The association between muscle mass quantity and its quality in physically active older women.

In this study, the authors aim to determine whether lower limb strength is related to lower limb lean mass and whether this relationship is affected by lower limb functionality in physically active older women. Twenty-six women underwent measures of knee muscles strength and lean mass of lower limbs. Bilateral strength of the knee flexors and extensors was measured by an isokinetic dynamometer. The concentric peak torque was measured at an angular velocity of 60°/s. Lean mass of the lower limbs was measured by bio-impedance analysis. Pearson's correlation analysis revealed significant association between the strength of the knee flexors and lean mass on non-dominant limb only (r = .427, p = .03). Researchers revealed that strategies aiming to prevent lean mass and muscle strength losses should be specifically targeted to individual muscles or muscle groups, even in physically active older women. To improve overall mobility, the strengthening of larger muscle such as hamstring is crucial.

Advancing age is associated with more impaired mediolateral balance control after step down task.

BACKGROUND: To prevent the risk of stair descent falls and associated injuries in the older adults, it is important to understand the factors that affect this frequent locomotion of daily living. The fact that falls are in most cases the result of the interaction between intrinsic and extrinsic factors is very often underestimated when designing test protocols. RESEARCH QUESTION: This study aimed at evaluating balance control during and immediately after step down onto an unstable surface. METHODS: Physically active men and women aged 60-69 years (n = 28) and 70-79 years (n = 18) were asked to perform a step down onto a foam pad and stand still for 30 s (restabilization phase). Centre of pressure (CoP) velocity and standard deviation of CoP sway in anteroposterior and mediolateral direction were evaluated during the step down (CoP VAP, CoP VML, CoP SDAP, CoP SDML) and in the first 5 s of restabilization (CoP VAP5, CoP VML5, CoP SDAP5, CoP SDML5). In addition, time to complete step was investigated. RESULTS: Participants aged 70-79 years presented worse ML balance control after step down onto an unstable surface than their younger counterparts. This was represented by the significantly higher values of CoP SDML5 and CoP VML5 (p = 0.022 and p = 0.017). No other significant differences were detected. SIGNIFICANCE: Age is associated with a more significant ML center of pressure velocity and sway after step down onto a foam pad in physically active older adults. Exercises aimed at improving ML balance control in unstable conditions should be the subject of physical interventions even in older adults with overall good state of health and physical fitness.

The Three-Level Model of Factors Contributing to High-Intensity Intermittent Performance in Male Soccer Players.

High-intensity intermittent performance in soccer is widely assessed using the yo-yo intermittent recovery level 2 test (YYIR2). This test is usually associated with aerobic-anaerobic performance. However, less is known about the direct or indirect contributions of abilities, including the anaerobic component. This study aims to propose a three-level model of factors contributing to YYIR2 performance, based on the investigation of relationships with aerobic endurance, repeated-sprint ability (RSA), and the linear and change-of-direction speed and power variables. Eighteen soccer players performed the YYIR2, with a 20-m shuttle run test (20mSR), an RSA test with change-of-direction, 5-m and 20-m sprints, and a 505 test, countermovement jump, squat jump, and drop jump. The results showed a significant relationship between the YYIR2 distance and the 20mSR distance (r = 0.721, p = 0.001), as well as with the RSA test mean time (r = -0.594, p = 0.009). In the second level, the 20mSR distance performance was not associated with any of the speed and power variables. However, the RSA test mean time correlated with the 5-m sprint (r = 0.587, p = 0.010), 20-m sprint (r = 0.702, p = 0.001), and 505 test (r = 0.585 p = 0.011) performance. In the third level, the 20-m sprint time was related to the squat jump (r = -0.577 p = 0.012) and countermovement jump (r = -0.768 p < 0.001) heights. In addition to aerobic endurance, this study highlights the importance of the anaerobic component in YYIR2 performance. More specifically, aerobic endurance (52%) and RSA (36%) are the main determinants of YYIR2 performance. Subsequently, the RSA performance is determined by the linear (34-49%) and change-of-direction speed (35%), while the explosive power of lower limbs contributes to sprinting performance (33-59%). Coaches should focus on the development of these abilities to improve the high-intensity intermittent performance of soccer players.

Sport-specific training induced adaptations in postural control and their relationship with athletic performance.

Effects of various exercise programs on postural balance control in athletes and their underlying physiological mechanisms have been extensively investigated. However, little is known regarding how challenging sport-specific conditions contribute to the improvement of body balance and to what extent these changes may be explained by sensorimotor and/or neuromuscular function adaptations. Analysis of the literature could provide useful information on the interpretation of changes in postural sway variables in response to long-term sport-specific training and their association with performance measures. Therefore, the aim of this scoping review was (1) to analyze the literature investigating postural control adaptations induced by sport-specific training and their relationship with measures of athletic performance, and (2) to identify gaps in the existing research and to propose suggestions for future studies. A literature search conducted with Scopus, Web of Science, MEDLINE and Cochrane Library was completed by Elsevier, SpringerLink and Google Scholar with no date restrictions. Overall, 126 articles were eligible for inclusion. However, the association between variables of postural balance control and measures of sport-specific performance was investigated in only 14 of the articles. A relationship between static and/or dynamic balance and criterion measures of athletic performance was revealed in shooting, archery, golf, baseball, ice-hockey, tennis, and snowboarding. This may be ascribed to improved ability of athletes to perform postural adjustments in highly balanced task demands. However, the extent to which sport-specific exercises contribute to their superior postural stability is unknown. Although there is a good deal of evidence supporting neurophysiological adaptations in postural balance control induced by body conditioning exercises, little effort has been made to explain balance adaptations induced by sport-specific exercises and their effects on athletic performance. While an enhancement in athletic performance is often attributed to an improvement of neuromuscular functions induced by sport-specific balance exercises, it can be equally well ascribed to their improvement by general body conditioning exercises. Therefore, the relevant experiments have yet to be conducted to investigate the relative contributions of each of these exercises to improving athletic performance.

Age-related differences in stair descent balance control: Are women more prone to falls than men?

Stair descent is one of the most common forms of daily locomotion and concurrently one of the most challenging and hazardous daily activities performed by older adults. Thus, sufficient attention should be devoted to this locomotion and to the factors that affect it. This study investigates gender and age-related differences in balance control during and after stair descent on a foam mat. Forty-seven older adults (70% women) and 38 young adults (58% women) performed a descent from one step onto a foam mat. Anteroposterior (AP) and mediolateral (ML) centre of pressure velocity (CoP) and standard deviation of the CoP sway were investigated during stair descent and restabilization. A two-way analysis of variance (ANOVA) revealed the main effects of age for the first 5 s of restabilization. Older women exhibited significantly higher values of CoP sway and velocity in both directions compared to the younger individuals (CoP SDAP5, 55%; CoP SDML5, 30%; CoP VAP5, 106%; CoP VML5, 75%). Men achieved significantly higher values of CoP sway and velocity only in the AP direction compared to their younger counterparts (CoP SDAP5, 50% and CoP VAP5, 79%). These findings suggest that with advancing age, men are at higher risk of forward falls, whereas women are at higher risk of forward and sideways falls.

The Effect of Agility Training Performed in the Form of Competitive Exercising on Agility Performance.

Purpose: Simulated competition as a training tool has a relevant role in enhancement of exercise intensity, motivation and physical enjoyment. Including a competitive component into the agility training could represent another way to improve agility performance significantly more. The aim of this study was to assess the effect of agility training performed in the form of competitive exercising on agility performance. Methods: Twenty-two athletes were randomly assigned to an experimental or a control group. Both groups completed the same eight-week agility training, but only the experimental group performed exercises in the form of head-to-head competition. Prior to and after the training, agility time in the Agility Dual test (performed in pairs in the form of head-to-head competition) and Agility Single test (performed individually) was measured. In addition, simple and two-choice reaction time and speed of step initiation were also assessed. Results: A significant group × time interaction effect was observed for agility time in the Agility Dual test only (p = .002). This effect occurred in favor of experimental group (18%, p < .01). No further significant interactions were detected. Conclusions: Competitive agility training led to significant improvement of agility time under competitive conditions only. This training does not contribute to more pronounced improvements of other reaction and speed abilities.

Ankle-knee coupling responses to ankle Kinesio™ taping during single-leg drop landings in collegiate athletes with chronic ankle instability.

BACKGROUND: Ankle Kinesio-taping (KT) is being globally used an intervention to provide the ankle joint complex with sufficient support against sudden excessive mechanical stress during various activities. However, its effects on proximal joints are unclear. This study investigated the impact of ankle KT on ankle-knee joint coupling in sagittal, frontal and transverse planes. METHODS: Adopting a pretest post-test study design, 30 collegiate athletes with chronic ankle instability performed 3 single-leg drop landings in each non-taped and Kinesio-taped conditions and their movement kinematics were recorded using 6 optoelectronic cameras. RESULTS: The ankle angular velocities in sagittal (P=0.038, d=0.64) and transverse planes (P=0.001, d=0.95) decreased after KT application, while the knee internal rotation velocities increased (P=0.020, d=0.51). The coupling angles revealed that the ankle movement ratios significantly decreased in 3 planes in comparison with knee movement ratios. CONCLUSIONS: Outcomes of this study illustrated that application of ankle KT leaves the individuals with a stiffer ankle joint, which increases the mechanical stresses to this joint and decreases its stiffness in absorbing the applied shocks. Further, ankle KT application resulted in more knee internal rotation moments and may increase the risk of knee injuries during landing after a long-term usage in patients with instability ankle sprain.

Acute Effect of Ankle Kinesio™ Taping on Lower-Limb Biomechanics During Single-Legged Drop Landing.

CONTEXT: Chronic ankle instability is documented to be followed by a recurrence of giving away episodes due to impairments in mechanical support. The application of ankle Kinesiotaping (KT) as a therapeutic intervention has been increasingly raised among athletes and physiotherapists. OBJECTIVES: This study aimed to investigate the impacts of ankle KT on the lower-limb kinematics, kinetics, dynamic balance, and muscle activity of college athletes with chronic ankle instability. DESIGN: A crossover study design. PARTICIPANTS: Twenty-eight college athletes with chronic ankle sprain (11 females and 17 males, 23.46 [2.65] y, 175.36 [11.49] cm, 70.12 [14.11] kg) participated in this study. SETTING: The participants executed 3 single-leg drop landings under nontaped and ankle Kinesio-taped conditions. Ankle, knee, and hip kinematics, kinetics, and dynamic balance status and the lateral gastrocnemius, medial gastrocnemius, tibialis anterior, and peroneus longus muscle activity were recorded and analyzed. RESULTS: The application of ankle KT decreased ankle joint range of motion (P = .039) and angular velocities (P = .044) in the sagittal plane, ground reaction force rate of loading (P = .019), and mediolateral time to stability (P = .035). The lateral gastrocnemius (0.002) and peroneus longus (0.046) activity amplitudes also experienced a significant decrease after initial ground contact when the participants' ankles were taped, while the application of ankle KT resulted in an increase in the peroneus longus (0.014) activity amplitudes before initial ground contact. CONCLUSIONS: Ankle lateral supports provided by KT potentially decreases mechanical stresses applied to the lower limbs, aids in dynamic balance, and lowers calf muscle energy consumption; therefore, it could be offered as a suitable supportive means for acute usage in athletes with chronic ankle instability.

Balance control during stair descent on compliant surface is associated with knee flexor and ankle plantar flexor strength in older adults.

Balance and lower limb strength deficits are associated with a high incidence of falls in older adults. This study investigated the association between balance control during and after stair descent onto a compliant surface and lower limb strength. Thirty-five women and 14 men participated in this study. Stair descent time, mean center of pressure velocity in anteroposterior and mediolateral direction during stair descent (CoP VAP and CoP VML), and CoP velocity in the first 5 s of restabilization phase (CoP V5) were evaluated. Bilateral strength of the knee flexors and extensors, and ankle plantar and dorsal flexors was evaluated. Spearman correlation analysis with Bonferroni correction yielded a significant association between the strength of the knee flexors on the trailing limb and stair descent time in women (r = 0.502, p = 0.002, R2 = 0.246). The same analysis in men revealed a significant association between the strength of the knee flexors on the trailing limb and CoP VAP (r = -0.820, p < 0.001, R2 = 0.280) and CoP VML (r = -0.697, p = 0.006, R2 = 0.359). The strength of the ankle plantar flexors on the trailing limb was significantly associated with stair descent time (r = 0.684, p = 0.007, R2 = 0.429) and CoP VAP (r = -0.723, p = 0.003, R2 = 0.408) in men. Stair descent balance control is associated with knee flexion strength on trailing limb in women, and with ankle plantar flexion and knee flexion strength on the same limb in men.

Is There a Relationship Between Workload and Occurrence of Back Pain and Back Injuries in Athletes?

The back is subjected to a great deal of strain in many sports. Up to 20% of all sports injuries involve an injury to the lower back or neck. Repetitive or high impact loads (e.g., running, gymnastics, skiing) and weight loading (e.g., weightlifting) affect the lower back. Rotation of the torso (e.g., golf, tennis) causes damage to both, the lumbar and thoracic spine. The cervical spine is most commonly injured in contact sports (e.g., boxing, football). One of the factors that increases the odds of injuries in athletes is excessive and rapid increases in training loads. In spite of currently emerging evidence on this issue, little is known about the balance between physiological loading on the spine and athletic performance, versus overloading and back pain and/or injury in athletes. This scoping review aims (i) to map the literature that addresses the association between the training load and the occurrence of back pain and/or injury, especially between the Acute:Chronic Workload Ratio (ACWR) and back problems in athletes of individual and team sports, and (ii) to identify gaps in existing literature and propose future research on this topic. A literature search of six electronic databases (i.e., MEDLINE, PubMed, Web of Science, SCOPUS, SportDiscus, and CINAHL) was conducted. A total of 48 research articles met the inclusion criteria. Findings identified that fatigue of the trunk muscles induced by excessive loading of the spine is one of the sources of back problems in athletes. In particular, high training volume and repetitive motions are responsible for the high prevalence rates. The most influential are biomechanical and physiological variations underlying the spine, though stress-related psychological factors should also be considered. However, limited evidence exists on the relationship between the ACWR and back pain or non-contact back injuries in athletes from individual and team sports. This may be due to insufficiently specified the acute and chronic time window that varies according to sport-specific schedule of competition and training. More research is therefore warranted to elucidate whether ACWR, among other factors, is able to identify workloads that could increase the risk of back problems in athletes.

The effect of ankle Kinesio™ taping on ankle joint biomechanics during unilateral balance status among collegiate athletes with chronic ankle sprain.

OBJECTIVES: To determine the effects of ankle Kinesio-taping (KT) on postural sway, lower limb ROM, and muscle activity during a unilateral balance tasks. DESIGN: Case control study design. SETTING: Data were collected at the human movement analysis laboratory. PARTICIPANTS: 30 collegiate athletes with chronic ankle sprain (11 females and 19 males, 23.91 ± 2.58 years). MAIN OUTCOME MEASURE: Hip, knee and ankle joints ranges of motion (ROMs); postural sway area and velocities in both anteroposterior and mediolateral directions; and muscular activity amplitudes (% peak) of lateral and medial gastrocnemius, tibialis anterior and peroneus longus in a 20s single leg balance test in two non-taped (control) and KT (intervention) conditions. RESULTS: Significant decrease observed in ankle lateral ROM (p = 0.048, d = 0.52), mediolateral postural sway velocity (p = 0.029, d = 1.25), and peroneus longus activity amplitudes (p = 0.042, d = 0.55) after KT application. CONCLUSION: Acute application of KT among athletes with chronic ankle instability could provide lateral mechanical support to the ankle, potentially decreasing the velocity of frontal plane sway, and decreasing the magnitude of muscle activation. These data suggest that KT may be beneficial for improving static joint stability among individuals with chronic ankle sprain, and thus could be considered an option to allow safe return-to-activity.

Effect of aging on the association between ankle muscle strength and the control of bipedal stance.

Previous studies reported a significant association between postural control and lower-limb strength of several muscle groups, however, they were focused especially on knee muscles and ankle plantar and dorsal flexors. The aim of the present study is to examine the correlation between the muscle strength of ankle invertors, evertors, plantar flexors, and dorsal flexors and the control of bipedal stance in young and older adults. Thirty one young (aged 22.8 ± 2.6 years) and thirty one older adults (aged 70.5 ± 7.2 years) voluntarily participated in this study. Ankle muscle strength was evaluated by an isokinetic dynamometer. Normalized peak torque and work were averaged for four repetitions and for both lower limbs. The control of bipedal stance was evaluated by the sample entropy derived from an accelerometer placed on the lumbar spine while the subject stood on a foam pad with eyes open. Results showed significant age-related differences in ankle muscle strength and sample entropy in medial-lateral direction. More interestingly, the correlation between ankle muscle strength and the sample entropy was significantly different between young and older adults. Indeed, no significant correlation was observed in the younger adults. Conversely, in the older adults, the work of the ankle evertors positively correlated with sample entropy in the medial-lateral direction during bipedal stance (r = 0.36), whereas the peak torque and work of the dorsal flexors were significantly correlated with sample entropy in the anterior-posterior direction during bipedal stance (r = 0.44 for both variables). In the young adults, results suggest that, standing on foam with eyes open is a relatively easy postural task that does not require the full ankle muscle strength capacity. Taken together, the present findings suggest that older adults have a different association between ankle muscle strength and the sample entropy during bipedal stance.

The effect of balance training intervention on postural stability in children with asthma.

OBJECTIVE: Pulmonary rehabilitation is mainly focused on exercise training and breathing retraining in children with asthma. Conversely, balance training is not usually recommended for the treatment, although postural deficits were found in these patients. Therefore, this study assessed the effect of balance training intervention on postural stability in children with asthma. METHODS: Nineteen children with mild intermittent asthma (age 11.1 ± 2.1 years, height 147.6 ± 13.9 cm, weight 41.8 ± 13.3 kg) were randomly assigned to an experimental group or a control group and completed a four-week physiotherapy program including breathing exercises and aerobic physical training (six times/week, 45 minutes). Both groups performed the same training, but only the experimental group underwent exercises on balance devices. The center of pressure (CoP) velocity in the anteroposterior (Vy) and mediolateral (Vx) directions, and total CoP velocity (Vtot) were recorded before and after training in the preferred and the adjusted stances under eyes open (EO) and eyes closed (EC) conditions. RESULTS: The addition of balance intervention led to significant improvements of Vtot (p = 0.02, p = 0.04) in both types of stance, Vx in the preferred stance (p = 0.03) and Vy in the adjusted stance (p = 0.01) under EO conditions. Significant improvements were also found in Vy in the adjusted stance (p = 0.01) under EC conditions. CONCLUSIONS: Results of this study support the effectiveness of balance training as a part of physiotherapy treatment for improving balance performance, predominantly under EO conditions, in children with mild asthma.

Muscular Power during a Lifting Task Increases after Three Months of Resistance Training in Overweight and Obese Individuals.

BACKGROUND: This study evaluates the effect on power produced during a modified lifting task in the overweight and obese after three months of either resistance or aerobic training. METHODS: Seventeen male subjects divided randomly into two groups performed deadlift and deadlift high pull, both with increasing weights up to maximal power, prior to and after the training programs (three sessions per week). RESULTS: Their mean power increased significantly during the deadlift at 20 kg (14.3%, p = 0.026), 30 kg (17.7%, p = 0.008), 40 kg (16.5%, p = 0.011), 50 kg (14.5%, p = 0.020), and 60 kg (14.3%, p = 0.021) and during the deadlift high pull at 30 kg (9.9%, p = 0.037), 40 kg (10.1%, p = 0.035), and 50 kg (8.2%, p = 0.044) after the resistance training. However, the group that participated in the aerobic training failed to show any significant changes in power performance during either the deadlift or deadlift high pull. CONCLUSION: Three months of resistance training enhances power outputs during a lifting task with weights from 30 to 50 kg (~40%⁻60% of 1-repetition maximum) in the overweight and obese. Because this test was sensitive in revealing pre-post training changes in lifting performance, it should be implemented in the functional diagnostics for overweight and obese individuals and also complement existing testing methods.

Balance Performance During Perturbed Standing Is Not Associated With Muscle Strength and Power in Young Adults.

The authors investigate the ways in which varied postural responses to translating platform perturbations are associated with the variables of strength and power. Twenty-four physically active and 27 sedentary young adults were exposed to a set of postural perturbations at varied velocities (10 and 20 cm/s) and the respective accelerations (6.4 and 6.9 m/s2), constant distance (6 cm), and 4 directions of platform motion (forward, backward, left-lateral, and right-lateral). They also performed maximum voluntary isometric contraction (MVC) and chair rising/chair jumping tests. The analysis of variance revealed significant interaction effect for peak center of pressure displacement, direction by velocity: F3,129 = 24.43, p = .002; and direction by acceleration: F3,129 = 34.18, p = .001. There were no significant correlations between peak center of pressure displacements and peak force and peak rate of force development measured during MVC in either standing (r = .27-57) or sitting positions (r = .12-51) and peak power during chair jumping (r = .47-.59) in all participants. As such, only a small proportion of variance was explained (9-39%, 3-23%, and 23-41%, respectively). In conclusion, interaction effects indicate that the composition of stimuli strongly influences compensatory responses and this effect is more pronounced in sedentary than in physically active young adults. Nevertheless, the dynamic balance is not associated with muscle strength and power in either group.

Unilateral Stability and Visual Feedback Body Control Improves After Three-Month Resistance Training in Overweight Individuals.

The authors evaluated the effect of 3 months of resistance and aerobic training (3 sessions/week) on body balance in a group of 25 overweight and obese individuals. Prior to and after the training, they performed static and task-oriented balance tests under various conditions. Mean center of pressure (CoP) velocity and mean trace length of the CoP in the y-axis registered during a one-legged stance significantly decreased after the resistance training (19.1%, p = .024; 29.3%, p = .009). Mean trace length of the CoP in the y-axis decreased significantly also during a bipedal stance on a foam surface with eyes open and closed (10.9%, p = .040; 18.2%, p = .027). In addition, mean CoP distance and mean squared CoP distance in the anteroposterior direction during a visually guided center of mass (CoM) tracking task significantly improved (14.7%, p = .033; 28.2%, p = .016). However, only mean trace length of the CoP in the y-axis during a bipedal stance on a foam surface with eyes open and closed significantly decreased after the aerobic training (10.3%, p = .047; 16.5%, p = .029). It may be concluded that resistance training is more efficient for the improvement of the anteroposterior unilateral stability and the accuracy of the regulation of the CoM anteroposterior position than aerobic training in overweight and obese individuals.

Upper and Lower Body Muscle Power Increases After 3-Month Resistance Training in Overweight and Obese Men.

This study evaluates the effect of 3 months resistance and aerobic training on muscle strength and power in 17 male overweight and obese men. Subjects underwent either a resistance or aerobic training for a period of 3 months (three sessions per week). Peak isometric force, rate of force development, peak power and height of countermovement and squat jumps, reactive strength index, and mean power in the concentric phase of bench presses were all assessed prior to and after completing the training program. Results identified a significant increase of mean power during both countermovement bench presses at 30 kg (18.6%, p = .021), 40 kg (14.6%, p = .033), and 50 kg (13.1%, p = .042) and concentric-only bench presses at 30 kg (19.6%, p = .017) and 40 kg (13.9%, p = .037) after the resistance training. There was also a significant increase in the height of the jump (12.8%, p = .013), peak power (10.1%, p = .026), and peak velocity (9.7%, p = .037) during the countermovement jump and height of the jump (11.8%, p = .019), peak power (9.6%, p = .032), and peak velocity (9.5%, p = .040) during the squat jump. There were no significant changes in the reactive strength index, peak force, and the rate of force development after the resistance training. The aerobic group failed to show any significant improvements in these parameters. It may be concluded that 3 months of resistance training without caloric restriction enhances upper and lower body muscle power in overweight and obese men.

Three months of resistance training in overweight and obese individuals improves reactive balance control under unstable conditions.

BACKGROUND: Contrary to static and dynamic balance, there is a lack of scientific evidence on the training induced changes in reactive balance control in response to unexpected perturbations in overweight and obese individuals. OBJECTIVE: This study evaluates the effect of 3 months of resistance and aerobic training programs on postural responses to unexpected perturbations under stable and unstable conditions in the overweight and obese. METHODS: A group of 17 overweight and obese subjects, divided into two groups, underwent either resistance or aerobic training for a period of 3 months (3 sessions per week). Prior to and after completing the training, they performed the load release balance test while standing on either a stable or unstable surface, with eyes open and closed. RESULTS: Peak posterior center of pressure (CoP) displacement, and the time to peak posterior CoP displacement during a bipedal stance on a foam surface with eyes open (17.3%, p = 0.019 and 15.4%, p = 0.029) and eyes closed (15.0%, p = 0.027 and 13.2%, p = 0.034), decreased significantly. In addition, the total anterior to posterior CoP displacement, and the time from peak anterior to peak posterior CoP displacement, both with eyes open (18.1%, p = 0.017 and 12.2%, p = 0.040) and eyes closed (16.3%, p = 0.023 and 11.7%, p = 0.044), also significantly decreased. However, after completing the resistance training, the parameters registered while standing on a stable platform, both with eyes open and closed, did not change significantly. The group that underwent an aerobic training also failed to show any significant changes in parameters of the load release balance test. CONCLUSION: Three months of resistance training in overweight and obese subjects improves reactive balance control in response to unexpected perturbations under unstable conditions, both with and without visual cues. Due to the fact that this unstable load release balance test was found to be sensitive in revealing post-training changes, it would be suitable for implementing in the functional diagnostic for this group, in addition to complementing existing testing methods.

Postural stability in school-age children with mild bronchial asthma disease (a pilot study).

OBJECTIVE: This study assessed the postural stability in children with asthma using balance tests under conditions of a comfortable foot placement and with a foot placement provoking instability. METHODS: A group of 10 school children from 8 to 10 years old with mild intermittent asthma and 10 healthy children of the same age range performed four balance tests in a randomized order: preferred stance, adjusted stance, and tandem stance each under both conditions of eyes opened (EO) and eyes closed (EC), as well as a one-legged stance with eyes-opened conditions. To determine postural stability, the center of pressure (CoP) movement was recorded. Basic stabilographic parameters were calculated: CoP velocity in the anterior-posterior direction, CoP velocity in the medial-lateral direction, and the total CoP velocity. RESULTS: Statistically significant differences between the groups were found only for the one-legged stance. Significantly greater anterior-posterior CoP velocity (p = 0.05) and total CoP velocity (p = 0.03) were found in children with asthma when standing on the preferred foot. A significantly greater medial-lateral velocity (p = 0.02) was also found in the non-preferred foot of children with asthma. CONCLUSIONS: We can conclude that standing on one leg might be an appropriate test with which to identify balance differences between young children with mild intermittent asthma and healthy children.

The role of lateral preference of lower limbs in a postural stabilization task.

OBJECTIVE: Postural control is a complex skill based on the interaction of dynamic sensorimotor processes. This study assessed the effect of lateral perturbations on postural re-stabilization regarding lower limb preference. METHODS: A group of 14 physically active individuals (9 male, 5 female) randomly underwent postural perturbations in lateral-left and lateral-right directions at a velocity of 0.2 m.s-1 and a platform shift of 6 cm. Perturbation to the preferred limb side (PS) was noted when the contralateral body movement was primarily controlled by the preferred limb and perturbation to the non-preferred limb side (NS) was noted when the contralateral body movement was primarily controlled by the non-preferred (stabilizing) limb. Prior to, during and after the perturbation centre of pressure (CoP) was registered using a computerized motor driven FiTRO Dynamic Posturography System based on force plate (Fitro Sway Check) with a sampling rate of 100 Hz. The basic stabilographic parameters of peak displacement (Peak 1), peak-to-peak displacement (Peak 2), time to peak displacement (Time 1), time to peak-to-peak displacement (Time 2) and re-stabilization time (Time 3) were analyzed. RESULTS: Results showed significantly larger Time 3 on PS than on NS (2.81 ± 1.32 s and 1.73 ± 1.10 s; p=0.02). However, there were no significant differences in other parameters between PS and NS. CONCLUSION: It may be concluded that the observed shorter re-stabilization time at NS was due to the stabilization role of the non-preferred limb.