•Voluntary activation was consistently overestimated when using the central activation ratio compared with the percent activation derived from the interpolated twitch technique.•Constant current and ...constant voltage electrical stimulators yield similar estimates of voluntary activation in those with anterior cruciate ligament reconstruction.•Activation estimates derived using the central activation ratio are affected by the number of electrical pulses used during testing.•The interpolated twitch technique yields better estimates of voluntary activation and is less affected by pulse train conditions or stimulators used during the testing.
Accurate quantification of voluntary activation is important for understanding the extent of quadriceps dysfunction in individuals with anterior cruciate ligament reconstruction (ACLR). Voluntary activation has been quantified using both percent activation derived from the interpolated twitch technique and central activation ratio (CAR) derived from the burst superimposition technique, as well as by using different types of electrical stimulators and pulse train conditions. However, it is unclear how these parameters affect voluntary activation estimates in individuals with ACLR. This study was performed to fill this important knowledge gap in the anterior cruciate ligament literature.
Quadriceps strength and voluntary activation were examined in 18 ACLR participants (12 quadriceps/patellar tendon graft, 6 hamstring tendon graft; time since ACLR: 1.06 ± 0.82 years, mean ± SD) at 90° of knee flexion using 2 stimulators (Digitimer and Grass) and pulse train conditions (3-pulse and 10-pulse). Voluntary activation was quantified by calculating both CAR and percent activation.
Results indicated that voluntary activation was significantly overestimated by CAR when compared with percent activation (p < 0.001). Voluntary activation estimates were not affected by pulse train conditions when using percent activation; however, 3-pulse stimuli resulted in greater overestimation than 10-pulse stimuli when using CAR (p = 0.003). Voluntary activation did not differ between stimulators (p > 0.05); however, the Digitimer evoked greater torque at rest than the Grass (p < 0.001).
These results indicate that percent activation derived from the interpolated twitch technique provides superior estimates of voluntary activation than CAR derived from burst superimposition and is less affected by pulse train conditions or stimulators in individuals with ACLR.
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Abstract The aim of the present study was to examine differences in gait characteristics across the adult lifespan and to test the hypothesis that such differences are attributable at least in part ...to the decline in muscle strength. The data presented here are from 190 participants of the Baltimore Longitudinal Study of Aging (BLSA) aged from 32 to 93 years. Based on two age thresholds that best capture the effect of age on walking speed, participants were divided into three age groups: middle-age (32–57 years; N = 27), old-age (58–78 years; N = 125), and oldest-age (79–93 years; N = 38). Participants were asked to walk at their preferred and maximum speeds while recorded with 3D gait analysis system. In addition, maximum isokinetic knee extensor strength was assessed. While walking at preferred speed, range of motion (ROM) and mechanical work expenditure (MWE) of the ankle were lower within middle-age ( p < 0.001, p = 0.047, respectively), while hip ROM and MWE were lower ( p = 0.006) and higher ( p < 0.001), respectively within oldest-age with older age. Deterioration in ankle function during customary walking initiates already at middle-age. Differences in the maximum walking speed and ankle ROM between middle-age and old-age were explained by knee strength.
Abstract Background Autologous chondrocyte implantation has become an established technique for addressing knee cartilage defects. Despite reported improvement in pain and regeneration of ...hyaline-like repair tissue, little has been reported on the recovery of knee strength. Methods Knee strength assessment was undertaken in 60 patients at 5 years following autologous chondrocyte implantation. Using an isokinetic dynamometer, and during isokinetic knee extension and flexion angular velocities of 60°, 90° and 120°/s, the peak torque, torque at 45° of knee flexion and hamstrings/quadriceps ratio was obtained, in both the operated and non-operated limbs. Pain at the time of assessment was obtained. Independent sample t-tests were used to assess differences in the operated and non-operated sides. Findings There were no significant differences (p > 0.05) between the operated and non-operated legs in the peak knee flexor torque or knee flexor torque at a knee flexion angle of 45°, at all angular velocities (60°, 90° and 120°/s). While the peak knee extensor torque was less in the operated leg at all angular velocities, these differences were not significant (p > 0.05). However, a significantly reduced (p < 0.05) knee extensor torque at a knee flexion angle of 45°, was observed at all speeds. Interpretation While patients had recovered their knee flexor strength, they still demonstrated a reduced knee extensor strength profile at 5 years. This demonstrates that the early supervised rehabilitation phase following autologous chondrocyte implantation is not sufficient to restore long-term knee strength, and ongoing patient advice and rehabilitation is required extending beyond this early period. It is unknown how this prolonged reduction in strength may affect long-term graft outcome.
만성 뇌졸중 환자의 보행속도와 보행 비대칭에 영향을 미치는 무릎근력과 발목 관절가동범위 원종임; Jong Im Won; 안창만 ...
Han'guk Chŏnmun Mulli Ch'iryo Hakhoe chi = Journal of the Korean Academy of University Trained Physical Therapists,
06/2015, Volume:
22, Issue:
2
Journal Article
Open access
The common features of walking in patients with stroke include decreased gait velocity and increased asymmetrical gait pattern. The purpose of this study was to identify important factors related to ...impairments in gait velocity and asymmetry in chronic stroke patients. The subjects were 30 independently ambulating subjects with chronic stroke. The subjects’ impairments were examined, including the isokinetic peak torque of knee extensors, knee flexors, ankle plantarflexors, and ankle dorsiflexors. Passive and active ranges of motion (ROM) of the ankle joint, ankle plantarflexor spasticity, joint position senses of the knee and ankle joint, and balance were examined together. In addition, gait velocity and temporal and spatial asymmetry were evaluated with subjects walking at their comfortable speed. Pearson correlations and multiple regressions were used to measure the relationships between impairments and gait speed and impairments and asymmetry. Regression analyses revealed that ankle passive ROM and peak torque of knee flexors were important factors for gait velocity (R2=.41), while ankle passive ROM was the most important determinant for temporal asymmetry (R2=.35). In addition, knee extensor peak torque was the most significant factor for gait spatial asymmetry (R2=.17). Limitation in ankle passive ROM and weakness of the knee flexor were major contributors to slow gait velocity. Moreover, limited passive ROM in the ankle influenced the level of temporal gait asymmetry in chronic stroke patients. Our findings suggest that stroke rehabilitation programs aiming to improve gait velocity and temporal asymmetry should include stretching exercise for the ankle joint.
Abstract Purpose Knee function is reduced in patients with Benign Joint Hypermobility Syndrome. The aim was to study knee function in children and adults with Generalised Joint Hypermobility (GJH) ...and Non-GJH (NGJH)). Materials and methods In a matched comparative study, 39 children and 36 adults (mean age children 10.2 years; adults 40.3 years) were included, comprising 19 children and 18 adults with GJH (Beighton ≥ 5/9; Beighton ≥ 4/9), minimum one hypermobile knee, no knee pain (children), and 20 children and 18 adults with NGJH (Beighton < 5; Beighton < 4). Totally, 85% of the adults were parents to these children. Knee function was determined by self-reported physical fitness (100 mm VAS), Knee injury and Osteoarthritis Outcome Score (KOOS) (only adults), measured maximum isokinetic knee strength (60°/s) and peak vertical jump displacement (PVJD), with calculated knee strength balance, Hamstring/Quadriceps (H/Q) ratio and peak rate of force development (PRFD). Results Adults with GJH had lower knee function (KOOS: pain, p = 0.001; symptoms, p = 0.001; Activities of Daily Living, p = 0.001; Sport/Recreation, p = 0.003; knee-related quality of life, p < 0.001), and H/Q ratio (0.46 vs. 0.54, p = 0.046) than adults with NGJH, regardless of age and knee pain. Both GJH groups had normal physical fitness, isokinetic knee strength, and (only children) H/Q ratio. Conclusions Children at 10 years with GJH have normal, but adults with GJH have impaired knee function. To track the risk of developing impaired knee function, children with GJH must be followed longitudinally. Meanwhile, attention to knee function may be given to children with GJH who have parents presenting GJH.
Previous studies have demonstrated that healthy young people typically have side-to-side differences in knee strength of about 10% when the peak torque generated by the stronger leg is contrasted ...with that of the weaker leg. However, the mechanisms responsible for side-to-side differences in knee strength have not been clearly defined. The current study tested the hypothesis that side-to-side knee extensor strength differences are explained by inter-limb variations in voluntary activation, antagonistic hamstrings activity, and electrically evoked torque at rest. Twenty-two volunteers served as subjects. Side-to-side differences in quadriceps activation and electrically evoked knee extensor torque explained 69% of the strength differences by side. Antagonistic hamstrings activity did not contribute significantly. The results suggest both central and peripheral mechanisms contribute to inter-limb variations in strength.
The aim of this study was to investigate the effect of quantification method on estimates of voluntary quadriceps muscle activation. Twenty‐two people with no history of serious lower extremity ...injuries underwent voluntary quadriceps activation testing at 60° of knee flexion. Estimates of quadriceps activation were derived with: (1) a formula based on the interpolated twitch technique (ITT); (2) the central activation ratio (CAR); and (3) a modified central activation ratio. Predictive equations were developed that describe the relationships between the three methods. Significant differences (P < 0.001) were observed between the estimates of voluntary quadriceps muscle activation obtained using the three methods (ITT percent activation = 93.0 ± 6.4%, CAR = 95.9 ± 3.8%, modified CAR = 98.5 ± 4.1%). Excellent correlation (r = 0.995) was observed between ITT‐based percent activation and the CAR method. The associations between these methods and the modified CAR approach were weaker. Quantification method affects activation estimates. The equations developed will assist scientists in accurately comparing the results of studies that use different methods of quantifying activation. Muscle Nerve, 2010
Objective: This study investigated whether relative strength between the back and knees can differentiate and predict lifting strategy and the effects of gender, load magnitude, and knowledge of ...strength on the strategy. Background: Although muscular strength is thought to play a vital role in the mechanics of lifting, how localized joint strengths and their relations influence lifting strategy remains unclear. Method: Thirty-two participants (16 men and 16 women) underwent isokinetic strength tests and were then divided into two groups: one provided with the knowledge of their strength test results and the other not. They subsequently performed the same set of simulated lifting tasks while their lifting kinematics were being recorded. Postural indices to quantify the lifting strategies were derived from the kinematic data. Results: The ratio of back strength versus total knee strength and gender had significant effects on measures quantifying the lifting strategy. A statistical model incorporating gender, strength, and anthropometry achieved an R
2 value of .64 and predicted correctly 76% of lifting strategies used by individual participants. Conclusion: Individuals with back strength greater than their total knee strength tended to use a back-preferred lift strategy, and vice versa, suggesting that muscular strength is a determining factor of lifting strategy. Application: An emphasis on additional knee strengthening in a training program may change the tendency of using and overstressing the back. Application of modeling and simulation technology for ergonomics design can be enhanced by more individually and accurately specified lifting strategies based on anthropometry and strength profiles.
Purpose
Despite providing adequate pain relief, a femoral nerve block can induce postoperative muscle weakness after total knee arthoplasty (TKA). Fentanyl has been shown to have peripheral effects ...but has not been used as a perineural infusate alone after TKA.
Methods
Sixty patients scheduled for TKA were randomized to one of three blinded groups: a continuous 24 h infusion of either fentanyl 3 μg/ml, ropivacaine 0.1 %, or 0.9 % normal saline through a femoral nerve sheath catheter at 10 ml/h. The main outcome was maximum voluntary isometric contraction (MVIC) in the quadriceps femoris (knee extension), measured by a handheld dynamometer (Nm/kg). Other variables assessed were preoperative and postoperative visual analog scale (VAS) scores, hamstrings MVIC (knee flexion), active range of motion of the operative knee, distance ambulated, incidence of knee buckling, supplemental morphine usage, postoperative side effects, and serum fentanyl levels.
Results
Quadriceps MVIC values were significantly greater in the fentanyl group compared to the group that received ropivacaine (median values, 0.08 vs. 0.03 Nm/kg;
p
= 0.028). The incidence of postoperative knee buckling upon ambulation was higher in the ropivacaine group compared to the fentanyl group, although not statistically significant (40 % vs. 15 %, respectively;
p
= 0.077). VAS scores while ambulating were not significantly different between the fentanyl group and the ropivacaine group (
p
= 0.270). Postoperative morphine consumption, nausea and vomiting, and resting VAS scores were similar among the three groups.
Conclusions
A continuous perineural infusion of fentanyl produced greater strength retention than ropivacaine post-TKA.
To examine bilateral and ipsilateral peak torque values of quadriceps (Q) and hamstring (H) muscles in elite judokas.
16 elite male judokas were tested in concentric isokinetic strength of the ...quadriceps (Q) and hamstrings (H) muscles at 60° and 180° sec
. Variables comprised average peak torque and the traditional H/Q, Q/Q, H/H ratios. Asymmetries between legs and differences between isokinetic muscle strength ratios were examined using paired t-tests and Cohen's d.
In right (Rs) and left (Ls) extremity peak torque values, no significant difference was found between 60° and 180° sec
angular velocities (p>0.05). In peak torque values between PLs and NPLs, significant difference was found only in extension (Ex) phase at 60° sec
angular velocity p=0.001). (Significance was identified between (Q/Q) and (H/H) muscle ratios at 60° sec
(p=0.029). No significant difference was found in ipsilateral strength ratios at 60° and 180° sec
angular velocity (p>0.05).
The Ex knee strength of PLs was high, particularly at low angular velocities, leading to differences of bilateral asymmetry in the Q muscle group. Regarding ipsilateral strength ratios, there were no differences in the H and Q muscle groups at both angular velocities, indicating that both legs were similar in terms of ipsilateral asymmetry.
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