Maximal Isometric Knee Extensor Strength Research Articles

Influence of menstrual cycle phase and oral contraceptive phase on exercise performance in endurance-trained females.

Limited data exists on the influence of menstrual cycle (MC) phase and oral contraceptive (OC) phase on physical performance in endurance-trained females due to poor control regarding MC verification and differentiation. We aimed to evaluate exercise performance and the respiratory response to exercise in three distinct phases of the MC and OC cycle in endurance-trained females. Using a prospective cohort study design, we recruited trained females (Vo<inf>2max</inf> 52±4 mL O<inf>2</inf>/min/kg) who were either not using oral contraceptives (NOC) or using monophasic OCs. NOC were tested in the early and late follicular phase (FP) and the mid-luteal phase (LP). OC-users were tested in the withdrawal phase (WP) and two times in the active OC phase (OCP). The test battery included DXA scans, blood sampling, a submaximal bike test, a maximal isometric knee-extensor strength test, 4 and 20-second bike sprints, and a 6 min time trial on a bike. MC phases were verified by the use of ovulation kits and circulating sex hormone levels. After the exclusion of four NOCs due to inadequate sex hormone levels, 11 NOC and 13 OC users were included in the final analysis. 6 min time trial performance, sprint performance, and most submaximal exercise intensity variables did not differ between MC phases and OC cycle phases. However, in NOC, ventilation (L/min) during exercise at 30% of aerobic peak power was 7.6% lower in the late FP compared to the LP (P<0.05). In OC users, muscle strength was 3.9% higher in the early OCP compared to WP (P<0.05), whereas body mass was higher in the late OCP compared to WP (P<0.05). Collectively, our study suggests that MC phase and OCP influence exercise performance to a limited extent in endurance-trained females.

Sit-to-stand power predicts functional performance and patient-reported outcomes in patients with advanced knee osteoarthritis. A cross-sectional study

BackgroundLower limb muscle power is positively associated with functional performance and patient-reported outcomes (PROMs) and suggested as an important variable to evaluate in patients with advanced knee osteoarthritis (OA). ObjectivesTo explore the association between muscle power derived from the 30-sec sit-to-stand test (STS power) with functional performance and PROMs compared to maximal isometric knee extensor strength (KE MVC) in male- and female patients with advanced OA. Study designCross-sectional design. MethodsEighty-six patients (66.6 [64.9–67.7]years) with advanced knee OA were included. Dependent variables were STS power and KE MVC. Independent variables were Timed Up&Go (TUG), 40-m fast-paced walk test (40mFWT), Knee injury and Osteoarthritis Outcome Score (KOOS) subscales. CovariateAge. AnalysesSimple linear- and multiple regression analyses with and without adjusting for age. Pitman's test was used to evaluate differences in correlation strength among dependent variables. ResultsSTS power demonstrated a statistical relationship with TUG and 40mFWT for both sexes (β coefficients −1.11 to −4.36 (p < 0.05), r2 = 0.47–0.55 (p < 0.05)), and with KOOS Pain, ADL, and Sport for male patients (β coefficients 6.53 to 7.17 (p < 0.05), r2 = 0.29–0.33 (p < 0.05)). Knee extensor MVC demonstrated no relationship with any outcomes for male patients or female patients. STS power displayed statistically stronger correlation to functional performance. ConclusionSTS power was associated with functional performance in both male patients and female patients suffering from advanced knee OA. Moreover, STS power was associated with KOOS Pain, Sport, and ADLin male patients. The assessment of STS power should be considered in the evaluation of patients with advanced knee OA. Trial registration numberNCT04081493.

Effects of blood-flow restricted exercise versus conventional resistance training in musculoskeletal disorders—a systematic review and meta-analysis

ObjectiveTo compare the effect of low-load blood flow restricted resistance training (BFR-RT) versus high-load resistance training (HL-RT) on muscle strength, muscle mass, physical function, patient-reported outcomes, and adherence to training in clinical musculoskeletal populations.Data sourcesWeb of Science, Cochrane Central, Medline, Embase, SportDiscus was searched on the 30th May 2022.Review methodsThis study was conducted as a systematic review and meta-analysis. Randomized Controlled Trials (RCTs) were included if they (i) included patients, (ii) comprised of a BFR-RT intervention protocol and a group who performed HL-RT (≥ 70%1RM) for at least eight exercise sessions, and (iii) involved at least 1 exercise that targeted the lower limbs. The Cochrane Risk of Bias tool was used to evaluate the risk of bias. The meta-analyses were performed using a random effects model with an adjustment to the confidence interval.ResultsSeven RCTs comprising 303 participants (BFR-RT: n = 151; HL-RT: n = 152) were identified. HL-RT and BFR-RT showed similar gains in dynamic (1-10RM) knee extensor strength and leg press strength, quadriceps cross sectional area, sit-to-stand performance, and patient reported pain and function. There was a moderate effect favoring BFR-RT for increasing maximal isometric knee extensor strength. The grading of certainty in evidence was low-to-very low for all outcome variables.ConclusionThis systematic review and meta-analysis extends our current knowledge about BFR-RT and HL-RT as equally effective exercise methods for inducing gains in maximal muscle strength in healthy populations, by now also comprising patients suffering from various clinical musculoskeletal conditions. The certainty in the estimates was low-to-very low, prompting the inclusion of future higher-quality trials.Trial registrationPROSPERO ID (CRD42022337173). Registered June 18th 2022.

Abstract 13472: Physical Incapacity in Heart Failure Patients is Associated With Skeletal Muscle Mitochondrial Dysfunction

Introduction: The role of skeletal muscle mitochondrial dysfunction in exercise intolerance in heart failure patients is unknown. Therefore, this study aimed to identify the relationship between physical capacity and skeletal muscle mitochondrial function in patients with heart failure and reduced ejection fraction (HFrEF). Methods A total of 53 HFrEF patients and 20 age- and sex-matched controls underwent dual-energy X-ray absorptiometry to assess muscle mass by the appendicular lean mass index (ALMI), cardiopulmonary exercise testing (peakVO2), 6-minute walking test (6MWD) and maximal isometric knee-extensor strength test. In skeletal muscle biopsies from vastus lateralis, mitochondrial respiratory capacity was measured by high resolution respirometry. We performed Pearson correlations to examine the relationships between physical capacity tests and mitochondrial function. Results Mean age of the study cohort was 71.7 ±7.0 years. Compared with healthy controls, HFrEF patients had a lower peakVO2 (14.6 ±4.1 vs. 26.2 ±8.0 mL/kg/min, p &lt;0.001) and a shorter 6MWD (429 ±106 vs. 581 ±93 m, p &lt;0.001). HFrEF patients had a lower ALMI (0.74 ±0.15 vs. 0.86 ±0.16 kg/(kg/m 2 ), p = 0.005). Maximal coupled mitochondrial respiration was decreased in HFrEF patients compared with healthy controls (59.1 ±19.0 vs. 92.6 ±38.8 ρmol O 2 *s -1 mg -1 , p &lt;0.001) as well as the respiratory control ratio (7.2 ±2.5 vs. 9.7 ±3.1). Maximal coupled mitochondrial respiration was correlated to peakVO2 (r = 0.58, p &lt;0.001) and 6MWD (r = 0.44, p &lt;0.001), but not to muscle mass or maximal knee-extensor strength. Conclusions HFrEF patients had a lower peakVO2, shorter 6MWD and impaired skeletal muscle mitochondrial function as compared with controls. Maximal coupled mitochondrial respiration was correlated with physical capacity across the population of HFrEF patients and healthy controls establishing an association between skeletal muscle mitochondrial dysfunction and physical incapacity.

How to identify patients with low muscle mass linked to physical capacity and physical activity in heart failure

Abstract Introduction Skeletal muscle wasting is frequent in heart failure (HF) patients, and low muscle mass (MM) is associated with increased morbidity and mortality. Current recommendations suggest the usage of dual-energy X-ray absorptiometry (DXA)-derived appendicular lean mass (ALM) adjusted for height squared to identify low MM. However, it has recently been suggested that ALM adjusted for body mass index (BMI) has a higher predictive value. The relationships between low MM, muscle strength, exercise capacity and daily physical activity (PA) are poorly understood in heart failure with reduced ejection fraction (HFrEF). Purpose This study examined the relationships between low MM defined by two different indices and muscle strength, physical capacity tests and accelerometer measurements. Methods A total of 104 HFrEF patients underwent DXA, maximal isometric knee-extensor strength test, cardiopulmonary exercise testing, 6-minute walking test and accelerometry. Two adjusted indices for low MM were assessed: ALM/m2 and ALM/BMI. We performed Pearson correlations to examine the relationships between low MM and muscle strength, exercise capacity and daily PA. Furthermore, we identified patients with low MM based on the two indices. For ALM/m2 we used guideline-recommended cut-offs and for ALM/BMI we used the mean value since no cut-offs has been validated. Results The ALM/m2-index showed no significant correlation to peak oxygen uptake (VO2peak), 6-minute walking distance (6MWD), average PA or daily time spent in moderate-to-vigorous physical activity (MVPA). A moderate correlation was found to maximal muscle strength was found (r=0.61, p&amp;lt;0.001). The ALM/BMI-index was moderately correlated to maximal muscle strength (r=0.65, p&amp;lt;0.001), VO2peak (r=0.40, p&amp;lt;0.001), 6MWD (r=0.41, p&amp;lt;0.001), average daily PA (r=0.27, p=0.012) and daily time spent in MVPA (r=0.29, p=0.007). Patients with low MM identified by ALM/m2 did not differ from patients with preserved MM with regards to VO2peak, 6MWD or accelerometer measurements. A difference in maximal muscle strength was found (95.7±35.6 Nm vs 116±44.8, p=0.02). Patients with low MM identified by ALM/BMI had lower maximal muscle strength (94.8±36.1 Nm vs 121.9±44.4 Nm, p=0.001), lower VO2peak (13.2±3.5 mL/kg/min vs 16.4±3.7 mL/kg/min, p&amp;lt;0.001), shorter 6MWD (370.5±99.4 m vs 467.3±93.9 m, p&amp;lt;0.001), average daily PA (15.1±4.4 ENMO* vs 17.3±5.3 ENMO*, p=0.04) and daily time spent in MVPA (14.2±16.7 min vs 24.7±21.6 min, p=0.01) compared to patients with preserved MM. Conclusion In HFrEF patients low MM identified by ALM/BMI seems to correlate better to well-established markers for physical capacity (VO2peak and 6MWD), muscle strength and daily PA compared to ALM/m2. No cut-offs have been established for ALM/BMI and there is a need for longitudinal studies to determine the association with mortality in HFrEF patients. *ENMO = Euclidean Norm Minus One, an acceleration metric. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): The Karen Elise Jensens Foundation

The effects of vertical trunk supportability improvement on one-leg rebound jump efficiency.

The purpose of this study was to examine the effects of vertical trunk supportability improvement on activities. The study participants were 36 people. Trunk function and physical performance were evaluated using the following tests: trunk righting test (TRT), maximal isometric knee extensor strength test, side hop test, triple hop distance test, stabilometry of one-leg standing, and one-leg rebound jump. The measurement was performed three times: pre-trunk training (pre), post-trunk training for 1 month (post), and 2 months after the second measurement (detraining). Details of trunk training: Two sets of 30-s maximal lateral reach exercises on each side, following the four sets of 15-s maximal raising trunk exercises on each side. The results with TRT in post-training were significantly larger than those in pre-and detraining. Similarly, the results with one-leg rebound jump efficiency in post-training were significantly larger than those in pre-and detraining. Our findings indicate that jump efficiency changes in proportion to the change in vertical trunk supportability.

Relationship between vastus medialis Hoffmann reflex excitability and knee extension biomechanics during different tasks in women with patellofemoral pain

BackgroundImpaired knee extension biomechanics and spinal excitability have been reported in women with patellofemoral pain, but their relationship has not been explored. A significant relationship between them could indicate the need for investigating the potential benefits of disinhibitory interventions for women with patellofemoral pain. Thus, this study aimed to investigate the relationship between vastus medialis Hoffmann reflex and (1) maximal isometric, concentric and eccentric knee extensor strength and rate of torque development; (2) knee extensor torque steadiness; and (3) knee extensor moment during functional tasks; in women with patellofemoral pain. MethodsSpinal excitability of twenty-four participants was assessed by the amplitude of maximal vastus medialis Hoffmann reflex. Knee extensor strength, rate of torque development and torque steadiness were assessed using an isokinetic dynamometer. Knee extensor moment during step-down and stair descent tasks were obtained using a three-dimensional motion analysis system. FindingsA moderate negative relationship was found between vastus medialis Hoffmann reflex and knee extensor torque steadiness (r = −0.35; p = 0.05); whereas a moderate positive relationship was found with maximal isometric knee extensor strength (r = 0.37; p = 0.044). No significant relationships were found between vastus medialis Hoffmann reflex and the other variables. InterpretationOur findings provide insight on the relationship between spinal excitability and neuromuscular control of maximal and submaximal isometric torque production in women with patellofemoral pain. Conversely, spinal excitability does not seem to be related with dynamic torques and moments of the knee extensors in women with patellofemoral pain.

Immobilization leads to alterations in intracellular phosphagen and creatine transporter content in human skeletal muscle.

The role of dysregulated intracellular creatine (Cr) metabolism in disuse atrophy is unknown. In this study, skeletal muscle biopsy samples were obtained after 7 days of unilateral leg immobilization (IMMOB) and from the nonimmobilized control limb (CTRL) of 15 healthy men (23.1 ± 3.5 yr). Samples were analyzed for fiber type cross-sectional area (CSA) and creatine transporter (CreaT) at the cell membrane periphery (MEM) or intracellular (INT) areas, via immunofluorescence microscopy. Creatine kinase (CK) and AMP-activated protein kinase (AMPK) were determined via immunoblot. Phosphocreatine (PCr), Cr, and ATP were measured via enzymatic analysis. Body composition and maximal isometric knee extensor strength were assessed before and after disuse. Leg strength and fat-free mass were reduced in IMMOB (~32% and 4%, respectively; P < 0.01 for both). Type II fiber CSA was smaller (~12%; P = 0.028) and intramuscular PCr lower (~13%; P = 0.015) in IMMOB vs. CTRL. CreaT protein was greater in type I fibers in both limbs (P < 0.01). CreaT was greater in IMMOB vs. CTRL (P < 0.01) and inversely associated with PCr concentration in both limbs (P < 0.05). MEM CreaT was greater than INT CreaT in type I and II fibers of both limbs (~14% for both; P < 0.01 for both). Type I fiber CreaT tended to be greater in IMMOB vs. CTRL (P = 0.074). CK was greater and phospho-to-total AMPKThr172 tended to be greater, in IMMOB vs. CTRL (P = 0.013 and 0.051, respectively). These findings suggest that modulation of intracellular Cr metabolism is an adaptive response to immobilization in young healthy skeletal muscle.

Clinical validation of fully automated segmentation of thigh muscle and adipose tissue cross sectional areas using maching learning with a convolutional neural network

Clinical validation of fully automated segmentation of thigh muscle and adipose tissue cross sectional areas using maching learning with a convolutional neural network

Plasticity in central neural drive with short-term disuse and recovery - effects on muscle strength and influence of aging

While short-term disuse negatively affects mechanical muscle function (e.g. isometric muscle strength) little is known of the relative contribution of adaptions in central neural drive and peripheral muscle contractility. The present study investigated the relative contribution of adaptations in central neural drive and peripheral muscle contractility on changes in isometric muscle strength following short-term unilateral disuse (4 days, knee brace) and subsequent active recovery (7 days, one session of resistance training) in young (n = 11, 24 yrs) and old healthy men (n = 11, 67 yrs). Maximal isometric knee extensor strength (MVC) (isokinetic dynamometer), voluntary muscle activation (superimposed twitch technique), and electrically evoked muscle twitch force (single and doublet twitch stimulation) were assessed prior to and after disuse, and after recovery. Following disuse, relative decreases in MVC did not differ statistically between old (16.4 ± 3.7%, p < 0.05) and young (−9.7 ± 2.9%, p < 0.05) (mean ± SE), whereas voluntary muscle activation decreased more (p < 0.05) in old (−8.4 ± 3.5%, p < 0.05) compared to young (−1.1 ± 1.0%, ns) as did peak single (−25.8 ± 6.6%, p < 0.05 vs −7.6 ± 3.3%, p < 0.05) and doublet twitch force (−23.2 ± 5.5%, p < 0.05 vs −2.0 ± 2.6%, ns). All parameters were restored in young following 7 days recovery, whereas MVC and peak twitch force remained suppressed in old. Regression analysis revealed that disuse-induced changes in MVC relied more on changes in single twitch force in young (p < 0.05) and more on changes in voluntary muscle activation in old (p < 0.05), whereas recovery-induced changes in MVC mainly were explained by gains in voluntary muscle activation in both young and old. Altogether, the present data demonstrate that plasticity in voluntary muscle activation (~central neural drive) is a dominant mechanism affecting short-term disuse- and recovery-induced changes in muscle strength in older adults.

Relationship between trunk function evaluated using the trunk righting test and physical function in patients with knee osteoarthritis.

[Purpose] The present study was to validate the importance of the trunk function evaluated by trunk righting test (TRT) with motor function in patients with knee osteoarthritis (OA) and to show the clinical use of TRT. [Subjects and Methods] This study included 50 patients with knee osteoarthritis who underwent total knee arthroplasty in our hospital. Correlations between physical functional test, such as muscle strength, balance function, and performance and TRT were statistically evaluated. [Results] The independent factors for ipsilateral TRT were maximal isometric knee extensor strength test and ipsilateral step test. The operator and non-operator side TRT were significantly associated with TUG. [Conclusion] The results showed that the physical functions are correlated with the trunk function evaluated by TRT of patients with knee OA, suggesting that healthcare workers must take into consideration the trunk function, as well as lower extremity function to improve physical function.

The effect of whole-body vibration therapy on bone metabolism, motor function, and anthropometric parameters in women with postmenopausal osteoporosis

Purpose: To review the research literature on the effectiveness of whole-body vibration (WBV) therapy in women with postmenopausal osteoporosis.Methods: A systematic review was conducted by two independent reviewers. Mean differences (MDs), standardized mean differences (SMDs), and 95% confidence intervals (CIs) were calculated, and heterogeneity was assessed with the I2 test. The Cochrane risk of bias tool was used to assess the methodological quality of the selected studies.Results: Nine randomized controlled trials involving 625 patients met the inclusion criteria. No significant improvement was found in bone mineral density (BMD) (SMD = −0.06, 95%CI= −0.22–0.11, p = 0.50); bone turnover markers (MD = −0.25, 95%CI= −0.54–0.03, p = 0.08); anthropometric parameters, including muscle mass, fat mass, body mass index (BMI), and weight (SMD = 0.02, 95%CI= −0.16–0.21, p = 0.81); or maximal isotonic knee extensor strength (SMD = 0.16, 95%CI= −0.63–0.95, p = 0.69). However, maximal isometric knee extensor strength improved (SMD = 0.71, 95%CI = 0.34–1.08, p = 0.0002).Conclusions: WBV is beneficial for enhancing maximal isometric knee extensor strength, but it has no overall treatment effect on BMD, bone turnover markers, anthropometric parameters, or maximal isotonic knee extensor strength in women with postmenopausal osteoporosis.Implication of rehabilitationOsteoporosis is the leading underlying cause of fractures in postmenopausal women, whole body vibration (WBV) has received much attention as a potential intervention for the management of osteoporosis in recent years.Whole body vibration is beneficial for enhancing maximal isometric knee extensor strength in women with postmenopausal osteoporosis.Whole body vibration has no overall treatment effect on bone mineral density, bone turnover markers, anthropometric parameters and maximal isotonic knee extensor strength in women with postmenopausal osteoporosis.

Muscle strength and hypertrophy occur independently of protein supplementation during short-term resistance training in untrained men.

Short-term resistance training has consistently demonstrated gains in muscular strength, but not hypertrophy. Post-resistance training protein ingestion is posited to augment the acute anabolic stimulus, thus potentially accelerating changes in muscle size and strength. The purpose of this investigation was to examine the effects of 4 weeks of resistance training with protein supplementation on strength and muscle morphology changes in untrained men. Participants (mean ± SD; N = 18; age, 22.0 ± 2.5 years; body mass index, 25.1 ± 5.4 kg · m(-2)) were randomly assigned to a resistance training + protein group (n = 9; whey (17 g) + colostrum (3 g) + leucine (2 g)) or a resistance training + placebo group (n = 9). One-repetition maximum (1RM) strength in the leg press (LP) and leg extension (LE) exercises, maximal isometric knee extensor strength (MVIC), and muscle morphology (thickness (MT), cross-sectional area (CSA), pennation angle) of the dominant rectus femoris (RF) and vastus lateralis (VL) was assessed before and after training. Participants performed LP and LE exercises (3 × 8-10; at 80% 1RM) 3 days/week for 4 weeks. Data were analyzed using 2-way ANOVA with repeated measures. Four weeks of resistance training resulted in significant increases in LP (p < 0.001), LE (p < 0.001), MVIC (p < 0.001), RF MT (p < 0.001), RF CSA (p < 0.001), VL MT (p < 0.001), and VL CSA (p < 0.001). No between-group differences were observed. Although nutrition can significantly affect training adaptations, these results suggest that short-term resistance training augments muscle strength and size in previously untrained men with no additive benefit from postexercise protein supplementation.

Proliferation of myogenic stem cells in human skeletal muscle in response to low‐load resistance training with blood flow restriction

Low-load resistance training with blood flow restriction has been shown to elicit substantial increases in muscle mass and muscle strength; however, the effect on myogenic stem cells (MSCs) and myonuclei number remains unexplored. Ten male subjects (22.8 ± 2.3 years)performed four sets of knee extensor exercise (20% 1RM) to concentric failure during bloodflow restriction (BFR) of the proximal thigh (100 mmHg), while eight work-matched controls(21.9 ± 3.0 years) trained without BFR (control, CON). Twenty-three training sessions were performed within 19 days. Maximal isometric knee extensor strength (MVC) was examined pre- and post-training, while muscle biopsies were obtained at baseline (Pre), after 8 days intervention(Mid8) and 3 (Post3) and 10 days (Post10) post training to examine changes in myofibre area (MFA), MSC and myonuclei number. MVC increased by 7.1% (Post5) and 10.6% (Post12)(P <0.001) with BFR training, while type I and II MFA increased by 38% (Mid8), 35 – 37%(Post3) and 31 – 32% (Post10) (P <0.001). MSCs per myofibre increased with BFR training from 0.10 ± 0.01 (Pre) to 0.38 ± 0.02 (Mid8), 0.36 ± 0.04 (Post3) and 0.25 ± 0.02 (Post10) (P <0.001). Likewise, myonuclei per myofibre increased from 2.49 ± 0.07 (Pre) to 3.30 ± 0.22(Mid8), 3.20 ± 0.16 (Post3) and 3.11 ± 0.11 (Post10), (P<0.01). Although MFA increased in CON at Mid8, it returned to baseline at Post3. No changes in MSC or myonuclei number were observed in CON. This study is the first to show that short-term low-load resistance exercise performed with partial blood flow restriction leads to marked proliferation of myogenic stem cells and resulting myonuclei addition in human skeletal muscle, which is accompanied by substantial myofibre hypertrophy.

Physical Function Is Weakly Associated with Angiotensin-Converting Enzyme Gene I/D Polymorphism in Elderly Japanese Subjects

Background: The turning point in the deterioration of physical function seems to occur between the ages of 70 and 80 years. In particular, muscle strength may decline even more in subjects older than 75. A recent study found that the angiotensin-converting enzyme (ACE) genotype also affects physiological left ventricular hypertrophy. A very limited number of papers have examined genetic differences in resistance and endurance forms of a single sporting discipline. Objective: The purpose of this study was to evaluate the relationship between ACE genotype and physical function by controlling the known confounding factors including dental status. Methods:We selected 431 subjects who were aged 76 years and did not require special care for their daily activities. We conducted a medical examination, followed by 5 physical function tests, as follows: (1) maximum hand grip strength, (2) maximal isometric knee extensor strength, (3) maximal stepping rate for 10 s, (4) one-leg standing time with eyes open and (5) 10-meter maximum walking speed. Subjects were genotyped for the ACE intron 16 Alu insertion. In addition, serum concentrations of total cholesterol, total protein, IgA and IgG were measured at a commercial laboratory. The Eichner index was used as an indicator of occlusal condition. Multiple linear regression analysis was performed to evaluate the relationship between the ACE gene insertion/deletion (I/D) polymorphism and physical function considering confounding factors. Results: The ACE gene I/D polymorphism was positively associated with hand grip strength and 10-meter maximum walking speed. Betas of hand grip strength were 0.09 for I/D (p = 0.022) and 0.12 for insertion/insertion (I/I; p = 0.004). Betas of 10-meter walking speed were –0.11 for I/D (p = 0.093) and –0.14 for I/I (p = 0.039). Dental status such as Eichner index class C was significantly associated with one-leg standing time with eyes open (beta –0.11; p = 0.028). Conclusion: This study suggests that there is a significant relationship between ACE genotype and physical function. In particular, subjects with the ACE deletion/deletion genotype were associated with upper extremities.

Genetic effects in common on maximal walking speed and muscle performance in older women

The purpose was to examine whether maximal walking speed, maximal isometric knee extensor strength, and leg extensor power share genetic or environmental effects in common. The data was collected from 103 monozygotic and 114 dizygotic female twin pairs aged 63-76 years. Maximal walking speed over 10 m was measured in the laboratory corridor using photocells for timing. Isometric knee extensor strength and leg extensor power were measured using an adjustable dynamometer. The genetic models showed that strength, power, and walking speed had a genetic effect in common which accounted for 52% of the variance in strength, 36% in power, and 34% in walking speed. Strength and power had a non-shared environmental effect in common explaining 13% of variation in strength and 14% in power. The remaining variance was accounted for by trait-specific effects. Some people may be more prone to functional limitation in old age due to their genetic disposition, but this does not rule out that changes in the lifestyle of predisposed subjects may also have a major effect. Approximately half of the variation in each trait was explained by environmental effects, which suggests the importance of the physical activity to improve performance and prevent functional limitation.

The effect of strength training on control of force in older men and women.

Age-related structural alterations in motor units and consequential functional manifestations are asserted to underlie the decline in the ability to finely grade, or control, muscular force in upper extremity musculature of older adults. Functional activities requiring appropriately graded muscular action, such as control of balance, may therefore be negatively affected by these changes. Recent investigations of smaller intrinsic hand muscles have suggested that strength training may attenuate the normal age-related decrease in strength and control of force resulting in increased strength and control. The effects of strength training on the larger, more powerful, anti-gravity muscle of the quadriceps, where age-related changes are noted earlier, are unknown. Thus, the purpose of this study was to assess the effects of 12 weeks of high intensity strength training on strength and the ability to control muscular force in untrained older adults. Twenty-two subjects aged 59-83 years (11 males, 11 females) were compared to 5 untrained, age-matched controls 58-76 years of age (3 females, 2 males). Maximal isometric knee extensor strength and control of force at 30, 60, and 90% of maximum were measured at 0, 6, and 12 weeks. Significant increases in quadriceps strength were noted in the exercise group but neither group showed a change in the ability to control sub-maximal forces. These findings suggest that high intensity strength training may be efficacious for improving strength but does not improve the ability to control sub-maximal isometric forces.