Bilateral Force Deficit in Proximal Effectors Versus Distal Effectors in Lower Extremities.

Purpose: Bilateral force deficit occurs when the maximal generated force during simultaneous bilateral muscle contractions is lower than the sum of forces generated unilaterally. Neural inhibition is stated as the main source for bilateral force deficit. Based on differences in bilateral neural organization, there might be a pronounced neural inhibition for proximal compared to distal effectors. The aim of the present experiment was to evaluate potential differences in bilateral force deficit in proximal compared to distal effectors in lower extremities. Methods: Fifteen young adults performed single-joint maximal voluntary contractions in isometric dorsiflexion of ankle (distal) and knee (proximal) extension unilaterally and bilaterally. Results: Results showed a significant absolute bilateral force deficit for both proximal (123.46 ± 59.51 N) and distal effectors (33.00 ± 35.60 N). Interestingly, the relative bilateral force deficit for knee extension was significantly larger compared to dorsiflexion of ankle, 19.98 ± 10.04% and 10.27 ± 9.57%, respectively. Our results indicate a significantly higher bilateral force deficit for proximal effectors compared to distal effectors. Conclusion: Plausible explanations are related to neuroanatomical and neurophysiological differences between proximal effectors and distal effectors where proximal muscles have a higher potential for bilateral communication compared to distal muscles. In addition, higher forces produced with proximal effectors could cause a higher perceived exertion and cause a more pronounced bilateral force deficit to proximal effectors.

Relative difference in muscle strength between patients with knee osteoarthritis and healthy controls when tested bilaterally and joint-inclusive: an exploratory cross-sectional study.

BACKGROUND: To improve the goal-directedness of strength exercises for patients with knee osteoarthritis (KOA), physical rehabilitation specialists need to know which muscle-groups are most substantially weakened across the kinetic chain of both lower extremities. The purpose was to improve the knowledge base for strength exercise therapy. The objective was to explore the relative differences in muscle strength in the main directions bilaterally across the hip, knee, and ankle joints between patients with light-to-moderate symptomatic and radiographic KOA and people without knee complaints. METHODS: The design was an exploratory, patient vs. healthy control, and cross-sectional study in primary/secondary care. Twenty-eight patients with mild to moderate KOA (18 females, mean age 61) and 31 matched healthy participants (16 females, mean age 55), participated. Peak strength was tested concentrically or isometrically in all main directions for the hip, knee, and ankle joints bilaterally, and compared between groups. Strength was measured by a Biodex Dynamometer or a Commander II Muscle Tester (Hand-Held Dynamometer). Effect sizes (ES) as Cohen's d were applied to scale and rank the difference in strength measures between the groups. Adjustment for age was performed by analysis of covariance. RESULTS: The most substantial muscle weaknesses were found for ankle eversion and hip external and internal rotation in the involved leg in the KOA-group compared to the control-group (ES [95% CI] -0.73 [-1.26,-0.20], - 0.74 [-1.26,-0.21], -0.71 [-1.24,-0.19], respectively; p < 0.01). Additionally, smaller but still significant moderate muscle weaknesses were indicated in four joint-strength directions: the involved leg's ankle inversion, ankle plantar flexion, and knee extension, as well as the uninvolved leg's ankle dorsal flexion (p < 0.05). There was no significant difference for 17 of 24 tests. CONCLUSIONS: For patients with KOA between 45 and 70 years old, these explorative findings indicate the most substantial weaknesses of the involved leg to be in ankle and hip muscles with main actions in the frontal and transverse plane in the kinetic chain of importance during gait. Slightly less substantial, they also indicate important weakness of the knee extensor muscles. Confirmatory studies are needed to further validate these exploratory findings.

Relative difference among 27 functional measures in patients with knee osteoarthritis: an exploratory cross-sectional case-control study.

BACKGROUND: To raise the effectiveness of interventions, clinicians should evaluate important biopsychosocial aspects of the patient's situation. There is limited knowledge of which factors according to the International Classification of Function, Disability, and Health (ICF) are most deviant between patients with knee osteoarthritis (KOA) and healthy individuals. To assist in measures' selection, we aimed to quantify the differences between patients with KOA and healthy controls on various measures across the ICF dimensions of body function, activity, and participation. METHODS: We performed an exploratory cross-sectional case-control study. In total, 28 patients with mild-to-moderate KOA (mean age 61 years, 64% women) referred by general physicians to a hospital's osteoarthritis-school, and 31 healthy participants (mean age 55 years, 52% women), volunteered. We compared between-group differences on 27 physical and self-reported measures derived from treatment guidelines, trial recommendations, and trial/outcome reviews. Independent t-test, Chi-square, and Mann-Whitney U test evaluated the significance for continuous parametric, dichotomous, and ordinal data, respectively. For parametric data, effect sizes were calculated as Cohen's d. For non-parametric data, ds were estimated by p-values and sample sizes according to statistical formulas. Finally, all ds were ranked and interpreted after Hopkins' scale. An age-adjusted sensitivity-analysis on parametric data validated those conclusions. RESULTS: Very large differences between patients and controls were found on the Pain numeric rating scale1, the Knee Injury and Osteoarthritis Scale (KOOS, all subscales)2, as well as the Örebro Musculoskeletal psychosocial scale3 (P < 0.0001). Large differences were found on the Timed 10-steps-up-and-down stair climb test4 and Accelerometer registered vigorous-intensity physical activity in daily life5 (P < 0.001). Respectively, these measures clustered on ICF as follows: 1body function, 2all three ICF-dimensions, 3body function and participation, 4activity, and 5participation. LIMITATIONS: The limited sample excluded elderly patients with severe obesity. CONCLUSIONS: Very large differences across all ICF dimensions were indicated for the KOOS and Örebro questionnaires together for patients aged 45-70 with KOA. Clinicians are suggested to use them as means of selecting supplementary measures with appropriate discriminative characteristics and clear links to effective therapy. Confirmative studies are needed to further validate these explorative and partly age-unadjusted conclusions.

Frame-difference analysis of video-recorded laser-beam projections.

Laser beams have been applied in many human motion research contexts to project movements in specific motor tasks. Currently, there are no objective analysis methods for laser projection recordings. The principal aim of this study was to investigate the feasibility of quantifying motion by applying frame differencing and image analysis methods to video streams of laser beam projections. The laser projection was controlled by a mechanical device that produced pseudo random rotations. The 2D motion recorded by the video was compared with recordings obtained with an electromagnetic system where a sensor was fixed to the same device as the laser. High correlations in the time and frequency domains were found between the methods. We conclude that the proposed method can accurately quantify complex motion patterns from laser beam projections.

Medical Exercise Therapy for Treating Musculoskeletal Pain: A Narrative Review of Results from Randomized Controlled Trials with a Theoretical Perspective.

BACKGROUND AND PURPOSE: The purpose of this narrative review is to present an overview and theoretical rationale of medical exercise therapy (MET) as a physiotherapeutic rehabilitation treatment for musculoskeletal pain conditions. Results from randomized controlled trials (RCTs) conducted on MET are also presented. METHODS: Computerized searches for any RCTs were conducted on the MET concept in the databases PubMed, Medline, Embase and ISI Web of science up to 2013. RESULTS: Overall findings from five included MET RCTs are long-term (≥1 year) reductions in pain and improved physical and functional capabilities. These results are interpreted in the context of the biopsychosocial model, advancing the view of a dynamic interaction among physiologic, psychological and social factors that influence pain modulation. DISCUSSION: MET is a biopsychosocial treatment that reduces pain and improves activities of daily living in patients with a musculoskeletal pain condition. Pain modulation is a key feature of MET, and an important area for further research is to elucidate the specific mechanisms behind the treatment effects.

Individual differences in timing of discrete and continuous movements: a dimensional approach.

This study investigated aspects of individual differences in timing of continuous and discontinuous movements to different pacing signals (auditory or visual), pacing intervals (500, 650, 800, 950 ms), and across effectors (dominant versus non-dominant hand). Correlation and principal component analysis demonstrated that a single statistical dimension accounted for up to 60% of the explained variance in discontinuous tasks and 25% of the variance in continuous tasks, when applied to performance obtained from tasks conducted with different effectors and at different pacing rates. Correlation analysis of factor scores representing effector and rate independent task performances showed that timing of discrete or continuous movements can be associated with modality independent mechanisms. Timing variability from discrete and continuous trials was not significantly correlated. This study goes beyond previous correlational work on individual differences in discrete and continuous movements, demonstrating that individual differences in discrete (event-based) or continuous (emergent) motor timing tasks can be modeled as distinctive statistical components with dissimilar capability to capture effector, rate, and modality independent variance.

Exploring individual differences in children's mathematical skills: a correlational and dimensional approach.

Individual differences in mathematical skills are typically explained by an innate capability to solve mathematical tasks. At the behavioural level this implies a consistent level of mathematical achievement that can be captured by strong relationships between tasks, as well as by a single statistical dimension that underlies performance on all mathematical tasks. To investigate this general assumption, the present study explored interrelations and dimensions of mathematical skills. For this purpose, 68 ten-year-old children from two schools were tested using nine mathematics tasks from the Basic Knowledge in Mathematics Test. Relatively low-to-moderate correlations between the mathematics tasks indicated most tasks shared less than 25% of their variance. There were four principal components, accounting for 70% of the variance in mathematical skill across tasks and participants. The high specificity in mathematical skills was discussed in relation to the principle of task specificity of learning.

Heart rate variability in fibromyalgia patients and healthy controls during non-REM and REM sleep: a case-control study.

OBJECTIVES: To investigate heart rate variability (HRV) in fibromyalgia (FM) patients and healthy controls (HCs) during different sleep stages, and to examine the association of HRV with pain and sleep quality. METHOD: Polysomnography was recorded from 23 female FM patients and 22 age- and sex-matched HCs. HRV was recorded from bedtime until awakening including the standard deviation of normal-to-normal intervals (SDNN), the root mean square successive difference (RMSSD), and the low (LF; 0.04-0.15 Hz) and high (HF; 0.15-0.4 Hz) frequency power. Subjective scores of neck/shoulder pain and sleep quality were obtained at bedtime and awakening. RESULTS: Both patients and HCs showed high incidence of arousals per hour (FM: 16 ± 9.7; HCs: 17 ± 11). RMSSD was lower in patients than HCs during non-rapid eye movement (non-REM) stage 2 (N2) sleep (mean ± SD; 30 ± 12 ms vs. 42 ± 13 ms, p < 0.002) and during REM sleep (23 ± 11 ms vs. 37 ± 16 ms, p < 0.003). HRV did not differ between groups during N3 sleep (p > 0.19 for all comparisons). In patients, SDNN, RMSSD, and HF power showed modest positive correlations with sleep quality (HF power during N3 sleep showed the highest correlation; Spearman's ρ = 0.54) and modest negative correlations with neck/shoulder pain (RMSSD during N3 sleep showed the highest correlation with pain at bedtime; Spearman's ρ = -0.51). CONCLUSIONS: RMSSD, indicative of parasympathetic predominance, is attenuated in FM patients compared to HCs during N2 sleep and REM sleep. This difference was not present for the HF component. HRV during sleep in FM patients is moderately and positively associated with sleep quality and moderately and negatively associated with neck/shoulder pain.

Timing continuous or discontinuous movements across effectors specified by different pacing modalities and intervals.

Sensorimotor synchronization is hypothesized to arise through two different processes, associated with continuous or discontinuous rhythmic movements. This study investigated synchronization of continuous and discontinuous movements to different pacing signals (auditory or visual), pacing interval (500, 650, 800, 950 ms) and across effectors (non-dominant vs. non-dominant hand). The results showed that mean and variability of asynchronization errors were consistently smaller for discontinuous movements compared to continuous movements. Furthermore, both movement types were timed more accurately with auditory pacing compared to visual pacing and were more accurate with the dominant hand. Shortening the pacing interval also improved sensorimotor synchronization accuracy in both continuous and discontinuous movements. These results show the dependency of temporal control of movements on the nature of the motor task, the type and rate of extrinsic sensory information as well as the efficiency of the motor actuators for sensory integration.