J. Brent Feland

A COMPARISON OF VOLUNTARY AND INVOLUNTARY MEASURES OF ELECTROMECHANICAL DELAY

Electromechanical delay (EMD) is a measurement used to assess the mechanical lag between muscle activation onset and force production. EMD measurements may be performed by voluntary or electrically evoked muscle activation. This study compared gastrocnemius EMD during voluntary and involuntary contractions and assessd the intrasession reliability of each set of measurements. Subjects were 15 volunteers (age 21 ± 2 years, ht 171.8 ± 10.0 cm, mass 76.1 ± 13.4 kg). EMD measurements were recorded from the medial head of the gastrocnemius of each subject during voluntary and involuntary contractions. Order was counterbalanced between subjects. Subjects stood with the dominant leg on a force plate, the nondominant next to the force plate, and with their hands in contact with a bar in front of them. A supramaximal percutaneous stimulus was applied to the tibial nerve in the popliteal fossa for involuntary (electrically evoked) contractions. For voluntary contractions, subjects were instructed to rise up on the toes as quickly as possible. Four trials were collected for each condition with 30 s of rest between each. Repeated measures ANOVAs were performed for each condition to calculate an ICC (2,1). Means of the 4 trials for each condition were used to detect differences between groups. EMD was greater in the voluntary condition (22.8 ± 8.2 ms) compared to the involuntary condition (9.7 ± 3.1 ms; p < .001). Intrasession reliability for each condition was very strong (involuntary ICC (2,1) = .977; voluntary ICC (2,1) = .972). EMD measured during a single leg stance is much shorter when measured during an electrically evoked (voluntary) contraction. The difference in EMD between conditions is likely the result of differences in recruitment during the two types of contractions. Reliability within a measurement session was very strong for each of the conditions.

Whole-body vibration strengthening compared to traditional strengthening during physical therapy in individuals with total knee arthroplasty

ABSTRACT This study investigated the use of whole-body vibration (WBV) as an alternative strengthening regimen in the rehabilitation of individuals with total knee arthroplasty (TKA) compared with traditional progressive resistance exercise (TPRE). Individuals post TKA (WBV n = 8; TPRE n = 8) received physical therapy with WBV or with TPRE for 4 weeks. Primary dependent variables were knee extensor strength, quadriceps muscle activation, mobility, pain, and range of motion (ROM). There was a significant increase in knee extensor strength and improvements in mobility, as measured by maximal volitional isometric contraction and the Timed Up and Go Test (TUG), respectively, for both groups (p < 0.01). The WBV knee extensor strength improved 84.3% while TPRE increased 77.3%. TUG scores improved 31% in the WBV group and 32% for the TPRE group. There were no significant differences between groups for strength or muscle activation (Hotellings T2 = 0.42, p = 0.80) or for mobility (F = 0.54; p = 0.66). No adverse side effects were reported in either group. In individuals with TKA, both WBV and TPRE showed improved strength and function. Influence of WBV on muscle activation remains unclear, as muscle activation levels were near normal for both groups.

Reliability of 16 Balance Tests in Individuals with down Syndrome

To assess test-retest reliability scores on 16 balance tests of 21 individuals with Down syndrome whose ages ranged from 5 to 31 yr., participants performed a standing test on firm and soft surfaces with the eyes open and closed, the balance subset of the Bruininks-Oseretsky test, full turn, timed-up-and-go test, forward reach, and sit-to-stand. Each participant completed all 16 tests twice in one day and then again on a subsequent day for a total of 4 sessions. The interclass reliability correlation coefficients (ICC) value for each measure of balance varied considerably by age and sex. Based on having an ICC > .50, only 3 tests were reliable in young males and young females, whereas 5 tests could reliably be used in adult females and 9 tests could reliably be used in adult males. The results of this study raise suspicions as to the reliability of tests commonly used to assess balance and differences in reliability due to age and sex. Results of balance tests should be interpreted with caution in males and females with Down syndrome across the age span.

Effect of Whole Body Vibration on Skin Blood Flow and Nitric Oxide Production

Background: Vascular dysfunction due to hyperglycemia in individuals with diabetes is a factor contributing to distal symmetric polyneuropathy (DSPN). Reactive oxygen species reduce the bioavailability of nitric oxide (NO), a powerful vasodilator, resulting in reduced circulation and nerve ischemia. Increases in blood NO concentrations and circulation have been attributed to whole body vibration (WBV). The purpose of this study was to the determine the effects of low-frequency, low-amplitude WBV on whole blood NO concentrations and skin blood flow (SBF) in individuals with symptoms of DSPN. Methods: Ten patients with diabetes and impaired sensory perception in the lower limbs participated in this crossover study. Each submitted to 2 treatment conditions, WBV and sham, with a 1-week washout period between. Blood draws for NO analysis and laser Doppler imager scans of SBF were performed before, immediately after, and following a 5-minute recovery of each of the treatments. Results: Low-frequency, low-amplitude WBV significantly increased SBF compared to the sham condition (F2,18 = 5.82, P = .0115). Whole blood NO concentrations did not differ between the WBV and sham conditions immediately or 5 minutes after treatment (F2,18 = 1.88, P = .1813). Conclusions: These findings demonstrate that patients with diabetes respond to WBV with increased SBF compared to the sham condition. The implication is that WBV is a potential nonpharmacological therapy for neurovascular complications of diabetes.

Static stretching does not alter pre and post-landing muscle activation

BackgroundStatic stretching may result in various strength and power deficiencies. Prior research has not determined, however, if static stretching causes a change in muscle activation during a functional task requiring dynamic stability. The purpose of this study was to determine if static stretching has an effect on mean pre and postlanding muscle (vastus medialis VM, vastus lateralis VL, medial hamstring MH, and biceps femoris BF) activity.Methods26 healthy, physically active subjects were recruited, from which 13 completed a 14-day static stretching regimen for the quadriceps and hamstrings. Using the data from the force plate and EMG readings, a mean of EMG amplitude was calculated for 150 msec before and after landing. Each trial was normalized to an isometric reference position. Means were calculated for the VM, VL, MH, and BF from 5 trials in each session. Measures were collected pre, immediately following the 1st stretching session, and following 2 weeks of stretching.ResultsA 14-day static stretching regimen resulted in no significant differences in pre or postlanding mean EMG amplitude during a drop landing either acutely or over a 14-day period.ConclusionsStatic stretching, done acutely or over a 14-day period does not result in measurable differences of mean EMG amplitude during a drop landing. Static stretching may not impede dynamic stability of joints about which stretched muscles cross.

Performance on the Functional Movement Screen in older active adults

Background The Functional Movement Screen (FMS™) has become increasingly popular for identifying functional limitations in basic functional movements. This exploratory and descriptive study was undertaken to confirm feasibility of performing the FMS™ in older active adults, assess prevalence of asymmetries and to evaluate the relationship between functional movement ability, age, physical activity levels and body mass index (BMI). Methods This is an observational study; 97 men (n = 53) and women (n = 44) between the ages of 52 and 83 participated. BMI was computed and self-reported physical activity levels were obtained. Subjects were grouped by age (5-year intervals), BMI (normal, over-weight, and obese) and sex. Each participants performance on the FMS™ was digitally recorded for later analysis. Results The youngest age group (50–54 years) scored highest in all seven tests and the oldest age group (75+) scored lowest in most of the tests compared to all other age groups. The subjects in the “normal weight” group performed no different than those who were in the “overweight” group; both groups performed better than the “obese” group. Of the 97 participants 54 had at least one asymmetry. The pairwise correlations between the total FMS™ score and age (r = −0.531), BMI (r = −0.270), and the measure of activity level (r = 0.287) were significant (p < 0.01 for all). Conclusion FMS™ scores decline with increased BMI, increased age, and decreased activity level. The screen identifies range of motion- and strength-related asymmetries. The FMS™ can be used to assess functional limitations and asymmetries. Future research should evaluate if a higher total FMS™ score is related to fewer falls or injuries in the older population.

A Comparison of Voluntary and Involuntary Measures of Electromechanical Delay: 1688

Electromechanical delay (EMD) is a measurement used to assess the mechanical lag between muscle activation onset and force production. EMD measurements may be performed by voluntary or electrically evoked muscle activation. This study compared gastrocnemius EMD during voluntary and involuntary contractions and assessd the intrasession reliability of each set of measurements. Subjects were 15 volunteers (age 21 +/- 2 years, ht 171.8 +/- 10.0 cm, mass 76.1 +/- 13.4 kg). EMD measurements were recorded from the medial head of the gastrocnemius of each subject during voluntary and involuntary contractions. Order was counterbalanced between subjects. Subjects stood with the dominant leg on a force plate, the nondominant next to the force plate, and with their hands in contact with a bar in front of them. A supramaximal percutaneous stimulus was applied to the tibial nerve in the popliteal fossa for involuntary (electrically evoked) contractions. For voluntary contractions, subjects were instructed to rise up on the toes as quickly as possible. Four trials were collected for each condition with 30 s of rest between each. Repeated measures ANOVAs were performed for each condition to calculate an ICC (2,1). Means of the 4 trials for each condition were used to detect differences between groups. EMD was greater in the voluntary condition (22.8 +/- 8.2 ms) compared to the involuntary condition (9.7 +/- 3.1 ms; p < .001). Intrasession reliability for each condition was very strong (involuntary ICC (2,1) = .977; voluntary ICC (2,1) = .972). EMD measured during a single leg stance is much shorter when measured during an electrically evoked (voluntary) contraction. The difference in EMD between conditions is likely the result of differences in recruitment during the two types of contractions. Reliability within a measurement session was very strong for each of the conditions.