Relationship between physical activity and incidence of dementia in people aged 50 and over in Europe.

OBJECTIVE: The aim of this study was to analyse the relationship between physical activity and the incidence of dementia in a cohort of people aged 50 years or older without dementia from different countries in Europe between the years 2013 and 2015. METHODS: Prospective longitudinal design study (2013-2015) with a sample of 46,141 people without dementia in 2013 who participated in the SHARE project in waves 5 and 6, where 15 European countries participated. We defined dementia as a self-report of Alzheimer's disease, organic brain syndrome, senility, or any other serious memory impairment during follow-up. The frequency of moderate, vigorous and moderate-to-vigorous physical activity in 2013 was obtained from a validated questionnaire. Incidences of dementia by year (between 2013 and 2015) were calculated for each category of physical activity. Poisson regression models with robust variance were fitted for the association between physical activity and dementia. RESULTS: The incidence of dementia was 7.4 [95%CI = 6.8-7.9] cases per 1000 persons per year. Very frequent moderate physical activity is a protective factor for dementia independently of the frequency of vigorous physical activity and inversely. The risk of dementia was 2.36 [95%CI = 1.77-3.14] higher in people who hardly ever, or never did moderate-to-vigorous physical activity comparing to people engaged in it more than once a week independently of the baseline cognitive level. CONCLUSION: Physical activity is associated with the incidence of dementia in people aged 50 and over in both men and women in Europe.

Children's strategies in drop-landing.

Introduction: Landing is a critical motor skill included in many activities performed in the natural environment by young children. Yet, landing is critically relevance to ensure proper stability and reduce injury. Furthermore, landing is an integral part of many fundamental motor skills which have been linked to greater physical activity, sport participation, and perceived competence in children. Our aim was to examine the drop-landing strategies of young children focusing on the lower extremity with a multi-variant approach. Methods: Forty-four children divided into four age groups (G1:3-4.5 y, G2:4.5-6 y, G3:6-7.5 y, G4:7.5-9 y) performed 20 drop-land trials in four different conditions: predictable stationary landing, running to the left, to the right, and stay in place. Fifteen reflective markers, two force plates, and ten surface electromyography (sEMG) sensors were used to collect data. MANOVAs (Group x Condition) were conducted separately for the kinematic, kinetic, and sEMG variables. Results: Only significant group effects were found (kinematic MANOVA p = 0.039, kinetic MANOVA p = 0.007, and sEMG MANOVA p = 0.012), suggesting that younger groups (G1, G2) differed to the older groups (G3, G4). G1 showed less knee flexion and slower ankle dorsi-flexion during the braking phase compared to G3, while G2 presented smaller ankle dorsi-flexion at the braking phase and smaller ankle range of motion than G3. Overall kinetic variables analysis showed a group difference but no group differences for any single kinetic variable alone was found. Regarding sEMG, G1 during the flight phase exhibited longer tibialis anterior and hamstrings activity than G3 and G3 & G4, respectively; and an earlier start of the hamstrings' impact burst than G4. In addition, distal to proximal control was primarily used by all groups to coordinate muscle activity (in response to impact) and joint motion (after impact). Discussion: Perhaps a developmental critical point in landing performance exists at 4-5 years of age since G1 presented the largest differences among the groups. This suggests that to improve landing strategies could start around this age. Future studies should examine if playground environments that include equipment conducive to landing and practitioners in the kindergarten schools are adequate vehicles to empower this type of intervention.

Electromyographic and Kinematic Analysis of Trunk and Limb Muscles During a Holding Task in Individuals With Chronic Low Back Pain and Healthy Controls.

BACKGROUND: Chronic low back pain (CLBP) affects a large proportion of the population and has been associated with different muscle dysfunctions. However, there is no consensus regarding muscle electromyography and kinematic patterns during fatiguing tasks. OBJECTIVE: To examine whether trunk and limb muscle fatigability and activation patterns of individuals suffering CLBP differ from those of healthy participants during a holding task. DESIGN: Cross-sectional study. SETTING: Clinical research laboratory. PARTICIPANTS: Twenty-four participants with CLBP and 26 matched healthy controls. METHODS: Both groups performed a static holding task, in a semisquat position, until exhaustion. The performance variable was time to failure. Electromyography signs, such as median frequency and root mean square, were used to quantify fatigability by applying linear regression to each of the 3 successive test periods. Kinematic variables were monitored throughout the holding task. MAIN OUTCOME MEASUREMENTS: Independent t tests were used to compare time to failure. Electromyography-based measures of muscle fatigability were examined through a two-way, repeated-measures analysis of variance (mixed-model), whereas kinematic analysis was based on 2 multivariate analyses of variance. RESULTS: Although the groups differed in time to failure (healthy group: mean 201.6 seconds, SD 98.9 seconds; CLBP: mean 132.4 seconds, SD 78.9 seconds; P =.009), no statistically significant differences were found in electromyography-based measures of muscle fatigability, except for the internal oblique muscle. Kinematic variables were similar in the 2 groups. CONCLUSION: Despite similar electromyography fatigability in the 2 groups, individuals with CLBP seem to be more sensitive to certain effects of back muscle fatigue. Significant differences in electromyography measurements in the internal oblique muscle, both between groups and across periods, suggest that individuals with CLBP trigger a subtly different activation pattern to control the spine. In a holding task, compared with healthy people, this may represent a compensatory behavior aimed at adapting to certain deficits in spine control or pain. LEVEL OF EVIDENCE: II.

The influence of fatigue and chronic low back pain on muscle recruitment patterns following an unexpected external perturbation.

BACKGROUND: Chronic low back pain (CLBP) has been associated with altered trunk muscle responses as well as increased muscle fatigability. CLBP patients and fatigued healthy subjects could experience similar neuromuscular strategies to attempt to protect the spine. The current study examined muscle activation differences between healthy and CLBP subjects following a perturbation. In addition, the possible role of muscle fatigue was evaluated by investigating the healthy control subjects in a non-fatigued and a fatigued condition. Both experiments were combined to evaluate possible similar strategies between CLBP and fatigued samples. METHODS: Cross-sectional study where 24 CLBP subjects and 26 healthy subjects were evaluated. Both groups (CLBP vs. healthy) and both conditions (non-fatigued and a fatigued condition) were evaluated while a weight was suddenly dropped on a held tray. Erector spinae, multifidus, obliques and biceps brachii were recorded using surface electromyography. Variables describing the bursts timing and variables describing the amount of muscle activity (number of bursts and amplitude increase) post impact were studied. The analysis between groups and conditions was carried out using ANOVAs with repeated measurements for the muscle factor. RESULTS: CLBP subjects reacted similarly to healthy subjects regarding muscle activity post impact. However, the CLBP group showed temporal characteristics of muscle activity that were in between the fatigued and non-fatigued healthy group. Clear differences in muscle activity were displayed for healthy subjects. Fatigued healthy subjects presented more reduced activity after impact (upper limb and trunk muscles) than non-fatigued healthy subjects and different temporal characteristic in the same way than CLBP patients. This same temporal characteristic with CLBP and healthy fatigued people was a delay of the first burst of muscle activity after impact. CONCLUSION: Though similar muscle pattern existed between CLBP and healthy people, CLBP temporal characteristics of muscle activity showed a pattern in between healthy people and fatigued healthy people. While the temporal muscle pattern dysfunction used by CLBP subjects could be related to maladaptive patterns, temporal and muscle activity characteristics used by healthy fatigued people may lead to back injuries.

An algorithm for detecting EMG onset/offset in trunk muscles during a reaction- stabilization test.

BACKGROUND: Most of the EMG analysis algorithms developed to date don't detect the whole sequence of rhythmic and subtle changes that take place during the process of trunk stabilization. Indeed, the few recent methods that are capable of assessing these important EMG characteristics are highly complex and not accessible in most applied clinic contexts. OBJECTIVE: To validate and disseminate a software program suitable for detecting multiple and relatively small EMG bursts during a trunk stabilization response. METHODS: Ninety EMG recordings randomly selected from 50 individuals (24 with chronic low back pain) were analysed by our algorithm based on means and standard deviations and an experienced examiner (as a gold standard). Concordance, sensitivity, specificity, positive predictive value and negative predictive value were considered to analyse reliability. RESULTS: Results showed a high degree of concordance between the two methods (87.2%), high sensitivity and specificity rates (79.5 and 89.2%), a moderate-low positive predicted value (66.9%) and a high negative predicted value (94.4%). CONCLUSION: The program provided is flexible and useful to detect EMG activity. The selected parameters of the program were able to detect onset/offset EMG bursts and were valid for the purpose of this study with a small tendency to over-detect bursts.

Reliability and validity of a custom-made instrument including a hand-held dynamometer for measuring trunk muscle strength.

BACKGROUND: Measuring isometric strength is necessary in many areas of health and sport. However, trunk muscles have some particular characteristics that make them difficult to evaluate with simple, inexpensive instruments. OBJECTIVE: To evaluate the reliability and validity of an instrument constructed with a hand-held dynamometer and a metallic structure (HHD+S) for measuring maximum isometric voluntary trunk muscle strength. METHODS: Maximum isometric voluntary trunk muscle strength (extension, flexion and lateral flexion) was measured in 20 healthy individuals using the custom-made instrument (HHD+S) and the gold standard Back-Check (BC). RESULTS: The results showed that the two instruments had high and similar intra-subject reliability. The validity of the HHD+S was demonstrated by the high Pearson coefficient correlation between the two instruments (r ⩾ 0.78). CONCLUSIONS: Given the good trial reliability and the close correlation between the two instruments, we believe that the use of a hand-held dynamometer together with the custom-made metallic structure (HHD+S) allows an evaluation of the maximum isometric voluntary trunk muscle strength to be made, that is very similar in quality, accuracy and reliability to the BC.