Bilateral Knee Flexion Research Articles

Effects of Rest Duration Between Sets of Resistance Training on Hormonal Responses in Young Women

PURPOSE: The purpose of this study was to examine the acute hormonal response to three different rest periods between sets of a traditional lower body resistance training session in young women. METHODS: Twelve apparently healthy, resistance trained females (26.83 ± 3.93 yrs) participated in the study protocol. On three separate sessions of a lower body resistance exercise protocol, subjects were assigned in a random order a rest interval of either 30 (P30), 60 (P60) or 120 (P120) seconds between sets. The resistance exercise session consisted of four lower body exercises (bilateral knee extension, bilateral knee flexion, leg press, and squat) with 3 sets of 10 repetitions at 10-repetition maximum (RM) load. Blood samples were drawn for determination of serum growth hormone (GH) and cortisol concentrations before exercise (T0), immediately after each training session (T1), and 5 (T5), 15 (T15), and 30 (T30) minutes of recovery. Statistical evaluation of the data was measured using a 3 × 5 repeated measures analysis of variance [rest interval (30, 60, and 120 s) × time (T0, T1, T5, T15, T30)]. The probability level of statistical significance was set at p < 0.05 in all comparisons. RESULTS: There were no differences between protocols (P30, P60 and P120) in the serum GH and cortisol concentrations at baseline (T0). However, as compared to T0, all protocols led to acute increases (p < 0.05) in serum GH and cortisol concentrations after each training session. The GH concentrations between protocols were significantly higher for P30 (24.34 ng/ml) and P60 (23.07 ng/ml) as compared to P120 (17.13 ng/ml) at T1. The P30 GH concentrations were significantly higher at T5, T1 5, and T30 as compared to P60 and P120. The cortisol concentrations were significantly higher in P30 at T15 (452.02 nmol/L) and T30 (449.72 nmol/L) as compared to P60 (367.64 for T15, and 354.99 nmol/L for T30) andP120 (363.73 nmol/L for T15, and 346.02 nmol/L for T30). CONCLUSIONS: Exercise-induced metabolic stress is associated with acute GH and cortisol responses following a typical hypertrophic resistance training session. The magnitude of acute hormonal responses in previously strength-trained women appears greater with a 30-second rest interval between sets compared to longer rest periods of 60- or 120-seconds.

Bilateral deficit during short-term, high-intensity cycle ergometry in girls and boys

Peak torque during an isokinetic bilateral knee extension or flexion is usually lower than the summed peak torque of two unilateral contractions, and this phenomenon is designated as bilateral deficit (BD). The objectives of this study were to determine whether a BD also exists for more complex, alternating movements (e.g., short-term, high-intensity cycling), and to assess the possible effects of gender and maturity. Forty children and adolescents performed two unilateral (ULWAnT) and one bilateral Wingate anaerobic test (BLWAnT). The highest power reached in any 3-s interval (peak power; PP), and the total mechanical work (TMW) performed during the test was determined. Individual BD for PP (BDpp, %) was calculated by dividing the PP in the BLWAnT by the sum of the PP values of both ULWAnTs. The BD for TMW (BDTMw) was calculated in the same way. The sum of PP generated during the two ULWAnTs was larger than the PP measured in the BLWAnT (P<0.000001). The same difference was observed for TMW (P<0.0001). Maturity did not affect the BDpp or BDTMW (P=0.34). However, the BD was more pronounced in females compared to males (P= 0.03). In conclusion, a BD is evident during cycling exercise.

Activation and torque deficits in ACL-reconstructed patients 4 months post-operative

This study compares knee extension and flexion torques and electromyographic (EMG) activity of normal and anterior cruciate ligament (ACL)-reconstructed knees during maximal unilateral isometric and isokinetic tests performed 4–5 months after ACL reconstruction. The subjects consisted of 3 age- and activity-matched groups of 6 subjects: a healthy control group (Ctrl) and 2 groups of patients, with Kenneth-Jones technique using autologous patellar-ligament graft (KJ group) and autologous graft from the semitendinosus tendon (ST group). When compared to the Ctrl group values, each patient group had significant bilateral extension torque deficits in isometric and at slow velocity concentric conditions. In the Op leg, this deficit was associated with lower quadriceps EMG activation. In all tests, bilateral hamstring co-activation level was lower in the patient groups. Flexion torque deficits were observed in the Op leg of both patient groups and in the Nop leg of the KJ group, with minor differences in either hamstring EMG activation or quadriceps co-activation. The inter-leg difference in extension and flexion torques were significant for both patient groups, but only in the isometric strength test, and with no difference in activation. These data demonstrate bilateral knee extension and flexion torque deficits a few months after ACL reconstruction. The observed deficit in quadriceps activation emphasizes the interest to perform combined EMG and strength testings quite early during the rehabilitation period.

Case Study: Improving Knee Extension with Floor-Reaction Ankle-Foot Orthoses in a Patient with Myelomeningocele and 20?? Knee Flexion Contractures

Floor-reaction ankle-foot orthoses (FRAFOs) were fit to a patient with an L-5 le el myelomeningocele to show their effect on increasing knee extension and the knee extension moment in the presence of 20° bilateral knee flexion contractures. It was hypothesized that FRAFOs would pre ent the crouchedtype gait pattern commonly seen in those with myelomeningoceles. Because of the rigid nature of the FRAFO, it was thought this would increase the external knee-extension moment and extend the knees to their maximum range. A patient with myelomeningocele underwent gait analysis testing while barefoot and while wearing FRAFOs set in 10° dorsiflexion. Joint kinetic and kinematic, along with electromyographic data on the astus lateralis and rectus femoris were determined. Results showed a peak plantarflexor moment in late stance of 0.70 N-m/kg body weight while the patient was barefoot and 1.32 N»m/kg body weight while the patient was wearing the FRAFO (P <.0001). Knee extension during the barefoot trails was 20.5°, and was 12.3° during the FRAFO trials (P <.0001). Electromyographic acti ity of the rectus femoris in terminal stance decreased significantly during FRAFO trials compared to the barefoot trials (307 mV ersus 53 mV; P <.0001) consistent with the impro ed knee extension. FRAFOs set in 10° dorsiflexion pro ided a significant increase in knee extension and knee-extension moment during gait for this patient with myelomeningocele, despite 20° bilateral knee-flexion contractures

Quantification of full-range-of-motion unilateral and bilateral knee flexion and extension torque ratios

Objectives: To evaluate the reliability and variability of repeated measurements of isometric knee flexion and extension strength, to quantify the extent of measurement error that may occur due to gravity, and to quantify isometric knee flexion/ extension torque ratios at multiple angles through a full range of motion. Design: Reliability assessment. Setting: A university exercise center. Participants: Seventy-seven healthy men and women recruited from a university and surrounding community. Intervention: Isometric knee flexion and extension strength tests. Main Outcome Measures: Knee flexion/extension strength was measured at 6°, 24°, 42°, 60°, 78°, 96°, and 108° of knee flexion. Before each contraction, subjects were instructed to completely relax the limbs to measure the mass of the lower leg. Torque values obtained during relaxation at each angle were added to or subtracted from “Total Torque” (TTQ) at peak exertion. The adjusted value was recorded as “Net Muscular Torque” (NMT). Results: Reliability for the unilateral and bilateral tests was high ( r = .88 to r = .98) and measurement variability low (SEM% = 5.1% to 12.6%). There was a statistically significant difference at each angle of measurement between the TTQ and NMT values for both knee flexion and extension. Knee flexion/extension ratios were highly dependent on the angle tested, ranging from 1.30 (at 6°) to .31 (at 108°). Conclusions: Isometric testing, using standardized angles, can reliably quantify knee flexion/extension strength. Furthermore, these findings emphasize the importance of correcting for the mass of the lower leg when assessing muscle function. Angle-specific knee flexion/extension torque ratios should provide clinicians with a more precise method of evaluating muscular balance (imbalance) throughout the range of motion.

RESISTANCE TRAINING PROGRAM WITH ELDERLY NURSING HOME RESIDENTS LEADS TO IMPROVED BALANCE AND MOBILITY

1524 Thirty-four elderly nursing home (NH) residents were recruited to participate in a 12-wk resistance training program (RTP) to determine if the strength gains following the RTP would be associated with improved balance, mobility, level of assistance needed by NH staff, and self-perceived health status. Subjects were medically stable, ambulatory for at least short distances and without serious cognitive impairment. A 5-rep maximum was used to determine strength in elbow flexion, elbow extension, overhead shoulder press, bilateral shoulder row, knee flexion, and knee extension. Balance and mobility were assessed using the Berg Balance, Duke Mobility Skills, and Sit-to-Stand tests. The Functional Independence Measure (FIM) was used to determine the usual level of assistance provided by the NH staff, and the European Quality of Life Instrument (EuroQOL) and Geriatric Depression Scale(GDS) were used to determine self-perceived health status. Testing was conducted before and after the RTP. In addition, half of the subjects were tested 12 wk before the program began, to provide control data. The other half of the subjects were tested 12 weeks after the program ended, to quantify post-training changes. The RTP was held 3x/wk and consisted of four leg and four arm exercises. Subjects progressed from one to three sets of 8-12 reps of each exercise, with gradually increased resistance. ANOVA and paired t-tests were used to guide analyses. Twenty-four subjects completed the program (age: 84 ± 7 yr; time in NH: 17 ± 16 mo; RTP attendance: 90 ± 12%). There was no change in any variable during the control period. After the RTP, strength scores improved 63 - 147% (p <.0001) and balance and mobility tests improved 10 - 34% (p <.006). However, 12 weeks after the RTP ended, elbow extension, knee extension, overhead press, and the Sit-to-Stand mobility test had relapsed 21 - 38% (p <.03). The improvements did not carry over to a decreased level of assistance provided by the NH staff, nor did it affect self-perceived health status, as the FIM, EuroQOL, and GDS scores did not change throughout the study. Following a 12-wk RTP with elderly nursing home residents, gains in strength were associated with improvements in balance and mobility.

Effect of resistance training volume on strength and muscle thickness.

The purpose of this study was to determine the effects of different volumes of high-intensity resistance training on isometric torque and muscle thickness. Training was conducted three times per week using one set (low volume, EX-1, N = 18) or three sets (high volume, EX-3, N = 20) of dynamic variable resistance exercise. Ten subjects acted as nontraining controls (CONT). Bilateral knee extension (KEXT) and flexion (KFLEX) exercise was performed to fatigue within 8-12 repetitions for 14 wk. Maximal isometric KEXT and KFLEX torque was tested at 6 degrees, 24 degrees, 42 degrees, 60 degrees, 78 degrees, 96 degrees, and 108 degrees of KFLEX using a MedX (Ocala, FL) KEXT/KFLEX ergometer. The anterior (ANT), lateral (LAT), and posterior (POST) right thigh, the medialis muscle (MED), and the lateralis muscle (LATER) were assessed for thickness by B-mode ultrasound (ULTRA). Both training groups improved torque output at most angles, but there was no difference between EX-1 and EX-3 (P > or = 0.05). ULTRA detected increases in muscle thickness for EX-1 at 60% LAT and 40% and 60% POST. EX-3 increased muscle thickness at the MED, and 40% and 60% POST. In conclusion, one set of high intensity resistance training was as effective as three sets for increasing KEXT and KFLEX isometric torque and muscle thickness in previously untrained adults.

Surgery combined with continuing post operative stretching and management for knee flexion contractures in cases of multiple sclerosis - a report of six cases

Contractures are a common complication of advanced multiple sclerosis. In consequence the care load is increased. Sitting in the wheelchair becomes difficult if not impossible and there is a high risk of pressure sores due to inadequate weight distribution. The greatest impedance to care and maintenance was thought to be the bilateral knee flexion contractures and unilateral hip adduction contracture frequently found in the severely paralysed MS patient. It was postulated that release of contracture would ease the care load and management. Comfort and quality of life would improve as a result. Surgery to release the bilateral knee flexion contracture was combined with passive stretching to associated contractures in an attempt to improve the physical condition. A routine regimen of maintenance was introduced postoperatively and continued indefinitely. A comparison of postoperative method to increase range using continuous passive motion (CPM) and plaster of Paris (POP) serial splinting was carried out. The results of the six reported cases show a markedly increased range of movement at the knee, a reduction in care load and an improved sitting posture postoperatively which was maintained when reassessed at nine months. Little difference between the postoperative regimens of CPM and POP fixation was found.

The Effects of Simulated Knee-Flexion Contractures on Standing Balance

The effects of simulated unilateral and bilateral knee-flexion contractures on standing balance were studied by testing 15 normal subjects on a Kistler force platform. Postural sway (mediolateral and anteroposterior travel) and the mean position of the center of pressure (as a percentage of the distance between the midlines of the feet and from heels to toes) were determined from 20 s of data. Unilateral and bilateral knee-flexion contractures of 15 degrees and 30 degrees were simulated for each subject by means of an adjustable line from the subject's waist to the sole of each foot. Paired t tests were used to compare balance parameters while standing with the simulated contractures with those during relaxed standing. Mediolateral travel increased by a mean difference of 3.6 cm with a 30 degree unilateral contracture (P less than 0.01) and by 5.0 cm with 30 degrees bilateral contractures (P less than 0.01). Anteroposterior travel increased by 4.7 cm (P less than 0.05) and 8.8 cm (P = 0.08) with 15 degrees and 30 degrees bilateral contractures, respectively. With a unilateral contracture of 30 degrees, the center of pressure shifted 15.6% (P less than 0.0005) toward the unflexed side, changes that were not eliminated by correction of the induced leg-length discrepancy. The center of pressure moved anteriorly by 8.3% with 30 degrees bilateral contractures (P less than 0.001). The results provide insight into how knee-flexion contractures alter standing balance, and underline the importance of preventing and treating this common disorder.