Validity of lower extremity strength and power utilizing a new closed chain dynamometer

Strength and Step Activity After Eccentric Resistance Training in Those With Incomplete Spinal Cord Injuries

Background: Individuals with spinal cord injuries (SCIs) often experience general weakness in the lower extremities that undermines daily step activity. Objective: To investigate the efficacy of eccentrically biased resistance training on lower extremity strength and physical activity of individuals with spinal injuries. Methods: Individuals with long-standing incomplete SCIs (N = 11) capable of completing a 10-meter walk assessment were included. All participants who completed the familiarization period finished the training. Individuals trained two times per week for 12 weeks on a lower body eccentric resistance training machine. It was hypothesized that the outcome variables (eccentric strength, isometric strength, and daily step physical activity) would improve as a result of the training intervention. Results: Eccentric strength [F(1.27, 12.71) = 8.42, MSE = 1738.35, H-F p = .009] and isometric strength [F(1.97, 19.77) = 7.10, MSE = 11.29, H-F p = .005] improved as a result of the training while daily step activity remained unchanged [F(2.00, 18.00) = 2.73, MSE = 216,836.78, H-F p = .092]. Conclusions: Eccentric resistance training improves eccentric and isometric strength. These physiological adaptations may translate to improved gait mechanics, but further study is required to identify this potential crossover effect.

Effect of diet-induced weight loss on muscle strength in adults with overweight or obesity - a systematic review and meta-analysis of clinical trials

We conducted a systematic review and meta-analysis to identify how diet-induced weight loss in adults with overweight or obesity impacts on muscle strength. Twenty-seven publications, including 33 interventions, most of which were 8-24 weeks in duration, were included. Meta-analysis of seven interventions measuring knee extensor strength by isokinetic dynamometry in 108 participants found a significant decrease following diet-induced weight loss (-9.0 [95% confidence interval: -13.8, -4.1] N/m, P < 0.001), representing a 7.5% decrease from baseline values. Meta-analysis of handgrip strength from 10 interventions in 231 participants showed a non-significant decrease (-1.7 [-3.6, 0.1] kg, P = 0.070), with significant heterogeneity (I(2)  = 83.9%, P < 0.001). This heterogeneity may have been due to diet type, because there was a significant decrease in handgrip strength in seven interventions in 169 participants involving moderate energy restriction (-2.4 [-4.8, -0.0] kg, P = 0.046), representing a 4.6% decrease from baseline values, but not in three interventions in 62 participants involving very-low-energy diet (-0.4 [-2.0, 1.2] kg, P = 0.610). Because of variability in methodology and muscles tested, no other data could be meta-analyzed, and qualitative assessment of the remaining interventions revealed mixed results. Despite varying methodologies, diets and small sample sizes, these findings suggest a potential adverse effect of diet-induced weight loss on muscle strength. While these findings should not act as a deterrent against weight loss, due to the known health benefits of losing excess weight, they call for strategies to combat strength loss - such as weight training and other exercises - during diet-induced weight loss. © 2016 World Obesity.

Hand-held dynamometry correlation with the gold standard isokinetic dynamometry: a systematic review

OBJECTIVE

To examine the current evidence regarding the reliability and validity of hand-held dynamometry for assessment of muscle strength in the clinical setting.

DATA SOURCES

A search was conducted of the following databases: Cochrane, MEDLINE, PubMed, PEDro, OTseeker, Index to Chiropractic Literature (ICL), and MANTIS, from inception until January 29, 2010.

STUDY SELECTION

The MeSH subject heading "muscle strength dynamometer" was searched, in isolation and in combination with the text word phrases "hand-held dynamometer" and "isokinetic." Four hundred fifty-four different studies met this search and were reviewed for possible inclusion.

DATA EXTRACTION

Two independent reviewers assessed the quality of the included manuscripts. The PEDro data collection system was used in conjunction with the Cochrane Diagnostic Test Accuracy Description. A third reviewer was used when there was disagreement between the primary reviewers.

DATA SYNTHESIS

Seventeen manuscripts met the inclusion criteria for this review, with a total of 19 studies (2 of the manuscripts involved 2 separate studies) that compared hand-held dynamometry with an identified reference standard (isokinetic muscle strength testing). The results demonstrated minimal differences between hand-held dynamometry and isokinetic testing.

CONCLUSIONS

Considering hand-held dynamometry's ease of use, portability, cost, and compact size, compared with isokinetic devices this instrument can be regarded as a reliable and valid instrument for muscle strength assessment in a clinical setting.

One-repetition maximum strength test represents a valid means to assess leg strength in vivo in humans

Skeletal muscle strength is often determined to evaluate the adaptive response to an exercise intervention programme. Although dynamometry is considered the "gold standard" for the assessment of muscle strength in vivo, one-repetition maximum (1-RM) testing performed on training-specific equipment is more commonly applied. We assessed the validity of specific knee extension 1-RM testing by comparison with dynamometry in a heterogeneous population (n=55). All participants performed 1-RM tests on regular leg extension and leg press machines. Additionally, isometric (at seven different knee angles) and isokinetic (at four different velocities) knee extension peak torques were determined. Pearson's r was calculated for the relationship between 1-RM data and peak torques for the entire population and for subgroups defined by age and gender. One-repetition maximum strength correlated strongly with the dynamometer results. One-repetition maximum leg extension correlated more strongly with peak torques than did 1-RM leg press (0.78<or=r<or=0.88 vs. 0.72<or=r<or=0.77; P<0.001). Similar correlations were observed in all subgroups. We conclude that 1-RM testing represents a valid means to assess leg muscle strength in vivo in young and elderly men and women. Considering the importance of training specificity in strength assessment, we argue that 1-RM testing can be applied to assess changes in leg muscle strength following an exercise intervention.

Optimal loading during two different leg-press movements in female rowers

PURPOSE

The purpose of this study was to determine the optimal load for power during concentric only (CO) and stretch-shortening cycle (SSC) leg-press movements during the initial portion of the concentric phase as well as throughout the entire concentric phase in trained female rowers.

METHODS

Thirty female rowers (age = 19.6 +/- 1.2 yr) were tested for strength (1RM), mean power (MP), peak power (PP), as well as power output at 50, 100, 150, and 200 ms (P50-P200) during both CO and SSC leg-press movements and across six different loads (30-80% 1RM) on the Omnikinetic dynamometer.

RESULTS

Split-split plot analysis indicated that MP and PP were maximized at approximately 60% 1RM in both CO and SSC movements. There were no significant differences in P50 and P100 across all loads for both CO and SSC. P150 was greatest at 30, 40, 50, and 60% 1RM for CO and SSC movements. P200 was maximized at 30, 40, and 50% 1RM during CO. P200 was maximized at 50, 60, and 70% 1RM during SSC.

CONCLUSIONS

There was no difference in the optimal loads for MP (40, 50, and 60% 1RM) and PP (50, 60, and 70% 1RM) between CO and SSC movements. An enhancement of power during the initial 200 ms of the concentric phase of SSC movements was observed. Greater time to reach PP was the reason for the enhancement in PP output observed in CO movements. The CO training regimen associated with the sport of rowing also may have lessened the effect of the SSC.

Effects of ankle joint effusion on lower leg function

BACKGROUND

Inversion ankle sprains are among the most frequently encountered injuries in and outside of sport. Altered feedback from joint damage and/or edema may negatively affect dynamic stabilization, thereby increasing the patients' susceptibility to further injury. In order to understand better how the sensorimotor system responds to the presence of ankle edema during a functional task, further examination is warranted.

OBJECTIVE

To quantify muscle activation in the peroneal, tibialis anterior, and soleus musculature as well as to determine ankle joint peak torque, peak power, and root mean square (RMS) power during a closed kinetic chain activity following artificial ankle effusion.

DESIGN

Dependent variables were compared within subjects across time intervals and between groups.

SETTING

All data were collected in the biomechanics laboratory.

PARTICIPANTS

Subjects were 20 healthy, neurologically sound volunteers (age 21.9 +/- 2.1 y, height 174.5 +/- 9.3 cm, mass 79.3 +/- 15.9 kg) with no lower extremity injuries.

INTERVENTIONS

Subjects were prepared for surface electrodes on the peroneus longus (PL), tibialis anterior (TA), soleus (Sol), and medial malleolus (ground). Anthropometric measures for the lower extremity were recorded for use by the Omnikinetic closed chain dynamometer. Measurements were taken prior to ankle effusion (baseline), immediately following effusion (post), and again at 30 minutes.

MAIN OUTCOME MEASUREMENTS

Testing consisted of 6 repetitions at 35% of 1-repetition max and a constant speed of 1.5 Hz. Separate two-way MANOVAs with repeated measures on time intervals were used to detect differences between groups (effusion and control) over time for torque, power, and RMS power and for peak and average EMG.

RESULTS

An overall time x group interaction was detected for EMG (F4,72=3.878; P=0.007) and kinetic variables (F6,70=5.55; P=0.0001). Average and peak PL EMG decreased immediately following effusion (Sidak's; P=0.048), and average EMG remained depressed 30 minutes following effusion (Sidak's; P=0.02). Immediately posteffusion, a decrease in ankle torque was detected (Sidak's; P=0.007). No differences in TA or Sol EMG, power, or RMS power were detected (P>0.05).

CONCLUSIONS

Decreases in ankle plantarflexion torque and PL EMG indicate that a neuromuscular deficit exists in the presence of edema that could increase the susceptibility for further ankle injury.

Fidedignidade inter e intradias de um teste de potência muscular

Com o envelhecimento há rápida e relevante perda de potência muscular (PM), prejudicando a autonomia e a qualidade de vida, tornando conveniente avaliar a PM. O objetivo do estudo foi determinar a fidedignidade inter e intradias de um teste simples de PM, realizado em uma carga previamente individualizada. Avaliamos 18 jovens adultos saudáveis, sendo 12 mulheres, inexperientes quanto a exercícios de fortalecimento. Determinou-se inicialmente 1RM com medida simultânea da velocidade e da potência (Fitrodyne, Bratislava), no exercício remada alta, até a altura mesoesternal na posição ortostática, obtendo-se ainda a carga na qual se conseguia a maior PM. Na semana seguinte, por cinco dias consecutivos, eles realizaram em quatro dias 2x2 repetições e em um dia 10x2 repetições (3s de intervalo entre as repetições), o mais rápido possível na fase concêntrica, com a carga de PM. Comparando os resultados pela ANOVA para medidas repetidas e teste de Bonferroni, verificou-se que a PM máxima não diferia - médias entre 262 e 267W (p = 0,69). Para a variabilidade dos dados individuais, encontraram-se valores de 3 e 8%, respectivamente, para o coeficiente de variação (CV) e para a média da variação dos resultados pela média dos indivíduos M-m/X. Nas dez séries consecutivas os valores ficaram entre 242 e 263W, somente identificando-se diferenças entre as séries 1 e 4 e 6 (p < 0,05). Excluindo-se os dados da primeira série (cinco dos 18 avaliados tiveram valores excepcionalmente baixos nela), as diferenças desaparecem (p = 0,13). Dados da variabilidade individual demonstraram 6 e 20%, respectivamente, para CV e M-m/X, nas dez séries consecutivas. Os autores concluem que a PM máxima obtida em um teste simples apresenta alta fidedignidade inter e intradias e variabilidade relativamente baixa, quando comparadas com outras mensurações freqüentemente usadas em ciências do exercício. Esse teste pode ser recomendado para medidas de PM em programas voltados para a saúde e a aptidão física, nos quais a utilização de materiais e protocolos mais sofisticados pode ser inapropriada ou inviável.