Knee Muscle Strength Research Articles

Comparative assessment of knee extensor and flexor muscle strength measured using a hand-held vs. isokinetic dynamometer.

[Purpose] To compare measurements of knee extensor and flexor muscle strength performed using a hand-held dynamometer and an isokinetic dynamometer in apparently healthy subjects. [Subjects and Methods] Thirty adult volunteers underwent knee muscle strength evaluation using an isokinetic or a hand-held dynamometer. [Results] Strong positive correlations were found between the 2 methods, with correlation coefficients r ranging from 0.72 (95% confidence interval [CI], 0.48−0.86) to 0.87 (95% CI, 0.75−0.94), depending on the muscle group and the isokinetic evaluation mode. The reproducibility of the hand-held dynamometer findings was good, judged by a coefficient of variation of 3.2–4.2%. However, the correlation between the 2 methods for the assessment of flexor/extensor ratios ranged from −0.04 to 0.46. [Conclusion] Knee extensor and flexor muscle strength recorded with a hand-held dynamometer is reproducible and significantly correlated with the isokinetic values, indicating that this method may in some cases be a useful replacement for isokinetic strength measurement. However, for strength ratio assessment, and when judged against the isokinetic standard, a hand-held dynamometer is not a valid option.

Does meniscal pathology alter gait knee biomechanics and strength post-ACL reconstruction?

Individuals following anterior cruciate ligament reconstruction (ACLR) with concomitant meniscal pathology have a higher risk of developing knee osteoarthritis (OA) compared to those with isolated ACLR. Knee extensor weakness and altered dynamic knee joint biomechanics have been suggested to play a role in the development of knee OA following ACLR. This study investigated whether these factors differ in people following ACLR who have concomitant meniscal pathology compared to patients with isolated ACLR. Thirty-three patients with isolated ACLR and 34 patients with ACLR and meniscal pathology underwent strength and gait assessment 12-24months post-operatively. Primary measures were peak isometric knee extensor torque and knee adduction moment (peak and impulse). Secondary measures included peak knee flexion moment and knee kinematics (sagittal and transverse). There were no between-group differences in knee extensor strength [mean difference (95% CI) 0.09 (-0.23 to 0.42)Nm/kg, n.s.], peak knee adduction moment [-0.02 (-0.54 to 0.49)Nm/(BW×HT)%, n.s.] or knee adduction moment impulse [0.01 (-0.15 to 0.17)Nm/(BW×HT)%, p=n.s.]. No between-group differences were found for any secondary measures. No evidence was found to suggest that the higher prevalence of OA in patients with ACLR and meniscal pathology compared to patients with isolated ACLR is attributed to reduced knee muscle strength or altered knee joint biomechanics assessed 1-2years post-surgery. Given that there is a higher incidence of knee OA in patients with concomitant meniscal pathology and ACLR, further investigation is needed so that population-specific rehabilitation protocols can be developed. III.

Quadriceps strength asymmetry predicts loading asymmetry during sit-to-stand task in patients with unilateral total knee arthroplasty.

This study aimed to examine interlimb differences in muscle strength and sit-to-stand (STS) kinetics in persons who underwent unilateral total knee arthroplasty (TKA) and to determine whether knee pain, quadriceps or hip abductor weakness contributes to altered STS performance. It was hypothesized that the operated limb would have weaker muscles, lower mechanical loading and that operated knee pain and muscle strength symmetry would predict loading symmetry between limbs during STS. One hundred and forty-two patients, 6 or 12months post-unilateral TKA, underwent 3D motion analysis (VICON) of the STS task and isometric strength testing of the quadriceps and hip abductors. Knee pain was also quantified using a question from the Knee Outcome Survey-Activities of Daily Living Scale. The operated limb had weaker quadriceps (P<0.001), lower hip (P=0.004) and knee extension moments (P<0.001), and lower vertical ground reaction forces (P<0.001). Operated knee pain and quadriceps strength symmetry were related to symmetry in knee extension moment (P<0.04), and vertical ground reaction forces (P<0.02) 6months after surgery, while quadriceps strength symmetry was related to symmetry in vertical ground reaction forces (P=0.03), 1year after surgery. Patients with unilateral TKA unload the operated limb and shift the mechanical load to the joints of the contralateral limb even 1year after surgery. Knee pain and quadriceps strength asymmetry may play a role in the asymmetrical loading during STS post-TKA. Clinicians should consider addressing these modifiable impairments to resolve the loading asymmetry. III.

A study of isokinetic trunk and knee muscle strength in patients with chronic sciatica

To evaluate trunk and knee muscle strength in patients with chronic sciatica in order to optimize the program of management in a rehabilitation setting. This is a prospective study which included 68 subjects. The first group (G1) comported 28 patients with right-side chronic sciatica. The second group (G2) comported 40 healthy controls. The strength of both trunk and knee muscles was evaluated by the isokinetic dynamometer. Quadriceps and hamstring muscle strength were evaluated at concentric velocities of 60 and 120°/s and the trunk muscles were evaluated at concentric velocities of 60 and 90°/s. The two groups were comparable. The peak torque values for the trunk flexors were lower in the group G1 ( P < 0.002 and P = 0.01, respectively at 60° and 90°). Similarly, the peak torque values for the trunk extensors was lower in this group ( P < 0.001 and P = 0.001, respectively at angular velocities of 60° and 90°). The deficit was higher in the group of the extensor muscles. The peak torque values for the right quadriceps and hamstrings at angular velocities of 60 and 120°/s were also lower in group G1. The differences were statistically significant ( P < 0.001). In G1, the quadriceps and hamstrings were significantly weaker on the sciatica side than on the unaffected side. The isokinetic muscle strength evaluation allows the therapeut to optimize the management of patients with chronic sciatica. Some studies showed a reduction in both trunk and knee muscle strength in those patients, when compared with healthy subjects. Neurologic reason appears to be unlikely. This deficit may possibly be explained by muscle atrophy secondary to immobilization imposed by chronic pain. Therefore, the therapeutic program should control the pain but also strengthen both the trunk and lower extremity muscles. Some authors say that muscle atrophy mainly affects selective type II muscle fiber, which leads us to propose a strengthening at different contraction speeds especially the faster one (180°/s) to ensure a successful recovery [1] .

Relationships between the Fibromyalgia Impact Questionnaire, pain severity, psychological profile and Muscle Strength in Female Patients with Fibromyalgia

The aim of this study was to compare various performances between women with fibromyalgia (FM) and healthy female controls and to assess the relationship between muscular function, pain intensity, disease severity and psychological profile in the fibromyalgia. We included forty-six women divided into two groups: the first group included 21 fibromyalgia patients and the second group included 25 healthy controls. All subjects had an evaluation of the trunk and knee muscular strength in the dominant limb using an isokinetic dynamometer. This assessment involved a measurement of the maximal concentric isokinetic muscle strength of the knee flexors and extensors at both 60°/s and 180°/s angular velocity, and a measurement of the maximal concentric isokinetic muscle strength of the trunk flexors and extensors at 60 and 150°/s. Muscular resistance to fatigue is assessed when the subject has performed 30 chained concentric contractions of maximum intensity at an angular velocity of 180°/s. The measured parameters were the peak of torque and the cumulative work. We evaluated the pain intensity both at rest and during exercise using visual analogical scale, the psychological profile via HAD scale, and the disease severity using the fibromyalgia impact questionnaire (FIQ). The strength and endurance of knee and trunk muscles were lower in fibromyalgia. The difference between these groups was significant ( P < 0.05). The isokinetic trunk deficit predominated on the trunk extensors ( P < 0.001). Mean decrease were 34.5% ( P < 0.05) for trunk flexors, 70% ( P < 0.05) for the trunk extensors, 20% ( P < 0.05) for the knee flexors and extensors, and 75% ( P < 0.001) for fatigue resistance. There were no significant correlations between isokinetic parameters, FIQ, pain intensity and psychological profile. Muscular strength and endurance were decreased in both knee and trunk muscles in fibromyalgia patients. The relationship between muscular strength, psychological profile and disease severity is weak. This implies that separate evaluations and treatments for every single co-morbidity are imposed.

Comparative study on the assessment of the strength of the knee extensor and flexor muscles by hand-held dynamometer and isokinetic dynamometer

The strength of the knee extensor and flexor muscles is a relevant clinical indicator of the health status and functional capacities of an individual. For its evaluation, the practitioner must have simple and reliable measuring tools. Currently, the use of hand-held dynamometers is widespread both in the clinical practice and in research. However, their reliability for assessing the performance of strong muscles, such as the knee extensors and flexors, needs to be fully validated. The aim of this study is to compare the knee extensor and flexor muscle strength measurements using a hand-held dynamometer and the “gold standard” isokinetic dynamometer in a population of healthy individuals. The strength of the knee extensors and flexors was measured in 30 volunteers with a hand-held dynamometer (MicroFet 2, Hogan Health Industries, Inc 8020 South 1300 West, West Jordan, USA) and with an isokinetic dynamometer (Con-Trex MJ, CMV AG, Dübendorf, Switzerland). The correlations between the mean values of maximal isometric voluntary contraction measured with the hand-held dynamometer and the peak torque values in concentric, eccentric and isometric testing mode were then analyzed. Cross-sectional study. The reproducibility of the hand-held dynamometer was very good with coefficients of variation ranging from 3.2% (95%CI, 2.6–3.8%) to 4.2% (95% CI, 3.5–4.9%) depending on the muscle group. Strong positive correlations were found between hand-held and the isokinetic dynamometers. The correlation coefficients ( r ) ranged from 0.715 (95% CI, 0.478–0.855) to 0.872 (95% CI, 0.747–0.938) according to the muscle group and the isokinetic evaluation mode ( P < 0.01). The force values of the knee extensor and flexor muscles recorded with the hand-held dynamometer are reproducible and strongly and positively correlated with the values obtained with the three isokinetic evaluation modes, indicating that hand-held dynamometry represents a potential alternative tool for knee muscle strength assessment.

The relationship between isokinetic and isometric knee muscle strength and maximal step-up height after stroke: A pilot study

BACKGROUND: A novel way to evaluate muscle strength and functioning in the lower limbs is to measure how high a person could step up on a platform, the so called Maximal Step-up Test (MST). Studies of healthy persons and overweight women have shown that the maximal step-up height (MSH) is associated with both muscle strength and physical function, but no study has assessed persons after stroke. OBJECTIVE: To evaluate the relationship between isokinetic and isometric knee muscle strength and maximal step-up height after stroke. METHODS: A convenience sample of 21 ambulatory persons with stroke (13 men and eight women; mean age 63 +/- 12 years; mean time since stroke onset 26 +/- 36 months). Isokinetic concentric knee extension and knee flexion strength at 60 degrees/s and isometric knee extension strength at 90. were measured for both lower limbs with a Biodex dynamometer. Maximal step-up height was measured using a 40 cm x 60 cm platform, which could be raised from 3 cm to 45 cm with 3 cm intervals. The relationship between knee muscle strength (normalized to body weight) and the maximal step-up height was analysed with the Pearson's correlation coefficient (r). RESULTS: There were significant but only moderate relationships between the paretic isokinetic knee extension, and flexion, strength and maximal step-up height, r = 0.49; p < 0.05, and r = 0.57; p < 0.01, respectively. CONCLUSION: These moderate relationships indicate that muscle weakness is only partially associated with maximal step-up height after stroke. The MST may therefore have limited value in the assessment of muscle strength after stroke. (Less)

Neuromuscular Exercise post Partial Medial Meniscectomy: Randomized Controlled Trial.

This study aimed to evaluate the effects of a 12-wk, home-based, physiotherapist-guided neuromuscular exercise program on the knee adduction moment (an indicator of mediolateral knee load distribution) in people with a medial arthroscopic partial meniscectomy (APM) within the past 3-12 months. An assessor-blinded, randomized controlled trial including people age 30-50 yr with no to mild pain after medial APM was conducted. Participants were randomly allocated to either a 12-wk neuromuscular exercise program that targeted neutral lower limb alignment or a control group with no exercise. The exercise program included eight individual sessions with one of seven physiotherapists in private clinics, together with home exercises. Primary outcomes were the peak external knee adduction moment during normal-paced walking and during one-leg sit-to-stand. Secondary outcomes included additional measures of knee joint load distribution, patient-reported outcomes, maximal knee and hip muscle strength, and physical function measures. Of 62 randomized participants, 60 (97%) completed the trial. There were no significant between-group differences in the change in peak knee adduction moment during normal-paced walking (mean difference (95% confidence interval), 0.22 (-0.11 to 0.55) N·m/body weight × height %, P =0.19) or during one-leg sit-to-stand (-0.01 (-0.33 to 0.31) N·m/body weight × height %, P = 0.95). There were also no significant between-group differences for any of the secondary outcomes. In patients 3-12 months after a medial APM, a neuromuscular exercise program did not alter the peak knee adduction moment, a key predictor of osteoarthritis structural disease progression. (Australia and New Zealand Clinical Trials Registry, #ACTRN12612000542897.).

Moderate varus/valgus malalignment after total knee arthroplasty has little effect on knee function or muscle strength

Background and purpose — Postoperative muscle strength and component alignment are important factors affecting functional results after total knee arthroplasty (TKA). We are not aware of any studies that have investigated the relationship between them. We therefore investigated whether coronal malalignment of the mechanical axis and/or of individual implant components would affect knee muscle strength and function 1 year after TKA surgery.Patients and methods — We included 120 consecutive osteoarthritis (OA) patients admitted for TKA. Preoperative active range of motion (ROM) of the knee, patient age, sex, and BMI were recorded and the Knee Society score (KSS) and knee joint extensor/flexor muscle strength were assessed. At 1-year follow-up, the mechanical and coronal component alignment was measured from a postoperative long standing radiograph, and ROM, KSS, and muscle strength measurements were taken in 91 patients. Functional outcome and muscle strength measurements were compared between normally aligned and malaligned TKA groups.Results — 29 of 91 TKAs were malaligned, i.e. they deviated more than 3° from the neutral mechanical axis. 18 femoral components and 15 tibial components were malaligned. Before surgery, the malaligned and normally aligned groups were similar regarding sex distribution, BMI, ROM, KSS, and muscle strength. At the 1-year follow-up, the differences between the groups regarding knee joint function and muscle strength were small, not statistically significant, and barely clinically relevant.Interpretation — Moderate varus/valgus malalignment of the mechanical axis or of individual components has no relevant clinical effect on function or muscle strength 1 year after TKA surgery.

Relationship between lower extremity isokinetic strength and anaerobic power in weightlifters, basketball and soccer players

BACKGROUND: Little is known about the comparative relationships between knee muscles strength and anaerobic power in weightlifters, basketball and soccer players, popular sports that rely on lower extremity muscles strength. METHODS:Ten weightlifters, 12 basketball and 19 soccer players participated inthe study. Concentric peak torque of hamstring (H) and quadriceps (Q) of the dominant (D) and non-dominant leg (ND) was evaluated at 60 and 240 ◦ /s. Subjects also performed Wingate Anaerobic Test (WAnT) 48 h after isokinetic measurements. RESULTS:Normalized peak moment of the hamstring (NPMh) of D in soccer players was significantly greater than inbasketball players and weightlifters at 60 and 240 ◦ /s. At 60 ◦ /s, weightlifters presented a greater NPMq when compared to soccer players in D. Significant correlations were observed between NPMq of both legs and peak and mean power at 60 and 240 ◦ /s in basketball. In soccer, significant correlations were found between the bilateral NPM of both muscles and the peak and mean power at 240 ◦ /s. CONCLUSIONS: Knee flexion strength plays a more decisive role in soccer due to the fast movement pattern while knee extension strength is more important in basketball and weightlifting due to vertical movement patterns.

Effect of exercise therapy compared with arthroscopic surgery on knee muscle strength and functional performance in middle-aged patients with degenerative meniscus tears: a 3-mo follow-up of a randomized controlled trial.

The aim of this study was to compare the effect of a 12-wk exercise therapy program and arthroscopic partial meniscectomy on knee strength and functional performance in middle-aged patients with degenerative meniscus tears. A total of 82 patients (mean age, 49 yrs; 35% women) with a symptomatic, unilateral, magnetic resonance imaging-verified degenerative meniscus tear and no or mild radiographic osteoarthritis were randomly assigned to a supervised neuromuscular and strength exercise program or arthroscopic partial meniscectomy. Outcomes assessed 3 mos after intervention initiation were isokinetic knee muscle strength, lower extremity performance, and self-reported global rating of change. Mean difference in isokinetic knee extension peak torque between the two groups was 16% (95% confidence interval, 7.1-24.0) (P < 0.0001), favoring the exercise group. Patients in the exercise group improved isokinetic knee extension peak by a mean of 25 Nm (range, 18-33 Nm) from baseline to follow-up. Furthermore, patients assigned to exercise therapy showed statistically significant improvements (P ≤ 0.002) in all other measured variables, with moderate to large effect sizes (0.5-1.3). Patients reported a similar and positive effect of both interventions. A 12-wk supervised exercise therapy program yielded clinically relevant and statistically significant improvement in isokinetic quadriceps strength immediately after completion of the program, as compared with treatment with arthroscopic partial meniscectomy.

Men With Late Effects of Polio Decline More Than Women in Lower Limb Muscle Strength: A 4-Year Longitudinal Study

BackgroundIn persons with prior paralytic poliomyelitis, progressive muscle weakness can occur after a stable period of at least 15 years. Knowledge is limited about which factors influence changes in lower limb muscle strength in these persons. ObjectiveTo assess changes in lower limb muscle strength annually over 4 years in persons with late effects of polio and to identify prognostic factors for changes in muscle strength. DesignA prospective, longitudinal study. SettingUniversity hospital outpatient program. ParticipantsFifty-two ambulant persons (mean age ± standard deviation: 64 ± 6 years) with verified late effects of polio. MethodsMixed linear models were used to analyze changes in muscle strength and to identify determinants among the following covariates: gender, age, age at acute polio infection, time with late effects of polio, body mass index, and estimated baseline muscle weakness. Main Outcome MeasurementsKnee extensor and flexor and ankle dorsiflexor muscle strength were measured annually with a Biodex dynamometer. ResultsThe men (n = 28) had significant linear change over time for all knee muscle strength measurements, from −1.4% (P < .05) per year for isokinetic knee flexion in the less-affected lower limb to −4.2% (P < .001) for isokinetic knee extension in the more-affected lower limb, and for 2 ankle dorsiflexor muscle strength measurements (−3.3%-1.4% per year [P < .05]). The women (n = 24) had a significant linear change over time only for ankle dorsiflexor measurements (4.0%-5.5% per year [P < .01]). Gender was the strongest factor that predicted a change in muscle strength over time. ConclusionsOver 4 years, men had a greater decline in muscle strength than did women, but the rate of decline did not accelerate. This finding indicates that gender could be a contributing factor to the progressive decline in muscle strength in persons with late effects of polio.

A randomised trial into the effect of an isolated hip abductor strengthening programme and a functional motor control programme on knee kinematics and hip muscle strength.

BackgroundDynamic knee valgus and internal femoral rotation are proposed to be contributory risk factors for patellofemoral pain and anterior cruciate ligament injuries. Multimodal interventions including hip abductor strengthening or functional motor control programmes have a positive impact of pain, however their effect on knee kinematics and muscle strength is less clear. The aim of this study was to examine the effect of isolated hip abductor strengthening and a functional motor control exercise on knee kinematics and hip abductor strength.MethodsThis prospective, randomised, repeated measures design included 29 asymptomatic volunteers presenting with increase knee valgus and femoral internal rotation. Participants completed either isolated hip abductor strengthening or a functional motor control exercise for 5 weeks. Knee kinematics were measured using inertial sensors during 2 functional activities and hip abductor strength measured using a load cell during isometric hip abduction.ResultsThere were no significant differences in dynamic knee valgus and internal rotation following the isolated hip abductor or functional motor control intervention, and no significant differences between the groups for knee angles. Despite this, the actual magnitude of reduction in valgus was 10° and 5° for the functional motor control group and strengthening group respectively. The actual magnitude of reduction in internal rotation was 9° and 18° for the functional motor control group and strengthening group respectively. Therefore there was a tendency towards clinically significant improvements in knee kinematics in both exercise groups. A statistically significant improvement in hip abductor strength was evident for the functional motor control group (27% increase; p = 0.008) and strengthening group (35% increase; p = 0.009) with no significant difference between the groups being identified (p = 0.475).ConclusionsIsolated hip strengthening and functional motor control exercises resulted in non-statistically significant changes in knee kinematics, however there was a clear trend towards clinically meaningful reductions in valgus and internal rotation. Both groups demonstrated similar significant gains in hip abductor strength suggesting either approach could be used to strengthen the hip abductors.

The Relationship Between The Operation Of Kick Start And Isokinetic Knee Strength In Swimmers

PURPOSE: The purpose of this study was to examine the relationship between the operation of kick start and isokinetic knee strength in swimmers using three-dimensional (3D) analysis. METHODS: This study included 11 male university student swimmers, who usually used the kick-start technique. We filmed the operation of kick start using 3 high-speed cameras (300 scenes; shutter speed, 1/250 s). The cameras could record over an area measuring 6.05 × 1.90 × 2.00 m. After we took a video of operation, we vertically set up calibration-pole which applied the control-point at intervals of 0.5m at the seven places within the range of taking a picture as ground and the surface of the water. Motion analysis was performed using Frame-DIASIV System (DKH) software. The 3D coordinates of 23 points on each subject’s body were determined using direct linear transformation. Tests of isokinetic knee strength were performed using an isokinetic dynamometer (BIODEX, System 4). For each measurement, we set the angular velocity as 60, 180, and 300°/s, and repetitions were conducted 5, 10 and 15 times, respectively. In the analysis, we divided muscle strength by weight, for each participant. We used Spearman’s rank correlation coefficient to assess the relationship between the operation of kick start and isokinetic strength. Statistical significance was set at 5%. RESULTS: There was a significant relationship between the average center of gravity, horizontal acceleration before take-off, and flexion muscle strength of the front knee at 60°/s (r = 0.718) and 180°/s (r = 0.636) and extension muscle strength of the rear knee at 300°/s (r = 0.500). Similarly, there was a significant relationship between the time from the start signal to take-off and flexion muscle strength of the front knee at 60°/s (r = -0.651) and 180°/s (r = -0.651) and extension muscle strength of the rear knee at 300°/s (r = -0.433). CONCLUSION:These results suggest that swimmers with high muscle strength of the front knee at flexion can obtain a high horizontal acceleration in the acceleration phase, because they can quickly move the body forward. In addition, it is thought that this may shorten the take-off time

Activin Receptor 1b (acvr1b) Rs2854464 Distribution Among Brazilian Elite Athletes

Myostatin up-regulation activates transcription factors that inhibit muscle growth. It is possible that common genetic variants on these genes are capable of modulating the activity of myostatin. These could partly explain the individual variation in response to training. In this regard, not only the myostatin gene has been evaluated, but other key genes of myostatin signaling are being investigated. A fine exploration of a previously identified linkage peak for knee strength on chr12q12-14 has shown strong associations between ACVR1B genotypes and knee muscle strength. In caucasians, rs2854464 A/A individuals were approximately 2% stronger than G-allele carriers. Thus far, we have no information regarding this polymorphism in Brazilian athletic populations. PURPOSE: To compare the frequency of the polymorphism rs2854464 between three groups of Brazilians: endurance athletes, strength/power athletes and non-athletes adults. METHODS: A total of 379 Brazilians (men and women) were genotyped (101 endurance elite athletes; 166 strength/power elite athletes and 112 non-athletes). Genotyping was conducted using a pre-designed specific TaqMan® SNP Genotyping Assay. X2 test and Fisher exact test were used to evaluate differences between groups of athletes and non-athletes in the genotype distribution. RESULTS: The Minor Allele Frequency (MAF) presented in this study (G=0.334) was very similar to the overall value presented by the 1000 genomes (G=0.3684). Meaning that our sample was similar to other samples in different populations. The percentages of each genotype found for each group were: Non-athletes, G/G= 13.39 %, G/A= 40.18 %, A/A = 46.43 %; Endurance athletes, G/G= 12.87 %, G/A= 46.53 %, A/A = 40.59 %; Strength/Power athletes, G/G= 15.06 %, G/A= 48.19 %, A/A = 36.75 %. The distribution of the genotypes was not different between groups. CONCLUSION: The frequencies of genotypes for the polymorphism rs2854464 of ACVR1B gene, a transmembrane receptor involved in the signaling pathway of myostatin were not different among a cohort of athletes and non-athletes. Although only top athletes were included in this analysis, we could not confirm the association between this polymorphism and competitive success. João Paulo L. F. Guilherme is supported by the Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP 2012/22516-6).

Falls Associated with Muscle Strength in Patients with Knee Osteoarthritis and Self-reported Knee Instability.

We aimed to evaluate the associations between knee muscle strength (MS) and falls, controlling for knee joint proprioception, varus-valgus knee joint laxity, and knee pain, among patients with knee osteoarthritis (OA) reporting knee instability. A sample of 301 subjects (203 women, 98 men, 35-82 yrs) with established knee OA and self-reported knee instability was studied. The occurrence of at least 1 fall in the previous 3 months was assessed by questionnaire. Maximum knee extension and flexion strength were measured isokinetically. Additionally, proprioception, varus-valgus laxity, and pain were assessed. Student t tests were used to assess differences between subgroups. The association of muscle strength and falls was calculated using univariate and multivariate logistic regression analysis. Over 10% of the subjects (31 out of 301) reported a fall in the previous 3 months. High knee extension muscle strength (crude OR 0.3, 95% CI 0.1-0.8, p = 0.022) and high knee flexion muscle strength (crude OR 0.2, 95% CI 0.0-1.0, p = 0.048) were associated with a lower risk of falls. Proprioception and laxity did not confound this relationship. After adjusting for pain, extensor strength had an adjusted OR of 0.5 (95% CI 0.2-1.4, p = 0.212) for falls and flexor strength had an adjusted OR of 0.4 (95% CI 0.1-2.3, p = 0.312). High knee extension and flexion muscle strength decreased the risk of falls in patients with knee OA and self-reported knee instability. After considering the effect of pain, there was insufficient statistical power to detect an association between muscle strength and falls, which might be because of the low number of subjects who fell (n = 31).

Vitamin D Is Associated With Functional Mobility Not With Muscle And Balance In Osteoporotic Women

PURPOSE: The aim of this study was to evaluate the different levels of vitamin D are associated with knee muscle strength, postural balance and functional mobility in women with postmenopausal osteoporosis. METHODS: This is a cross-sectional observational study, without intervention, of 63 osteoporotic elderly women. The volunteers were divided into four groups according to the vitamin D blood level. Participants then underwent the Timed Up and Go Test to measure functional mobility. The postural balance was assessed on the AccuSway Plus portable force platform. Isokinetic dynamometry was performed using the Biodex® Multi-joint System 3. Data are reported as mean ± standard deviation or 95% confidence interval (CI), and were analyzed with the subjects divided into quartiles according to their 25(OH)D level. Statistical significance was set at P<0.05. RESULTS: No significant differences between groups were observed in all demographic and clinical variables, strength, or postural balance, except for the 25(OH)D level, which showed a significant different between groups (P<0.001). However, significant differences were found in the Timed Up and Go Test: the women with the highest 25(OH)D levels (G4) showed greater performance than those with lowest 25(OH)D levels (G1) (P<0.008) (Figure 1). CONCLUSIONS: Women of G2 and G3 showed intermediate Timed Up and Go Test performances that were not statically different from both G1 and G4. Vitamin D blood level was associated with functional mobility in women with postmenopausal osteoporosis.

Short-Term Effects of Blood Flow Restricted Resistance Training in Older Adults at Risk of Mobility Limitations

Improvements in muscle strength in older adults have been observed following short-term (6-weeks) high-load (HL) resistance training. Blood flow restricted (BFR) resistance training using low loads has also resulted in strength gains. However, it is unknown whether HL and BFR resistance exercise produce similar effects on hypertrophy and strength gains following short duration training. PURPOSE: To compare lower extremity strength, hypertrophy and functional adaptations to 6-weeks of HL and BFR training in older adults at risk of mobility limitations. METHODS: Twenty-six older adults (76.7 ± 7.8 years; 26.2 ±3.4 kg·m-2) who possessed low knee muscle strength placing them at risk of developing mobility limitations participated in the study. They were randomly assigned to perform twice weekly sessions of HL (70% 1-RM), BFR (30% 1-RM coupled with a vascular restriction of 1.5 times systolic blood pressure at the proximal thigh) or attention control (CON) for six-weeks. HL and BFR groups engaged in three sets of leg extension (LE), leg press (LP), and leg curl resistance training to muscular failure. The CON group performed three sets of light upper body resistance and flexibility training that was not expected to result in muscle adaptations. LE and LP 1-RM, quadriceps cross-sectional area (CSA) via magnetic resonance imaging, and 400 m walking speed were assessed before and after training. RESULTS: There were clear changes in CSA and strength (group x time interaction, P<0.01) in the training groups and there were no changes in the CON group (P>0.05). HL and BFR groups demonstrated a 3% and 4% increase in CSA, respectively (P<0.05). LE 1-RM increased following HL (40%; P<0.01) and BFR (22%; P<0.01) training. LP 1-RM increased 18% and 8% in the HL and BFR groups, respectively (P<0.01). There were no differences in the CSA and strength adaptations between the HL and BFR groups (P>0.05). Walking speed did not significantly change in any group (P>0.05). CONCLUSION: Short-term HL and BFR resistance training show similar improvements in lower extremity muscle strength and CSA in older adults at risk of mobility limitations. This suggests that BFR resistance training may be a viable modality for older adults who are unable to perform HL training. Supported by NIH grant 1R15 A6040700-01A1.

Core stability, knee muscle strength, and anterior translation are correlated with postural stability in anterior cruciate ligament-reconstructed patients.

The purpose of this study was to investigate the relationship of postural stability and lower extremity performance with core stability, knee laxity, and muscle strength in patients with anterior cruciate ligament reconstruction. Twenty-eight anterior cruciate ligament-reconstructed subjects were included in the study. Anterior knee laxity tests, isokinetic knee muscle strength tests, and core stability tests were performed. Single-limb postural stability was assessed in both eyes-open and eyes-closed positions on a static surface and an eyes-open condition on a foam surface. A single-legged hop test was performed to assess lower extremity performance. To detect differences between the operated and healthy leg, a Mann-Whitney U test was performed, and a correlation analysis was performed using the Spearman correlation coefficient. Knee muscle strength and laxity were different between the operated and healthy legs (P < 0.05). Postural stability scores correlated with core stability tests (P < 0.05) in both the operated and healthy legs. In the operated leg, knee laxity and muscle strength correlated with the mediolateral sway index on a foam surface (P < 0.05). Knee flexor and extensor muscle strength correlated with the single-legged hop for both legs (P < 0.05). Decreased core stability, decreased knee muscle strength, and increased knee laxity correlated with single-limb postural stability. Better hop performance was demonstrated with better knee flexor and extensor muscle strength and was independent from core stability.

Relationship between vitamin D and lung function, physical performance and balance on patients with stage I-III chronic obstructive pulmonary disease.

vitamin D is important for muscle function and it affects different aspects of muscle metabolism. This study aim to determine whether serum 25(OH) D levels are related to lung functions, physical performance and balance in patients with chronic obstructive pulmonary disease (COPD). in 90 patients with COPD and 57 healthy controls lung function tests, physical performance tests (time up and go, gait velocity test, sit-to-stand test, isometric strength, isokinetic strength), static (functional reach test) and dynamic (time up and go) balance tests and the association of 25(OH)D levels with lung functions, physical performance and balance were evaluated. the COPD patients had significantly more deficit in physical function and balance parameters, and in dynamic balance test (p<0.005). Isokinetic knee muscle strength (flexor and extensor) in COPD patients was significantly lower than in the controls (p<0.05); FEV1 (p=0.008), FVC (p=0.02), FEV1/FVC (p=0.04), TLC (p=0.01) were lower in COPD patients with vitamin D deficiency [25(OH) D less than 15 ng/mL] than in COPD patients without vitamin D deficiency. Hand grip test (p=0.000) and isokinetic knee muscle strength (flexor and extensor) (p<0.05) were also lower in COPD patients with vitamin D deficiency. Vitamin D deficiency was more pronounced in patients with stage III COPD (p<0.05). patients with COPD had worst physical functioning, poor balance and less muscle strength. Severe disturbed lung and peripheral muscle functions are more pronounced in COPD patients with vitamin D deficiency.