Klaus Pfeifer

Neuromuscular training for sports injury prevention: a systematic review.

PURPOSE The aim of this systematic review was to assess the effectiveness of proprioceptive/neuromuscular training in preventing sports injuries by using the best available evidence from methodologically well-conducted randomized controlled trials and controlled clinical trials without randomization. METHODS Two independent researchers performed a literature search in various electronic databases and reference lists. The reviewers independently assessed trials for inclusion criteria and methodological quality and extracted the data. Focusing on studies of high methodological quality, relative risks (RR) and 95% confidence intervals (CI) were used to estimate treatment effects. RESULTS From a total of 32 relevant studies, 7 methodologically well-conducted studies were considered for this review. Pooled analysis revealed that multi-intervention training was effective in reducing the risk of lower limb injuries (RR = 0.61, 95% CI = 0.49-0.77, P < 0.01), acute knee injuries (RR = 0.46, 95% CI = 0.28-0.76, P < 0.01), and ankle sprain injuries (RR = 0.50, 95% CI = 0.31-0.79, P < 0.01). Balance training alone resulted in a significant risk reduction of ankle sprain injuries (RR = 0.64, 95% CI = 0.46-0.9, P < 0.01) and a nonsignificant risk reduction for injuries overall (RR = 0.49, 95% CI = 0.13-1.8, P = 0.28). Exercise interventions were more effective in athletes with a history of sports injury than in those without. CONCLUSION On the basis of the results of seven high-quality studies, this review showed evidence for the effectiveness of proprioceptive/neuromuscular training in reducing the incidence of certain types of sports injuries among adolescent and young adult athletes during pivoting sports. Future research should focus on the conduct of comparative trials to identify the most appropriate and effective training components for preventing injuries in specific sports and populations.

Dose-Response Relationship of Resistance Training in Older Adults: A Meta-Analysis

PURPOSE The purpose of this study was to determine the dose-response relationship of resistance training (RT) to improve strength and function in older adults. METHODS A systematic literature search was performed in relevant databases and study reference lists to identify randomized controlled trials. Randomized controlled trials comparing the effects of different doses of strength training in older people (65 yr and older) on strength and functional outcomes were eligible. Two independent reviewers decided on study inclusion, extracted data, and assessed methodological quality. Standardized mean difference (SMD) and 95% confidence intervals (CI) were calculated for relevant outcomes and pooled using a random-effects model. RESULTS Twenty-nine trials with a total of 1313 subjects (mean age = 65-81 yr) are summarized in this review. Trials comparing different training intensities show strong effects of progressive resistance training (PRT) on maximal strength in a dose-dependent manner, with high-intensity (HI) PRT being more effective compared with moderate (MI)- and low-intensity (LI) PRT (SMD [HI vs LI] = 0.88, 95% CI = 0.21-1.55; SMD [HI vs MI] = 0.62, 95% CI = 0.22-1.03). PRT was also successful for improving functional outcomes, but gains were independent of training intensity. Power training (PT) was more effective for improving muscle power (SMD [PT vs PRT] = 1.66, 95% CI = 0.08-3.24) and functional outcomes than PRT. There was only little information available on training volume and frequency. DISCUSSION Higher training intensities are superior to lower intensities for improving maximal strength but not necessarily for functional performance of older adults. PT has shown to be a particularly effective method for enhancing muscle power and functional performance. More research is necessary to identify the effect of different training volumes and frequencies and the dose-response relationship for very old and frail populations.

Sclerostin and its association with physical activity, age, gender, body composition, and bone mineral content in healthy adults.

CONTEXT Sclerostin is produced by osteocytes and inhibits bone formation through the Wnt/β-catenin-signaling pathway. Only limited data are available on circulating sclerostin levels in healthy subjects. OBJECTIVE We aimed to evaluate the correlation between sclerostin and physical activity, anthropometric, and biochemical variables. DESIGN, SETTING, AND PARTICIPANTS We conducted a cross-sectional observational study in 161 healthy adult men and premenopausal women aged 19 to 64 yr (mean age, 44 ± 10). INTERVENTION(S) There were no interventions. MAIN OUTCOME MEASURE(S) Serum sclerostin levels were associated with body composition, bone mineral density, physical activity, and various biochemical parameters. RESULTS A positive correlation between age and sclerostin in both men (r = 0.37; P < 0.001) and premenopausal women (r = 0.66; P < 0.001) was found. Men had significantly higher sclerostin levels than women (49.8 ± 17.6 vs. 37.2 ± 15.2 pmol/liter; P < 0.001). However, after adjustment for age, bone mineral content (BMC), physical activity, body mass index (BMI), and renal function, sclerostin levels did not differ (P = 0.543). Partial correlation analysis adjusted for age, gender, and kidney function revealed a significant positive correlation between sclerostin levels and BMC, bone mineral density, BMI, and android/gynoid fat and a significant negative correlation with serum osteocalcin and calcium. The most physically active quartile had significantly lower sclerostin levels compared to the least active quartile in a univariate analysis. CONCLUSIONS In healthy adults, sclerostin serum levels correlate positively with age, BMI, and BMC and negatively with osteocalcin and calcium. Further studies in larger populations are needed to confirm our findings and to better understand their clinical implications.

Balance Training for Neuromuscular Control and Performance Enhancement: A Systematic Review

OBJECTIVE As a result of inconsistencies in reported findings, controversy exists regarding the effectiveness of balance training for improving functional performance and neuromuscular control. Thus, its practical benefit in athletic training remains inconclusive. Our objective was to evaluate the effectiveness of training interventions in enhancing neuromuscular control and functional performance. DATA SOURCES Two independent reviewers performed a literature search in Cochrane Bone, Joint and Muscle Trauma Group Register and Cochrane Controlled Trials Register, MEDLINE, EMBASE, PEDro (Physiotherapy Evidence Database), and SCOPUS. STUDY SELECTION Randomized controlled trials and controlled trials without randomization with healthy and physically active participants aged up to 40 years old were considered for inclusion. Outcomes of interest were postural control, muscle strength, agility, jump performance, sprint performance, muscle reflex activity, rate of force development, reaction time, and electromyography. DATA EXTRACTION Data of interest were methodologic assessment, training intervention, outcome, timing of the outcome assessment, and results. Standardized mean differences and 95% confidence intervals were calculated when data were sufficient. DATA SYNTHESIS In total, 20 randomized clinical trials met the inclusion criteria. Balance training was effective in improving postural sway and functional balance when compared with untrained control participants. Larger effect sizes were shown for training programs of longer duration. Although controversial findings were reported for jumping performance, agility, and neuromuscular control, there are indications for the effectiveness of balance training in these outcomes. When compared with plyometric or strength training, conflicting results or no effects of balance training were reported for strength improvements and changes in sprint performance. CONCLUSIONS We conclude that balance training can be effective for postural and neuromuscular control improvements. However, as a result of the low methodologic quality and training differences, further research is strongly recommended.

Influences of nonspecific low back pain on three-dimensional lumbar spine kinematics in locomotion

Study Design. A three-dimensional kinematic analysis of lumbar spinal movements with an ultrasonic measuring system was used to distinguish patients with chronic low back pain from those without such pain. Objectives. To investigate the effects of chronic low back pain on the three-dimensional movements of the lumbar spine, and to identify variables that would allow discrimination among patients with chronic low back pain and control subjects. Summary of Background Data. To the authors’ knowledge, no previous studies have described or identified altered spinal and pelvic gait kinematics caused by nonspecific chronic low back pain in all anatomic planes. Methods. In this study, 34 participants with chronic low back pain and 22 subjects without such pain were monitored during treadmill gait. Data from the measuring system operating at 30 Hz were low-pass filtered and normalized to a percentage of the gait cycle. Results. Cross-correlations showed almost identical patterns of pelvic (S1) and thoracic (T12) movement curves in all anatomic planes between groups. No statistical group differences were detected for either pelvic or thoracic oscillation amplitudes. However, Student’s t test showed significantly higher coefficients of variation (P < 0.01) in all anatomic planes of patients with chronic low back pain than in healthy control patients. Conclusions. The phasic patterns and angular spinal displacements of patients with nonspecific low back pain were shown to be within normal limits. However, the patients demonstrated higher degrees of stride-to-stride variability, representing increased fluctuations in dynamic thoracic and pelvic oscillations. These findings, resulting in less than optimal gait patterns, must be considered in the rehabilitation of patients with chronic low back pain.

The Fried Frailty Criteria as Inclusion Criteria for a Randomized Controlled Trial: Personal Experience and Literature Review

Background: Among current operational definitions of frailty, the criteria proposed by Fried and colleagues have attracted great scientific interest. However, these criteria have usually been applied in epidemiological and only rarely in interventional studies. Objective: The present paper aims at testing the applicability of the Fried frailty criteria in the context of the recruitment process of a randomized controlled trial in prefrail older persons, and it discusses the respective scientific literature. Methods: Recruitment was promoted by newspaper articles as well as by targeted mail to customers of a local health insurance company and to recently treated patients of a geriatric day clinic. Furthermore, presentations were given in assisted living facilities. Potential candidates were screened for prefrailty, i.e. to see whether they met 1 or 2 of the Fried criteria (weight loss, handgrip strength, gait speed, exhaustion, physical activity). Results: A total of 298 people were screened. Among them 181 were not frail, 116 were prefrail and 1 was diagnosed as frail. The most prevalent criterion was exhaustion (24% of those screened). The second most prevalent criterion was low handgrip strength (20%). Low gait speed (8%), low physical activity (2%) and weight loss (2%) had a lower prevalence. According to the Geriatric Depression Scale, 14% of those who met the criterion ‘exhaustion’ were depressed. With regard to the Minnesota Leisure Time Physical Activity Questionnaire, used for the evaluation of ‘physical activity’, only 3 activities among the 18 selected by Fried were applicable to our cohort. Conclusions: Under the study conditions, good applicability of the Fried criteria was observed. Nevertheless, further refinement may be expedient in several criteria, especially exhaustion and physical activity, to enhance clinical usefulness. It may be helpful to adapt the cutoffs when applying the criteria to a European population.

Multiple sclerosis relapses are not associated with exercise

Since multiple sclerosis (MS) often affects physically active young individuals, it is important to know if exercise can result in increased disease activity. Therefore we used a self-report questionnaire to examine the relationship of different levels of sports activity and relapses in 632 patients with MS. In order to analyse whether subjective recall might have biased the results, we performed, in a subgroup of our sample, an objective assessment of clinical data and physical fitness parameters. We were unable to find any association between sports activity and clinical relapses in either of the two analyses. The group with highest activity even shows the lowermost mean values, standard deviations and range concerning the number of relapses. Our data suggest that physical activity has no significant influence on clinical disease activity.

Physical activity, exercise, and sarcopenia – future challenges

ZusammenfassungGRUNDLAGEN: Viele Studien haben nachgewiesen, dass die Ethologie von Sarkopenie multikausal und sehr komplex ist. Die Verminderung der Muskelmasse führt zu einem Verlust von Muskelkraft, später zu einem abnehmenden funktionellem Status mit eingeschränkter Mobilität, damit wiederum zu einem höheren Sturzrisiko und zum Schluss zu einem höheren Mortalitätsrisiko. Aktuelle Empfehlungen und Leitlinien geben an, dass körperliche Inaktivität oder ein abnehmendes Niveau der körperlichen Aktivität Teil des Entstehungszyklus von Sarkopenie sind und deshalb körperliche Aktivität als wichtige Säule bei der Entwicklung und Behandlung von Sarkopenie berücksichtigt werden muss. THEMA: Ergebnisse zum Zusammenhang von körperlicher Aktivität und dem Alternsprozess haben nicht immer eindeutige Resultate gezeigt. Diese Inkonsistenz der wissenschaftlichen Ergebnisse ist zum Einen darauf zurückzuführen, dass Begriffe und das zugrunde liegende Konstrukt nicht einheitlich benutzt werden. Zum Anderen beruhen die unterschiedlichen Ergebnisse in der Heterogenität der Zielpopulation, Art der Interventionen oder auch den eingesetzten Messinstrumentarien. Diese Aspekte werden in dem Artikel thematisiert. Mit Bezug auf die zukünftigen Herausforderungen für die Rolle und den Einsatz von körperlicher Aktivität werden zusätzlich in diesem Artikel mögliche Barrieren und Anregungen zur Prävention und Behandlung von Sarkopenie diskutiert. Eine Vielzahl von Studien zeigt, dass strukturierte und gut geplante Trainingsprogramme, bestehend aus progressivem Krafttraining oder einem Schnellkrafttraining, positive Effekte auf die Sarkopenie oder Sarkopenie bezogene Komponente haben. Weniger eindeutig ist allerdings der Erkenntnisstand zum Transfer dieser Ergebnisse auf funktionelle Parameter. SCHLUSSFOLGERUNGEN: Beides, körperliche Aktivität und Training, haben gezeigt, dass sie das Sarkopenierisiko und den Beginn von funktionellen Einschränkungen bei älteren Menschen reduzieren können. Unglücklicherweise weist die Kohorte älterer Menschen gerade die höchsten Anteile von inaktiven oder gering aktiven Menschen auf. Deshalb scheint es zwingend notwendig, ältere Menschen zu motivieren, ihr körperliches Aktivitätsniveau zu erhöhen und sicheren Zugang sowie entsprechenden Trainingsprogramme bereit zu stellen.SummaryBACKGROUND: Numerous studies have demonstrated that the etiology of sarcopenia is multi-causal and very complex process. The degradation of muscle mass leads to a loss of strength, later on to a decreased functional status, impaired mobility, a higher risk of falls, and eventually an increased risk of mortality. Present guidelines state that physical inactivity or a decreased physical activity level is a part of the underlying mechanisms of sarcopenia and therefore physical activity can be seen as an important factor to reverse or modify the development of sarcopenia. TOPIC: Results in the area of physical activity and aging have not always been homogeneous. The inconsistent findings in this research area are related to the different understanding of terms and underlying constructs along with different population, type of intervention, or measurement methods. These aspects will be discussed in the paper. With regard to the formulated future role of physical activity this article will discuss in addition different barriers and challenges in the prevention and treatment of sarcopenia. A multitude of studies shows that structured exercise programs including progressive resistance or power training have positive effects on sarcopenia and sarcopenia-related outcomes but less or inconclusive information is available for the transfer to functional outcomes. CONCLUSIONS: Both physical activities and exercise have shown to decrease risk of sarcopenia and onset of functional limitations in older persons. Unfortunately the cohort of older persons is the one with the highest percentage of individuals classified as inactive or sedentary. Therefore motivating older persons to increase their physical activity level as well as providing safe access to exercise programs seems to be a mandatory task.

Residual effects of muscle strength and muscle power training and detraining on physical function in community-dwelling prefrail older adults: a randomized controlled trial

BackgroundAlthough resistance exercise interventions have been shown to be beneficial in prefrail or frail older adults it remains unclear whether there are residual effects when the training is followed by a period of detraining. The aim of this study was to establish the sustainability of a muscle power or muscle strength training effect in prefrail older adults following training and detraining.Methods69 prefrail community-dwelling older adults, aged 65–94 years were randomly assigned into three groups: muscle strength training (ST), muscle power training (PT) or controls. The exercise interventions were performed for 60 minutes, twice a week over 12 weeks. Physical function (Short Physical Performance Battery=SPPB), muscle power (sit-to-stand transfer=STS), self-reported function (SF-LLFDI) and appendicular lean mass (aLM) were measured at baseline and at 12, 24 and 36 weeks after the start of the intervention.ResultsFor the SPPB, significant intervention effects were found at 12 weeks in both exercise groups (ST: p = 0.0047; PT: p = 0.0043). There were no statistically significant effects at 24 and 36 weeks. In the ST group, the SPPB declined continuously after stop of exercising whereas the PT group and controls remained unchanged. No effects were found for muscle power, SF-LLFDI and aLM.ConclusionsThe results showed that both intervention types are equally effective at 12 weeks but did not result in statistically significant residual effects when the training is followed by a period of detraining. The unchanged SPPB score at 24 and 36 weeks in the PT group indicates that muscle power training might be more beneficial than muscle strength training. However, more research is needed on the residual effects of both interventions. Taken the drop-out rates (PT: 33%, ST: 21%) into account, muscle power training should also be used more carefully in prefrail older adults.Trial registrationThis trial has been registered with clinicaltrials.gov (NCT00783159)

Effects of Strength Training versus Power Training on Physical Performance in Prefrail Community-Dwelling Older Adults

Background: It has been unclear which training mode is most effective and feasible for improving physical performance in the risk group of prefrail community-dwelling older adults. Objective: The purpose of the present study was to compare the effects of strength training (ST) versus power training (PT) on functional performance in prefrail older adults. This study was registered at clinicaltrials.gov as NCT00783159. Methods: 69 community-dwelling older adults (>65 years) who were prefrail according to the definition of Fried were included in a 12-week exercise program. The participants were randomized into an ST group, a PT group and a control group. All participants were supplemented with vitamin D3 orally before entering the intervention period. The primary outcome was the global score on the Short Physical Performance Battery (SPPB). Secondary outcomes were muscle power, appendicular lean mass (aLM) measured by dual energy X-ray absorptiometry and self-reported functional deficits (Short Form of the Late-Life Function and Disability Instrument, SF-LLFDI). Results: Regarding changes in the SPPB score during the intervention, significant heterogeneity between the groups was observed (p = 0.023). In pair-wise comparisons, participants in both training groups significantly (PT: p = 0.012, ST: 0.009) increased their SPPB score (PT: Δmean = 0.8, ST: Δmean = 1.0) compared to the control group, with no statistical difference among training groups (p = 0.301). No statistical differences were found in changes in aLM (p = 0.769), muscle power (p = 0.308) and SF-LLFDI (p = 0.623) between the groups. Muscle power significantly increased (p = 0.017) under vitamin D3 intake. Conclusions: In prefrail community-dwelling adults, PT is not superior to ST, although both training modes resulted in significant improvements in physical performance. With regard to dropout rates, ST appears to be advantageous compared to PT. The high prevalence of vitamin D3 deficiency and the slight improvement of physical performance under vitamin D3 supplementation among study participants underline the relevance of this approach in physical exercise interventions.