Knee Extension Machine Research Articles

Poster 323: Factors Impacting Return to Sport Timing Following ACL Reconstruction

Objectives: Forty-one percent of sports injuries are knee injuries. One-fifth of knee injuries involve the anterior cruciate ligament (ACL). The high incidence of ACL injuries results in approximately 129,000 ACL reconstructions in the United States each year. Timing of return to sport (RTS) after ACL reconstruction (ACLR) depends on clearance by the medical team, patients meeting objective RTS criteria, and patient selected timing. A criterion-based approach to RTS commonly includes measurements of quadriceps strength, hop performance, and subjective knee function to guide the decision-making of orthopedic surgeons and physical therapists regarding patient readiness and safety to RTS. Therefore, the purpose of this study was to assess patient-related predictors (age, sex, graft type, psychological readiness, and the duration of physical therapy) of time to pass RTS criteria. We hypothesized that patients with more positive psychological readiness, those who were still completing physical therapy, and male patients would pass RTS testing at earlier time points, while graft type and age would have no effect. Methods: Fifty-four participants between the ages of 10 and 25 years and within 5 to 15 months of ACL reconstruction who were planning to return to at least 50 hours per year of cutting and pivoting activities were included. Patients with a previous history of surgery to either knee or concomitant posterior cruciate ligament reconstruction were excluded from the study. Participants completed clinic testing when RTS was being planned. Testing included unilateral quadriceps strength in each limb (isometric at 90° knee flexion using a crane scale and 1-repetition maximum using a knee extension machine), 4 single-legged hop tests (single, crossover and triple hop for distance; 6-meter timed hop), and self-reported knee function (International Knee Documentation Committee Subjective Knee Form 2000 [IKDC], Global Rating Scale). In order to pass, participants needed scores of at least 90% symmetry for both quadriceps strength measures and all 4 single-legged hop tests as well as 90% on the IKDC and Global Rating Scale. Participants repeated clinic testing until they passed the entire testing battery in a single session. On the day of passing all RTS criteria, psychological readiness was assessed using the ACL Return to Sport after Injury (ACL-RSI) survey. The ACL-RSI is a valid and reliable outcome tool that assesses the participant’s emotional wellbeing, confidence in performance, and risk appraisal. An additional survey question was used to identify if participants were still participating in physical therapy (PT) at the time of passing RTS testing or when they had finished working with a physical therapist. PT was categorized as either a) <6 months of PT, b) 6-8 months of PT, or c) >8 months of PT or still currently in PT. Multivariate linear regression was used to assess the association between age, sex, graft type, ACL-RSI score, and duration of PT on the time to passing RTS testing after ACL reconstruction. An alpha level of p<0.05 was set a priori. Results: The mean age of the participants in this study was 17.3±2.7 years and 50% were female. Graft type and duration of physical therapy data are presented in Table 1. The mean time for passing all components of the RTS test battery was 10.3 ±2.6 months. At the time of passing RTS testing, the mean ACL-RSI score was 86.1±14.2%. Age, sex, graft type, ACL-RSI scores and duration of PT accounted for 44.5% of the variation in the time to pass RTS testing (p<0.001). Sex (β=-0.426; p<0.001), graft type (β=0.340; p=0.008), and age (β=0.194; p=0.111) were the strongest predictors of time to pass RTS testing with younger age correlating with shorter RTS times. Sex (Male: 8.6±3.1 months; Female: 11.1±3.5 months) and graft type (Hamstring: 7.7± 3.9 months; Quadriceps Tendon: 10.8±2.7 months; Patellar Tendon: 11.5±2.6 months; Allografts and IT band: 7.2±1.4 months), were significant predictors of time to pass RTS criteria while PT duration and ACL-RSI were not significant predictors. Conclusions: Female patients and patients with a patellar tendon or quadriceps graft took longer to meet objective RTS criteria after ACL reconstruction. Education with female patients and those with quadriceps and patellar tendon autografts may be required to establish realistic expectations for RTS readiness. While many factors impact graft choice, time to pass RTS criteria is an additional consideration for surgeons and patients. Additionally, previous studies have shown that male patients are more likely to experience graft retear following ACLR than females. This finding could be the result of male patients returning to sport earlier than females, giving the graft less time to heal. [Table: see text]

The Effect of Resistance Training With Electrical Muscle Stimulation on Atrogin-1 and Muscle Ring Finger-1 in Elite Male Athletes After Anterior Cruciate Ligament Surgery

Background and Aims The cellular mechanisms preventing muscle atrophy after Anterior Cruciate Ligament (ACL) regeneration are not well understood. The aim of the present study was to evaluate the effect of resistance training combined with electrical muscle stimulation on serum levels of atrogin-1 and muscle RING finger-1 (MuRF1) in elite athletes following ACL surgery. Methods Among the elite athletes of Razavi Khorasan Province, 20 athletes voluntarily participated in the study and were divided into two groups (ten cases each), including 1) resistance training- electrical muscle stimulation (RT-EMS), and 2) resistance training (RT). The subjects in both groups performed 2-4 sets of resistance exercises (knee extension machine, squat, and knee flexion machines) at an intensity of 30-70% of ten repetitions for 12 weeks. The subjects in the RT-EMS group performed the exercises in combination with electrical stimulation at 35-70 Hz. Blood samples were collected from all subjects before and 48 hours after the last training session to measure atrogin-1 and MuRF1 levels. Analysis of covariance (ANCOVA) and paired t-test were used to compare between- and within-group changes, respectively, and a P<0.05 was considered significant. Results The results showed that 12 weeks of resistance training- electrical muscle stimulation significantly decreased serum levels of atrogin 1 (P=0.013) and MuRF1 (P=0.008) in the post-test compared to the pre-test. In addition, the between-groups comparison showed a significant difference in atrogin 1 levels between the RT-EMS and RT groups (P=0.047). Conclusion It can be suggested that resistance training in combination with electrical muscle stimulation is associated with lower levels of muscular atrophy proteins, such as atrogin-1 and MuRF1, and therefore, can be more effective than resistance training alone.

Does the Muscle Action Duration Induce Different Regional Muscle Hypertrophy in Matched Resistance Training Protocols?

Diniz, RCR, Tourino, FD, Lacerda, LT, Martins-Costa, HC, Lanza, MB, Lima, FV, and Chagas, MH. Does the muscle action duration induce different regional muscle hypertrophy in matched resistance training protocols? J Strength Cond Res 36(9): 2371-2380, 2022-The manipulation of the muscle action duration (MAD) can influence the instantaneous torque along the range of motion, which can lead to adaptations of regional muscle hypertrophy. The aim of this study was to compare the effects of matched resistance training (RT) on the knee extension machine with different MAD in the cross-sectional area (CSA) responses within the quadriceps femoris (QF) and its muscles. Forty-four subjects were allocated into a control and 3 experimental groups. For a period of 10 weeks, subjects in the experimental groups performed the training protocols that were different only by the MAD: group 5c1e (5s concentric action [CON] and 1s eccentric action [ECC]; group 3c3e (3s CON and 3s ECC) and group 1c5e (1s CON and 5s ECC). Magnetic resonance imaging was performed (before and after the intervention) to determine the relative change (%) in CSA of the QF muscles along proximal (30%), middle (50%), and distal regions (70% distal of the femur). The change in CSA of the rectus femoris at the middle region are greater in 5c1e (6.8 ± 6.5%) and 1c5e (7.4 ± 6.0%) groups than 3c3e (3.4 ± 6.6%) and control groups (0.2 ± 1.8%). In addition, vastus lateralis at the distal region (5c1e = 15.9 ± 11.8%; 1c5e = 14.4 ± 10.0%) presenting greater increases in change of CSA than the others vastus only 5c1e (vastus lateralis [VI] = 5.0 ± 4.7%; vastus medialis [VM] = 4.2 ± 3.2%) and 1c5e groups (VI = 4.7 ± 3.6%; VM = 3.4 ± 3.1%). In conclusion, this study showed that matched RT protocols with different MAD resulted in different region-specific muscle hypertrophic across the individual muscles of QF.

The Effects of a Preconditioning Rolling Session on Subsequent Eccentric Exercise-Induced Muscle Damage.

West, JT, Miller, WM, Jeon, S, and Ye, X. The effects of a preconditioning rolling session on subsequent eccentric exercise-induced muscle damage. J Strength Cond Res 34(8): 2112-2119, 2020-The aim of this study was to examine the effects of a preexercise unilateral quadriceps muscle rolling intervention on subsequent ipsilateral (IPSI) or contralateral (CTRA) knee extension eccentric exercise-induced muscle damage. Twenty-seven healthy volunteers (14 men) underwent an eccentric exercise protocol (6 sets of 10 repetitions with 75% of the maximal isometric strength) with a single-leg knee extension machine. Before the eccentric exercise, the subjects were randomly assigned to either (a) IPSI group: rolling the ipsilateral knee extensor muscles, (b) CTRA: rolling the contralateral muscles, or (c) Control: sitting for 6 minutes (same duration as the rolling intervention protocol) relaxed. The muscle soreness, passive knee extension range of motion, and knee extension isometric strength were measured before, immediately, 24 hours, and 48 hours after exercise. The magnitudes of the range of motion decrement were attenuated in both the IPSI (p = 0.031) and CTRA (p = 0.014) groups 24 hours after the eccentric exercise, when compared with the control. Isometric strength (p = 0.783) and muscle soreness (p = 0.586) responses were not significantly different among the 3 groups (time points and sexes merged). Additionally, women displayed an overall faster recovery than men in isometric strength (p = 0.001) and muscle soreness (p = 0.024), evidenced by the measurements at 48 hours after exercise. Our study suggests that unilateral quadriceps rolling intervention before high-intensity muscle-damaging exercise has a beneficial effect on maintaining range of motion in both the ipsilateral and contralateral muscles.

Ability of Isokinetic Dynamometer to Predict Isotonic Knee Extension 1-Repetition Maximum

Resistance training exercise prescription is often based on exercises performed at a percentage of a 1-repetition maximum (1RM). Following knee injury, there is no consensus when a patient can safely perform 1RM testing. Resistance training programs require the use of higher loads, and loads used in knee injury rehabilitation may be too low to elicit gains in strength and power. A maximum isometric contraction can safely be performed during early stages of knee rehabilitation and has potential to predict an isotonic knee extension 1RM. To determine whether a 1RM on an isotonic knee extension machine can be predicted from isometric peak torque measurements. Descriptive laboratory study. University research laboratory. A total of 20 (12 males and 8 females) healthy, physically active adults. An isokinetic dynamometer was used to determine isometric peak torque (in N·m). 1RM testing was performed on a knee extension machine. Linear regression was used to develop a prediction equation, and Bland-Altman plots with limits of agreement calculations were used to validate the equation. There was a significant correlation (P < .001, r = .926) between peak torque (283.0 [22.6]N·m) and the knee extension 1RM (69.1 [22.6]kg). The prediction equation overestimated the loads (2.3 [9.1]kg; 95% confidence interval, -15.6 to 20.1kg). The results show that isometric peak torque values obtained on an isokinetic dynamometer can be used to estimate 1RM values for isotonic knee extension. Although the prediction equation tends to overestimate loads, the relatively wide confidence intervals indicate that results should be viewed with caution.

Effects of training volume on lower-body muscle strength in untrained young men: a contralateral control study

Aims: The purpose of this study was to examine the effects of training volume (1 vs. 3 sets) on lower-body muscle strength in untrained young men. Methodsː Eighteen untrained young men were recruited and their legs were trained with 1 or 3 sets (in a contralateral design) for 6 weeks, using a knee extension machine. Isokinetic peak torque and one repetition maximum (1RM) were assessed at pre- and post-training. Resultsː There was a similar improvement in the 1RM strength (1SET: +14.8% vs. 3SET: 16.3%, P > 0.05) and peak torque (1SET: +8.1% vs. 3SET: 9.3%, P > 0.05) for both conditions from pre- to post-training. The effect size (ES) for the change in 1RM was moderate for both conditions (1SET: 1.39 vs. 3SET: 1.41), and peak torque was trivial and small for 1SET (0.47) and 3SET (0.55), respectively. Additionally, there were no significant (P > 0.05) differences in the dietary intakes from pre- to post-training. Conclusionsː Our results indicate that 1 set is as effective as 3 sets for increasing lower-body muscle strength after a short-term RT period (6 weeks) in untrained young men.

Comparative performance of isometric and isotonic quadriceps strength testing in total knee arthroplasty

BackgroundEarly quadriceps muscle strength assessment after a total knee arthroplasty (TKA) provides timely information on progress, but little is known about the pain profile and predictive validity associated with common clinical muscle strength tests. This study aimed to, in patients with a recent TKA, examine the associations of isometric and isotonic quadriceps strength with gait speed, accounting for knee pain experienced during testing. MethodsA sample of 76 patients (mean age 68 years; 46 women) with a recent TKA (median, 1.5 months) participated. Quadriceps strength was measured on both limbs using a knee extension machine. Isotonic strength was assessed with a one-repetition maximum test. Isometric strength was measured at 40° and 70° of knee flexion using a custom-built load cell. To allow for valid comparisons between the tests, quadriceps strength symmetry ratios were calculated. Knee pain during testing was measured using an 11-point pain scale. Fast gait speed was measured using the 10-m walk test. ResultsCompared with isotonic test, quadriceps strength ratio was higher for the 40° flexion isometric test (P = 0.01), and this difference may be explained by the lower knee pain intensity elicited during the isometric tests (P's < 0.001). All strength measures were closely associated with fast gait speed after adjustment for knee pain and covariates (P's < 0.001). ConclusionsEarly in the post-TKA period, isometric and isotonic strength tests may be used to assess quadriceps strength but these tests are not interchangeable. Isometric quadriceps testing may be preferable to isotonic testing as it was associated with lower knee pain intensity.

Sports Physical Therapy Section Poster Presentations (Abstracts SPO1-SPO166).

These abstracts are presented here as prepared by the authors. The accuracy and content of each abstract remain the responsibility of the authors. In the identification number above each abstract, SPO designates a Sports Physical Therapy Section poster presentation. J Orthop Sports Phys Ther 2018;48(1):A203-A276. doi:10.2519/jospt.2018.48.1.A203.

Effectiveness of TENS Unit on Quadriceps Muscular Endurance During Weight Bearing Exercise

PURPOSE: To examine the effectiveness of TENS use on quadriceps muscular endurance during weight bearing exercise for healthy populations. METHODS: Fifteen male and fifteen female volunteers (Fifteen male and fifteen female volunteers (N = 30; AGE = 21.6 ± 3.0 yrs; HT = 172.1 ± 9.0 cm; BM = 72.8 ± 12.6 kg) provided informed consent prior to participation. In Session 1, participants height, body mass, and one repetition maximum (1-RM) for non-dominant quadriceps was assessed using a knee extension machine. In Session 2, participant’s baseline maximum repetitions of non-dominant knee extensions at 40% of 1-RM was attained. Participants were then randomly selected into three groups: EXP: TENS unit with TENS activation; CON: no TENS unit with no TENS activation; PLA: TENS unit with no TENS activation. In Session 3, EXP, CON, and PLA participants performed maximum repetitions of non-dominant leg at 40% of 1-RM on the knee extension machine. Participant characteristics were examined using ANOVA for continuous and chi-squared for categorical variables. Analysis of covariance (ANCOVA) was used to compare the change in repetitions from session 2 and session 3 between each treatment group, while controlling for baseline repetitions. Tukey Post-Hoc test was used to determine the location of significance between treatment groups. RESULTS: No significant differences were found between groups in number of repetitions achieved at baseline (p=0.703). The EXP group were able to perform significantly more repetitions (change=2.40 ± 3.27) than participants in either the CON group (change=-1.30 ± 2.31) (p=0.001) or PLA group (change=-0.20 ± 1.14) (p=0.011) when controlling for baseline repetitions. CONCLUSION: The use of TENS during weight-bearing quadriceps muscular endurance activity significantly improves the number of repetitions performed by healthy populations.

AN INEXPENSIVE METHOD TO MEASURE KNEE EXTENSORS' POWER IN OLDER ADULTS

Introduction: Measuring knee extensors' power in elderly population is crucial but not accessible to everyone. Objective: To provide a method to calculate knee extensors' power in a conventional knee extension machine. Method: Thirteen sedentary elderly women (69.3±4.1 years) performed six knee extensions as fast as possible. Kinematic data, an anthropometric model and Newtonian mechanics was used to write movement equations that allowed calculating knee extensors' power and work. The reliability was assessed by variables' coefficient of variation, intraclass correlation coefficient and standard measurement error. Results: Knee extensors' peak power and work values obtained were in agreement with the literature. We found high intraclass ICC values for both variables (93% and 97%, respectively) and low normalized SEM (10.13% and 2.09%, respectively). Conclusion: We provided an inexpensive method to assess a major physical dysfunction indicator in older adults which can also be used to evaluate the progression of an intervention.

The associations between quadriceps muscle strength, power, and knee joint mechanics in knee osteoarthritis: A cross-sectional study

BackgroundAbnormal knee joint mechanics have been implicated in the pathogenesis and progression of knee osteoarthritis. Deficits in muscle function (i.e., strength and power) may contribute to abnormal knee joint loading. The associations between quadriceps strength, power and knee joint mechanics remain unclear in knee osteoarthritis. MethodsThree-dimensional motion analysis was used to collect peak knee joint angles and moments during the first 50% of stance phase of gait in 33 participants with knee osteoarthritis. Quadriceps strength and power were assessed using a knee extension machine. Strength was quantified as the one repetition maximum. Power was quantified as the peak power produced at 40–90% of the one repetition maximum. FindingsQuadriceps strength accounted for 15% of the variance in peak knee flexion angle (P=0.016). Quadriceps power accounted for 20–29% of the variance in peak knee flexion angle (P<0.05). Quadriceps power at 90% of one repetition maximum accounted for 9% of the variance in peak knee adduction moment (P=0.05). InterpretationThese data suggest that quadriceps power explains more variance in knee flexion angle and knee adduction moment during gait in knee osteoarthritis than quadriceps strength. Additionally, quadriceps power at multiple loads is associated with knee joint mechanics and therefore should be assessed at a variety of loads. Taken together, these results indicate that quadriceps power may be a potential target for interventions aimed at changing knee joint mechanics in knee osteoarthritis.

Selective hypertrophy of the quadriceps musculature after 14 weeks of isokinetic and conventional resistance training

One of the fundamental adaptations observed with resistance training (RT) is muscle hypertrophy. Conventional and isokinetic machines provide different forms of mechanical stress, and it is possible that these two training modes could promote differing degrees of hypertrophic adaptations. There is a lack of data comparing the selective hypertrophy of the quadriceps musculature after training with a conventional knee extension machine versus an isokinetic machine. The purpose of this study was to evaluate the selective hypertrophy of the quadriceps musculature and knee extension maximal isometric torque after 14weeks of conventional versus isokinetic RT. Thirty-five men were assigned to three groups: control group and training groups (conventional and isokinetic) performed three sets of unilateral knee extensions per session with a progressive loading scheme twice a week. Prior to and following the intervention, maximal isometric knee extensor torque was measured using an isokinetic dynamometer, and muscle thickness (MT) of quadriceps femoris muscles was assessed via ultrasound. The results indicated non-uniform changes in MT between the muscles that comprise the quadriceps femoris group. For the conventional group, significantly greater increases in rectus femoris thickness were evident versus all other quadriceps muscles (14%). For the isokinetic group, increases in RF thickness (11%) were significantly greater in comparison with the vastus intermedius only. Although the muscle thickness did not increase for all the quadriceps femoris muscles, the relative rectus femoris adaptation suggested a selective hypertrophy favouring this portion.

Effects of added elastic tubes on open-chain knee extensor strength training

Attaching elastic tubes (ETs) to resistance training machines can affect the exercise load profile. The purpose of this study was to assess the training effects of added ETs, which were strategically attached to provide additional loads only during the deceleration phase of the knee extension exercise. Twenty-two healthy participants, assigned to either an experimental group (with ETs) or a control group (without ETs), participated in a 12-week strength-training program using a knee extension exercise machine. The acceleration effects were quantified and a method of attaching the ETs to the knee extension machine was developed. The effects of the added ETs were analysed by testing dynamic and isometric maximum contractions at four knee flexion angles (10°, 30°, 50°, and 80°). Analyses of covariance with the initial values as the covariate were used to examine the ET effects. A greater increase in isometric maximum strength was found in the experimental group than in the control group at knee flexion angles of 10° [effect size (ES) = 2.25] and 30° (ES = 1.18). No significant difference in the dynamic maximum strength was found between the groups. The use of ETs increased strength at smaller knee flexion angles with quadriceps that were relatively short.

Short-Term Effect of Plyometrics and Strength Training With and Without Superimposed Electrical Stimulation on Muscle Strength and Anaerobic Performance: A Randomized Controlled Trial. Part II

The purpose of this study was to compare the effects of combined strength and plyometric training with or without superimposed electromyostimulation (EMS) on muscle strength and anaerobic power. Twenty-nine subjects were randomly assigned to weight+plyometrics+EMS (EP), weight+plyometrics (VP), and control group (CG). Weight+plyometrics+EMS and VP performed 2 plyometric sessions and 2 weight training sessions per week throughout 4 weeks on a knee extension machine. Weight+plyometrics+EMS received EMS throughout the concentric phase of each action (120 Hz, 400 microseconds). Before, after training, and 2 weeks after the end of the training (detraining), maximal voluntary contraction, squat jump, countermovement jump, countermovement jump with free arms, and 20-minute sprint time were analyzed. After the training period, EP and VP increased their muscle strength (28.6 and 22.3%, respectively; p<0.001). After the detraining period, this gain remained above baseline values (28.1 and 18.0%, respectively; p<0.001 and p<0.01). After training and detraining, muscle strength was higher in EP than in VP (p<0.05). Vertical jump height was not modified for whichever group or test, except for the countermovement jump height with free arms, where a decrease for EP was observed after training (-6.3%; p<0.001) and detraining (-5.5%; p<0.001). Sprint performance improved in all groups in the detraining test (-0.8%; p<0.05). If a low number of training sessions are carried out, superimposed EMS leads to a higher strength gain than voluntary training alone. However, if anaerobic power is an important aim of the training, EMS should be applied isometrically instead of superimposed EMS and combined with plyometrics.

Short-Term Effect of Strength Training With and Without Superimposed Electrical Stimulation on Muscle Strength and Anaerobic Performance. A Randomized Controlled Trial. Part I

The purpose of this study was to compare strength training with and without superimposed electromyostimulation (EMS) on muscle strength and anaerobic power. Twenty-eight subjects were assigned to: weight+EMS (ES), weight (VOL), or control group (CG). ES and VOL performed 4 training sessions per week during 4 weeks on a knee extension machine (8 sets; 8 repetitions; 1-second concentric phase from 90 degrees to 0 degrees, 1-second eccentric phase from 0 degrees to 90 degrees , 1-second rest at 90 degrees; 3-minute rest between sets; 70% maximal voluntary contraction). Group ES received EMS in the concentric phase of each action (120 Hz, 400 microseconds). Before training, after training, and 2 weeks after the end of the training (detraining), maximal voluntary contraction, squat jump, countermovement jump (CMJ), countermovement jump with free arms (CMJA), and 20-m sprint time were analyzed. After the training period, ES and VOL increased their muscle strength (40.2% and 31.4%, respectively, p<0.001). After the detraining period, this gain remained above baseline values for ES and VOL (49.1% and 24.5%, respectively, p<0.001). Changes in muscle strength between baseline and detraining were higher in ES than in VOL (p<0.01). Anaerobic performance was not affected by training in any group, but percentage change between baseline and after training suggests that the CMJ and CMJA with free arms performance were impaired in ES with respect to VOL and CG. Superimposed EMS onto voluntary contractions increases strength more than voluntary training alone; nevertheless, a detraining period should be respected to observe this delayed adaptation. To improve anaerobic power with superimposed EMS, a complementary and specific work such as plyometrics should be carried out.

CORRELATES OF KNEE EXTENSOR TRAINING LOAD USED IN REHABILITATION AFTER KNEE SURGERY

Resistance training is one of the major components of rehabilitation after musculoskeletal injury and surgery. Despite the importance of resistance training and the frequency of its use in rehabilitation, little is known about factors that are related to training load that might be useful in devising and monitoring training in a patient and comparing training intensities between individuals and groups. We hypothesized that the following would show a statistically significant relationship to training load: injury chronicity, self-assessed knee function (Hughston Clinic questionnaire), knee swelling (injured-uninjured midpatellar knee girth), uninjured knee girth, and body mass. The purpose of this study was to evaluate whether factors such as body mass are related to the load used in training the knee extensors in rehabilitation after knee surgery. Thirty-six individuals undergoing early-phase rehabilitation after knee arthroscopic meniscectomy surgery participated in this study. Subjects were tested 5 days after surgery, just prior to commencing a 6- week outpatient rehabilitation program, and again soon after the end of this rehabilitation program. The independent variables evaluated were age, gender, body mass, meniscus injured, injury chronicity, knee function self-assessment, knee swelling (injured-uninjured midpatellar girth), uninjured knee girth, and knee flexion and extension passive range of motion (difference between injured and uninjured side). The dependent variable was the load used for training the knee extensors on the knee extension machine in the final training session prior to the post- test. The only variable exhibiting a statistically significant (p = 0.001) relationship to knee extensor final training was age (r = −0.529). This finding, that age was the only variable to have a significant relationship with training load, suggests that clinicians' expectation of training intensity should decrease with an increase in the patient's age in the range studied (20–58 years) for patients recovering from knee arthroscopic meniscectomy.

Número máximo de repetições em exercícios isotônicos: influência da carga, velocidade e intervalo de recuperação entre séries

INTRODUÇÃO: Pouco se sabe sobre o efeito da velocidade de execução e do intervalo entre séries sobre o desempenho no exercício contra-resistência. OBJETIVO: Comparar o número máximo de repetições até a fadiga voluntária (REPS) na cadeira extensora com o joelho dominante para diferentes cargas, velocidades e intervalos entre séries. MÉTODOS: Nove voluntários (35,8 ± 10,8 anos; 74,2 ± 16,7kg; 171,0 ± 10,0cm) reportaram ao laboratório para determinação de 1RM e REPS em seis situações, determinadas aleatoriamente e separadas por no mínimo 48h: uma série com 60% 1RM a 80°•s¹ e 25°•s-1; uma série com 80% 1RM a 25°•s¹; três séries com 80% 1RM a 80°•s-1 e intervalos de 3 min, 1 min e naquele que permitisse a estabilização da oxigenação muscular (RMox), medida por espectroscopia no infravermelho próximo. RESULTADOS: O teste t dependente mostrou que REPS foi significativamente (p &lt; 0,05) maior na carga leve que na pesada, nas velocidades lenta (leve = 8,8 ± 1,3; pesada = 5,9 ± 0,9) e rápida (leve = 16,3 ± 3,9; pesada = 9,4 ± 1,9), e significativamente maior na velocidade rápida que na lenta, para ambas as cargas. A ANOVA 3x3 não mostrou diferença entre os intervalos na série 1 (3 min = 9,4 ± 1,9; 1 min = 10,8 ± 3,2; RMox = 10,1 ± 3,0), porém, houve diferenças significativas nas séries 2 e 3 entre 3 min (série 2 = 7,0 ± 1,7; série 3 = 6,4 ± 1,3) e 1 min (série 2 = 5,6 ± 1,1; série 3 = 4,8 ± 1,2), mas não entre RMox (série 2 = 6,4 ± 1,7; série 3 = 6,1 ± 1,5) e os demais intervalos. Nos três intervalos, REPS na série 1 foi significativamente maior que nas demais. CONCLUSÕES: O desempenho no exercício contra-resistência é afetado pela carga, velocidade e intervalo entre séries e é independente da recuperação em oxigenação muscular. A prescrição do exercício e a avaliação do desempenho devem levar essas variáveis em consideração frente aos objetivos propostos.

Correlates of Knee Extensor Training Load Used in Rehabilitation After Knee Surgery

Resistance training is one of the major components of rehabilitation after musculoskeletal injury and surgery. Despite the importance of resistance training and the frequency of its use in rehabilitation, little is known about factors that are related to training load that might be useful in devising and monitoring training in a patient and comparing training intensities between individuals and groups. We hypothesized that the following would show a statistically significant relationship to training load: injury chronicity, self-assessed knee function (Hughston Clinic questionnaire), knee swelling (injured-uninjured midpatellar knee girth), uninjured knee girth, and body mass. The purpose of this study was to evaluate whether factors such as body mass are related to the load used in training the knee extensors in rehabilitation after knee surgery. Thirty-six individuals undergoing early-phase rehabilitation after knee arthroscopic meniscectomy surgery participated in this study. Subjects were tested 5 days after surgery, just prior to commencing a 6-week outpatient rehabilitation program, and again soon after the end of this rehabilitation program. The independent variables evaluated were age, gender, body mass, meniscus injured, injury chronicity, knee function self-assessment, knee swelling (injured-uninjured midpatellar girth), uninjured knee girth, and knee flexion and extension passive range of motion (difference between injured and uninjured side). The dependent variable was the load used for training the knee extensors on the knee extension machine in the final training session prior to the posttest. The only variable exhibiting a statistically significant (p = 0.001) relationship to knee extensor final training was age (r = -0.529). This finding, that age was the only variable to have a significant relationship with training load, suggests that clinicians' expectation of training intensity should decrease with an increase in the patient's age in the range studied (20-58 years) for patients recovering from knee arthroscopic meniscectomy.

Time under Tension and Blood Lactate Response during Four Different Resistance Training Methods

Mechanical stimuli have often been suggested to be the major determinant of resistance training adaptations; however, some studies suggested that metabolic changes also play an important role in the gains of muscle size and strength. Several resistance training methods (RTM) have been employed with the purpose of manipulating mechanical and metabolic stimuli; however, information about their physiological effects are scarce. The objective of this study was to compare the time under tension (TUT) and blood lactate responses among four different RTM reported in the literature. The four RTM were performed in a knee extension machine at 10 repetition maximum (RM) load by 12 recreationally trained young men. The RTM tested were: 10RM, super-slow (SL-subjects performed one 60-second repetition with 30 seconds for eccentric and 30 seconds for concentric phase), functional isometrics (FI-in each repetition, a five-second maximal isometric contraction was executed with the knees fully extended) and adapted vascular occlusion (VO-subjects performed a 20-second maximal isometric contraction with the knees fully extended and immediately proceeded to normal isoinertial lifts). According to the results, all RTM produced significant increases in blood lactate levels. However, blood lactate responses during FI (4.48+/-1.57 mM) and VO (4.23+/-1.66 mM) methods were higher than the SL method (3.41+/-1.14 mM). The TUT for SL (60 s), FI (56.33+/-6.46 s), and VO (53.08+/-4.76 s) methods were higher than TUT for 10RM (42.08+/-3.18 s). Additionally, TUT for the SL method was higher than TUT during the VO method. Therefore, the SL method may not be recommended if one wants to provide a high metabolic stimulus. The FI method appeared to be especially effective in promoting both type of stimuli.

Reliability Of Vastus Lateralis Oxygenation Measured By Near Infrared Spectroscopy During Resistance Exercise

Near infrared spectroscopy (NIRS) is a non-invasive optical technique that has been extensively used to monitor muscle oxygenation (Mox) during various tasks in different populations. However, its use during exercise has been restricted to aerobic or isometric activities, with very few attempts to investigate Mox during dynamic resistance exercise. PURPOSE To determine the reliability of vastus lateralis (VL) Mox measured by NIRS during isotonic knee extensions. METHODS Informed consent was obtained from 9 healthy volunteers (37.2 ± 10.2 yr; 74.1 ± 16.7 kg; 170.5 ± 9.6 cm) who randomly completed 4 sessions of 1 set of maximum repetitions (REPS) of the dominant leg on a knee extension machine with 80% 1RM at slow (SS: ∼25°·s−1) and fast (FS: ∼80°·s−1) speeds. A repetition was considered valid if range of motion was at least 60°. Test/ retest measurements were undertaken within a two-week period. The NIRS probe was positioned over VL (∼16 cm above knee joint) and Mox was continuously monitored during 2 min rest, REPS, and 3 min recovery. Variables considered for analysis after adjustment for baseline were: minimum during REPS plus recovery (MIN), range from MIN to maximum during recovery (RANGE), and time for half-recovery after REPS (T1/2). RESULTS Bland-Altman analysis revealed an outlier on FS REPS and one on SS Mox whose data were discarded. Mox data was further discarded for one subject in each speed due to probe displacement. Number of REPS were 6.1 ± 0.8 and 6.3 ± 0.9 for test and retest, respectively, for SS (n = 9; intraclass correlation coefficient, ICC = .674; p = .016); and 9.3 ± 1.9 and 9.9 ± 1.6, respectively, for FS (n = 8; ICC = .560; p = .046). For SS (n = 7), MIN (ICC = .730; p = .014), RANGE (ICC = .795; p = .006) and T1/2 (ICC = .780; p = .007) showed significant reliability, but only MIN (ICC = .854; p = .002) and RANGE (ICC = .973; p = .000) were reliable for FS (n = 7), with ICC = .309 for T1/2 (p = .773). CONCLUSIONS Reproducibility of Mox measurements of VL was moderately high at 80% 1RM during dynamic knee extensions to voluntary fatigue. NIRS is a suitable technique for evaluating Mox changes during resistance exercise. Partly supported by CAPES/Ministry of Education, FAPERJ (E-26/170.774/2003), and Righetto Fitness Equipment, Brazil.