Maximal Isometric Knee Extension Strength Research Articles

Free-Living Sit-to-Stand Characteristics as Predictors of Lower Extremity Functional Decline Among Older Adults.

Habitual strength and power-demanding activities of daily life may support the maintenance of adequate lower-extremity functioning with ageing, but this has been sparingly explored. Hence, we examined whether the characteristics of free-living sit-to-stand (STS) transitions predict a decline in lower-extremity functioning over a 4-year follow-up. 340 community-dwelling older adults (60% women, age 75, 80 or 85 years) participated in this prospective cohort study. At baseline, a thigh-worn accelerometer was used continuously (3-7 days) to monitor the number and intensity of free-living STS transitions. A decline in lower-extremity functioning was defined as a drop of ≥2 points in the Short Physical Performance Battery (SPPB) from baseline to follow-up. Maximal isometric knee-extension strength was measured in the laboratory. 85 participants (75% women) declined in SPPB over 4 years. After adjusting for age, sex, and baseline SPPB points, higher free-living peak STS angular velocity (odds ratio [OR] = 0.70; 95% confidence interval [CI] = 0.52-0.92, per 20 deg/s increase) protected against a future decline. When adjusting the model for maximal isometric knee-extension strength, the statistical significance was attenuated (OR = 0.72; 95% CI = 0.54-0.96, per 20 deg/s increase). Performing STS transitions at higher velocities in the free-living environment can prevent a future decline in lower-extremity function. This indicates that changes in daily STS behavior may be useful in the early identification of functional loss. Free-living peak STS angular velocity may be a factor underlying the longitudinal association of lower-extremity strength and performance.

The Impact of Multimorbidity Patterns on Changes in Physical Activity and Physical Capacity Among Older Adults Participating in a Year-Long Exercise Intervention.

This study investigated the impact of multimorbidity patterns on physical activity and capacity outcomes over the course of a year-long exercise intervention, and on physical activity 1year later. Participants were 314 physically inactive community-dwelling men and women aged 70-85years, with no contraindications for exercise at baseline. Physical activity was self-reported. Physical capacity measurements included five-time chair-stand time, 6-minute walking distance, and maximal isometric knee-extension strength. The intervention included supervised and home-based strength, balance, and walking exercises. Multimorbidity patterns comprised physician-diagnosed chronic disease conditions as a predictor cluster and body mass index as a measure of obesity. Multimorbidity patterns explained 0%-12% of baseline variance and 0%-3% of the change in outcomes. The magnitude and direction of the impact of unique conditions varied by outcome, time point, and sex. Multimorbid older adults with no contraindications for exercise may benefit from multimodal physical training.

Maximal Lower Limb Strength in Patellar Tendinopathy: A Systematic Review With Meta-Analysis.

To investigate whether lower limb strength is reduced in people with patellar tendinopathy (PT) compared with asymptomatic control individuals or the asymptomatic contralateral limb. MEDLINE, PubMed, Scopus, and Web of Science. To be included in the systematic review and meta-analysis, studies were required to be peer reviewed, published in the English language, and case control investigations; include participants with a clinical diagnosis of PT and an asymptomatic control or contralateral limb group; and include an objective measure of lower limb maximal strength. We extracted descriptive statistics for maximal strength for the symptomatic and asymptomatic limbs of individuals with PT and the limb(s) of the asymptomatic control group, inferential statistics for between-groups differences, participant characteristics, and details of the strength-testing protocol. The risk of bias was assessed using the Joanna Briggs Institute critical appraisal tool for analytical cross-sectional studies. Of the 23 included studies, 21 reported knee strength, 3 reported hip strength, and 1 reported ankle strength. Random-effects models (Hedges g) were used to calculate the pooled effect sizes (ESs) of muscle strength according to the direction of joint movement and type of contraction. The pooled ESs (95% CI) for maximal voluntary isometric contraction knee-extension strength, concentric knee-extension strength, and concentric knee-flexion strength were 0.54 (0.27, 0.80), 0.78 (0.30, 1.33), and 0.41 (0.04, 0.78), respectively, with all favoring greater strength in the asymptomatic control group. Researchers of 2 studies described maximal eccentric knee-extensor strength with no differences between the PT and asymptomatic control groups. In 3 studies, researchers measured maximal hip strength (abduction, extension, and external rotation), and all within-study ESs favored greater strength in the asymptomatic control group. Isometric and concentric knee-extensor strength are reduced in people with PT compared with asymptomatic control individuals. In contrast, evidence for reduced eccentric knee-extension strength in people with PT compared with asymptomatic control individuals is limited and inconsistent. Although evidence is emerging that both knee-flexion and hip strength may be reduced in people with PT, more examination is needed to confirm this observation.

Comparing the associations between muscle strength, walking speed, and mortality in community-dwelling older adults of two birth cohorts born 28 years apart

Reduced age-specific mortality and increased muscle strength and walking speed of current older adults may have altered the relationships between these factors as more people may be above the reserve capacity threshold. We compared the cross-sectional associations between muscle strength and walking speed, and the associations of muscle strength and walking speed with five-year mortality between two population-based cohorts of 75- and 80-year-old people born 28 years apart. Maximal isometric grip and knee extension strength and walking speed were measured in 2017–2018 (n = 726). Mortality was ascertained from registers. The associations were compared with data of same-aged people studied in 1989–1990 with identical protocols (n = 500). The knee extension strength-walking speed relationship showed plateauing at higher strength levels among the later-born men, whereas the earlier-born men and women of both cohorts with lower strength levels were on the linear part of the curve. In the later-born women with lower five-year mortality rate (1.16 vs. 5.88 per 100 person-years), the association between grip strength and mortality was markedly different from the earlier cohort (HR 1.13 [95% CI 0.47–2.70] vs. 0.57 [0.37–0.86]). For knee extension strength and walking speed, the mortality hazards were similar between the cohorts, although statistically non-significant in the later-born women. In men, the later-born cohort showed similar associations as observed in the earlier-born cohort despite having lower mortality rate (2.93 vs. 6.44). Current older adults have more functional reserve that will likely help them to maintain walking ability for longer while also contributing to better survival.

Muscle typology influences the number of repetitions to failure during resistance training

This study examined whether muscle typology (muscle fiber type composition) is related to maximal strength and whether it can explain the high inter-individual variability in number of repetitions to failure during resistance training. Ninety-five resistance training novices (57 males) were assessed for their maximal isometric knee extension strength and muscle typology. Muscle typology was estimated by measuring carnosine in the soleus, gastrocnemius and/or vastus lateralis using proton magnetic resonance spectroscopy. Forty-four subjects (22 males) performed dynamic strength tests (1RM) and 3 sets of leg extensions and curls to failure (60%1RM) to determine the association between muscle typology and (total) number of repetitions. Twenty-one subjects performed additional biceps curls and triceps extensions (60%1RM) to assess influence of exercise, 23 subjects performed additional leg extensions and curls at 80% and 40%1RM to evaluate influence of training load. There was a weak but significant relationship between muscle typology and maximal isometric strength (r = 0.22, p = 0.03) favoring the fast typology individuals. Slow and fast typology individuals did not differ in upper arm and upper leg 1RM. Total number of repetitions was related to muscle typology at 80% (r = -0.42; p = 0.04) and 60% (p = -0.44; p = 0.003) but not at 40%1RM. Slow typology individuals performed more repetitions to failure at 60%1RM in the leg extension (p = 0.03), leg curl (p = 0.01) and biceps curl (p = 0.02). In conclusion, muscle typology has a small contribution to maximal isometric strength but not dynamic strength and partly determines the number of repetitions to failure during resistance training. This insight can help individualizing resistance training prescriptions.

Weight History Association With Current Cardiorespiratory And Muscular Fitness

High cardiorespiratory and muscular fitness are often associated with lower body fat mass. Age-associated increases in body mass might be attenuated by maintaining a higher level of fitness into middle-age. PURPOSE: This study aimed to compare the cardiorespiratory and muscular fitness of individuals who have maintained body mass during adulthood to those who have had substantial increases and/or decreases in body mass in adulthood. METHODS: Obese, overweight, and non-obese adults were recruited to participate. Long-term health and weight history was collected retrospectively on 79 individuals. Total body composition, maximal oxygen consumption, grip strength, and maximal isometric knee extension strength were measured. Participants were subsequently categorized based on short term and long-term weight loss history, cardiorespiratory fitness, and muscle function for further analysis. RESULTS: Participants (31 Male, 45 female, aged 41.0 ± 12.3 years) were 29.2 ± 10.1% body fat having gained 9.3 ± 11.7 kg since 20 years of age. Current cardiorespiratory fitness as indicated by relative maximal oxygen consumption was 36.6 ± 12.0 ml*kg-1*min-1. No significant relationship existed between weight gain since age 20 and current cardiorespiratory fitness (r = -0.12). No differences in weight history were observed after classification of participants into high vs. low cardiorespiratory fitness nor high vs. low muscular fitness. CONCLUSIONS: Current cardiorespiratory and muscular fitness are independent of past body weight history. Despite the limitations of retrospective analysis of weight history and inability to determine previous levels of fitness, these results imply that high fitness might not be protective against age-associated body mass increases, but also that low fitness might not destine an individual to larger than normal gains in body mass

Relationship Between Quadriceps Rate Of Torque Development And Knee Joint Power During Jumping Post-acl Reconstruction

Relationship Between Quadriceps Rate Of Torque Development and Knee Joint Power During Jumping Post-ACL Reconstruction.Kelsey A. Reeves, Darren L. Johnson, Chris Fry, Brian Noehren. University of Kentucky, Lexington, KYThe inability to generate knee joint power after an anterior cruciate ligament (ACL) reconstruction limits athletic performance and contributes to low return to sports rates. However, the underlying factors contributing to a lack of knee joint power in the injured limb remain unclear. Rate of torque development (RTD) of the quadriceps may play a critical role in the development of knee joint power. To date, there is no work on the relationship between early and late stage RTD and knee joint power. Late stage RTD may be more relevant for concentric (CON) movements because of the time it takes to generate power in the knee. PURPOSE: To evaluate the relationship between RTD and knee joint power during the CON phase of a drop vertical jump (DVJ) in patients who were 6 months post ACL reconstruction. METHODS: Three DVJs were recorded for each subject (n = 20, age 20.5 ± 6, BMI 24.0 ± 3.4, 9 female) using instrumented 3D motion analysis. Knee joint power was calculated during the CON phase of the DVJ using custom computer code. RTD was obtained from the subject’s maximal voluntary isometric knee extension strength using an isokinetic dynamometer. Early and late stage RTD were defined as 0-100 ms and 100-200 ms from muscle activation onset, respectively. Relationships between variables were determined using Pearson Product Moment Correlations. RESULTS: Average peak knee joint power was 3.0 ± 1.3 W/kg. Average early and late stage RTD were 6.4 ± 3.6 Nm/kg/s and 2.9 ± 1.3 Nm/kg/s, respectively. Late stage RTD was significantly correlated with knee joint power (r = 0.75, p = 0.000) whereas early stage RTD was not (r = 0.27, p = 0.243). CONCLUSION: Late stage RTD is an important contributing factor to the development of knee joint power during athletic movements such as a jump following an ACL reconstruction. Interventions should look to target late stage RTD to help restore an athlete’s ability to generate power and safely return to sport.

A Practical Application of Blood Flow Restriction Exercise

Exercise with blood flow restriction (BFR) is emerging as an effective training option to increase muscle size and strength, in healthy, clinical, and athletic populations. However, the need for specialized equipment and associated costs present a major barrier to its accessibility. The purpose of this study was to develop a practical method to implement BFR in the lower body using a thigh sphygmomanometer. Specifically, we aimed to 1) explore what factors should be accounted for when setting pressures with this type of restrictive cuff and 2) generate both a lab‐based and field‐based prediction equation to estimate arterial occlusion pressure (AOP). We hypothesized that measures of limb size and blood pressure would constitute significant predictors of lower body AOP. We also hypothesized that a multiple linear regression model including significant predictors would explain approximately 50% of the variance in AOP. Thirty‐eight normotensive healthy adults (age: 24±5 yrs, BMI: 25±4) visited the laboratory for one testing session. Brachial and femoral systolic (SBP) and diastolic (DBP) blood pressures were taken in the seated position. Next, thigh circumference, muscle thickness of the anterior thigh, and maximal isometric knee extension strength was assessed. Lean thigh volume was estimated using anthropometric measures. Lastly, lower body AOP was assessed in the seated position using an 18cm wide thigh sphygmomanometer and Doppler ultrasound (156±12 mmHg). A multiple linear regression analysis including brachial and femoral SBP and DBP, thigh circumference, muscle thickness, lean thigh volume, and maximal isometric knee extension strength was performed to assess which variables constituted significant predictors of AOP. Regression analysis was then repeated with only significant variables to generate both a lab‐based and field‐based prediction equation for AOP. Thigh circumference (β = 0.322, part = 0.876), brachial SBP (β = 0.362, part = 0.463) and isometric knee extension strength (β = 0.421, part = 0.076) constituted significant predictors of AOP. A lab‐based model including thigh circumference (β=0.278, part = 0.754), brachial SBP (β=0.492, part = 0.549), and isometric knee extension strength (β=0.306, part = 0.055) explained 56% of the variance in AOP. A field‐based model including only thigh circumference (β=0.316, part = 0.857) and brachial SBP (β=0.515, part = 0.658) explained 47% of the variance in AOP. Our results indicate that thigh circumference, brachial SBP, and isometric knee extension strength serve as predictors of AOP in the lower body when utilizing an 18cm wide sphygmomanometer as a restrictive cuff. Further, a field‐based prediction equation including thigh circumference and brachial SBP offers a practical way to estimate AOP. Future work will build upon this prediction equation by utilizing subjective measures of cuff tightness, effort, and muscle pain to further adjust exercising cuff pressures to an appropriate level. Results will help to provide researchers and practitioners with a practical way to implement BFR without the need for specialized equipment.

Mitochondrial calcium retention capacity correlates with markers of muscle mass, strength, power and functional capacities in young and old adults

RationaleThe aging‐related loss of muscle mass and function is a major risk factor for falls, fractures, frailty, loss of independence, institutionalization and even death. Although the underlying cellular and molecular mechanisms remain partly understood, impaired mitochondrial permeability transition pore (mPTP) function has been proposed as a potential mechanism. Indeed, altered mitochondrial calcium retention capacity (mCRC), a marker of mPTP function, has been documented with aging in both rodent and human skeletal muscles and mPTP opening was shown to cause muscle atrophy. However, studies on the impact of aging on mPTP function in humans remain scarce, and whether impaired mPTP function correlates with markers of muscle mass, performance and functional capacities remain unknown.ObjectiveThe present study aimed at investigating whether mCRC is associated with markers of muscle mass, muscle function and functional capacities in humans.MethodsTwelve young (29.4 ± 4.4y) and fourteen old (80 ± 7.4y) healthy men were enrolled in the present study. Leg lean mass (leg LM) was assessed using DEXA. Maximal isometric knee extension strength (iKES) and power were measured using a strain gauge system attached to a chair and the Nottingham Leg Extensor Power rig, respectively. To assess functional capacities, the performance at the 6‐min walk test and the step test (maximum number of steps in 20s) were evaluated. To assess mPTP function, mCRC was measured in permeabilized myofibers prepared from muscle biopsies obtained in the vastus lateralis.ResultsAs compared to young adults, old individuals displayed significantly lower leg LM (p<0.01), iKES (p<0.01), and power (p<0.01). The performance at the 6‐min walk test (p<0.01) and the step test (p<0.01) were also lower in old individuals. Old individuals also displayed a significantly lower mCRC (p<0.01). mCRC was significantly correlated with leg LM (r=0.34; p=0.045), iKES (r=0.35; p=0.04) and muscle power (r=0.41; p=0.02). In addition, mCRC was significantly correlated with the performance at the 6‐min walking test (r=0.42;p=0.01) and step test (r=0.46; p<0.01).ConclusionsThese results indicate that mPTP function is altered with aging in humans and highlight positive associations between mPTP, muscle mass, strength, power, and functional capacities. These findings therefore strengthen the emerging view that altered mPTP function contributes to the aging‐related loss of muscle mass and function in humans.

Relationship between Echo Intensity of Vastus Lateralis and Knee Extension Strength in Patients with Type 2 Diabetes Mellitus.

This study aimed to determine the association between echo intensity (EI) of vastus lateralis and knee extension strength (KES) in patients with type 2 diabetes mellitus (T2DM). This retrospective study included a total of 304 patients (189 males and 115 females) with T2DM who were hospitalized for treatment or care. EI and muscle thickness (MT) of the right vastus lateralis were assessed from transverse ultrasound images. Maximal isometric KES was evaluated using a dynamometer and normalized for body weight (%KES). %KES was significantly positively correlated with MT and stages of change for exercise behavior, and significantly negatively correlated with age, T2DM duration, and EI. %KES was significantly higher in male than in female. %KES was significantly higher in non-diabetic peripheral neuropathy (DPN) than in DPN. Stepwise multiple regression analysis showed that sex, age, T2DM duration, EI, and stages of change for exercise behavior were significant determinants of %KES. The study results suggest that EI is associated with %KES in patients with T2DM.

Feasibility and preliminary effect of anabolic steroids in addition to strength training and nutritional supplement in rehabilitation of patients with hip fracture: a randomized controlled pilot trial (HIP-SAP1 trial)

BackgroundAnabolic steroid has been suggested as a supplement during hip fracture rehabilitation and a Cochrane Review recommended further trials. The aim was to determine feasibility and preliminary effect of a 12-week intervention consisting of anabolic steroid in addition to physiotherapy and nutritional supplement on knee-extension strength and function after hip fracture surgery.MethodsPatients were randomized (1:1) during acute care to: 1. Anabolic steroid (Nandrolone Decanoate) or 2. Placebo (Saline). Both groups received identical physiotherapy (with strength training) and a nutritional supplement. Primary outcome was change in maximal isometric knee-extension strength from the week after surgery to 14 weeks. Secondary outcomes were physical performance, patient reported outcomes and body composition.ResultsSeven hundred seventeen patients were screened, and 23 randomised (mean age 73.4 years, 78% women). Target sample size was 48. Main limitations for inclusion were “not home-dwelling” (18%) and “cognitive dysfunction” (16%). Among eligible patients, the main reason for declining participation was “Overwhelmed and stressed by situation” (37%). Adherence to interventions was: Anabolic steroid 87%, exercise 91% and nutrition 61%. Addition of anabolic steroid showed a non-significant between-group difference in knee-extension strength in the fractured leg of 0.11 (95%CI -0.25;0.48) Nm/kg in favor of the anabolic group. Correspondingly, a non-significant between-group difference of 0.16 (95%CI -0.05;0.36) Nm/Kg was seen for the non-fractured leg. No significant between-group differences were identified for the secondary outcomes. Eighteen adverse reactions were identified (anabolic = 10, control = 8).ConclusionsEarly inclusion after hip fracture surgery to this trial seemed non-feasible, primarily due to slow recruitment. Although inconclusive, positive tendencies were seen for the addition of anabolic steroid.Trial registrationClinicaltrials.gov NCT03545347.

The effect of custom-fitted compression garments worn overnight for recovery from judo training in elite athletes

ABSTRACT This study investigated the effects of custom-fitted compression garments (CG) worn during recovery over a multi-day training camp in elite judo players (judoka). A single blind, placebo-controlled study was carried out in 11 elite judoka, using a two-way crossover design. Two three-day training camps were completed in CG and placebo conditions in a random order. Changes in performance and physiological markers were compared between conditions. Judoka were assessed before training for (maximal) isometric knee extension and grip strength, countermovement jump performance and bench-press velocity, alongside soreness, limb circumferences, plasma creatine kinase activity (CK) and perceived bruising. Measurements were repeated after 12, 36 and 43 h of training, whereupon judoka rated the effectiveness of each intervention. Knee extension and bench-press performance demonstrated significant familiarization (p < 0.001), and were excluded from subsequent analysis. Jump performance was unaffected by training (p > 0.05). Grip strength declined throughout training (p < 0.001), with peak decrements of −9.7% indicating mild muscle damage. Increases in bruising, CK and soreness demonstrated highly variable, if significant (p < 0.001) responses. Although CG were perceived as significantly more effective than placebo for recovery (p = 0.046), no effects were observed for any other outcome (p > 0.05). Compression conferred no statistically significant impact upon recovery markers in elite judoka throughout training. Muscle damage responses were inconsistent in this population. Individual athletes would be advised to monitor habitually-used performance measures while using CG to ascertain whether perceptual benefits translate into enhanced recovery. Highlights Compression garments were perceived as more effective for recovery than placebo by elite judoka. However, no measures of performance or muscle damage were enhanced by CG. Randori was associated with inconsistent muscle damage responses in elite judoka, while lower-body performance was not impaired. Individual athletes would be advised to monitor habitually-used performance measures while using CG to ascertain whether perceptual benefits translate into enhanced recovery.

Sirolimus for treatment of patients with inclusion body myositis: a randomised, double-blind, placebo-controlled, proof-of-concept, phase 2b trial.

Inclusion body myositis is the most frequent myositis in patients older than 50 years. Classical immunosuppressants are ineffective in treating inclusion body myositis, and to date there are no recommendations for pharmacological approaches to treatment. When used after organ transplantation, sirolimus can block the proliferation of effector T cells, while preserving T regulatory cells, and induce autophagy, all of which are processes that are impaired in inclusion body myositis. In this pilot study, we aimed to test the efficacy of sirolimus in patients with inclusion body myositis. This randomised, double-blind, placebo-controlled, proof-of-concept, phase 2b trial was done at a single hospital in Paris, France. The study included men and women (aged 45-80 years) who had a defined diagnosis of inclusion body myositis according to established criteria. Eligible participants were randomly assigned (1:1) to receive once-daily oral sirolimus 2 mg or placebo. Centralised balanced block randomisation (blocks of four) was computer generated without stratification. The study comprised a 15-day screening period (days -15 to 0) and a 52-week treatment period (day 0 to month 12). The primary endpoint was the relative percentage change from baseline to month 12 in maximal voluntary isometric knee extension strength. Secondary endpoints included the following assessments at months 6 and 12: 6-min walking distance, isometric muscle strength for hand grip (finger flexors), knee flexion and elbow flexion and extension, forced vital capacity, muscle replacement with fat measured by quantitative nuclear MRI, Inclusion Body Myositis Weakness Composite Index (IBMWCI), Inclusion Body Myositis Functional Rating Scale (IBMFRS), Health Assessment Questionnaire without Disability Index (HAQ-DI), and analyses of T-cell subpopulations by mass cytometry. The primary analysis was done on the intention-to-treat population. The trial is registered at ClinicalTrials.gov, NCT02481453. Between July 15, 2015, and May 13, 2016, we screened 285 patients, 44 of whom were randomly allocated to sirolimus (22 patients) or placebo (22 patients). We observed no difference in the primary outcome of relative percentage change from baseline to month 12 of the maximal voluntary isometric knee extension strength (median difference 3·78, 95% CI -10·61 to 17·31; p=0·85). For secondary outcomes, differences between the groups were not significant for changes in strength of other muscle groups (grip, elbow flexion and extension, or knee flexion), IBMWCI, IBMFRS, and lower limb muscle fat fraction. However, we observed significant differences in favour of sirolimus between the study groups for HAQ-DI, forced vital capacity, thigh fat fraction, and 6-min walking distance. Ten (45%) of 22 patients in the sirolimus group had a serious adverse event compared with six (27%) of 22 patients in the placebo group. Four (18%) patients in the sirolimus group stopped their treatment because of adverse events (severe mouth ulcers, aseptic pneumonia, renal insufficiency, and peripheral lower limb oedema), which resolved after treatment discontinuation. Canker sores were the most frequent side-effect and were mainly mild or moderate in ten patients. We found no evidence for efficacy of sirolimus for treating inclusion body myositis based on maximal voluntary isometric knee extension strength and other muscle strength measures, and the side-effects of treatment were substantial for some patients. However, we believe there was enough evidence of benefit in certain secondary outcomes to pursue a multicentre phase 3 trial to further assess the safety and efficacy of sirolimus. Institut national de la santé et de la recherche médicale, Direction générale de l'offre de soins, and Association Française contre les Myopathies.

Maximal isometric knee extension strength and stair-mounting ability in 75- and 80-year-old men and women

The objective was to study whether the ability to mount different step heights depends on knee extension strength, and if this dependence varies according to age or sex among elderly persons. Altogether, 198 independently living 75-year-old women, 98 75-year-old men, 117 80-year-old women and 45 80-year-old men participated in the study. Maximal isometric knee extension strength was measured in a sitting position using a custom-built dynamometer chair. Results were standardized for body mass and height. In the stair-mounting test 10 cm high boxes were combined to form steps with heights of 10 to 50 cm. Older subjects, especially the women, exhibited poorer results in both tests. However, when groups based on maximum step height were analysed separately for strength, three-way analysis of variance revealed no sex effects. Although the number of men in the analysis was quite small, it was concluded that the strength requirements for mounting a certain step height were similar for both sexes. Owing to their sex-related lower average strength, old women may be at greater risk than old men of becoming impaired in certain motor tasks.

Mortality Risk Among Older People Who Did Versus Did Not Sustain a Fracture: Baseline Prefracture Strength and Gait Speed as Predictors in a 15-Year Follow-Up.

Physiological reserve, as indicated by muscle strength and gait speed, may be especially determinant of survival in people who are exposed to a health stressor. We studied whether the association between strength/speed and mortality risk would be stronger in the time period after a fracture compared to other time periods. Participants were population-based sample of 157 men and 325 women aged 75 and 80 years at baseline. Maximal 10-m gait speed and maximal isometric grip and knee extension strength were tested at the baseline before the fracture. Subsequent fracture incidence and mortality were followed up for 15 years. Cox regression analysis was used to estimate fracture time-stratified effects of gait speed and muscle strength on mortality risk in three states: (i) nonfracture state, (ii) the first postfracture year, and (iii) after the first postfracture year until death/end of follow-up. During the follow-up, 20% of the men and 44% of the women sustained a fracture. In both sexes, lower gait speed and in women lower knee extension strength was associated with increased mortality risk in the nonfracture state. During the first postfracture year, the mortality risk associated with slower gait and lower strength was increased and higher than in the nonfracture state. After the first postfracture year, mortality risk associated with lower gait speed and muscle strength attenuated. Lower gait speed and muscle strength were more strongly associated with mortality risk after fracture than during nonfracture time, which may indicate decreased likelihood of recovery.

Specific and general adaptations following motor imagery practice focused on muscle strength in total knee arthroplasty rehabilitation: A randomized controlled trial.

BackgroundMotor imagery (MI) has been a widely used strategy in the past two decades to enhance physical capabilities among orthopaedic patients. However, its effectiveness is still questioned, since the demonstrated effects were likely task-dependent, with little evidence of transfer to tasks not specifically trained with MI.ObjectiveThe aim of this study was to investigate whether an MI practice focused on maximal isometric knee extension strength, causes additional specific and general adaptations upon neuromuscular and functional variables when compared to conventional rehabilitation only, in patients submitted to total knee arthroplasty (TKA).DesignParallel group randomized controlled clinical trial.ParticipantsThirty-four patients (56% man) submitted to TKA.ProgramPatients were randomly assigned to an MI practice group (MIp: 15 minutes per day/5 days per week in addition to routine physical therapy) or control group (CON) that performed routine physical therapy alone for four weeks.Outcome measuresThe maximal isometric knee extension strength of the operated leg was defined as the primary outcome. Secondary outcomes were spatial and temporal gait parameters, 30-second chair sit-to-stand performance, a self-reported physical function assessed by the Lower Extremity Functional Scale (LEFS) questionnaire, and an MI ability score. All measurements were conducted before and one month after TKA.ResultsSignificant differences in treatment effects were observed for the MIp group compared to CON: the MIp showed less strength decrease (ES = 1.15, 95% CI: 0.32, 1.99, p = 0.022); faster self-selected speed under single (ES = 2.12, 95% CI: 1.16, 3.08, p = 0.001) and dual task (ES = 1.59, large, 95% CI: 0.67, 2.50, p = 0.002) conditions; brisk-pace gait speed during single (ES = 1.32, 95% CI: 0.47, 2.17, p = 0.020) and dual task conditions (ES = 1.31, large, 95% CI: 0.38, 2.23, p = 0.013); improved chair sit-to-stand (ES = 1.45, large, 95% CI: 0.58, 2.31, p = 0.004) performance; and a higher score on MI ability questionnaires for kinaesthetic imagery (KI) (ES = 0.55, 95% CI: -0.23, 1.34, p = 0.010) and internal visual imagery (EVI) (ES = 0.99, 95% CI: 0.18, 1.80, p = 0.039) scales, respectively. In addition, only MIp showed unaltered single and double support periods, as well as stride length and cadence during single task self-selected gait condition. Finally, analysis showed that the improved MI ability score achieved at the end of MI training was significantly correlated with the changes in the strength of the operated leg (kinaesthetic imagery: r = 0.741, p = 0.004; and internal visual imagery: r = 0.623, p = 0.023).ConclusionsMI training, when added in a corollary to routine physical therapy, led to improvements in both specific and general adaptations that were related to patients’ physical capabilities. While future studies must also evaluate the long-term effects, conducting MI training during acute and post-acute rehabilitation phases is advised, especially when the extent and range of physical exercise is limited or made impossible.Trial registrationClinicalTrials.gov NCT03684148.

Influence of Oral Contraceptive Use on Adaptations to Resistance Training.

Introduction: The majority of young women use oral contraceptives (OCs). Use of OCs has been associated with lower myofibrillar protein and tendon collagen synthesis rates, but it is unknown whether OCs will limit the adaptive response of myotendinous tissue to resistance training.Design and Methods: Fourteen healthy untrained young regular OC users (24 ± 1 years, fat% 32 ± 1, 35 ± 2 ml⋅min-1⋅kg-1) and 14 NOC users (non-OC, controls) (24 ± 1 years, fat% 32 ± 2, 34 ± 2 ml⋅min-1⋅kg-1) performed a 10-week supervised lower extremity progressive resistance training program. Before and after the intervention biopsies from the vastus lateralis muscle and the patellar tendon were obtained. Muscle (quadriceps) and tendon cross-sectional area (CSA) was determined by magnetic resonance imaging (MRI) scans, and muscle fiber CSA was determined by histochemistry. Maximal isometric knee extension strength was assessed by dynamometry while 1 repetition maximum (RM) was determined during knee extension.Results: Training enhanced CSA in both muscle (p < 0.001) and tendon (p < 0.01). A trend toward a greater increase in muscle CSA was observed for OC (11%) compared to NOC (8%) (interaction p = 0.06). Analysis of mean muscle fiber type CSA showed a trend toward an increase in type II muscle fiber area in both groups (p = 0.11, interaction p = 0.98), whereas type I muscle fiber CSA increased in the OC group (n = 9, 3821 ± 197 to 4490 ± 313 mm2, p < 0.05), but not in NOC (n = 7, 4020 ± 348 to 3777 ± 354 mm2, p = 0.40) (interaction p < 0.05). Post hoc analyses indicated that the effect of OCs on muscle mass increase was induced by the OC-users (n = 7), who used OCs containing 30 μg ethinyl estradiol (EE), whereas the response in users taking OCs with 20 μg EE (n = 7) did not differ from NOC. Both the OC and NOC group experienced an increase in maximal knee strength (p < 0.001) and 1RM leg extension (p < 0.001) after the training period with no difference between groups.Conclusion: Use of OCs during a 10-week supervised progressive resistance training program was associated with a trend toward a greater increase in muscle mass and a significantly greater increase in type I muscle fiber area compared to controls. Yet, use of OCs did not influence the overall increase in muscle strength related to training.

Psychophysical effects of an exercise therapy during pediatric stem cell transplantation: a randomized controlled trial.

This study evaluates the physical and psychosocial effects of an inpatient exercise program for children and adolescents undergoing hematopoietic stem cell transplantation (HSCT). Participants (n = 70) were randomized to an exercise intervention (IG: resistance, endurance, and flexibility training) or a non-exercise control group (CG: mental and relaxation training). Pre- (prior hospital admission; T0) and post- (day of discharge; T1) measurements included maximal isometric knee extension strength (KES; strain gauge force transducer), hand grip strength (HGS; JAMAR dynamometer), distance walked in 6 min (6MWD; 6-minute walk test), quality of life (QoL; KINDL-R) and medical parameters. Fifty-seven patients (IG: n = 28; 11.0 (5-17) years; CG: n = 29; 12.0 (6-18) years) completed the study. During hospitalization the IG and CG attended on average 3.1 (2-4) or 2.9 (0.3-4) training sessions weekly. KES, 6MWD, and HGS significantly decreased (p < 0.05) in the CG, while there were no changes in the IG. Pre- to post-changes in 6MWD and HGS differed significantly between groups (p < 0.05). QoL declined in both groups (p < 0.05). Our results indicate that a moderate exercise program is feasible and might counteract a treatment-associated decline of physical performance.

Association between knee-to-hip flexion ratio during single-leg vertical landings, and strength and range of motion in professional soccer players

The aim of this study was to test the correlation between knee-to-hip flexion ratio during a single leg landing task and hip and knee strength, and ankle range of motion. Twenty-four male participants from a professional soccer team performed a continuous single leg jump-landing test during 10s, while lower limb kinematics data were collected using a motion analysis system. After biomechanical testing, maximal isometric hip (abduction, extension, external rotation), knee extension and flexion strength were measured. Maximum ankle dorsiflexion range of motion was assessed statically using the weight bearing lunge test. Pearson correlation coefficients were calculated to determine the associations between the predictor variables (knee and hip strength, and ankle ROM) and the main outcome measure (knee-to-hip flexion ratio). Correlation between knee-to-hip flexion ratio and hip abductors strength was significant (r = −0.47; p = 0.019). No other significant correlations were observed among the variables (p > 0.05). These results demonstrated that a lower hip abductors strength in male soccer players was correlated with a high knee-to-hip flexion ratio during landing from a single leg jump, potentially increasing knee overload by decreasing energy absorption at the hip. The results provide a novel proposal for the functioning of hip muscles to control knee overload.

Cholecalciferol or 25-Hydroxycholecalciferol Supplementation Does Not Affect Muscle Strength and Physical Performance in Prefrail and Frail Older Adults

Vitamin D supplementation is proposed as a potential treatment strategy to counteract functional decline in older adults. However, data from randomized trials are either limited or inconsistent. This study investigated the effect of daily supplementation with 25-hydroxycholecalciferol [25(OH)D3] or cholecalciferol (vitamin D3) on muscle strength and physical performance in older adults. This was a randomized, double-blind, placebo-controlled trial of 6 mo including 78 prefrail or frail (according to the Fried criteria), community-dwelling older adults (n=43 men) aged ≥65 y, with a baseline 25-hydroxyvitamin D [25(OH)D] concentration between 20 and 50 nmol/L. Participants were supplemented daily with 10 µg 25(OH)D3, 20 µg vitamin D3, or a placebo capsule. Serum 25(OH)D was measured by liquid chromatography-tandem mass spectrometry. The primary outcome was maximal isometric knee-extension strength (Biodex System 4); secondary outcomes included knee-flexion and hand grip strength, Short-Physical Performance Battery score, Timed Up and Go score, postural sway, muscle mass (dual-energy X-ray absorptiometry), and muscle fiber type and size. The mean baseline serum 25(OH)D concentration was 37.7 nmol/L (95% CI: 35.4, 39.9 nmol/L). After 6 mo of supplementation, concentrations increased to 98.7 nmol/L (95% CI: 93.1, 104.4 nmol/L) in the 25(OH)D3 group and to 72.0 nmol/L (95% CI: 66.1, 77.8 nmol/L) in the vitamin D3 group, compared with 47.5 nmol/L (95% CI: 41.8, 53.3 nmol/L) in the placebo group (P-interaction < 0.01). Knee-extension strength did not significantly change in the 25(OH)D3 group (5.9 Nm; 95% CI: -6.2, 18.0 Nm), in the vitamin D3 group (5.5 Nm; 95% CI: -6.8, 17.8 Nm), or in the placebo group (1.8 Nm; 95% CI: -10.7, 14.4 Nm) (P-interaction=0.74). Furthermore, mean changes in physical performance tests, muscle mass, and muscle fiber type and size did not differ between the groups. Increasing the serum 25(OH)D concentration over a period of 6 mo did not significantly change muscle strength and physical performance in prefrail and frail older adults. This trial was registered at www.clinicaltrials.gov as NCT02349282.