Balance Differences between North and South American Older Adults: A Cross-Sectional, Age and Sex Matched Study.

This study aimed to characterize the risk of falling in low-, moderate- and high-risk participants from two different geographical locations using a portable force-plate. A sample of 390 older adults from South and North America were matched for age, sex, height and weight. All participants performed a standardized balance assessment using a force plate. Participants were classified in low, moderate and high risk of falling. No differences were observed between South and North American men, nor comparing North American men and women. South American women showed the significantly shorter center of pressure path length compared to other groups. The majority of the sample was categorized as having low risk of falling (male: 65.69% and female: 61.87%), with no differences between men and women. Moreover, no differences were found between North vs. South Americans, nor between male and female groups compared separately. In conclusion, South American women had better balance compatible with the status of the 50-59 years' normative age-range. The prevalence of low falls risk was~61-65%; the prevalence of moderate to high risk was~16-19%. The frequency of fall risk did not differ significantly between North and South Americans, nor between males and females.

Test-Retest of a Novel Wii Board-Based Device to Assess Eccentric Knee Flexor Strength During the Nordic Hamstring Exercise.

This study aimed to assess the test-retest reliability of a Wii board-based device to assess the eccentric knee strength. Healthy participants (n = 20, 22.7 [3.4] y, 1.71 [0.09] m, 69 [13] kg) performed 2 assessments-days 1 and 2-of the Nordic hamstring exercise (3 trials per day, 3 min of rest between trials, and 48 h between trials) on a padded board with an attached Wii Balance Board (WBB). A ratchet inelastic strap made the contact between the participant's distal aspect of both legs and the inverted upper surface of the WBB. The means among 3 trials were used to extract the absolute strength and the left and the right limb strengths. No between-session differences were found (P range = .691-.981). The intraclass correlation coefficient range showed excellent results (.905-.926), as the Cronbach α test (above .94). The correlation was high (r > .91; .820 < r2 < .862). The Bland-Altman analysis returned high levels of agreement. The standard error of measurement ranged from 5.56 to 11.07 N and the minimal detectable change from 15.42 to 30.68 N. The percentage of standard error of measurement values were 2.95%, 3.74%, 2.88%, respectively, for absolute strength, right limb strength, and left limb strength. The adapted system showed an excellent cost-benefit relationship with optimal test-retest reliability. The findings suggest that the adapted system, using the WBB, is a reliable method for measuring the eccentric knee strength.

Validity and Test-Retest Reliability of a Novel Push Low-Cost Hand-Held Dynamometer for Knee Strength Assessment during Different Force Ranges.

The objective was to assess the instrumental validity and the test-retest reliability of a low-cost hand-held push dynamometer adapted from a load-cell based hanging scale (tHHD) to collect compressive forces in different ranges of compressive forces. Three independent raters applied 50 pre-established compressions each on the tHHD centered on a force platform in three distinct ranges: ~70 N, ~160 N, ~250 N. Knee isometric strength was also assessed on 19 subjects in two sessions (48 h apart) using the tHHD anchored by an inelastic adjustable strap. Knee extension and flexion were assessed with the participant seated on a chair with the feet resting on the floor, knees, and hips flexed at 90°. The isometric force peaks were recorded and compared. The ICC and the Cronbach's α showed excellent consistency and agreement for both instrumental validity and test-retest reliability (range: 0.89-0.99), as the correlation and determination coefficients (range: 0.80-0.99). The SEM and the MDC analysis returned adequate low values with a coefficient of variation less than 5%. The Bland-Altman results showed consistency and high levels of agreement. The tHHD is a valid method to assess the knee isometric strength, showing portability, cost-effectiveness, and user-friendly interface to provide an effective form to assess the knee isometric strength.

Validity of a portable hanging scale to assess the isometric muscle strength during knee movement.

Inexpensive and practical equipment to assess muscle strength can disseminate objective measures, which can provide valid information to implement effective treatment and exercise training. The purpose of the study was to examine the instrumental validity of the hanging scale (HS) to assess the muscle strength during knee flexion and extension by comparing the peak force values to a standard equipment (laboratory-grade load cell [LLC]). Knee isometric strength was assessed on thirty-two subjects (16 women and 16 men, 22 [5] years, 171 [9] cm, 69 [15] kg, 23 [4] kg/m2). The knee flexion was tested by placing the volunteer's body in prone with the knee flexed at 90°. Knee extension was assessed with the volunteer seated on a chair with the feet resting on the floor, knees, and hips flexed at 90°. No differences were observed comparing the isometric peak forces between a laboratory-grade load cell and a HS (p > 0.05). The intraclass correlation coefficient (ICC)1,1 returned values above 0.90. The Cronbach's α test also returned values above 0.90 for all comparisons. Bland-Altman results showed high levels of agreement with low risk of bias. The HS appears to be a valid method to assess the knee isometric strength. The portability, the cost-effectiveness and the simple user-friendly system provides an effective way to assess the knee isometric strength.

Scapular Retraction under Adduction Load: An Alternative to Overhead Exercises to Activate Infraspinatus, Upper, and Lower Trapezius in Subjects with and without Shoulder Pain.

Exercises for lower trapezius (LT) often use overhead positions, causing compressive forces to the subacromial space. Scapular retraction would be an alternative to activate LT muscle. The present study aimed to assess the excitation levels of infraspinatus, upper trapezius, and lower trapezius muscles during a scapular retraction exercise under progressive adduction loads in subjects with and without painful shoulder. Electromyography of infraspinatus (IS), upper trapezius (UT), and LT was recorded during scapular retraction under progressive adduction loads of 42 participants, divided into two groups: with (SP, n = 26) and without shoulder pain (nSP, n = 16). The adduction loads of 20%, 30%, 40%, and 50% of the maximal voluntary contraction (MVC) were applied using a load cell. Normalized electromyography and the ratio between UT and LT (UT:LT) were used for statistical analysis. No differences were observed between groups, but a condition effect occurred for all muscles: UT showed higher values at 50% vs. 20% of MVC (p = 0.004); LT showed higher values on 40% and 50% of MVC (p = 0.001; 0.006). Higher values for IS were noted at 40% of MVC (vs. 20% of MVC; p = 0.04) and at 50% of MVC (vs. 20% of MVC; p = 0.001, vs. 30% of MVC, p = 0.001; vs. 40% of MVC; p = 0.001). UT:LT showed lower values at 50% of MVC (vs. 20% of MVC; p = 0.001 and vs. 30% of MVC; p = 0.016). Scapular retraction with adduction loads at 40-50% is an alternative to overhead exercises aiming to activate the LT and the IS muscles. The exercise ensures higher levels of LT and IS excitation without increasing UT excitation.

Acceleration Profiles and the Isoinertial Squatting Exercise: Is There a Direct Effect on Concentric-Eccentric Force, Power, and Neuromuscular Efficiency?

OBJECTIVE: To examine the selective influences of distinct acceleration profiles on the neuromuscular efficiency, force, and power during concentric and eccentric phases of isoinertial squatting exercise. DESIGN: Cross-sectional study. SETTING: Biomechanics laboratory of the university. PARTICIPANTS: A total of 38 active adults were divided according to their acceleration profiles: higher (n = 17; >2.5 m/s2) and lower acceleration group (n = 21; <2.5 m/s2). INTERVENTION: All subjects performed squats until failure attached to an isoinertial conic pulley device monitored by surface electromyography of rectus femoris, vastus medialis, vastus lateralis, biceps femoris, and semitendinosus. MAIN OUTCOME MEASURES: An incremental optical encoder was used to assess maximal and mean power and force during concentric and eccentric phases. The neuromuscular efficiency was calculated using the mean force and the electromyographic linear envelope. RESULTS: Between-group differences were observed for the maximal and mean force (Prange = .001-.005), power (P = .001), and neuromuscular efficiency (Prange = .001-.03) with higher significant values for the higher acceleration group in both concentric and eccentric phases. CONCLUSION: Distinct acceleration profiles affect the neuromuscular efficiency, force, and power during concentric and eccentric phases of isoinertial squatting exercise. To ensure immediate higher levels of power and force output without depriving the neuromuscular system, acceleration profiles higher than 2.5 m/s2 are preferable. The acceleration profiles could be an alternative to evolve the isoinertial exercise.