Effects of Strength Training Using Unstable Surfaces on Strength, Power and Balance Performance Across the Lifespan: A Systematic Review and Meta-analysis

A Practice Guide for Physical Therapists Prescribing Physical Exercise for Older Adults

INTRODUCTION

Physical activity and exercise are protective factors for physical and cognitive decline in older adults, but recent studies reveal that a large percentage of this population do not practice exercise at the levels recommended by international guidelines. The frequency, intensity, type, time, volume, and progression (FITT-VP) principles are a widely used method for prescribing physical exercise, allowing the development of a personalized exercise program that meets the needs of each individual.

OBJECTIVES

This masterclass is intended to serve as a professional application tool for physical therapists who prescribe physical exercise for older adults. We present a section for each FITT-VP principle to facilitate handling these principles individually when prescribing exercise for this population.

METHODS

Review of the scientific literature and international guidelines on the prescription of physical exercises for older adults.

RESULTS

Aerobic, mobility, resistance, balance, and flexibility exercises, as well as functional training, should be included in an exercise program for older adults, which should be progressed using different methods for each of the exercise modalities.

CONCLUSIONS

An exercise program for older adults should integrate different exercise modalities. Exercise progression should be performed following the FITT-VP principles and some specific progression factors recommended for each exercise modality.

SIGNIFICANCE

Considering the challenge faced by clinicians in designing a viable exercise program for older adults that responds to international recommendations, with this masterclass we hope to help physical therapists to plan an exercise program that is feasible and at the same time, responds to the expected needs of this population.

Comparative effects of cognitive and instability resistance training versus instability resistance training on balance and cognition in elderly women

This study investigates the effects of integrated instability resistance training and cognitive training (IRCT) versus isolated instability resistance training (IRT) on balance, gait, muscle strength, and cognitive functions in elderly women.This randomized controlled trial included 36 participants, with 18 in the IRCT group and 18 in the IRT group. The sample size was estimated to achieve a statistical power of 0.95 with a large effect size (0.40; n = 12 each group). The closed-eye single-leg stand test was measured for static balance, the closed-eye stepping test, and the Timed Up and Go Test (TUGT) were measured for dynamic balance. Dual-task balance was assessed by combining the TUGT with cognitive tasks (TUGT-C) and motor tasks (TUGT-M). Gait performance was evaluated using a gait function system. Lower limb muscle strength was measured with the 30-Second Chair Stand Test. Cognitive function was assessed through the Trail Making Test (TMT), Digit Span Test (DST), Stroop Color and Word Test (Stroop), and Digit Symbol Substitution Test (DSST). Results IRCT group showed better improvements in both cognitive (p < 0.001) and motor (p = 0.812 for baseline; p < 0.001 for post-intervention) dual-task abilities, IRCT also experienced better enhancement in certain cognitive functions, particularly in the TMT (p = 0.001) and DSST (p = 0.022) compared to the IRT group. Both groups demonstrated enhancements in walking abilities as shown on selective markers of the gait performance test (p < 0.05) and leg muscle strength via 30-Second Chair (p < 0.001 for time main effect). These results suggest that combining cognitive exercises with physical training more effectively addresses the complex challenges associated with aging in women. The study highlights the potential of comprehensive training approaches in boosting health and quality of life for the elderly, with implications for developing tailored exercise programs focused on reducing fall risks and enhancing quality of life in this population.

Age-Related Changes in Postural Stability in Response to Varying Surface Instability in Young and Middle-Aged Adults

As individuals transition into middle age, subtle declines in postural control may occur due to gradual reductions in neuromuscular control. The current study aimed to examine the effect of age on bipedal postural control across three support surfaces with varying degrees of instability: a firm surface, a foam pad, and a multiaxial balance board. The effect of surface stability was also assessed. Postural accelerations were recorded using a tri-axial accelerometer placed over the lumbar spine (L5) in 24 young female adults (23.9 ± 5.3 years) and 24 middle-aged female adults (51.4 ± 5.9 years). Sample entropy (SampEn) was used to analyze the complexity of postural control by measuring the regularity of postural acceleration. The main results show significant age-related differences in the mediolateral and anteroposterior acceleration directions (p ≤ 0.012). Young adults exhibit more irregular fluctuations in postural acceleration (high SampEn), reflecting greater efficiency or automaticity in postural control compared to middle-aged adults. Increased surface instability also progressively decreases SampEn in the mediolateral direction (p < 0.001), reflecting less automaticity with increased instability. However, no interaction effects are observed. These findings imply that incorporating balance training on unstable surfaces might help middle-aged adults maintain postural control and prevent future falls.

Acute and chronic effects of stretching on balance: a systematic review with multilevel meta-analysis

Introduction

Balance is a multifactorial construct with high relevance in, e.g., everyday life activities. Apart from sensorimotor control, muscle strength and size are positively linked with balance performance. While commonly trained for via resistance training, stretch training has emerged as a potential substitution in specific conditions. However, no review has investigated potential effects of stretching on balance, yet.

Methods

PubMed, Web of Science and Scopus were searched with inception to February, 2024. Studies were included if they examined acute and/or chronic effects of any stretching type against passive and/or active controls on balance parameters - without any population-related restrictions concerning sex/gender, age, health status, activity level. Methodological quality was assessed using PEDro scale. Meta-analyses were performed if two or more studies reported on the same outcome. Certainty of evidence was determined based on GRADE criteria.

Results

Eighteen acute and eleven chronic effect studies were included. Stretching studies exhibited significant improvements for sway parameters with eyes open against passive controls of moderate magnitude for chronic (ES: 0.63, p = 0.047) and of small magnitude for acute studies (ES: 0.21, p = 0.032). Most other subgroups against passive controls as well as actively-controlled comparisons resulted in trivial and/or non-significant effects.

Conclusion

Even though some pooled effects slightly reached the level of significance, the overall results are biased by (very) low certainty of evidence (GRADE criteria downgrading for risk of bias, imprecision, publication bias). Moderators suggested by literature (strength, muscle size, flexibility, proprioception) were rarely assessed, which prevents conclusive final statements and calls for further, high quality evidence to clarify potential mechanisms-if any exist.

Adapted Training to Boost Upper Body Sensorimotor Control and Daily Living Functionality in Visually Impaired Baseball Players

Background and Objectives: Vision significantly contributes to postural control, balance, coordination, and body kinematics, thus deeply influencing everyday functionality. Sight-impaired subjects often show upper body anatomofunctional and kinetic chain alterations negatively impacting daily living efficiency and autonomy. The present study aimed to investigate and train, for the first time, upper body sensorimotor control in an Italian blind baseball team to boost global and segmental functionality while contemporarily prevent injuries. Materials and Methods: The whole team underwent a validated test battery using both quantitative traditional tools, such as goniometric active range of motion and muscular/functional tests, and an innovative biofeedback-based device, a Libra proprioceptive board. Consequently, a 6-week adapted training protocol was designed and leaded to improve sensorimotor control and, hence, counteract disability-related deficits and sport-specific overuse syndromes. Results: Statistically significant improvements were observed in all the investigated parameters. Noteworthy, an overall boost of global and segmental stability was detected through an orthostatic dynamic balance enhancement during the Y Balance test (p = 0.01) and trunk multiplanar control improvement on the Libra board (p = 0.01). Concurrently, the comparison of baseline vs. post-intervention outcomes revealed a consistent increase in upper body mobility (p < 0.05 for all the assessed districts), core recruitment (p = 0.01 for all the administered functional tests), and proprioceptive postural control (p = 0.01 for the Libra board validated test). Conclusions: Our findings suggest that a tailored sensorimotor training, conceived and led by an adapted physical activity kinesiologist, may effectively improve upper body functional prerequisites and global proprioceptive control, thus potentially promoting autonomy, quality of life, and physical activity/sport practice adherence in visually impaired individuals.

Multimodal training protocols on unstable rather than stable surfaces better improve dynamic balance ability in older adults

BACKGROUND

There has been growing interest in using unstable devices in training protocols. This study aimed to assess the effectiveness of two multimodal exercise interventions (i.e., on stable and unstable surfaces) on dynamic balance control and lower limb strength in older adults.

METHODS

Sixty-two older adults were randomly assigned to two intervention groups (N = 20, stable group; N = 19, unstable group), and to a control group (N = 18). In this single-blinded randomized controlled study, the two intervention groups underwent a 12-week training program twice a week for 45 min, consisting of strength and balance exercises. The stable (ST) group performed the training program over stable surfaces, while the unstable (UNST) group over unstable surfaces. Dynamic balance was assessed by computing the center of pressure (CoP) trajectory while a driven movable platform induced an unexpected perturbation of the base of support. Specifically, we considered the following CoP-related parameters within a 2.5-s temporal window from the beginning of the perturbation: displacement (Area95), mean velocity (Unit Path), anterior-posterior first peak (FP), post perturbation variability (PPV), and maximal oscillations (ΔCoPMax). The dominant quadriceps strength was measured through an isometric maximal voluntary contraction on an instrumented chair.

RESULTS

Four out of five CoP-related parameters (i.e., Area95, Unit Path, ΔCoPMax, and PPV) significantly improved in the UNST group from a minimum of 14.28% (d = 0.44) to a maximum of 52.82% (d = 0.58). The ST group significantly improved only in two (i.e., ΔCoPMax, and PPV) out of five CoP-related parameters with an enhancement of 12.48% (d = 0.68) and 19.10% (d = 1.06). Both intervention groups increased the maximal isometric quadriceps strength (UNST:17.27%, d = 0.69; ST:22.29%, d = 0.98). The control group did not show changes in any of the parameters considered.

CONCLUSIONS

Stable surfaces promoted faster increments of muscular strength. Unstable surfaces were more effective in enhancing dynamic balance efficiency. These findings suggested the employment of multimodal training on unstable rather than stable surfaces to potentially lower the incidence of falls in older adults.

TRIAL REGISTRATION

NCT05769361, retrospectively registered 13 March 2023, https://clinicaltrials.gov/study/NCT05769361?lat=45.3661864&lng=11.8209139&locStr=Padova,%20Italy&distance=50&page=11&rank=107 .

A 12-week Taijiquan practice improves balance control and functional fitness in fall-prone postmenopausal women

Purpose

Falls are the leading cause of accidental death among older persons, with postmenopausal women facing a greater hazard of falling due to osteoporosis. This study aimed to examine the effects of Taijiquan practice on balance control and functional fitness in at-risk females.

Methods

Chinese women who self-reported a tendency to fall and had a baseline one-leg stand test time (4.1 s in the Taijiquan group) below the national average for their age group (60-64 years: 10.9 s, 65-69 years: 9.9 s) were assigned to either a control group (n = 26, mean age = 63.9 years) or a Taijiquan group (n = 24, mean age = 63.9 years). The Taijiquan group participated in a 12-week supervised intervention, while the control group maintained their daily activities. The average duration of each exercise session was 52 min. Static balance and functional fitness were assessed at the beginning and end of the intervention.

Results

After 12 weeks, the Taijiquan group significantly outperformed the control group in terms of balance, flexibility, and muscular fitness (all p < 0.05). Participants in the Taijiquan group improved their one-leg stand by 61.0% (+2.5 s, Hedge's g = 0.85), arm curl by 8.3% (+1.7 repetitions, g = 0.53), handgrip strength by 8.3% (+1.9 kg, g = 0.65), and sit-and-reach by 163.2% (+6.2 cm, g = 1.17).

Conclusion

The improvement in balance, coupled with other functional fitness benefits, suggests that Taijiquan could serve as a useful exercise for older women with an elevated risk of falling.

Resistance Training with Instability Does Not Hamper Total Training Volume and Muscle Strength Gains in Older Adults: a Secondary Analysis from REI Study

Background

Resistance training with instability (REI) emerged as a promising training modality for older adults aiming to counteract age-related changes.

Objectives

We compared the effects of 12 weeks of REI and traditional resistance exercise (RE) on muscle strength in older adults with cognitive impairment. We further explored if total training volume (TTV) significantly differs among training groups.

Methods

This is a secondary analysis of the REI study. Participants were randomly assigned to REI (n=22) or RE (n=23). RE protocol involved moderate-intensity, free-weight, and machines-based resistance exercises (3 sets, 10-15 repetitions). REI received a similar training protocol, in which exercises were simultaneously performed with instability/unstable devices (e.g., squat exercise under a foam pad or Bosu® ball). Maximal isometric strength and isokinetic parameters were assessed at baseline and after completion of a 12-week intervention through a hydraulic handgrip and isokinetic dynamometer, respectively. TTV (sets × repetitions × load) was computed based on external training load over the 12 weeks.

Results

No differences were observed between groups (p=.35) after the intervention. Over 12 weeks, REI and RE improved isometric handgrip strength (p<.001) and isokinetic performance (p=.04). We also did not find differences in the TTV between training groups (p=.28).

Conclusion

We demonstrated that both REI and RE training induced similar gains in muscle strength. Combining unstable surfaces/instability devices did not hamper TTV, which may have clinical applications in the context of exercise for older adults.

Effect of core stabilization versus rebound therapy on balance in children with cerebral palsy

OBJECTIVE

This study aimed to compare the effect of core stabilization exercises and rebound therapy on balance in children with hemiplegic cerebral palsy (CP).

METHODS

Fifty- two children of spastic hemiplegic CP aged 5 up to 8 years from both genders were assigned randomly into two groups: core stability and rebound therapy groups. Both groups received 3 sessions/week, 1.5-h training per session, for 12 successive weeks. The measurement was performed at baseline and post-treatment. Balance as a primary outcome for this study was measured by a Biodex Balance System (BBS), and knee extensor strength and functional capacity as secondary outcomes were assessed using a hand-held dynamometer, and a six-minute walk test (6MWT), respectively.

RESULTS

All variables showed a significant improvement after intervention in each group (p < 0.0001), with significant improvement in all stability indices (overall, anteroposterior, and mediolateral) in core stability group when compared to rebound therapy group.

CONCLUSION

Core stability exercises and rebound therapy are recommended in the rehabilitation of children with hemiplegic CP. Core stability exercises were more effective than rebound therapy for balance improvement.

TRIAL REGISTRATION NUMBER

NCT05739396.

The Duration of Non-Local Muscle Fatigue Effects

Non-local muscle fatigue (NLMF) refers to a transient decline in the functioning of a non-exercised muscle following the fatigue of a different muscle group. Most studies examining NLMF conducted post-tests immediately after the fatiguing protocols, leaving the duration of these effects uncertain. The aim of this study was to investigate the duration of NLMF (1-, 3-, and 5-minutes). In this randomized crossover study, 17 recreationally trained participants (four females) were tested for the acute effects of unilateral knee extensor (KE) muscle fatigue on the contralateral homologous muscle strength, and activation. Each of the four sessions included testing at either 1-, 3-, or 5-minutes post-test, as well as a control condition for non-dominant KE peak force, instantaneous strength (force produced within the first 100-ms), and vastus lateralis and biceps femoris electromyography (EMG). The dominant KE fatigue intervention protocol involved two sets of 100-seconds maximal voluntary isometric contractions (MVIC) separated by 1-minute of rest. Non-dominant KE MVIC forces showed moderate and small magnitude reductions at 1-min (p < 0.0001, d = 0.72) and 3-min (p = 0.005, d = 0.30) post-test respectively. The KE MVIC instantaneous strength revealed large magnitude, significant reductions between 1-min (p = 0.021, d = 1.33), and 3-min (p = 0.041, d = 1.13) compared with the control. In addition, EMG data revealed large magnitude increases with the 1-minute versus control condition (p = 0.03, d = 1.10). In summary, impairments of the non-exercised leg were apparent up to 3-minutes post-exercise with no significant deficits at 5-minutes. Recovery duration plays a crucial role in the manifestation of NLMF.

Comparison of the Electromyography Activity during Exercises with Stable and Unstable Surfaces: A Systematic Review and Meta-Analysis

The effect of electromyographic (EMG) activity on agonist muscles during exercises performed on stable and unstable surfaces remains uncertain. We aimed to review the literature regarding the comparison of the EMG activity of the agonist muscles of exercises performed on stable and unstable surfaces. Eighty-six studies that evaluated the EMG activity of 1783 individuals during exercises for the lower limbs, upper limbs, and core were included. The EMG activities of the pectoralis major (SMD = 0.28 [95% CI 0.09, 0.47]) and triceps brachii muscles (SMD = 0.45 [95% CI 0.25, 0.66]) were significantly increased when the unstable device was added to the exercise. Likewise, the EMG activity of all core muscles showed a significant increase with the unstable surface during the exercises, such as the rectus abdominis (SMD = 0.51 [95% CI 0.37, 0.66]), external oblique (SMD = 0.44 [95% CI 0.28, 0.61]), internal oblique (SMD = 1.04 [95% CI 0.02, 2.07]), erector spinae (SMD = 0.37 [95% CI 0.04, 0.71]), and lumbar multifidus (SMD = 0.35 [95% CI 0.08, 0.61]). However, the lower limb muscles did not show greater EMG activity during the exercise with unstable surfaces compared to the stable surface. In conclusion, unstable conditions increase the EMG activity of some upper limb and core muscles compared to a stable surface.

Effects of an integrative warm-up method on the range of motion, core stability, and quality of squat performance of young adults

Introduction

This research aims to determine the effects of an integrative warm-up method on the range of motion in joints of the lower extremities, the strength of the stabilizer trunk muscles, and the quality of the basic movement patterns in older adolescents.

Methods

The study sample consisted of 88 male students (age 20.1 ± 0.5). They were randomly divided into four groups: one control group (CG) (n = 17; 180.8 ± 7.9 cm; 82.3 ± 8.3 kg) and three experimental groups (EG): EG1 (n = 23; 180.9 ± 7.0 cm; 78.5 ± 9.5 kg), EG2 (n = 31; 182.2 cm ± 7.3 cm; 79.5 ± 11.5 kg), and EG3 (n = 17; 183.3 ± 4.9 cm; 77.5 ± 11.8 kg). The participants were subjected to a 6-week experimental treatment: EG1 once, EG2 twice, and EG3 three times a week. The experimental treatment consisted of four sub-phases representing the integrative warm-up Method: 1) Inhibition (self-myofascial release using a foam roller); 2) Lengthening (Static stretching in a maximum range of motion position); 3) Activation (Positional isometrics muscle activation of the trunk and gluteus); 4) Integration (Integrated all the previous phases into one complex movement pattern). Based on the covariance analysis (ANCOVA), statistically significant treatment effects were observed and positive changes were determined in all experimental groups.

Results

The differences between groups were observed in the following variables: Overhead Squat Assessment (p = 0.000; η p 2 = 0.318 ), range of motion of left hip flexion (p = 0.000; η p 2 = 0.371 ), range of motion of right hip flexion (p = 0.000; η p 2 = 0.051 ) and range of motion of right hip extension (p = 0.051; η p 2 = 0.088 ), Double Leg Lowering Test (F = 2.411; p = 0.014; η p 2 = 0.014 ) and range of combined motion (plantar and dorsiflexion) of left ankle joint (p = 0.000; η p 2 = 0.299 ). There was no significant difference in the Plank Test (F = 1.007; p = 1.007; η p 2 = 0.035 ), range of combined motion (plantar and dorsiflexion) of right ankle joint (p = 0.088; η p 2 = 0.170 ) and range of motion of left hip extension (p = 0.158; η p 2 = 0.060 ). The participants of CG statistically significantly differed from EG1, EG2, and EG3 in the squat performance after the applied treatment.

Discussion

The effect of the treatment was the occurrence of a transformational processes in almost all measured variables. It can be concluded that the integrative method is effective and applicable in practice for both young adults and recreational athletes.

Electromyography of scapular stabilizers in people without scapular dyskinesis during push-ups: a systematic review and meta-analysis

Background: Push-up (PU) is widely considered an effective exercise to stabilize the scapular, especially if performed on unstable surfaces. However, available studies cover a wide range of exercise variations and differ according to exercise prescription, muscle selection and study design. Therefore, findings are contradictory, and conclusions for a proper application of the PU are difficult to draw. Objective: To synthesize the available literature on the changes in the activity of the periscapular muscles in individuals without scapular dyskinesis while performing different types of PU on unstable surfaces. Search procedure: Four online databases were searched from the earliest publications to 9 August 2023, using predefined keywords. Out of the 2,850 potential references identified in the primary search, 92 studies were reviewed in detail, of which 38 met the inclusion criteria and were included. Methodological quality was evaluated using a standardized form based on the Newcastle‒Ottawa scale for observational studies. Data combination was performed using CMA (v3), and the random-effects model was used to calculate the standardized mean difference (SMD) with a 95% confidence interval (CI). Results: The use of unstable surfaces in people without scapular dyskinesis led to increased activity of the upper trapezius during the PU (p = 0.017; I2 = 84.95%; SMD = 0.425 [95% CI 0.077, 0.773]) and knee PU (p = 0.023; I2 = 70.23%; SMD = 0.474 [95% CI 0.066, 0.882]) exercises and increased activity of the middle trapezius (MT) (p = 0.003; I2 = 64.50%; SMD = 0.672 [95% CI 0.225, 1.119]) and serratus anterior (SA) (p = 0.039; I2 = 4.25%; SMD = 0.216 [95% CI 0.011, 0.420]) muscles during the push-up plus (PUP) exercise. Conclusion: Using an unstable support base during PU does not necessarily increase the activity of all scapular stabilizers. The amount of muscle activity depends on the type of PU other than the type of support base. If an unstable surface is used, PUP exercise appears to be the most effective modality to increase the quality of training, improve performance, and prevent the occurrence of scapular dyskinesis due to the increase in the activity of the MT and SA muscles. Systematic Review Registration: http://www.crd.york.ac.uk/PROSPERO, CRD42021268465.

The Evaluation of the Balance Test and MuscleLab Test for the Early Detection of Femoroacetabular Impingement

Femoroacetabular impingement (FAI) is a common source of hip pain affecting a wide range of subjects. In this work, we assessed two tests, namely the balance test and the MuscleLab test, in comparison with the flexion-abduction-external rotation (FABER) and flexion-adduction-internal rotation (FADIR) tests, in order to evaluate the functionality of the neural-musculoskeletal system of the subjects affected by FAI based on the measurement of biomechanical parameters. Our goal was to investigate the early detection of an altered hip joint and to monitor pathology progression over time. A total of 52 subjects, 29 females and 23 males, with an average age of 42 ± 13 years presenting hip impingement diagnosed using X-ray, were enrolled. Twenty-eight patients without signs of hip impingements were used as the control group. The balance test, which evaluates the capacity of a person to keep the orthostatic position against terrestrial gravity, and the MuscleLab test, which measures the force and power generated by active muscles during a movement, as well as FABER and FADIR tests, were performed in each subject. The balance and MuscleLab tests presented 100% sensitivity and higher sensitivity in FAI diagnosis, with 72.9% and 70.4%, respectively, in comparison with those obtained using FABER and FADIR tests, with 59.6% and 67.3%, respectively. The evaluation of the neural-musculoskeletal system using the balance and MuscleLab tests can help in the early detection of the severity of hip impingements and the assessment of non-operative treatments used over time.

Changes After a Conventional vs. an Alternative Therapy Program on Physical, Psychological, and Injury-Related Parameters in Male Youth Soccer Players With Patellar Tendinopathy During Return to Competition

ABSTRACT

Niering, M and Muehlbauer, T. Changes after a conventional vs. an alternative therapy program on physical, psychological and injury-related parameters in male youth soccer players with patellar tendinopathy during return to competition. J Strength Cond Res 37(9): 1834-1843, 2023-Changes after a conventional (CON) vs. alternative (ALT) therapy program on physical, psychological, and injury-related or pain-related parameters in soccer players with patellar tendinopathy (PT) during return to competition were examined. Thirty-four male youth soccer players (15-16 years) with PT were randomly assigned to a CON ( n = 18) or ALT ( n = 16) program. The ALT program consisted of 60 minutes of balance training, eccentric and isometric exercises, static stretching, and a dual-task progression. The CON program consisted of 30 minutes of eccentric and isometric exercises and static stretching. Both programs were conducted until painlessness was reported during full training load. Assessments of muscle power (drop jump, jump and reach), change of direction speed (CODS) (acyclic sprint), speed (tapping, 30-m linear sprint), endurance (Yo-Yo intermittent recovery test level-1), the Achievement Motives Scale Sport, and injury-related or pain-related correlates were performed immediately, 6 weeks, 16 weeks, and 20 weeks after the respective therapy program. Players in the ALT group required a shorter program duration (ALT: 47.1 ± 15.6 days, CON: 58.2 ± 24.6 days) and achieved the same (muscle power, speed, endurance) or greater (CODS) improvements in physical performances, the same enhancements in psychological measures (achievement motives), and better values for injury-related or pain-related correlates (injury incidence, pain-related training interruptions). Results indicate that both programs effectively improve relevant outcome parameters in players with PT. The ALT therapy is more time efficient than the CON therapy. Therapists should consider this multimodal training program for effective treatment of athletes to shorten their return to competition time and minimize the risk of secondary injuries.

Electromyographic and Stabilometric Analysis of the Static and Dynamic "Standing Bird Dog" Exercise

(1) Background: The "bird dog" exercise is considered one of the most effective therapeutic exercises for lumbopelvic rehabilitation and the prevention and treatment of low back pain. The "standing bird dog" (SBD) exercise, executed in a single-leg stance, constitutes a natural and challenging variation in the "bird dog"; nevertheless, this exercise has not yet been investigated. This study provides a stabilometric and electromyographic analysis of the SBD performed in static and dynamic conditions and in ipsilateral and contralateral variations; (2) Methods: A time-synchronized motion capture system, wireless electromyography sensors, and triaxial force platform were used to analyze the selected SBD exercises; (3) Results: In dynamic conditions, the gluteus maximum, multifidus, lumbar erector spinae, and gluteus medius reached a mean activation level higher than in the static condition, with peak activation levels of 80%, 60%, 55%, and a 45% maximum voluntary isometric contraction, respectively. In the static condition, balance control was more challenging in the mediolateral compared to the anteroposterior direction. In the dynamic condition, the balance challenge was higher in the anteroposterior direction and higher than the static condition in both directions; (4) Conclusions: The SBD was proved to be effective for strengthening the hip and lumbar extensor muscles and provided a powerful challenge to single-leg balance control in both mediolateral and anteroposterior directions.

Do Highly Trained Mountain Runners Differ from Recreational Active Non-Runners on Range of Motion and Strength in the Hip and Ankle as Well as Postural Control?

The rules governing mountain running force athletes to implement into their training programmes uphill and downhill running on unstable surfaces, which are demanding for hip and ankle as well as for the postural control system. The aim of the present cross-sectional study was to compare highly trained mountain runners (MR) and recreational active non-runners (NR) on range of motion (ROM) and strength in the hip and ankle, as well as dynamic postural control. Thirty MR and thirty-two NR were included in the study. ROM was assessed using a digital inclinometer. Strength was measured using a hand-held dynamometer. Postural control was evaluated using the lower quarter Y-balance test (YBT-LQ). The results showed that MR, in relation to NR, had statistically significant smaller hip external rotation ROM (p = 0.007), lower hip external rotator (p = 0.006) and extensor (p = 0.023) strength and greater normalised anterior reach in the YBT-LQ (p = 0.028). Mountain running training may reduce hip external rotation ROM as well as hip external rotator and extensor strength. Moreover, such training may improve postural control. MR should implement exercises targeted at developing hip ROM and strength. Furthermore, it seems that mountain running training may be a good way to improve postural control.

Exploring of two different equated instability resistance training programs on measure of physical fitness and lower limb asymmetry in pre-pubertal weightlifters

BACKGROUND

Although previous research in pediatric populations has reported performance enhancements following instability resistance training, the effects of different volumes on measures of balance, strength and power and lower limb asymmetry remain unclear.

OBJECTIVE

To compare the effect of two 8-week instability resistance training programs (IRT1: 2 sets x 8 repetitions, 20% one-repetition maximum (1RM); IRT2: 2 sets x 4 repetitions, 40% 1RM) in balance (center of pressure displacements), 1RM, single-leg jumps, and inter-limb asymmetry of prepubescent weightlifters.

METHODS

Thirty-two male athletes (10.94 ± 0.47 yrs, 17.05 ± 0.14 kg/m², and 6.44 ± 0.93% bodyfat) voluntarily participated and combined IRT (front and back squat, lunge, and deadlift) with their usual weightlifting training. Nonparametric tests evaluated the differences between pre- and post-intervention.

RESULTS

Significant improvements were encountered in all the variables for both groups (effect sizes [ES] from 0.46 to 2.60), except the inter-limb asymmetry and the velocity of displacement of the center of pressure, which did not improve in IRT2. It is also worth highlighting that in the single-leg jumps and center of pressure displacements, whereas no significant differences were observed between IRT1 and IRT2 in the baseline, significant differences appeared in the follow-up measurements.

CONCLUSION

IRT combined with weight-lifting training improves prepubescent weightlifters' performance; therefore, strength and conditioning coaches may consider including unstable devices with low loads into an overall conditioning program and warm-ups for prepuberal male weightlifters to promote their physical fitness and potentially decrease inter-limb asymmetry.

TRIAL REGISTRATION

This study does not report results related to healthcare interventions using human participants; therefore, it was not prospectively registered.

Variations induced by the use of unstable surface do not facilitate motor adaptation to a throwing skill

Induced variability by the use of unstable surfaces has been proposed to enhance proprioceptive control to deal with perturbations in the support base better. However, there is a lack of evidence about its benefits facilitating motor adaptions in upper body skills. In this experiment, practice on an unstable surface was applied to analyze the adaptations in an upper limb precision throwing skill. After a pretest, twenty-one participants were randomly allocated into two groups: one group practiced the throwing task on a stable surface and the other group practiced the same task on an unstable support base. Differences in throwing performance between pre- and post-practice were analyzed in accuracy, hand movement kinematics and variability of the throw in both surface conditions. Fuzzy entropy of the horizontal force was calculated to assess the complexity dynamics of postural sway. Participants improved their performance on the stable and the unstable surface. Induced variability using an unstable surface reduced participants' variability and the complexity of postural sway, but it did not facilitate a superior adaptation of the throwing task. The results suggest that the variations induced by unstable surfaces would fall far from the family of specific motor solutions and would not facilitate additional motor performance of the throwing task.

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.

Effects of stochastic resonance whole-body vibration on sensorimotor function in elderly individuals-A systematic review

Introduction

Due to demographic changes, falls are increasingly becoming a focus of health care. It is known that within six months after a fall, two thirds of fallers will fall again. Therefore, therapeutic procedures to improve balance that are simple and can be performed in a short time are needed. Stochastic resonance whole-body vibration (SR-WBV) may be such a procedure.

Method

An electronic search to assess the effectiveness of SR-WBV on balance in the elderly was conducted using databases that included CINAHL Cochrane, PEDro, and PubMed. Included studies were assessed using the Collaboration Risk of Bias Tool by two independent reviewers.

Results

Nine studies showing moderate methodological quality were included. Treatment parameters were heterogeneous. Vibration frequency ranged from 1 to 12 Hz. Six studies found statistically significant improvements of balance from baseline to post measurement after SR-WBV interventions. One article found clinical relevance of the improvement in total time of the "Expanded Time to Get Up and Go Test".

Discussion

Physiological adaptations after balance training are specific and may explain some of the observed heterogeneity. Two out of nine studies assessed reactive balance and both indicated statistically significant improvements after SR-WBV. Therefore, SR-WBV represents a reactive balance training.

Effects of instability resistance training on static postural control of cognitively impaired older adults

BACKGROUND: Mounting evidence has demonstrated functional and cognitive-related benefits after Instability Resistance Training (IRT) in individuals, healthy as wellas patients presenting with neurological disorders. However, whether IRT may play a significant role in the postural control of older adults has not been established. OBJECTIVE: To evaluate the effects of 12- weeks of IRT on static postural control of older adults with subjective cognitive impairment. METHODS: In this randomized controlled trial, a total of 67 participants (aged 65 years and older) were randomly assigned to either 12 weeks of IRT (n= 22), traditional resistance training (RT) (n= 23), or a health education control group (CON) (n= 22). Static postural control was assessed using a force platform that recorded the displacement amplitude of the center of pressure (CoP) in the anteroposterior (AP) and mediolateral (ML) directions in bipedal support (30 seconds) with eyes open and closed. RESULTS: All groups increased AP displacement in the conditions of eyes open and closed. During the eyes-closed condition, only the IRT group increased the ML displacement. No between-group differences were detected in any postural control (p> 0.05). CONCLUSIONS: 12 weeks of IRT does not improve the static postural control in older adults with cognitive impairment.

Innovative Use of Biodex Balance System to Improve Dynamic Stabilization and Function of Upper Quarter in Recreational Weightlifters: A Randomized Controlled Trial

Background and Objectives: Following an injury, upper-body strength and proprioception training is typically suggested. To our understanding, no prior research has looked into the impact of balance training on upper-body strength and stability. So, this study investigated the effects of Biodex balance training on enhancing the dynamic stability, strength, and function of the upper quarter (UQ) in recreational weightlifters. Materials and Methods: Fifty male weightlifters were randomly assigned into two groups. The experimental group received an upper-extremity Biodex balance training program three times/week for eight weeks, while the control group underwent a regular weightlifting training routine. Pre- and post-test scores of the upper-quarter dynamic stability, strength, and function were measured for both groups using the shoulder active repositioning accuracy test, two-minute push-up test, and the upper-quarter Y-balance test (UQ-YBT) and one-arm hop test, respectively. Results: Post-test values were significantly greater for the normalized UQ-YBT test than pre-test values in both groups (p < 0.05). Post-test values of the experimental group were significantly greater than the control group (p < 0.05). Regarding the shoulder active repositioning accuracy test and the time of the one-arm hop test, post-test values were significantly lower than pre-test values for both groups (p < 0.05), and post-test values of the experimental group were significantly lower than those of the control group (p < 0.05). The post-test value of the two-minute push-up test of each group was significantly higher than the pre-test value (p < 0.05), without any significant difference between both groups (p > 0.05). Conclusions: Adding upper-body Biodex balance training to a regular weightlifting training routine was effective in enhancing the upper quarter′s dynamic stability and function.

Effects of resistance training combined with balance training on physical function among older adults: a protocol for a randomised controlled trial

INTRODUCTION

The world's population is ageing. Age-related declines in physical function negatively affect the quality of life but may be ameliorated by certain types of exercise. The purpose of this study is to investigate the effects of combining resistance training (RT) with balance training on physical function in older community-dwelling adults to provide a reference for this type of exercise compared with other exercises and to provide a theoretical basis for optimising exercise plans to improve physical function among older adults.

METHODS

This single-blind randomised controlled trial will recruit 66 community dwelling adults 60-89 years of age with normal cognition. Participants will be randomly assigned to one of three groups: RT, RT combined with balance training or a control group with usual daily activities. Exercise interventions will be conducted in three 45 min sessions per week for 24 weeks. Primary physical function outcomes will be assessed using the timed up and go test, usual walking speed, maximal walking speed, 30 s chair stand and 30 s arm curl. Secondary assessments will be conducted using the 2 min step test, back scratch test and chair sit-and-reach test. All physical function assessments will be performed at baseline and after 12 and 24 weeks of exercise interventions. Exercise intensity will be monitored to maintain moderate intensity by heart rate, ratings of perceived exertion and OMNI-Resistance Exercise Scale. Data that conform to a normal distribution will be expressed as means±SD, otherwise as medians and interquartile intervals. Pretest, mid-test and post-test outcomes will be analysed for within-group and between-group comparisons using two-way repeated measures analyses of variance.

ETHICS AND DISSEMINATION

This proposal was reviewed and approved by the Shanghai University of Sport Research Ethics Committee (102772021RT067). The results will be disseminated to the trial participants and as a peer-reviewed publication.

TRIAL REGISTRATION NUMBER

ChiCTR2200056090.

Prospective comparative study between knee alignment-oriented static and dynamic balance exercise in patellofemoral pain syndrome patients with dynamic knee valgus

Exercise therapy has been reported as an effective treatment method for patellofemoral pain syndrome (PFPS). However, there is a lack of studies regarding the effectiveness of balance exercise in the treatment of patients with PFPS. This study aimed to prospectively compare changes in proprioception, neuromuscular control, knee muscle strength, and patient-reported outcomes between patients with PFPS treated with knee alignment-oriented static balance exercise (SBE) and dynamic balance exercise (DBE). The participants were divided into 2 groups: 17 knee alignment-oriented SBE group and 19 knee alignment-oriented DBE group. Proprioception was assessed by dynamic postural stability using postural stabilometry. Neuromuscular control and knee muscle strength were measured for acceleration time and peak torque in quadriceps muscle using an isokinetic device. Patient-reported outcomes were evaluated using a visual analog scale for pain and the Kujala Anterior Knee Pain Scale. There was greater improvement in dynamic postural stability (0.9 ± 0.3 vs 1.2 ± 0.5; 95% confidence interval [CI]: 0, 0.6; Effect size: 0.72; P = .021) and quadriceps AT (40.5 ± 14.3 vs 54.1 ± 16.9; 95% CI: 2.9, 24.2; Effect size: 0.86; P = .014) in the DBE group compared to the SBE group. Knee alignment-oriented DBE can be more effective in improving dynamic postural stability and quadriceps muscle reaction time compared with the knee alignment-oriented SBE in PFPS patients with dynamic knee valgus.

Functional and Traditional Resistance Training Are Equally Effective in Increasing Upper and Lower Limb Muscular Endurance and Performance Variables in Untrained Young Men

Background: Functional resistance training (FRT) has been proposed as a safe alternative to traditional resistance training (TRT) for developing neuromuscular adaptation capacity and improving muscular strength and competitive performance. This study sought to compare the effects of 6 weeks of FRT and TRT on upper and lower limb muscular endurance and performance variables in untrained young men.

Methods: Twenty-nine untrained healthy young males aged 18–29 years were randomly given 6 weeks of FRT [40% of 1repetition maximum (RM), 4,5 sets of 20 repetitions, 3 times/week] or TRT (70% of 1RM, 4,5 sets of 12 repetitions, 3 times/week). All participants underwent numerous tests before and after the 6-week training, such as muscular endurance (reps of bench press and leg flexion) and physical performance tests (sprint performance, pull-ups, throwing ability, and jumping ability).

Results: After the 6 weeks of training, the TRT and FRT groups showed an equally significant increase in muscular endurance (p &lt; 0.01), while the throwing and jumping abilities, 30-m sprint, and pull-ups performances in both the groups (p &lt; 0.01) also improved significantly. However, no differences were observed between the groups (p &gt; 0.05).

Conclusion: These findings indicate that both functional resistance training and traditional resistance training are effective training methods for improving the upper and lower limb muscular endurance and performance in untrained young men.

The Effects of Vision-Deprived Progressive Resistance Training on One-Repetition Maximum Bench Press Performance: An Exploratory Study

The objective of this study was to determine whether vision-occluded progressive resistance training would increase upper-extremity movement performance using the one-repetition maximum (1-RM) bench press. Participants (n = 57) were recruited from a historically black college and university (HBCU), cross-matched by sex, age (±1 year), 1-RM (±2.27 kg), 1-RM/weight (±0.1), and 1-RM/lean mass ratio (±0.1), and randomly assigned to either the experimental group (vision occluded) or the control group. Participants performed resistance training for 6 weeks prior to beginning the study, and 1-RM was assessed the week prior to the beginning of the study. Weight and body composition were measured using a BOD POD. Of the 57 participants who started the study, 34 completed the study (Experimental = 16, Control = 18) and were reassessed the week after completing the 6-week-long training protocol. Using a combination of Mann−Whitney U and Wilcoxon signed-rank tests, we found that when accounting for changes in lean muscle mass, individuals who trained with their vision occluded reported significantly greater improvements in 1-RM strength compared to those who did not (p < 0.05). The findings from our study suggest that vision-occluded progressive resistance training increases upper-extremity performance when assessed using the bench press. These findings may have significant practical implications in both sports and rehabilitation, as these techniques may be used to enhance performance in athletes and/or improve rehabilitation effectiveness.

Analysis of the Ability to Tolerate Body Balance Disturbance in Relation to Selected Changes in the Sagittal Plane of the Spine in Early School-Age Children

The study aimed to estimate the ability to tolerate body balance disturbance in relation to selected changes in the sagittal plane of the spine in early school-age children. The study involved 189 children with an average age of 8.3 ± 0.7 years (aged 7−10). The tests included an interview, clinical examination (measurement of body weight and height, assessment of the course of the spinous processes of the thoracic and lumbar vertebrae, assessment of the location of selected anatomical landmarks of the torso), and a physical examination in which the shape of the spine surface was examined with the use of the photogrammetric method and the moiré effect projection. Body balance disturbance tolerance skills (BBDTS) were measured with the rotational test (RT). In the rotational test, the results of body balance disturbance tolerance skills show a slight but statistically significant correlation with the bodyweight of the examined children (Rs = 0.35, p < 0.001). This relationship was also statistically significant in the groups by gender. Among the measured indicators of the curvature of the spine in the sagittal plane, the correlation with the RT test result was mostly related to the α angle and the value was Rs = 0.15 (p = 0.04). In the group of girls, this correlation was stronger and amounted to Rs = 0.26 (p = 0.015). Among other measured correlations, the dependence of variables such as the bodyweight of the subjects and the α angle was shown. In conclusion, increasing lumbar lordosis results in the deterioration of balance disturbance tolerance skills. As body weight increases, body balance disturbance tolerance skills decrease.

Core Muscle Activation With Foam Rolling and Static Planks

The objective of this study was to compare the activation of the core (trunk) musculature during quadriceps and hamstrings foam rolling (FR) vs. prone and supine/reverse static planks to determine if FR is a viable means of training the core musculature. Using a randomized allocation, nine recreationally trained, young adults (18-26 years) performed two sets each of quadriceps and hamstrings FR as well as supine/reverse and prone static planks for 30-s each with 1-min rest between sets and 5-min rest between exercises. Electromyographic (EMG) activity of the lower abdominals (LA), external obliques (EO), lumbosacral erector spinae (LSES), upper lumbar erector spinae (ULES) muscle groups were normalized to a maximum voluntary contraction and analyzed. Quadriceps FR exhibited a very large magnitude greater LA activity compared to reverse plank (p = 0.033, d = 4.42) and hamstrings FR (p = 0.020, d = 3.49), respectively. The prone plank demonstrated very large magnitude higher EO EMG activity compared to reverse plank (p = 0.001, d = 9.17), hamstrings FR (p = 0.002, d = 8.14), and quadriceps FR (p = 0.011, d = 5.97). Reverse plank (p = 0.003, d = 12.06), and quadriceps FR (p = 0.002, d = 7.84) induced greater ULES activity compared to the prone plank and hamstrings FR, respectively. Reverse plank also exhibited very large magnitude higher LSES activity compared to the prone plank (p < 0.001, d = 7.68), hamstrings FR (p = 0.002, d = 4.11), and quadriceps FR (p = 0.005, d = 2.34), respectively. In conclusion, whereas reverse plank was the most effective activator of dorsal core muscles, quadriceps FR may also be a time efficient alternative exercise to activate back (ventral core) muscles. The prone plank is effective for ventral core muscles activation.

Exercise-Based Training Strategies to Reduce the Incidence or Mitigate the Risk Factors of Anterior Cruciate Ligament Injury in Adult Football (Soccer) Players: A Systematic Review

Anterior cruciate ligament (ACL) is one of the most concerning injuries for football players. The aim of this review is to investigate the effects of exercise-based interventions targeting at reducing ACL injury rate or mitigating risk factors of ACL injury in adult football players. Following PRISMA guidelines, a systematic search was conducted in CINAHL, Cochrane Library, PubMed, Scopus, SPORTDiscus and Web of Science. Studies assessing the effect of exercise-based interventions in ACL injury incidence or modifiable risk factors in adult football players were included. 29 studies evaluating 4502 male and 1589 female players were included (15 RCT, 8 NRCT, 6 single-arm): 14 included warm-up, 7 resistance training, 4 mixed training, 3 balance, 1 core stability and 1 technique modification interventions. 6 out of 29 studies investigated the effect of interventions on ACL injury incidence, while the remaining 23 investigated their effect on risk factors. Only 21% and 13% studies evaluating risk of injury variables reported reliability measures and/or smallest worthwhile change data. Warm-up, core stability, balance and technique modification appear effective and feasible interventions to be included in football teams. However, the use of more ecologically valid tests and individually tailored interventions targeting specific ACL injury mechanisms are required.

Knee and Hip Isometric Force Steadiness Are Impaired in Women With Patellofemoral Pain

ABSTRACT

Ferreira, AS, de Oliveira Silva, D, Ferrari, D, Magalhães, FH, Pappas, E, Briani, RV, Pazzinatto, MF, and de Azevedo, FM. Knee and hip isometric force steadiness are impaired in women with patellofemoral pain. J Strength Cond Res 35(10): 2878-2885, 2021-The purposes were as follows: to compare knee extension and hip abduction force steadiness and maximal strength between women with patellofemoral pain (PFP) and pain-free women; and to investigate whether maximal strength, self-reported pain during force-matching tasks, self-reported knee function, symptoms duration, and physical activity level are associated with knee extension and hip abduction force steadiness. Thirty women with PFP and 30 pain-free women were recruited. Knee extension and hip abduction maximal voluntary isometric contractions and submaximal isometric force-matching tasks were evaluated using an isokinetic dynamometer. Subjects were asked to match a target force corresponding to 10% of their maximal isometric voluntary contraction while force steadiness was computed as the coefficient of variation (CV) of the exerted force. Women with PFP had significant 36% lower knee extension and 33% lower hip abduction peak strength. They also had significant 70% lower knee extension force steadiness and 60% lower hip abduction force steadiness (i.e., higher CV) than pain-free women. Self-reported pain and self-reported knee function were significantly associated (r = 0.61, p < 0.001; r = -0.35, p = 0.05) and able to predict 41% of the variance of knee extensor force steadiness. Hip abductor maximum strength was significantly associated (r = -0.57; p = 0.001) and able to predict 32% of the variance of hip abductor force steadiness. These findings indicate that muscle impairments in PFP go beyond only low knee and hip muscle strength because women with PFP also present deficits in knee extension and hip abduction force steadiness. Evidence-based treatments aiming at improving force steadiness may be a promising addition to PFP rehabilitation programs.

sEMG Activity in Superimposed Vibration on Suspended Supine Bridge and Hamstring Curl

Traditionally in strength and conditioning environments, vibration has been transmitted using platforms, barbells, dumbbells, or cables but not suspension devices. This study aimed to examine the effects on the lower limb of applying superimposed vibration on a suspension device. Twenty-one physically active men and women performed supine bridge and hamstring curl exercises in three suspended conditions (non-vibration, vibration at 25 Hz, and vibration at 40 Hz). In each exercise condition, the perceived exertion scale for resistance exercise (OMNI-Res) was registered, and the electromyographic signal was assessed for gastrocnemius (medialis and lateralis), biceps femoris, semitendinosus, gluteus maximus, and rectus femoris. A linear mixed model indicated a significant fixed effect for vibration at 25 Hz and 40 Hz on muscle activity in suspended supine bridge (p < 0.05), but no effect for suspended hamstring curl (p > 0.05). Likewise, the Friedman test showed a significant main effect for vibration at 25 Hz and 40 Hz in suspended supine bridge (p < 0.05) but not for suspended hamstring curl (p > 0.05) on OMNI-Res. Post hoc analysis for suspended supine bridge with vibration at 25 Hz showed a significant activation increase in gastrocnemius lateralis (p = 0.008), gastrocnemius medialis (p = 0.000), semitendinosus (p = 0.003) activity, and for semitendinosus under 40 Hz condition (p = 0.001) compared to the non-vibration condition. Furthermore, OMNI-Res was significantly higher for the suspended supine bridge at 25 Hz (p = 0.003) and 40 Hz (p = 0.000) than for the non-vibration condition. Superimposed vibration at 25 Hz elicits a higher neuromuscular response during the suspended supine bridge, and the increase in vibration frequency also raises the OMNI-Res value.

Evaluation of Training Load During Suspension Exercise

ABSTRACT

Giancotti, GF, Fusco, A, Varalda, C, Capelli, G, and Cortis, C. Evaluation of training load during suspension exercise. J Strength Cond Res 35(8): 2151-2157, 2021-The aims of this study were to evaluate body inclination and ground reaction force and to predict equations to estimate the training load distribution during suspension training (ST) static back-row at different lengths of the straps. Thirty volunteers (men = 16 and women = 14; age = 23.3 ± 1.7 years; body mass = 63.9 ± 13.3 kg; height = 167.9 ± 9.2 cm; body mass index [BMI] = 22.5 ± 3.4 kg·m-2) performed 14 static back-rows at 7 different lengths of the straps in 2 different elbow positions (flexed and extended). When the length of the straps increased, ground reaction force and body inclination decreased. Moreover, in the flexed elbow position, higher ground reaction force values were recorded with respect to the extended one. Two multilevel regression models (p < 0.05) were created. In the first one, ground reaction force was used as a dependent variable, whereas body inclination angle, body mass, height, BMI, and elbow position were used as independent variables. Significant (p < 0.05) effects were found for all variables included in the model, with an intraclass correlation coefficient (ICC) of 0.31. In the second model, the body inclination angle was replaced by the length of the ST device. Significant (p < 0.05) effects were found also in the second model for all variables included, with an ICC of 0.37. The proposed models could provide different methods to quantify the training load distribution, even if the use of the straps' length could result easier and faster than body inclination angle, helping practitioners and instructors to personalize the workout to reach specific purposes and provide load progression.

Sex differences in postural control under unstable conditions in schoolchildren with accelerometric assessment

BACKGROUND

Although the effects of balance training on unstable surfaces have been widely studied, the impact of exposure to an unstable surface in static balance throughout childhood has not been described to date.

RESEARCH QUESTION

How does postural stability vary between sexes in children 6-12 years of age during single leg static support on unstable surface? What are the normative values of centre of mass acceleration in the mentioned age range during such test? Is the postural stability on an unstable surface in the postural control of children aged 6-12 years during static single-leg stance. Secondarily, the normative acceleration values of the gravity centre, recorded during such tests and throughout the mentioned age range, were also provided.

METHODS

Descriptive, transversal study conducted with a total of 316 school children (girls = 158). The analysed variables were the mean and maximum values obtained in each of the three body axes and their root mean square during static single-leg support test on an unstable surface (a mat).

FINDINGS

Accelerations decreased in magnitude with the increasing age of the participants. The highest accelerometric values were recorded in the medio-lateral axis in both sexes and throughout the entire age range studied. Between sexes, the greatest differences were obtained between 8 and 11 year-olds. The regression models revealed significant values about the influence of sex on the accelerometric variables (girls were more likely to obtain less accelerations in postural adjustments with increasing age).

INTERPRETATION

Boys depend more on somatoaesthetic information, whereas girls would use more visual and vestibular information. In the age range of 8-11 years, the postural control system is significantly different between sexes regarding the hierarchy of the efferent information of the available postural control subsystems. Moreover, the reactions of straightening and postural control on single-leg stance are, fundamentally, flexion-extension movements.

Effect of Integrative Neuromuscular Training for Injury Prevention and Sports Performance of Female Badminton Players

Objectives

Investigate the effects of integrated neuromuscular training (INT) on injury prevention and the performance of professional female badminton athletes by comparing their preintervention and postintervention tests. The study hypothesized that integrated neuromuscular training can improve the asymmetry and improve the sport performance of female badminton players.

Methods

According to pretest value based on functional movement screening, 38 participants were divided into a high-risk group (HG) and a low-risk group (LG) with 22 and 16 people in each group. Two groups of athletes took part in an 8-week INT program consisting of four 90-min sessions each week. The asymmetries in movement, physical fitness, and special abilities were tested before and after the intervention. Independent sample t-test was used for the statistical analysis.

Results

This research found indicated that 8 weeks of INT influenced FMS scores in both groups (HG and LG). The change of inline lunge (ES_H = 0.42, ES_L = 0.21) and trunk stability push-up (ES_H = −0.58, ES_L = −0.20) showed significant differences (P < 0.05), and the change of the FMS scores (ES_H = 0.81, ES_L = 0.65), deep squat (ES_H = 0.6, ES_L = 0.3), and rotation stability (ES_H = −0.65, ES_L = −0.72) showed very significant differences (P < 0.01). Compared to the pretest, most of the physical fitness parameters improved significantly in the HG and LG groups except strength index, and special abilities of the HG and LG group women badminton athletes showed a substantial increase.

Conclusion

Integrated neuromuscular training can effectively improve the asymmetry of female badminton athletes' limbs, prevent sports injury, and improve the athlete's performance ability. However, athletes in different risk groups have certain differences in the degree of improvement in their motor skills.

The Effect of Nordic Walking Training with Poles with an Integrated Resistance Shock Absorber on the Body Balance of Women over the Age of 60

The aim of this study was to assess the changes in the balance of healthy, elderly women as a result of Nordic walking training using of two types of poles: classic poles, and poles with an integrated resistance shock absorber. Thirty-four women completed the experiment (Age = 66.8 ± 4.1 years). They were randomly assigned into the experimental group—training with poles with an integrated resistance shock absorber—EG (n = 17), and the control active group—training with classic poles—CG (n = 17). Body balance was measured with Romberg sharpened test and using the AccuGait ™ force platform before and after an intervention lasting for 8 weeks (2 training sessions × 75 min per week). In ANOVA analysis, the Romberg sharpened test showed a statistically significant effect of “time” (F = 18.62, p < 0.001, ɳ² = 0.37). No interaction effect or clear “time” effect was observed in the ANOVA analysis for the results of posturographic tests (p > 0.05). The lack of pre-post differences in posturographic tests indicates that further research is necessary, where, e.g., there are extended intervention times and more difficult examination tasks are performed. In the case of the Romberg test, both groups improved their results, which may indicate an improvement in perception and processing of sensory information, regardless of the type of training applied.

What to train first: Balance or explosive strength? Impact on performance and intracortical inhibition

Explosive strength and balance training are commonly applied to enhance explosive strength and balance performance. Even though both training methods are frequently implemented, ordering effects have largely been neglected. Therefore, the present study aimed to investigate ordering effects of balance and explosive strength training on explosive strength and balance performance as well as changes in short-interval intracortical inhibition (SICI). Two groups of subjects either participated in 4 weeks of balance training followed by 4 weeks of explosive strength training (BT-ET) or vice versa (ET-BT). Before, after 4 and 8 weeks, balance performance, as well as explosive strength, was tested. Additionally, SICI was tested during rest as well as during balance perturbations and explosive contractions. The results show a training specific increase in performance with an increase in balance control followed by an increase in explosive strength in the BT-ET, while the ET-BT increased its balance and explosive strength in the opposite order. There were no significant ordering effects. Both groups showed a significant decrease in SICI during the explosive contractions after the eight weeks of training. When SICI was tested during the balance perturbations, SICI initially increased after the first 4 weeks of training but returned to baseline until the end of the eight weeks. It is suggested that the decrease in SICI with prolonged training might show a disengagement of the motor cortex during the balance task. During the explosive contractions, the low SICI levels are beneficial to provide the necessary level of excitatory cortical drive.

Combining the Copenhagen Adduction Exercise and Nordic Hamstring Exercise Improves Dynamic Balance Among Male Athletes: A Randomized Controlled Trial

BACKGROUND

Copenhagen adduction exercise (CAE) and Nordic hamstring exercise (NHE) reduce the incidence of groin and hamstring injuries. Efficient dynamic balance can improve motor performance and reduce the risk of injuries in athletes. However, the effects of these exercises on dynamic balance have not been investigated.

HYPOTHESIS

CAE and NHE, as well as a combination of both exercises, would improve dynamic balance among amateur male athletes.

STUDY DESIGN

Randomized controlled trial.

LEVEL OF EVIDENCE

Level 1.

METHODS

A total of 200 male athletes aged 21.9 ± 2.4 years were included in the study and randomly assigned to 4 groups: CAE group (n = 50), NHE group (n = 50), CAE and NHE group (n = 50), and a control group (n = 50). A total of 177 male athletes completed the study. The primary outcome measure was the limit of stability (LoS), which was measured using the Biodex Stability System to assess the performance of the dynamic balance. The LoS of the athletes' performance was measured pre- and postintervention after 6 weeks.

RESULTS

The LoS significantly improved in all treatment groups, including CAE (44.5% ± 5.3%), NHE (43.2% ± 5.3%), and CAE + NHE (48.4% ± 5.1%) groups when compared with the control group (28.3% ± 4.8%) after 6 weeks (all Ps < 0.01). The improvement of LoS was significantly greater in the CAE + NHE group compared with other groups (CAE, NHE, and control groups).

CONCLUSION

There was a significant increase in dynamic balance performance postintervention among male athletes. CAE and NHE may improve injury prevention programs.

CLINICAL RELEVANCE

The results of this study provide evidence for athlete trainers and coaches to consider including the CAE and NHE as components of injury prevention programs to improve balance capacity and performance in athletes. Such improvements in balance may prevent injury risk and decrease absenteeism and injury-related financial burdens.

Periscapular activity in subjects with scapular dyskinesis during push-ups on stable and unstable support surfaces

BACKGROUND: The scapular dyskinesis has been described as a sign of scapular instability due to weakness or imbalance of scapular muscles. OBJECTIVE: The aim of this study was to compare the EMG activity of the periscapular and abdominal muscles of asymptomatic subjects without and with scapular dyskinesis type II during a push-up exercise performed on different surface stability conditions. METHODS: Twenty-seven physically active men were allocated into two groups: the Control group (n= 14); and the Dyskinesis group (n= 13). All participants performed three variations of the push-up exercise: Stable, Push-up with hand instability, and Push-up with hand and feet instability. The EMG activity of serratus anterior, upper (UT), middle (MT) and lower (LT) trapezius, external oblique (EO) and rectus abdominis (RA) was recorded during each task. RESULTS: The control group showed an increase in MT activity (mean difference -3.46 to 8.66) under both instability conditions compared to stable push-ups (p< 0.001). The comparison between groups showed that the control group had higher MT activity (mean difference -10.07 to 13.82) compared to the dyskinesis group under unstable conditions (p< 0.012). CONCLUSION: The insertion of unstable surfaces increased MT activity in the control group only. The insertion of the unstable surface, either the hands or the footrest, did not provide significant effects for the other muscles.

Effects on Strength, Power and Speed Execution Using Exercise Balls, Semi-Sphere Balance Balls and Suspension Training Devices: A Systematic Review

Research in instability has focused on the analysis of muscle activation. The aim of this systematic review was to analyse the effects of unstable devices on speed, strength and muscle power measurements administered in the form of controlled trials to healthy individuals in adulthood. A computerized systematic literature search was performed through electronic databases. According to the criteria for preparing systematic reviews PRISMA, nine studies met the inclusion criteria. The quality of the selected studies was evaluated using STROBE. The average score was 14.3 points, and the highest scores were located in ‘Introduction’ (100%) and ‘Discussion’ (80%). There is great heterogeneity in terms of performance variables. However, instability seems to affect these variables negatively. The strength variable was affected to a greater degree, but with intensities near to the 1RM, no differences are observed. As for power, a greater number of repetitions seems to benefit the production of this variable in instability in the upper limb. Instability, in comparison to a stable condition, decreases the parameters of strength, power, and muscular speed in adults. The differences shown are quite significant in most situations although slight decreases can be seen in certain situations.

Balance Training Reduces Postural Sway and Improves Sport-specific Performance in Visually Impaired Cross-Country Skiers

ABSTRACT

Kurz, A, Lauber, B, Franke, S, and Leukel, C. Balance training reduces postural sway and improves sport-specific performance in visually impaired cross-country skiers. J Strength Cond Res 35(1): 247-252, 2021-Balance training is highly effective in reducing sport injuries and causes improvements in postural stability and rapid force production. So far, the positive effects of balance training have been described for healthy athletes. In the present experiments, we questioned whether athletes with disabilities of the visual system can also benefit from balance training. Fourteen visually impaired cross-country skiers participated in this randomized controlled study. The intervention group (N = 7) completed 8 sessions of balance training over a period of 4 weeks (2 times per week), whereas a waiting control group (N = 7) received no training during that time. After training, postural sway was significantly reduced in the intervention group but not in the waiting control group. In addition, sport-specific performance, which was assessed by a standardized Cooper's 12-minute test on roller skis or rollerblades, increased in the intervention group. The change in postural sway from the premeasurement to the postmeasurement correlated with the change in sport-specific performance in all subjects. Our results indicate that balance training is useful for improving postural stability and sport-specific performance in visually impaired cross-country skiers. We propose that balance training should therefore be implemented as part of the training routine in athletes with disabilities of the visual system.

Effects of bodyweight neuromuscular training with and without instability on balance control in active universitarians

The purpose of this study was to analyse the effects of a nine-week unstable vs stable bodyweight neuromuscular training programme on balance control. Seventy-seven physically active universitarians were randomly distributed into an unstable training group (UTG), a stable training group (STG), and a control group (CG). The intervention was conducted three times a week for nine weeks. Pre- and post-intervention assessments included static balance control under an unstable surface (eyes open (EOFS), eyes closed (ECFS), challenging visual-vestibular system (CVVS)), assessed as centre-of-pressure fluctuations with a force plate. A mixed ANOVA was performed to test the within- and between-subjects factors. After the intervention, no significant differences were found between groups. All groups presented significant improvements in balance measurements in EOFS (p = 0.01), ECFS (p = 0.01; p = 0.02), and CVVS (p = 0.01) conditions. The training groups tended to have significantly better balance control (antero-posterior) than the CG on EOFS. In the CVVS condition, the UTG tended to have better balance control than the CG. There was no overall significant training advantage gained by using unstable or stable surfaces in terms of the improvement in static balance control in active universitarians. Both training groups exhibited similar training adaptations.

Use of unstable exercises in periscapular muscle activity: A systematic review and meta-analysis of electromyographic studies

BACKGROUND

The use of unstable surfaces has been proposed to increase the neuromuscular demand. This strategy has been adopted to generate an increase in the activity of periscapular muscles due to its role in the stabilization of the scapula. However, the influence of this instability on the EMG activity remains uncertain. The aim of this study was to analyze the effects of using unstable surfaces on the EMG activity of the periscapular muscles.

METHODS

A comprehensive search in the PubMed, EMBASE, SCIELO, Web of Science, SCOPUS, Cochrane and LILACS databases was undertaken from their year of inception up to December 2019. Studies which directly investigated the EMG activity of periscapular muscles in healthy individuals while performing exercises for the upper limbs in stable and unstable conditions.

RESULTS

A total of 33 studies which evaluated a total of 678 healthy individuals were found according to the eligibility criteria. A meta-analysis identified that the EMG activity of the upper trapezius showed a trivial increase with the insertion of the unstable surface (P = 0.04; SMD = 0.14 [95%CI 0.00, 0.27]). No significant effects were observed on the middle trapezius (P = 0.10) and lower trapezius (P = 0.25). A decrease of the anterior serratus EMG activity with a small effect size was observed by implementing an unstable surface (P = 0.01; SMD = -0.21 [95%CI -0.36, -0.05]).

CONCLUSION

The use of unstable surfaces generated a trivial increase in the upper trapezius activity, and a slight decrease in the anterior serratus activity. No effect was observed on the middle and lower trapezius.

Additional Functional Performance Gains After 24-Week Unstable Strength Training With Cognitive Training in Community-Dwelling Healthy Older Adults: A Randomized Trial

The authors investigated the effects of unstable strength training (UST) without or with cognitive training (C+UST) on functional performance in community-dwelling older adults. A total of 50 participants were randomly assigned (1:1) to either 24 weeks of thrice-weekly UST (n = 25) or C+UST (n = 25). All participants performed moderate-intensity strength exercises using unstable surfaces, and C+UST participants simultaneously received cognitive training in addition to UST. Primary outcomes included measures of functional performance: single- and dual-task timed up and go tests. Secondary outcomes included dynamic balance, mobility, handgrip strength, flexibility, quality of life, and concern about falling. The authors observed similar improvements on functional performance through the interventions. The C+UST group experienced additional gains at completion (single-task timed up and go: -0.90 s, 95% confidence interval [-2.38, -0.03]; dual-task timed up and go: -4.80 s, 95% confidence interval [-8.65, -0.95]) compared with the UST group. Moreover, significant differences were observed in mobility (sitting-rising test: -1.34, 95% confidence interval [-2.00, -0.20]) at 24 weeks. Both exercise modes improved single-task functional performance, while adding cognitive-training-optimized dual-task functional performance gains.

Effects of Combined Balance and Plyometric Training on Athletic Performance in Female Basketball Players

Bouteraa, I, Negra, Y, Shephard, RJ, and Chelly, MS. Effects of combined balance and plyometric training on athletic performance in female basketball players. J Strength Cond Res 34(7): 1967-1973, 2020-The purpose of this study was to examine the effect of 8 weeks combined balance and plyometric training on the physical fitness of female adolescent basketball players. Twenty-six healthy regional-level players were randomly assigned to either an experimental group (E; n = 16, age = 16.4 ± 0.5) or a control group (C; n = 10, age = 16.5 ± 0.5). C maintained their normal basketball training schedule, whereas for 8 weeks E replaced a part of their standard regimen by biweekly combined training sessions. Testing before and after training included the squat jump (SJ), countermovement jump (CMJ), drop jump (DJ), 5-, 10-, and 20-m sprints, Stork balance test (SBT), Y-balance test (YBT) and modified Illinois change of direction test (MICODT). Results indicated no significant intergroup differences in SJ and CMJ height; however, E increased their DJ height (p < 0.05, Cohens'd = 0.11). No significant intergroup differences were found for sprint performance or SBT, but dynamic YBT tended to a significant group interaction (p = 0.087, d = 0.006). Post hoc analysis also showed a significant increase of MICODT for E (Δ 6.68%, p = 0.041, d = 0.084). In summary, the addition of 8 weeks of balance and plyometric training to regular in-season basketball training proved a safe and feasible intervention that enhanced DJ height, balance, and agility for female adolescent basketball players relative to the standard basketball training regimen.

Effects of trunk exercise with physioball to improve trunk balance among subjects with stroke: a systematic review and meta-analysis

Poststroke subjects present with difficulties of reduced functional mobility and balance. Trunk impairment is common among stroke subjects which hinder the performance of upper and lower limb. In poststroke rehabilitation limbs are provided much attention than the trunk. Trunk function has been identified as an important early predictor of functional outcome after stroke. Physioball is commonly used among healthy subjects in performing trunk exercises. This systematic review with meta-analysis is conducted to investigate the effect of trunk exercises performed using physioball in improving trunk performance after stroke. Six authors identified relevant articles from the following databases: PubMed, Google Scholar, CINAHL (Cumulative Index and Nursing and Allied Health Literature), PEDro (Physiotherapy Evidence Database). Articles evaluating the effect of physioball exercise for improving trunk stability among stroke subjects were included. Databases were screened from 2009 and up to 2019. Qualitative synthesis of evidence was prepared and meta-analysis was implemented to draw pooled effects of physioball exercise on improving trunk performance and balance among stroke subjects. Eight papers were included, totaling 273 participants. All the articles included in this review demonstrated moderate to good quality. Meta-analysis performed with seven papers demonstrated statistical significance of physioball in improving trunk performance during acute and subacute stages of stroke. Brunnel Balance Assessment outcomes demonstrated statistically significant improvement of balance among overall stroke survivors. Trunk exercise performed over a physioball is effective during the acute and subacute stage. This meta-analysis could not find its significant effect in improving trunk performance in the chronic stages.