Neuromuscular electrical stimulation for quadriceps muscle strengthening after bilateral total knee arthroplasty: a case series

STUDY DESIGN: A case series. OBJECTIVES: The purpose of this case series was to assess the effect of high-intensity neuromuscular electrical stimulation (NMES) on quadriceps strength and voluntary activation following total knee arthroplasty (TKA). BACKGROUND: Following TKA, patients exhibit long-term weakness of the quadriceps and diminished functional capacity compared to age-matched healthy controls. The pain and swelling that results from surgery may contribute to quadriceps weakness. The use of high-intensity NMES has previously been shown to be effective in quickly restoring quadriceps strength in patients with weakness after surgery. METHODS AND MEASURES: All patients were treated for 6 weeks, 2 to 3 visits per week, in outpatient rehabilitation. Five patients (NMES group) participated in a voluntary exercise program for both knees and NMES for the weaker knee. Three patients (exercise group) participated in a voluntary exercise program for both knees without NMES. For each treatment session, 10 isometric electrically elicited muscle contractions were administered at maximally tolerated doses to the initially weaker leg of the NMES group. Quadriceps strength and muscle activation were repeatedly assessed up to 6 months after surgery using burst superimposition techniques. RESULTS: At 6 months, the weak NMES-treated legs of 4 of 5 patients in the NMES group had surpassed the strength of the contralateral leg. In contrast, none of the weak legs in the exercise group were stronger than the contralateral leg at 6 months. Changes in quadriceps muscle activation mirrored the changes exhibited in strength. CONCLUSION: When NMES was added to a voluntary exercise program, deficits in quadriceps muscle strength and activation resolved quickly after TKA.     

The use of neuromuscular electrical stimulation to improve activation deficits in a patient with chronic quadriceps strength impairments following total knee arthroplasty

STUDY DESIGN: Case report. BACKGROUND: Long-term deficits in quadriceps femoris muscle strength and impaired muscle activation are common among individuals with total knee arthroplasty (TKA). Failure to address strength-related impairments results in poor surgical and functional outcomes, which may accelerate the progression of osteoarthritis in other lower extremity joints. The purpose of the current case report was to implement a neuromuscular electrical stimulation (NMES) treatment protocol in conjunction with an intense weight-training program, with the aim of reversing persistent quadriceps muscle impairments after TKA. CASE DESCRIPTION: The patient was a 62-year-old male cyclist 12 months following simultaneous, bilateral TKA with impairments in left quadriceps strength and volitional muscle activation. His left quadriceps strength was 26% weaker than his right and central activation ratio (CAR) of his left quadriceps was 13% lower than his right quadriceps CAR. NMES to the left quadriceps was implemented for 6 weeks, in addition to an intense volitional weight-training program with emphasis on unilateral lower extremity exercises. OUTCOMES: The patient demonstrated a 25% improvement in left quadriceps femoris maximal volitional force output following 16 treatments of combined NMES and volitional strength training over a 6-week period. The patient's volitional muscle activation improved from a CAR of 0.83 before treatment to 0.97 after treatment. At discharge from physical therapy and at his 18-month postoperative follow-up, the patient's left quadriceps strength was only 4% lower than his right quadriceps strength. At the 24-month follow-up, the patient's left quadriceps strength was 6% stronger than his right quadriceps strength. DISCUSSION: The patient was able to achieve symmetrical quadriceps strength and complete muscle activation following 6 weeks of NMES and volitional strength training. An intense strengthening program may have the potential to reverse persistent strength-related impairments following TKA.     

Total knee arthroplasty: muscle impairments, functional limitations, and recommended rehabilitation approaches

SYNOPSIS: The number of total knee arthroplasty (TKA) surgeries performed each year is predicted to steadily increase. Following TKA surgery, self-reported pain and function improve, though individuals are often plagued with quadriceps muscle impairments and functional limitations. Postoperative rehabilitation approaches either are not incorporated or incompletely address the muscular and functional deficits that persist following surgery. While the reason for quadriceps weakness is not well understood in this patient population, it has been suggested that a combination of muscle atrophy and neuromuscular activation deficits contribute to residual strength impairments. Failure to adequately address the chronic muscle impairments has the potential to limit the long-term functional gains that may be possible following TKA. Postoperative rehabilitation addressing quadriceps strength should mitigate these impairments and ultimately result in improved functional outcomes. The purpose of this paper is to describe these quadriceps muscle impairments and discuss how these impairments can contribute to the related functional limitations following TKA. We will also describe the current concepts in TKA rehabilitation and provide recommendations and clinical guidelines based on the current available evidence. LEVEL OF EVIDENCE: Therapy, level 5.     

Quadriceps strength and volitional activation before and after total knee arthroplasty for osteoarthritis.

INTRODUCTION: Patients with osteoarthritis (OA) of the knee have quadriceps weakness and arthrogenous muscle inhibition (AMI). While total knee arthroplasty (TKA) reliably reduces pain and improves function in patients with knee OA, quadriceps weakness persists after surgery. The purpose of this investigation was to assess contributions of AMI to quadriceps weakness before and after TKA and to assess the effect of pain on AMI. METHODS: Twenty-eight patients with unilateral, end-stage, primary knee OA were tested an average of 10 days before and 26 days after TKA. The mean age at time of operation was 63 years (range 49-82 years). Measurements on the involved and uninvolved knees were performed using the burst-superimposition technique, where supramaximal electrical stimulation is superimposed on a voluntary contraction. Knee pain during contraction was measured using a numeric rating scale. RESULTS: The involved quadriceps were significantly weaker than the uninvolved prior to TKA (p<0.05). Quadriceps strength decreased by 60% (p<0.001) and activation decreased 17% (p<0.001) after TKA. Changes in muscle activation accounted for 65% of the variability in the change in quadriceps strength (r(2)=0.65) (p<0.001). Knee pain during muscle contraction accounted for a small, but significant portion of the change in voluntary activation (r(2)=0.22) (p=0.006). DISCUSSION: Exercise regimens that emphasize strong muscle contraction and clinical tools that facilitate muscle activation like biofeedback and neuromuscular electrical stimulation may be necessary to reverse the quadriceps activation failure and weakness in the patients with knee OA that worsens after TKA. The failure of current rehabilitation regimens to directly address activation deficits within the first months after surgery may explain the persistent quadriceps weakness in patients after TKA.     

Quadriceps strength and the time course of functional recovery after total knee arthroplasty

STUDY DESIGN: Prospective study with repeated measures. OBJECTIVES: The overall goal of this investigation was to describe the time course of recovery of impairments and function after total knee arthroplasty (TKA), as well as to provide direction for rehabilitation efforts. We hypothesized that quadriceps strength would be more strongly correlated with functional performance than knee flexion range of motion (ROM) or pain at all time periods studied before and after TKA. BACKGROUND: TKA is a very common surgery, but very little is known regarding the influence of impairments on functional limitations in this population. METHODS AND MEASURES: Forty subjects who underwent unilateral TKA followed by rehabilitation, including 6 weeks of outpatient physical therapy, were studied. Testing occurred at 5 time periods: preoperatively, and at 1, 2, 3, and 6 months after surgery. Test measures included quadriceps strength, knee ROM, timed up-and-go test, timed stair-climbing test, bodily pain, and general health and knee function questionnaires. RESULTS: Subjects experienced significant worsening of knee ROM, quadriceps strength, and performance on functional tests 1 month after surgery. Quadriceps strength went through the greatest decline of all the physical measures assessed and never matched the strength of the uninvolved limb. All measures underwent significant improvements following the 1-month test. Quadriceps strength was the most highly correlated measure associated with functional performance at all testing sessions. CONCLUSIONS: Functional measures underwent an expected decline early after TKA, but recovery was more rapid than anticipated and long-term outcomes were better than previously reported in the literature. The high correlation between quadriceps strength and functional performance suggests that improved postoperative quadriceps strengthening could be important to enhance the potential benefits of TKA.     

Knee strength after total knee arthroplasty

Fifty-two knees in normal healthy subjects and 32 knees more than 2 years after total knee arthroplasty (TKA) were evaluated. Average isometric extension peak torque values in TKA patients were reduced by up to 30.7% (P=.01). Isometric flexion peak torque values in patients with TKA were, on average, 32.2% lower than those from control subjects throughout the motion arc (P=.004). Knee Society Functional Scores were positively correlated to the average isometric extension peak torque (r=0.57; P=.004) and negatively correlated to the average isometric hamstring to quadriceps (H/Q) ratio (r=-0.78, P<.0001). Relatively greater quadriceps strength was associated with a better functional score. Older TKA patients (>/=70 years) generated lower isometric extension peak torque values in terminal extension than younger TKA patients (>24.2%; P=.05). Higher body mass index (BMI) was associated with relative quadriceps weakness (r=0.44; P=.007). These results suggest that more thorough rehabilitation after TKA would improve functional outcomes.     

Neuromuscular electrical stimulation (NMES) reduces structural and functional losses of quadriceps muscle and improves health status in patients with knee osteoarthritis

Knee osteoarthritis (OA) is associated with quadriceps atrophy and weakness, so muscle strengthening is an important point in the rehabilitation process. Since pain and joint stiffness make it often difficult to use conventional strength exercises, neuromuscular electrical stimulation (NMES) may be an alternative approach for these patients. This study was aimed at (1) identifying the associations of knee OA with quadriceps muscle architecture and strength, and (2) quantifying the effects of a NMES training program on these parameters. In phase 1, 20 women with knee OA were compared with 10 healthy female, asymptomatic, age‐matched control subjects. In phase 2, 12 OA patients performed an 8‐week NMES strength training program. OA patients presented smaller vastus lateralis thickness (11.9 mm) and fascicle length (20.5%) than healthy subjects (14.1 mm; 24.5%), and also had a 23% smaller knee extensor torque compared to the control group. NMES training increased vastus lateralis thickness (from 12.6 to 14.2 mm) and fascicle length (from 19.6% to 24.6%). Additionally, NMES training increased the knee extensor torque by 8% and reduced joint pain, stiffness, and functional limitation. In conclusion, OA patients have decreased strength, muscle thickness, and fascicle length in the knee extensor musculature compared to control subjects. NMES training appears to offset the changes in quadriceps structure and function, as well as improve the health status in patients with knee OA. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 511–516, 2013     

Minimally Invasive Total Knee Arthroplasty Improves Early Knee Strength But Not Functional Performance : A Randomized Controlled Trial

A prospective, randomized investigation compared early clinical outcomes of total knee arthroplasty (TKA) using conventional or minimally invasive surgical (MIS) approaches (n = 44). Outcome measures included isometric quadriceps and hamstrings strength, quadriceps activation, functional performance, knee pain, active knee range of motion, muscle mass, the Short Form-36, and Western Ontario and McMaster University Osteoarthritis Index, assessed preoperatively and 4 and 12 weeks after TKA. Four weeks after TKA, the MIS group had greater hamstring strength (P = .02) and quadriceps strength (P = .07), which did not translate to differences in other outcomes. At 12 weeks, there were no clinically meaningful differences between groups on any measure. Although MIS may lead to faster recovery of strength in patients undergoing TKA, there was no benefit on longer-term recovery of strength or functional performance.     

Strength and voluntary activation of quadriceps femoris muscle in total knee arthroplasty with midvastus and subvastus approaches

To determine and compare the influence of 2 different approaches on quadriceps femoris muscle function in total knee arthroplasty (TKA), 20 patients (14 women, 6 men) with bilateral knee osteoarthritis underwent a 1-stage bilateral TKA. Surgical approaches (subvastus, midvastus) were performed by a random selection. Measurements of quadriceps voluntary activation and maximal voluntary contraction were estimated by a twitch interpolation technique before, 3 and 6 months after TKA. Knee pain was quantified by the Lewis Score. There was no difference between the 2 approaches at 3 and 6 months after TKA with regard to maximal voluntary contraction (P = 0.84, F = 0.041) and voluntary activation (P = .863, F = 0.031). In the subvastus group was a significantly higher knee pain until 6 months after surgery (P = .02). The subvastus approach for TKA does not provide any advantages compared with the midvastus approach with respect to the quadriceps femoris muscle strength in the early postoperative period. Furthermore, the subvastus approach caused significantly more pain postoperatively.     

Systematic Review of Three Electrical Stimulation Techniques for Rehabilitation After Total Knee Arthroplasty

Background

The comparative effectiveness of neuromuscular electrical stimulation (NMES), transcutaneous electrical nerve stimulation (TENS), and electroacupuncture (EA) for improving patient rehabilitation following total knee arthroplasty (TKA) is controversial. Therefore we conducted this systematic review to assess the available evidence.

Electromyographic analysis of quadriceps fatigue after anterior cruciate ligament reconstruction

STUDY DESIGN: Prospective, observational study. OBJECTIVES: To document changes in surface electromyographic activity during sustained maximum quadriceps contractions in patients before and 5 weeks after anterior cruciate ligament (ACL) reconstruction. BACKGROUND: Quadriceps weakness after injury and reconstruction of the ACL is well documented. The effect of weakness on muscle fatigue, however, is not well understood. METHODS AND MEASURES: Electromyographic signals were recorded from the vastus lateralis, vastus medialis, and rectus femoris muscles during 30-second maximum isometric contractions at 30 degrees, in 42 patients preoperatively and 5 weeks postoperatively. Signal amplitude was quantified by integrating the rectified signal (iEMG) for the initial and final 5 seconds and comparing the involved and uninvolved sides. Median frequency (MF) was computed from 4,096 point fast Fourier Transforms performed at the beginning and end of the 30-second contractions. RESULTS: Patients had moderate preoperative quadriceps weakness (16% deficit) and gross postoperative weakness (41% deficit). Weakness was associated with deficits in both MF and iEMG (r = 0.69-0.67). During the preoperative fatigue test, torque declined similarly on the involved and uninvolved sides (significant fatigue effect). During the postoperative fatigue tests, however, torque increased on the involved side and declined on the uninvolved side (significant side by fatigue interaction). For the initial 5 seconds, MF was lower on the involved than the uninvolved side but subsequently showed a smaller decline over 30 seconds preoperatively and postoperatively (significant side by fatigue interactions). IEMG was lower on the involved side preoperatively and postoperatively. During the fatigue tests, iEMG increased similarly in the involved and uninvolved sides both preoperatively and postoperatively. CONCLUSION: Quadriceps endurance exercises are not indicated after ACL reconstruction. Quadriceps weakness after ACL reconstruction was associated with fatigue resistance. Lower initial MF and smaller decline in MF during sustained contraction is consistent with fast-twitch fiber atrophy and explains fatigue resistance.     

Early quadriceps strength loss after total knee arthroplasty. The contributions of muscle atrophy and failure of voluntary muscle activation

BACKGROUND: While total knee arthroplasty reduces pain and provides a functional range of motion of the knee, quadriceps weakness and reduced functional capacity typically are still present one year after surgery. The purpose of the present investigation was to determine the role of failure of voluntary muscle activation and muscle atrophy in the early loss of quadriceps strength after surgery. METHODS: Twenty patients with unilateral knee osteoarthritis were tested an average of ten days before and twenty-seven days after primary total knee arthroplasty. Quadriceps strength and voluntary muscle activation were measured with use of a burst-superimposition technique in which a supramaximal burst of electrical stimulation is superimposed on a maximum voluntary isometric contraction. Maximal quadriceps cross-sectional area was assessed with use of magnetic resonance imaging. RESULTS: Postoperatively, quadriceps strength was decreased by 62%, voluntary activation was decreased by 17%, and maximal cross-sectional area was decreased by 10% in comparison with the preoperative values; these differences were significant (p < 0.01). Collectively, failure of voluntary muscle activation and atrophy explained 85% of the loss of quadriceps strength (p < 0.001). Multiple linear regression analysis revealed that failure of voluntary activation contributed nearly twice as much as atrophy did to the loss of quadriceps strength. The severity of knee pain with muscle contraction did not change significantly compared with the preoperative level (p = 0.31). Changes in knee pain during strength-testing did not account for a significant amount of the change in voluntary activation (p = 0.14). CONCLUSIONS: Patients who are managed with total knee arthroplasty have profound impairment of quadriceps strength one month after surgery. This impairment is predominantly due to failure of voluntary muscle activation, and it is also influenced, to a lesser degree, by muscle atrophy. Knee pain with muscle contraction played a surprisingly small role in the reduction of muscle activation.     

Effects of home-based resistance training and neuromuscular electrical stimulation in knee osteoarthritis: a randomized controlled trial

ABSTRACT: BACKGROUND: Quadriceps femoris muscle (QFM) weakness is a feature of knee osteoarthritis (OA) and exercise programs that strengthen this muscle group can improve function, disability and pain. Traditional supervised resistance exercise is however resource intensive and dependent on good adherence which can be challenging to achieve in patients with significant knee OA. Because of the limitations of traditional exercise programs, interest has been shown in the use of neuromuscular electrical stimulation (NMES) to strengthen the QFM. We conducted a single-blind, prospective randomized controlled study to compare the effects of home-based resistance training (RT) and NMES on patients with moderate to severe knee OA. METHODS: 41 patients aged 55 to 75 years were randomised to 6 week programs of RT, NMES or a control group receiving standard care. The primary outcome was functional capacity measured using a walk test, stair climb test and chair rise test. Additional outcomes were self-reported disability, quadriceps strength and cross-sectional area. Outcomes were assessed pre- and post-intervention and at 6 weeks post-intervention (weeks 1, 8 and 14 respectively). RESULTS: There were similar, significant improvements in functional capacity for the RT and NMES groups at week 8 compared to week 1 (p<0.001) and compared to the control group (p<0.005), and the improvements were maintained at week 14 (p<0.001). Cross sectional area of the QFM increased in both training groups (NMES: +5.4%; RT: +4.3%; p=0.404). Adherence was 91% and 83% in the NMES and RT groups respectively (p=0.324). CONCLUSIONS: Home-based NMES is an acceptable alternative to exercise therapy in the management of knee OA, producing similar improvements in functional capacity. Trial registration: Current Controlled Trials ISRCTN85231954.     

Primary total knee arthroplasty in patients receiving workers' compensation benefits.

OBJECTIVE: To determine the influence of Ontario Workplace Safety and Insurance Board (WSIB) benefits on short-term clinical outcomes of primary unilateral total knee arthroplasty (TKA). METHODS: In a retrospective matched-cohort study at a single tertiary-care arthroplasty centre in Ontario, we compared a study cohort of 38 successive primary TKA patients receiving WSIB benefits from 1998 to 2002 to 38 controls, a matched cohort of non-WSIB patients, comparing Oxford Knee Score and Knee Society Score (both clinical and functional components) as well as flexion and pain variables, preoperatively and at postoperative intervals of 6 weeks, 6 months and 1 year. At least 1 year after their surgery, all patients were asked to complete a non-validated patient satisfaction survey. The number of clinic visits related to the operation was also compared, by means of Ontario Hospital Insurance Plan billing codes for each individual. RESULTS: Preoperative measurements showed the 2 groups to be similar. At follow-up, WSIB patients had significantly higher pain scores, poorer self-perceived functional outcomes and a lower range of knee flexion than the control group. WSIB patients also required more postoperative clinic visits and were more reluctant to answer questions about functional outcome. CONCLUSIONS: Short-term outcomes of primary TKA in patients receiving WSIB benefits are inferior to those of non-WSIB patients. WSIB patients are seen more frequently for postoperative follow-up, which we would attribute to the persistence of subjective complaints after TKA.     

Strength response in human femoris muscle during 2 neuromuscular electrical stimulation programs

STUDY DESIGN: Experimental mixed repeated-measures design. OBJECTIVE: To determine the effect of 2 versus 3 neuromuscular electrical stimulation (NMES) training sessions per week on the response to strength training of the quadriceps femoris muscle. BACKGROUND: Many studies have examined the influence of training intensity (percent maximal voluntary isometric contraction [MVIC]) during NMES on the strength response of the quadriceps femoris muscle. However, no study has examined the effects of the number of NMES sessions per week on the change in strength of the quadriceps femoris. METHODS AND MEASURES: Twenty-seven healthy subjects (mean age +/- SD, 23.2 +/- 3.2 years) volunteered for the study and were randomly assigned to 1 of 3 groups; control group (no electrical stimulation); group 2 (NMES 2 times per week); and group 3 (NMES 3 times per week). Groups 2 and 3 received NMES (10 minutes per session) over a 4-week period for a total of 8 and 12 NMES training sessions, respectively. The isometric quadriceps femoris muscle force produced during NMES was monitored during each treatment minute. The MVIC force of the quadriceps femoris was assessed prior to the first week and at the start of weeks 2, 3, and 4 of the 4-week training program, with a final measurement after the fourth week (5 total measurements) for all subjects. RESULTS: Only the mean percent change in quadriceps MVIC before and after the 4 weeks of training with NMES between the control group and group 3 was significantly different (P = .021). CONCLUSIONS: Based on the electrical stimulation parameters and healthy subjects used in this study, NMES caused significant increases in the quadriceps femoris muscle strength when used for 3 training sessions per week for 4 weeks. It is possible that the use of a different electrical stimulation paradigm and/or a different patient population may result in strength gains with 1 or 2 sessions per week.     

Factors affecting the quality of life after total knee arthroplasties:a prospective study

ABSTRACT: INTRODUCTION: To prospectively describe self-reported outcomes up to 12 months after primary total knee arthroplasty (TKA), and to determine whether preoperative patients' demographic and clinical characteristic influence the quality of life (QoL) 6 weeks, 3, 6, and 12 months after TKA. METHODS: A cohort of patients with osteoarthritis undergoing primary TKA at two hospitals (university regional and metropolitan) was prospectively followed for 12 months. Patients were assessed preoperatively and at the 4 postoperative time-points, with the use of self-reported measurements of pain, physical function and depression (Western Ontario and McMaster Osteoarthritis Index [WOMAC], Knee Society Scoring system [KSS], Centre for Epidemiological Studies Depression Scale, short form [CES-D10] and visual analog scale [VAS] for pain). Clinical and socio-demographic data were also noted. General linear modelling for repeated measures was used to evaluate the effect of each independent variable in time. Differences between groups at the measurement points were tested by the independent samples t-test. RESULTS: Of the 224 eligible patients, 204 (162 females, mean age 69.2) were included in the analysis. Response rate at one year was 90%. QoL was significantly improved 12 months after TKA according to WOMAC, KSS, CES-D10 and VAS scores (P<0.001). Most of the improvement was already established by 3 months postoperatively. At 6 weeks after surgery, despite significant improvement in pain and depressive mood, the physical function remained poor. Females scored worse in terms of quality of life, both preoperatively and 6 weeks after TKA. CES-D10 score was positively correlated with WOMAC and pain VAS scores at any follow-up assessment time point (P<0.001). Age, body mass index (BMI), place of residence, level of education and social support were not significant predictors of QoL after TKA. CONCLUSIONS: Patients experienced great improvement in QoL after TKA; though, the physical function remained poor 6 weeks after surgery. Differences in QoL between genders were detected preoperatively and 6 weeks postoperatively. After that period both sexes gained the same benefits. The greatest improvement in QoL was seen within the first 3 postoperative months with smaller changes thereafter.     

A modified neuromuscular electrical stimulation protocol for quadriceps strength training following anterior cruciate ligament reconstruction

STUDY DESIGN: Randomized clinical trial, single-masked. OBJECTIVES: To determine the effectiveness of using a modified neuromuscular electrical stimulation (NMES) training program as an adjunct treatment for improving quadriceps strength and physical function in rehabilitation following anterior cruciate ligament reconstruction (ACLR). BACKGROUND: NMES training for quadriceps strengthening has previously been shown to be an effective adjunct treatment following ACLR when performed against isometric resistance using a dynamometer with the knee positioned in flexion. We developed a modified version of published NMES protocol because some patients have difficulty tolerating the existing protocol and many clinics may not have instrumented dynamometers. There is a need to determine the effectiveness of this modified protocol. METHODS AND MEASURES: Forty-three subjects who had undergone ACLR were randomly assigned to either a group that received (NMES group) or did not receive (comparison group) the NMES treatment in conjunction with their rehabilitation. Group means for quadriceps strength and self-reported measures of knee function were compared after 12 and 16 weeks of rehabilitation. The proportion of subjects in each group achieving clinical criteria to initiate ambulation without crutches, treadmill running, and agility training at selected times during rehabilitation were also compared. RESULTS: The NMES group demonstrated moderately greater quadriceps strength at 12 weeks (effect size, 0.48), and moderately higher levels of self-reported knee function at both 12 (effect size, 0.72) and 16 (effect size, 0.65) weeks of rehabilitation compared to the comparison group. A greater proportion of subjects in the NMES group achieved clinical criteria for advancing to agility training at 16 weeks. CONCLUSIONS: The modified NMES quadriceps training protocol can be a useful adjunct to ACLR rehabilitation programs, but the treatment effect is smaller than what has been reported in previous studies.     

Alteration of Muscle Function After Electrical Stimulation Bout of Knee Extensors and Flexors

The purpose was to study the effects on muscle function of an electrical stimulation bout applied unilaterally on thigh muscles in healthy male volunteers. One group (ES group, n = 10) received consecutively 100 isometric contractions of quadriceps and 100 isometric contractions of hamstrings (on-off ratio 6-6 s) induced by neuromuscular electrical stimulations (NMES). Changes in muscle torque, muscle soreness (0-10 VAS), muscle stiffness and serum creatine kinase (CK) activity were assessed before the NMES exercise (pre-ex) as well as 24h (d+1), 48h (d+2) and 120h (d+5) after the bout. A second group (control group, n = 10) were submitted to the same test battery than the ES group and with the same time-frame. The between-group comparison indicated a significant increase in VAS scores and in serum levels of CK only in the ES group. In the ES group, changes were more pronounced in hamstrings than in quadriceps and peaked at d+2 (quadriceps VAS scores = 2.20 ± 1.55 a.u. (0 at pre-ex); hamstrings VAS scores = 3.15 ± 2.14 a.u. (0 at pre-ex); hip flexion angle = 62 ± 5° (75 ± 6° at pre-ex); CK activity = 3021 ± 2693 IU·l^-1 (136 ± 50 IU·l^-1 at pre-ex)). The results of the present study suggested the occurrence of muscle damage that could have been induced by the peculiar muscle recruitment in NMES and the resulting overrated mechanical stress. The sensitivity to the damaging effects of NMES appeared higher in the hamstrings than in quadriceps muscles.

Key points

• A stimulation bout of quadriceps and hamstrings that reflects usual application of NMES, increases indirect markers of muscle damage (muscle soreness, muscle weakness and stiffness and serum CK activity).
• The occurrence of muscle damage could have been induced by the peculiar muscle recruitment in NMES and the resulting overrated mechanical stress.
• The sensitivity to the damaging effects of NMES appears higher in the hamstrings than in quadriceps muscles.

Key words: Electrical stimulation, DOMS, muscle contraction, muscle damage     

Prediction of quadriceps strength recovery after anterior cruciate ligament reconstruction with a hamstring autograft: Decision tree analysis

Background

The wide variations in patient demographics and concomitant injuries make the prediction of which patients will regain strength quickly following anterior cruciate ligament (ACL) reconstruction challenging. This study aimed to identify the dominant factor affecting quadriceps strength recovery after ACL reconstruction with a hamstring tendon autograft and to construct a predictive model for quadriceps strength recovery using decision tree analysis.