Strength training to contraction failure increases voluntary activation of the quadriceps muscle shortly after total knee arthroplasty:a cross-sectional study

OBJECTIVE: The objective of this study was to investigate voluntary activation of the quadriceps muscle during one set of knee extensions performed until contraction failure in patients shortly after total knee arthroplasty. DESIGN: This was a cross-sectional study of 24 patients with total knee arthroplasty. One set of knee extensions was performed until contraction failure, using a predetermined 10 repetition maximum loading. In the operated leg, electromyographic (EMG) activity of the lateral and medial vastus, semitendinosus, and biceps femoris muscles was recorded during the set. Muscle activity (%EMGmax) and median power frequency of the EMG power spectrum were calculated for each repetition decile (10%–100% contraction failure). RESULTS: Muscle activity increased significantly over contractions from a mean of 90.0 and 93.6 %EMGmax (lateral vastus and medial vastus, respectively) at 10% contraction failure to 99.3 and 105.5 %EMGmax at 100% contraction failure (P = 0.009 and 0.004). Median power frequency decreased significantly over contractions from a mean of 66.8 and 64.2 Hz (lateral vastus and medial vastus, respectively) at 10% contraction failure to 59.9 and 60.1 Hz at 100% contraction failure (P = 0.0006 and 0.0187). CONCLUSION: In patients shortly after total knee arthroplasty, 10 repetition maximum–loaded knee extensions performed in one set until contraction failure increases voluntary activation of the quadriceps muscle during the set. CLINICAL TRIALS: Gov-identifier: NCT01713140 to the abstract to increase trial transparency

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 < 0.0001). Similarly, one-legged squat (and sit to stand) elicited higher voluntary peak quadriceps muscle activity than leg press in machine (86.7 vs. 66.8; mean difference, 19.9 %EMGmax [95% CI, 14.8 to 25.0]; P < 0.0001). Conclusions Strength training exercises in more simple forms elicited higher voluntary peak quadriceps muscle activity than strength training exercises in machines early after TKA. Consequently, simple home-based strength training exercises using e.g. elastic bands or the patients’ own bodyweight should be considered to alleviate muscle strength losses early after TKA. Trial registration ClinicalTrials.gov identifier: NCT01708980

Knee Pain during Strength Training Shortly following Fast-Track Total Knee Arthroplasty:A Cross-Sectional Study

Loading and contraction failure (muscular exhaustion) are strength training variables known to influence neural activation of the exercising muscle in healthy subjects, which may help reduce neural inhibition of the quadriceps muscle following total knee arthroplasty (TKA). It is unknown how these exercise variables influence knee pain after TKA.To investigate the effect of loading and contraction failure on knee pain during strength training, shortly following TKA.Cross-sectional study.Consecutive sample of patients from the Copenhagen area, Denmark, receiving a TKA, between November 2012 and April 2013.Seventeen patients, no more than 3 weeks after their TKA.In a randomized order, the patients performed 1 set of 4 standardized knee extensions, using relative loads of 8, 14, and 20 repetition maximum (RM), and ended with 1 single set to contraction failure (14 RM load). The individual loadings (kilograms) were determined during a familiarization session >72 hours prior. The patients rated their knee pain during each repetition, using a numerical rating scale (0-10).Two patients were lost to follow up. Knee pain increased with increasing load (20 RM: 3.1±2.0 points, 14 RM: 3.5±1.8 points, 8 RM: 4.3±2.5 points, P = 0.006), and repetitions to contraction failure (10% failure: 3.2±1.9 points, 100% failure: 5.4±1.6 points, P<0.001). Resting knee pain 60 seconds after the final repetition (2.7±2.4 points) was not different from that recorded before strength training (2.7±1.8 points, P = 0.88).Both loading and repetitions performed to contraction failure during knee- extension strength-training, increased post-operative knee pain during strength training implemented shortly following TKA. However, only the increase in pain during repetitions to contraction failure exceeded that defined as clinically relevant, and was very short-lived.ClinicalTrials.gov NCT01729520

RAPID KNEE-EXTENSIONS TO INCREASE QUADRICEPS MUSCLE ACTIVITY IN PATIENTS WITH TOTAL KNEE ARTHROPLASTY:A RANDOMIZED CROSS-OVER STUDY

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% [10(th)-90(th) 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: