Quadriceps muscle activity during commonly used strength training exercises shortly after total knee arthroplasty: implications for home-based exercise-selection.
ABSTRACT: BACKGROUND:In the early phase after a total knee arthroplasty (TKA), patients experience multi-level weakness in the operated leg, which is caused primarily by reduced central nervous system (CNS) activation failure of the muscles - especially the knee extensors (quadriceps muscle). Whether similar levels of neuromuscular activity of the muscles in the operated leg, elicited during strength training exercises in machines, can be reached during strength training exercises in more simple forms is unknown. Many clinicians are faced with the problem of not having strength training equipment at their institution or having to prescribe simple strength training exercises for home-based training. Therefore, the purpose of this study was to determine which strength training exercises that activated the muscles in the operated leg the most after TKA. The hypothesis was that strength training exercises performed in machines would elicit higher levels of voluntary peak quadriceps and hamstring muscle activity than strength training exercises performed in more simple forms, using elastic bands or the patients' own body weight. METHODS:A cross-sectional electromyographic study investigated voluntary peak muscle activity in the operated leg during 6 different strength training exercises. Twenty-four patients, who received a TKA 4 to 8?weeks earlier, performed the exercises in a randomized order, using a pre-determined loading of 10 RM (repetition maximum). Voluntary peak muscle activity (%EMGmax) was calculated for the quadriceps and hamstring muscles for each exercise. RESULTS:Knee extensions with elastic band showed significantly higher voluntary peak quadriceps muscle activity than knee extensions in machine (93.3 vs. 74.9; mean difference, 18.3 %EMGmax [95% confidence interval (CI), 11.7 to 24.9]; P?
Project description:<h4>Background</h4>Motor imagery (MI) is effective in improving motor performance in the healthy asymptomatic adult population. However, its possible effects among older orthopaedic patients are still poorly investigated. Therefore, this study explored whether the addition of motor imagery to routine physical therapy reduces the deterioration of quadriceps muscle strength and voluntary activation (VA) as well as other variables related to motor performance in patients after total knee arthroplasty (TKA).<h4>Methods</h4>Twenty-six patients scheduled for TKA were randomized to either MI practice combined with routine physical therapy group (MIp) or to a control group receiving physical therapy alone (CON). MIp consisted of maximal voluntary isometric contraction (MViC) task: 15 min/day in the hospital, then 5 times/week in their homes for 4 weeks. MViC and VA of quadriceps muscle, knee flexion and extension range of motion, pain level, along with a Timed Up-and-Go Test (TUG) and self-reported measure of physical function (assessed using the Oxford Knee Score questionnaire [OKS]) were evaluated before (PRE) and 1 month after surgery (POST).<h4>Results</h4>Significantly better rehabilitation outcomes were evident on the operated leg for the MIp group compared to CON: at POST, the MIp showed lower strength decrease (p = 0.012, ?<sup>2</sup> = 0.237) and unaltered VA, significantly greater than CON (p = 0.014, ?<sup>2</sup> = 0.227). There were no significant differences in knee flexion and extension range of motion and pain level (p > 0.05). Further, MIp patients performed better in TUG (p < 0.001, ?<sup>2</sup> = 0.471) and reported better OKS scores (p = 0.005, ?<sup>2</sup> = 0.280). The non-operated leg showed no significant differences in any outcomes at POST (all p > 0.05). In addition, multiple linear regression analysis showed that failure of voluntary activation explained 47% of the quadriceps muscle strength loss, with no significant difference in perceived level of pain.<h4>Conclusion</h4>MI practice, when added to physical therapy, improves both objective and subjective measures of patients' physical function after TKA, and facilitates transfer of MI strength task on functional mobility.<h4>Trial registration</h4>Retrospectively registered on ClinicalTrials.gov NCT03684148.
Project description:Resistance-training of the lower limbs can be performed using exercises moving one (single-joint exercises) or several joints (multi-joint exercises). This study compared the effects of training one multi-joint exercise (leg press) or two single-joint exercises (leg extension and kickback) on dynamic and isometric strength and the transferability of dynamic strength between exercises. Fifty-three physically active women were randomized to a multi-joint (MJ) training group (age = 21.95±0.82 years, mass = 64.85±5.76 kg, height = 167.35±2.47 cm; n = 20), single-joint (SJ) training group (age = 22.56±1.66 years, mass = 64.85±5.76 kg, height = 165.94±2.84 cm; n = 18), or a control (CON) group (age = 21.27±0.68 years, mass = 68.43±4.86 kg, height = 168.63±2.84 cm; n = 15). The training groups participated in an 8-week supervised single- or multi-joint lower limb training consisting of 18 sessions. Pre- and post-training, six repetitions maximum (RM) and maximal voluntary isometric contraction in the three exercises were assessed, along with electromyography of the superficial quadriceps muscles. Improvements in all dynamic exercises were greatest after training the specific exercises (ES = 1.26-2.14, P<0.001-0.025) and all were greater in the training groups than in the CON group (ES = 1.43-3.31, P<0.001-0.021). The SJ group improved 6RM in leg extension and kickback more than leg press (ES = 1.51 and 2.04, respectively, P<0.001), whereas the MJ group improved leg press 6RM more than kickback (ES = 1.10, P = 0.002). However, leg press and leg extension strength improved similarly in the MJ group (ES = 0.54, P = 0.072). All strength and electromyographic measures remained unchanged in the CON group (ES = 0.00-0.44, P = 0.412-0.966). Improved dynamic strength in leg press, kickback and leg extension is best attained by training the specific exercises, but both training modalities can improve strength across all exercises.
Project description:BACKGROUND:Developing alternative exercise programmes that can alleviate certain barriers to exercise such as psychological, environmental or socio-economical barriers, but provide similar physiological benefits e.g. increases in muscle mass and strength, is of grave importance. This pilot study aimed to assess the efficacy of an unsupervised, 4-week, whole-body home-based exercise training (HBET) programme, incorporated into daily living activities, on skeletal muscle mass, power and strength. METHODS:Twelve healthy older volunteers (63±3 years, 7 men: 5 women, BMI: 29±1 kg/m²) carried out the 4-week "lifestyle-integrated" HBET of 8 exercises, 3x12 repetitions each, every day. Before and after HBET, a number of physical function tests were carried out: unilateral leg extension 1-RM (one- repetition maximum), MVC (maximal voluntary contraction) leg extension, lower leg muscle power (via Nottingham Power Rig), handgrip strength and SPPBT (short physical performance battery test). A D 3-Creatine method was used for assessment of whole-body skeletal muscle mass, and ultrasound was used to measure the quadriceps cross-sectional area (CSA) and vastus lateralis muscle thickness. RESULTS:Four weeks HBET elicited significant (p<0.05) improvements in leg muscle power (276.7±38.5 vs. 323.4±43.4 W), maximal voluntary contraction (60°: 154.2±18.4 vs. 168.8±15.2 Nm, 90°: 152.1±10.5 vs. 159.1±11.4 Nm) and quadriceps CSA (57.5±5.4 vs. 59.0±5.3 cm 2), with a trend for an increase in leg strength (1-RM: 45.7±5.9 vs. 49.6±6.0 kg, P=0.08). This was despite there being no significant differences in whole-body skeletal muscle mass, as assessed via D 3-Creatine. CONCLUSIONS:This study demonstrates that increases in multiple aspects of muscle function can be achieved in older adults with just 4-weeks of "lifestyle-integrated" HBET, with a cost-effective means. This training mode may prove to be a beneficial alternative for maintaining and/or improving muscle mass and function in older adults.
Project description:Neuromuscular electrical stimulation (NMES) can facilitate the recovery of quadriceps muscle strength after total knee arthroplasty (TKA), yet the optimal intensity (dosage) of NMES and its effect on strength after TKA have yet to be determined.The primary objective of this study was to determine whether the intensity of NMES application was related to the recovery of quadriceps muscle strength early after TKA. A secondary objective was to quantify quadriceps muscle fatigue and activation immediately after NMES to guide decisions about the timing of NMES during rehabilitation sessions.This study was an observational experimental investigation.Data were collected from 30 people who were 50 to 85 years of age and who received NMES after TKA. These people participated in a randomized controlled trial in which they received either standard rehabilitation or standard rehabilitation plus NMES to the quadriceps muscle to mitigate strength loss. For the NMES intervention group, NMES was applied 2 times per day at the maximal tolerable intensity for 15 contractions beginning 48 hours after surgery over the first 6 weeks after TKA. Neuromuscular electrical stimulation training intensity and quadriceps muscle strength and activation were assessed before surgery and 3.5 and 6.5 weeks after TKA.At 3.5 weeks, there was a significant association between NMES training intensity and a change in quadriceps muscle strength (R(2)=.68) and activation (R(2)=.22). At 6.5 weeks, NMES training intensity was related to a change in strength (R(2)=.25) but not to a change in activation (R(2)=.00). Furthermore, quadriceps muscle fatigue occurred during NMES sessions at 3.5 and 6.5 weeks, whereas quadriceps muscle activation did not change.Some participants reached the maximal stimulator output during at least 1 treatment session and might have tolerated more stimulation.Higher NMES training intensities were associated with greater quadriceps muscle strength and activation after TKA.
Project description:Patients six months after total knee arthroplasty (TKA) demonstrate movement asymmetries and functional deficits, which may be related to poor functional performance. The aims of this study were to 1) compare biomechanical variables between subjects 6 months after TKA and an age-matched healthy control group during a step up and over task and 2) determine the relationship between quadriceps strength, movement patterns and stair climbing performance.Twenty patients 6 months following unilateral TKA and twenty healthy controls were enrolled. Participants completed questionnaires, isometric quadriceps strength testing and performance based tests to quantify functional performance. Motion analysis was performed during a step up and over task. Functional and biomechanical variables were analyzed using a 2 × 2 ANOVA. The symmetry ratios (operated/non-operated limb*100) for biomechanical variables were analyzed using independent t-tests. Pearson correlations were performed to determine the relationships between biomechanical variables, strength and stair climbing performance.In the TKA group, subjects had lower peak moments, power and sagittal plane excursion in the operated knee compared to the contralateral knee (P<0.05), while the hip on the operated side had greater power generation (P = 0.014). Compared to the control group, all symmetry ratios were significantly lower in the surgical group (P < 0.05). Stair climbing time was correlated with quadriceps strength of the operated limb (R = -0.762, P < 0.001).Individuals 6 months after TKA had worse performance with respect to biomechanics, quadriceps strength, and performance-based tests. Biomechanical asymmetries after TKA reduce the demand on the operated knee and increase reliance on the contralateral limb and ipsilateral hip.
Project description:OBJECTIVE:To compare the effects of conventional (constant load) eccentric training and isokinetic eccentric training on quadriceps muscle mass, strength and functional performance in recreational athletes following anterior cruciate ligament (ACL) reconstruction. METHODS:Thirty recreational male athletes (25 years old) undergoing ACL reconstruction received a standard rehabilitation program. Volunteers were randomized to conventional group (CG; n?=?15) or isokinetic group (IG; n?=?15) to be engaged in a 6-week (2 sessions/week) quadriceps eccentric training program at the extensor chair or at the isokinetic dynamometer, respectively. Assessments of quadriceps muscle mass (through magnetic resonance imaging), strength (through isokinetic dynamometry) and self-aware functionality (through questionnaire) were performed before and after the training programs. Single leg hop test performance was assessed only at post-training evaluation. RESULTS:IG had significantly higher improvements than CG (p?<?0.05) for all muscle mass outcomes (+17-23% vs. +5-9%), as well as for isometric (+34% vs. +20%) and eccentric (+85% vs. +23%) peak torques. There was no between-group difference (p?>?0.05) for concentric peak torque, Lysholm score, and single leg hop test. CONCLUSION:Isokinetic eccentric training promotes greater responses than conventional eccentric training on quadriceps muscle mass and strength of recreational athletes following ACL reconstruction.
Project description:The present study determined the effects of muscular endurance strength training on maximum strength and power, functional capacity, muscle activation and hypertrophy in older men and women. Eighty-one men and women acted as an intervention group while 22 acted as non-training controls (age range 64-75 y). Intervention training included super-sets (i.e., paired exercises, immediately performing the second exercises following completion of the first) with short rest intervals (30-60 s between sets) at an intensity of 50-60% one-repetition maximum (1-RM) for 15-20 repetitions. Concentric leg press actions measured maximum strength (1-RM) and concentric peak power. Functional capacity was assessed by maximum speed walking tests (i.e., forward walk, backward walk, timed-up-and-go, and stair climb tests). Quadriceps muscle activation was assessed by surface electromyogram and twitch interpolation technique. Vastus lateralis cross-sectional area was measured by panoramic ultrasound. Compared to control, the intervention groups increased maximum strength (1-RM; men: 10 ± 7% vs. 2 ± 3%, women: 14 ± 9% vs. 1 ± 6% both P < 0.01) and vastus lateralis cross-sectional area (men: 6 ± 7% vs. -3 ± 6%, women: 10 ± 10% vs. 0 ± 4% both P < 0.05). But there were no between-group differences in peak power, muscle activation or functional capacity (e.g., stair climb; men: -5 ± 7% vs. -4 ± 3%, women: -5 ± 6% vs. -2 ± 5% both P > 0.05). While benefits occurred during muscular endurance strength training, specific stimuli are probably needed to target all aspects of age-related health.
Project description:BACKGROUND:Inhibition of the quadriceps muscle and reduced knee-extension strength is common shortly following total knee arthroplasty (weeks to months), due to reduced voluntary activation of the quadriceps muscle. In healthy subjects, strength training with heavy loads is known to increase agonist muscle activity, especially if the exercise is conducted using rapid muscle contractions. PURPOSE:The purpose of this study was to examine if patients with total knee arthroplasty could perform rapid knee-extensions using a 10 RM load four to eight weeks after surgery, and the degree to which rapid knee-extensions were associated with greater voluntary quadriceps muscle activity during an experimental strength training session, compared to that elicited using slow knee-extensions. STUDY DESIGN:A randomized cross-over study. METHODS:Twenty-four patients (age 66.5) 4-8 weeks post total knee arthroplasty randomly performed one set of five rapid, and one set of five slow knee-extensions with the operated leg, using a load of their 10 repetition maximum, while surface electromyography recordings were obtained from the vastus medialis and lateralis of the quadriceps muscle. RESULTS:Data from 23 of the 24 included patients were analyzed. Muscle activity was significantly higher during rapid knee-extensions (120.2% [10th-90th percentile: 98.3-149.1]) compared to slow knee-extensions (106.0% [88.8-140.8]) for the vastus lateralis (p<0.01), but not for the vastus medialis (120.8% [90.4-134.0]) and (121.8% [93.0-133.0]) (p = 0.17), respectively. Slow and rapid knee-extensions were performed at a median angular velocity of 19.7 degrees/sec (13.7-24.4) and 51.4 degrees/sec (28.9-63.1), respectively. CONCLUSION:Four to eight weeks after their total knee arthroplasty, the patients in the present study were able to conduct rapid knee-extensions according to the experimental protocol with an approximately doubled angular velocity compared to slow knee-extensions. This was associated with increased muscle activity in the vastus lateralis when compared to slow knee-extensions, but not in the vastus medialis. Whether this significant, although relatively small, difference in vastus lateralis muscle activity has any clinical relevance needs further study. LEVEL OF EVIDENCE:3.
Project description:We investigated molecular and cellular parameters which set metabolic and mechanical functioning of knee extensor muscles in the operated and contralateral control leg of 9 patients with a chronically insufficient anterior cruciate ligament (ACL; 26.6 ± 8.3 years, 8 males, 1 female) after open reconstructive surgery (week 0), after ambulant physiotherapy under cast immobilization (week 9), succeeding rehabilitation training (up to week 26), and subsequent voluntary physical activity (week 260). Clinical indices of knee function in the operated leg were improved at 52 weeks and remained at a comparable level at week 260. CSA of the quadriceps (-18%), MCSA of muscle fibers (-24%), and capillary-to-fiber ratio (-24%) in m. vastus lateralis from the ACL insufficient leg were lower at week 0 than reference values in the contralateral leg at week 260. Slow type fiber percentage (-35%) and mitochondrial volume density (-39%) were reduced in m. vastus lateralis from the operated leg at weeks 9 and 26. Composition alterations in the operated leg exceeded those in the contralateral leg and, with the exception of the volume density of subsarcolemmal mitochondria, returned to the reference levels at week 260. Leg-specific deterioration of metabolic characteristics in the vasti from the operated leg was reflected by the down-regulation of mitochondrial respiration complex I-III markers (-41-57%) at week 9. After rehabilitation training at week 26, the specific Y397 phosphorylation of focal adhesion kinase (FAK), which is a proxy for mechano-regulation, was elevated by 71% in the operated leg but not in the contralateral leg, which had performed strengthening type exercise during ambulant physiotherapy. Total FAK protein and Y397 phosphorylation levels were lowered in both legs at week 26 resulting in positive correlations with mitochondrial volume densities and mitochondrial protein levels. The findings emphasize that a loss of mechanical and metabolic characteristics in knee extensor muscle remains detectable years after untreated ACL rupture, which may be aggravated in the post-operative phase by the deterioration of slow-oxidative characteristics after reconstruction due to insufficient load-bearing muscle activity. The reestablishment of muscle composition subsequent to years of voluntary physical activity reinforces that slow-to-fast fiber transformation is reversible in humans.
Project description:<h4>Objectives</h4>Physical therapy is standard care for mechanically ventilated patients, but there is no evidence, using nonvolitional, objective measurements, that physical therapy increases muscle strength in this population. The present study tested the hypothesis that 2 weeks of standard, conventional physical therapy provided at a ventilator weaning facility would increase quadriceps strength in mechanically ventilated patients.<h4>Design</h4>Prospective observational study.<h4>Setting</h4>Ventilator weaning unit.<h4>Patients</h4>Patients who were transferred from an acute care hospital because of failure to wean from mechanical ventilation and who were receiving physical therapy as prescribed by facility staff.<h4>Interventions</h4>None.<h4>Measurements and main results</h4>We employed a novel, nonvolitional objective technique, quadriceps twitch force generation in response to femoral nerve magnetic stimulation, to assess leg strength before and after 2 weeks of conventional physical therapy. The duration and specific exercises provided to patients were also recorded. In a subset of patients, we measured muscle activation intensity using wireless electromyogram recordings. Indices of respiratory function (maximum inspiratory pressure generation and the rapid shallow breathing index) were also assessed. Patients' responses to 2 weeks of physical therapy were poor; on average, quadriceps twitch fell by -1.02 ± 0.71 Newtons. Neither physical therapy duration nor specific forms of exercise were identified to positively impact quadriceps twitch. Electromyogram recordings indicated that during training, muscle activation was poor. Consequently, therapists spent substantial time performing exercises that elicited little muscle activation. Physical therapy did not improve respiratory function.<h4>Conclusions</h4>Standard physical therapy delivered in a ventilator weaning facility failed to improve quadriceps leg strength in a majority of mechanically ventilated patients. The fact that mechanically ventilated patients fail to achieve high levels of muscle activation during physical therapy provides a potential explanation as to why physical therapy may often be ineffective. We speculate that use of novel methods which increase muscle activation during exercise may improve responses of mechanically ventilated patients to physical therapy.