural drive during dorsiflexion. Fifteen left-footed (LF) and fifteen right-footed (RF) young adults performed 2 maximal voluntary contractions (MVC) and 3 steady submaximal isometric contractions at five target forces (5, 10, 20, 40 and 60% MVC) with the dorsiflexors of both legs. High-density electromyography (EMG) was used to record the discharge characteristics of motor units (MUs) of Tibialis Anterior. MVC force and EMG amplitude (root mean square) were similar between the two legs and groups (p > 0.05). Force fluctuations (Coefficient of Variation, CoV for force), mean discharge rate of MUs, discharge variability (CoV of interspike interval), and variability in neural drive (standard deviation of filtered cumulative spike train) were greater (p < 0.05) and the input-output gain of the MUs (ΔDR/ΔF) was lower (p < 0.05) for the LF relative to the RF group. The differences in force fluctuations during steady contractions with the dorsiflexors were associated with footedness but not with dominance. They reflect greater variability in motor neuron output, as suggested by coefficient of variation for interspike interval (independent input) and the standard deviation of the smoothed discharge times (common input).

Alternating or Bilateral Exercise Training does not Influence Force Control during Single-Leg Submaximal Contractions with the Dorsiflexors.

The aim of the study was to assess the influence of habitual training history on force steadiness and the discharge characteristics of motor units in tibialis anterior during submaximal isometric contractions. Fifteen athletes whose training emphasized alternating actions (11 runners and 4 cyclists) and fifteen athletes who relied on bilateral actions with leg muscles (7 volleyball players, 8 weight-lifters) performed 2 maximal voluntary contractions (MVC) with the dorsiflexors, and 3 steady contractions at 8 target forces (2.5%, 5%, 10%, 20%, 30%, 40%, 50% and 60% MVC). The discharge characteristics of motor units in tibialis anterior were recorded using high-density electromyography grids. The MVC force and the absolute (standard deviation) and normalized (coefficient of variation) amplitudes of the force fluctuations at all target forces were similar between groups. The coefficient of variation for force decreased progressively from 2.5% to 20% MVC force, then it plateaued until 60% MVC force. Mean discharge rate of the motor units in tibialis anterior was similar at all target forces between groups. The variability in discharge times (coefficient of variation for interspike interval) and the variability in neural drive (coefficient of variation of filtered cumulative spike train) was also similar for the two groups. These results indicate that athletes who have trained with either alternating or bilateral actions with leg muscles has similar effects on maximal force, force control, and variability in the independent and common synaptic input during a single-limb isometric task with the dorsiflexors.

Neuromuscular electrical stimulation improves reaction time and execution time of roundhouse kick in highly skilled martial arts athletes.

The purpose of the study was to evaluate the influence of neuromuscular electrical stimulation (NMES) on a roundhouse kick (RHK) and the rate of force development (RFD) and peak force during maximal isometric contractions with the knee extensors. Sixteen martial arts athletes were randomly assigned to either a training group (NMES + martial arts) or a control group (martial arts). The RHK was performed to a fixed target located approximately 1.5 m away from the athlete. The reaction time and execution time were quantified with a light-sensor system. Participants were tested before and after completing 15 sessions of training (5 weeks, 3 sessions/week, 90 min/session). In addition, the training group performed another 15 sessions (3 sessions/week, 30 min/session) in which electrical stimulation was superimposed on maximal isometric contractions of the quadriceps (100 Hz, 450 µs). There were no statistically significant changes in either RFD or maximal isometric force for either group (p > 0.05). However, the training group experienced significant reductions (p < 0.05) in both reaction time (-9.2%) and the execution time (-5.9%). The findings indicate that supplemental NMES training can improve sport-specific movements, such as the RHK, without any changes in maximal force capabilities in skilled martial arts athletes.

Is hamstrings-to-quadriceps torque ratio useful for predicting anterior cruciate ligament and hamstring injuries? A systematic and critical review.

BACKGROUND: For the past 30 years, the hamstring (H)-to-quadriceps (Q) (H:Q) torque ratio has been considered an important index of muscle strength imbalance around the knee joint. The purpose of this systematic review was to examine the value of H:Q torque ratio as an independent risk factor for hamstring and anterior cruciate ligament (ACL) injuries. METHODS: Database searches were performed to identify all relevant articles in PubMed, MEDLINE, Cochrane Library, and Scopus. Prospective studies evaluating the conventional (concentric H:Q), functional (eccentric H: concentric Q), and mixed (eccentric H at 30°/s: concentric Q at 240°/s) H:Q ratios as risk factors for occurrence of hamstring muscle strain or ACL injury were considered. Risk of bias was assessed using the Quality In Prognosis Studies tool. RESULTS: Eighteen included studies reported 585 hamstrings injuries in 2945 participants, and 5 studies documented 128 ACL injuries in 2772 participants. Best evidence synthesis analysis indicated that there is very limited evidence that H:Q strength ratio is an independent risk factor for hamstring and ACL injury, and this was not different between various ratio types. Methodological limitations and limited evidence for ACL injuries and some ratio types might have influenced these results. CONCLUSION: The H:Q ratio has limited value for the prediction of ACL and hamstring injuries. Monitoring strength imbalances along with other modifiable factors during the entire competitive season may provide a better understanding of the association between H:Q ratio and injury.

Hamstring Muscle Quality Properties Using Texture Analysis of Ultrasound Images.

The aim of this study was to examine the intra- and inter-muscular differences of the hamstring muscles using textural analysis of ultrasound (US) images, and the relationship between textural indicators with hamstring torque. Transverse US scans were obtained from 10 young males from four different measurement sites along the thigh of each individual hamstring muscle at rest. Maximum-knee-flexion isometric torque measurements were also obtained. Texture analysis was applied to US images, and five gray-level co-occurrence matrix (GLCM) features were quantified: entropy (ENT), angular second moment (ASM), inverse difference moment (IDM), contrast (CON) and correlation (COR). The intraclass correlation coefficients ranged from 0.77 to 0.99, and the standard error of measurement ranged from 0.06 to 10.05%, indicating high test-retest reliability. Analysis of the variance indicated significant differences between measurement sites and individual muscles, with the proximal measurement sites having greater values for ASM, IDM and COR and lower values for ENT and CON compared with the distal sites. Additionally, only the COR at the proximal measurement site exhibited a significant relationship (r = -0.66) with strength. The present study indicated significant differences among hamstrings and measurement locations with respect to the textural analysis and may provide a novel indicator of hamstring functional properties.

Is Muscle Architecture Different in Athletes with a Previous Hamstring Strain? A Systematic Review and Meta-Analysis.

Hamstring strains are a frequent injury in sports and are characterized by a high recurrence rate. The aim of this review was to examine the muscle and tendon architecture in individuals with hamstring injury. A systematic literature search in four databases yielded eleven studies on architecture following injury. Differences in the fascicle length (FL), pennation angle (PA) and muscle size measures (volume, thickness and physiological cross-sectional area) at rest were not significantly different between the previously injured limb and the contralateral limb (p > 0.05). There was moderate evidence that biceps femoris long head (BFlh) FL shortening was greater during contraction in the injured compared to the contralateral limb. The BFlh FL was smaller in athletes with a previous injury compared to uninjured individuals (p = 0.0015) but no differences in the FL and PA of other muscles as well as in the aponeurosis/tendon size were observed (p > 0.05). An examination of the FL of both leg muscles in individuals with a previous hamstring strain may be necessary before and after return to sport. Exercises that promote fascicle lengthening of both injured and uninjured leg muscles may be beneficial for athletes who recover from a hamstring injury.

Effect of knee joint angle on individual hamstrings morphology quantified using free-hand 3D ultrasonography.

Exercise responses and injury rates differ between individual hamstrings and this may be linked with their morphology. The aim of this study was to compare muscle length and tendon dimensions between the individual hamstrings at two knee joint angles using free hand three-dimensional ultrasound (3D US). Muscle-tendon length and distal tendon cross-sectional area (CSA), volume, length and echogenicity of biceps femoris long (BFlh) and short (BFsh) head, semimembranosus (SM) and semitendinosus (ST) of 16 individuals were measured using free-hand 3D US at 0° (full extension) and 45° of knee flexion. ST showed the greatest length than all muscles and BFsh the lowest (p < 0.05). No difference was observed between SM and BFlh length (p > 0.05). Of the four muscles, ST tendon was longer, with less volume and CSA but greater echogenicity than the other tendons. In contrast, SM and BFlh showed shorter tendons and lower echogenicity but a greater volume and CSA than ST (p < 0.05). Muscle and tendon lengthened from 45° to 0° knee flexion angle (p < 0.05) but this change was not statistically different between individual hamstrings (p > 0.05). Freehand 3D US indicated that hamstring muscle length and distal tendon dimensions differ between individual hamstrings. All muscles and tendons lengthened as the knee was extended but this change was similar for all individual hamstrings.

Is the Integration of Additional Eccentric, Balance and Core Muscles Exercises into a Typical Soccer Program Effective in Improving Strength and Postural Stability?

Soccer teams integrate specific exercises into their typical workout programs for injury prevention. The purpose of this study was to investigate whether the incorporation of a brief and supplementary training program that involves eccentric, balance, and core exercises into the weekly soccer schedule can cause positive neuromuscular adaptations. Twenty-one soccer players were randomly allocated to either a training (n = 11) or a control group (n = 10). All players followed their teams' typical program, consisting of 4-5 soccer-specific sessions plus 1 match, weekly. Training group players additionally performed biweekly, hamstring eccentric, balance, and core stability exercises for 8 weeks. Isokinetic concentric and eccentric peak torque (PT) of the hamstrings and quadriceps, changes in the center of pressure (COP) during a 30 s single-leg stance, and a supine bridge (trunk stability) test were assessed before and after the intervention. After the intervention, a 27% increase in hamstring concentric PT and a 33% reduction in COP sway in the stance test, were observed for the training group only (p < 0.05). These improvements were significant only for the non-dominant leg. Furthermore, the control group displayed an increase in COP sway during the bridge test compared to baseline values (p < 0.05), which reflects a deterioration in postural balance over time. Consequently, incorporating small doses of hamstring eccentric, proprioception, and core stability exercises into a typical training program of youth soccer players improves strength and postural balance in the non-dominant leg, as well as core muscle performance.

Anatomy, Morphology and Function of the Tensor of Vastus Intermedius: A Systematic Review.

The tensor of vastus intermedius is a newly discovered muscle that is located at the anterior compartment of the thigh. The aim of the present study is to report, assess and synthetize the existing evidence on the anatomy, variation and morphological characteristics of the TVI as well as to examine its clinical importance. A systematic review was performed evaluating both anatomical and medical imaging studies which provided information about TVI anatomy, prevalence, variations and morphological characteristics. The search strategy was conducted in major electronic databases. Two reviewers worked independently to screen all possible references via a title/abstract examination. Methodological quality was examined with the Anatomical Quality Assurance checklist. A total of 295 cadaveric knees were included in the nine studies where in 244 (82.7%) cases the TVI was identified. Based on this evidence, it appears that the TVI is located between the vastus lateralis and vastus intermedius. The muscle belly is located proximally, and it is combined with a broad and flat aponeurosis before forming a tendinous structure that is attached at the medial aspect of the patella. The TVI presented some morphological variations and complex muscle architecture that varied along its length. There is insufficient good quality evidence as more than half of the included studies were ranked as having a "High" risk of bias with various methodological issues. Higher quality studies are recommended to evaluate the TVI morphology to better understand its functional and clinical importance.

Reliability of Distal Hamstring Tendon Length and Cross-sectional Area Using 3-D Freehand Ultrasound.

The objective of this study was to investigate the reliability of distal hamstring tendon morphology using freehand 3-D ultrasound (US). Freehand 3-D US scans were acquired for 16 young males and females, in two sessions, spaced a week apart. The length, volume, cross-sectional area (CSA) and echo intensity (EI) of the semitendinosus (ST), biceps femoris long and short head and semimembranosus (SM) tendons were acquired. Measurements of the CSA and EI were obtained from three sites along each tendon. The intra-class correlation coefficients ranged from 0.88-0.99 of the examined variables, indicating high test-retest reliability. In addition, the minimal detectable change (MDC) ranged from 0.255-3.766 mm (MDC% of the mean: 0.406%-12.558%) for hamstring tendon length, from 0.036-0.077 mL (MDC%: 1.548%-3.178%) for tendon volume, from 0.512-1.948 mm2 (MDC%: 0.702%-3.586%) for CSA and from 0.898-2.586 au (MDC%: 1.145%-3.325%) for EI. Of the four hamstring tendons, ST had the greatest length (141.587 ± 10.701 mm) and EI (94.637 ± 5.536 au), while SM had the greatest volume (3.056 ± 0.421 mL) and CSA (115.277 ± 16.442 mm2) relative to other tendons. Freehand 3-D US appears to be a reliable tool for the evaluation of hamstring distal tendon morphology; hence, its use for in vivo evaluation of tendon properties is promising.

Lumbar Multifidus Muscle Thickness During Graded Quadruped and Prone Exercises.

Exercises for lumbar multifidus (LM) muscle are important for injury and low back pain prevention and treatment. This study examined the differences in LM contraction thickness between variations of the superman and bird dog exercises. Twenty-one recreational athletes performed the superman exercise from the prone position with the following grading: rest, right upper extremity lift (RU), right lower extremity (RL) and upper and lower extremities lift (UL). They also performed the following bird dog variations from the quadruped position: rest, RU, RL and left upper - right lower extremity lift (LURL). LM muscle thickness of both sides was recorded using two ultrasonography (US) devices. LM thickness during superman-UL, was significantly greater compared with the other exercises and significantly lower during upper extremity exercises compared with lower extremity exercises (p < 0.05). No significant differences in LM thickness between sides was found (p > 0.05). The US measurements of LM thickness displayed good to excellent intrarrater reliability for both muscle sides. It appears that superman-UL is the most effective exercise for a greater contraction thickness of LM. Further, in order to progressively increase LM muscle thickness, upper extremity tasks should be performed prior to lower extremity tasks and combined upper and lower lifting tasks.

Hamstring to quadriceps strength ratio and cross-sectional area of the quadriceps and hamstrings muscles assessed using extended field-of-view ultrasonography.

This study examined whether the association between hamstring (H) and quadriceps (Q) strength with size depends on the region and the muscle used to examined cross-sectional area (CSA). Maximum isometric contraction knee extension and flexion torque was obtained from 20 young participants while Q and H CSA was recorded using extended field of view ultrasonography at four sections along the thigh. Stepwise linear regression models using the maximum CSA of individual muscles showed a significant association of quadriceps (R2 = 0.793) and hamstring (R2 = 0.275) CSA with MVC torque (p < 0.05). The association was lower when maximum or section-specific muscle group CSAs were used as indices of size. The H:Q CSA ratio showed a significant association (R2 = 0.275, p < 0.05) and a moderate correlation (r = 0.48) with H:Q torque ratio. These results indicated that the association between muscle CSA and strength differs between the knee extensors and flexors. Amongst the various indices of muscle size, the combination of maximum CSA values of each muscle displayed the greatest relationship between strength and CSA. The H:Q CSA ratio can explain a significant but small part of the H:Q isometric strength ratio.

Assessment of Rectus Abdominis muscle thickness during isometric trunk and leg lifting exercises using extended field of view (EFOV) ultrasound.

AIM: The purpose of the present study was to establish which type of exercise is optimal for Rectus Abdominis (RA) muscle, by measuring thickness and length changes using the extended field of view ultrasonography (EFOV US) during different conditions. The second purpose was to estimate the reliability of EFOV US as a muscle morphology assessment tool. MATERIAL AND METHODS: Segmental muscle thickness and length of 11 young healthy adults was assessed during 1) rest and isometric 2) trunk lifting, 3) leg lifting and 4) combined trunk and leg lifting exercises with the use of EFOV US. RESULTS: RA muscle thickness was significantly greater during exercises compared to rest (p<0.05). It was also observed that proximal and proximal-middle segments showed significantly less thickness and length compared to distal-middle and distal segments (p<0.05). Even though no differences in thickness were observed between the exercises, leg lifting and combined trunk and leg lifting exercises affected more the distal segment of RA muscle (p<0.05). Moreover, no significant differences in length between exercises was found (p>0.05). Further, EFOV US displayed excellent reliability as the ICC values ranged from 0.82 to 0.97. CONCLUSIONS: According to our observations it seems that exercises that induce lifting of the legs might be more effective for the distal parts of RA muscle. EFOV appears to be a reliable diagnostic tool for measuring RA muscle thickness during rest and contracting states.

Transversus Abdominis Thickness at Rest and Exercise in Individuals with Poststroke Hemiparesis.

The activity of the transverse abdominal (TrA) muscle affects the stabilization of the trunk. It is known that after a stroke, people experience problems in performing daily activities. The purpose of this study was to examine whether there are differences in the transversus abdominal thickness between the two sides of the body in individuals with hemiparesis and controls. Eight patients with hemiparesis and nine controls matched for age and body mass index were examined by musculoskeletal ultrasound in four conditions: a) At rest, b) abdominal hollowing maneuver from the supine position, c) bridge, and d) abdominal hollowing maneuver from the bridge position. In each of the above conditions, the symmetry index was calculated as the absolute value of the difference in thickness between the two sides. Analysis of variance showed a lower TrA thickness at rest and exercise in patients compared to the control group (p < 0.05). Further, patients showed a lower contraction thickness ratio during exercise compared to controls (p < 0.05). The absolute symmetry of the TrA thickness was 12.59 ± 6.43% to 19.31 ± 10.43% in patients and it was significantly greater than the control group (3.01 ± 2.47% to 4.47 ± 2.87%). According to the above results, it seems that transverse abdominal activation exercises are particularly useful for improving the stability of patients with hemiparesis, as long as they are located and adapted to the deficit of each patient.

The Effect of Additional External Resistance on Inter-Set Changes in Abdominal Muscle Thickness during Bridging Exercise.

Bridging exercises with abdominal hollowing are often used as a regimen for improving spinal stability. Lately, this type of training has become very popular among elite athletes, creating a need for more demanding exercises. The purpose of this study was to investigate whether the use of additional external resistance is beneficial for abdominal muscle recruitment during bridge exercise. Tissue movement of the transversus abdominis (TrA) and the rectus abdominis (RA) was recorded with the use of two synchronized ultrasonic devices, in 20 healthy college students. From the hook-lying position participants were examined in eight different exercise conditions: a) rest, b) abdominal drawing-in maneuver (ADIM), c) bridge, d) bridge- ADIM, e) bridge with 10KG, f) bridge- ADIM with 10KG, g) bridge with 20KG and h) bridge-ADIM with 20KG. Analysis of variance (ANOVA) showed a statistically significant increase in TrA thickness when performing the bridge exercise combined with ADIM compared to rest mode (p < .05). RA thickness decreased when the ADIM was performed, compared to rest (p < 0.05). No significant difference in TrA and RA thickness when exercising with and without external resistance was observed (p > 0.05). The main outcome of this study was that external loading provided some extra level of difficulty, yet it was not beneficial for abdominal muscle recruitment, when performing a supine bridge exercise.