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At least 1,009 records · Page 56Linked to original sources

PubMed1995

Direct dynamics simulation of the impact phase in heel-toe running.

The influence of muscle activation, position and velocities of body segments at touchdown and surface properties on impact forces during heel-toe running was investigated using a direct dynamics simulation technique. The runner was represented by a two-dimensional four- (rigid body) segment musculo-skeletal model. Incorporated into the muscle model were activation dynamics, force-length and force-velocity characteristics of seven major muscle groups of the lower extremities: mm. glutei, hamstrings, m. rectus femoris, mm. vasti, m. gastrocnemius, m. soleus and m. tibialis anterior. The vertical force-deformation characteristics of heel, shoe and ground were modeled by a non-linear visco-elastic element. The maximum of a typical simulated impact force was 1.6 times body weight. The influence of muscle activation was examined by generating muscle stimulation combinations which produce the same (experimentally determined) resultant joint moments at heelstrike. Simulated impact peak forces with these different combinations of muscle stimulation levels varied less than 10%. Without this restriction on initial joint moments, muscle activation had potentially a much larger effect on impact force. Impact peak force was to a great extent influenced by plantar flexion (85 N per degree of change in foot angle) and vertical velocity of the heel (212 N per 0.1 m s-1 change in velocity) at touchdown. Initial knee flexion (68 N per degree of change in leg angle) also played a role in the absorption of impact. Increased surface stiffness resulted in higher impact peak forces (60 N mm-1 decrease in deformation).(ABSTRACT TRUNCATED AT 250 WORDS)

Ankle Joint↗

PubMed2004

Alterations in lower extremity movement and muscle activation patterns in individuals with knee osteoarthritis.

OBJECTIVE: The purpose of this study was to investigate lower extremity movement and muscle activation patterns in individuals with knee osteoarthritis and healthy age- and gender-matched control subjects. DESIGN: This study utilized a non-randomized case-control design to compare 24 subjects with unilateral symptomatic knee osteoarthritis to 24 age- and gender-matched control subjects without knee osteoarthritis. BACKGROUND: It is hypothesized that knee osteoarthritis is associated with altered lower extremity movement and muscle activation patterns. METHODS: A gait analysis was performed to determine the lower extremity movement and muscle activation patterns when walking on a level surface at 1.12 to 1.34 m/s and while descending a 20 cm step. Paired t-tests were used to compare the average of five trials between the groups. RESULTS: Subjects with knee osteoarthritis demonstrated less excursion of the knee in the sagittal plane from heelstrike to peak flexion before midstance (i.e. during loading). Subjects with knee osteoarthritis also demonstrated reduced peak vertical ground reaction forces relative to body weight. The muscle activity patterns were also different between the groups. The vastus lateralis, medial hamstrings, tibialis anterior and medial gastrocnemius were on approximately 1.5 times longer than the same muscles in the control subjects. Additionally, significant increases in muscle co-activation were also observed in individuals with knee osteoarthritis during walking. Similar findings were observed when the subject descended a 20 cm step.

Aged↗

PubMed2005

Biological risk indicators for recurrent non-specific low back pain in adolescents.

OBJECTIVES: A matched case-control study was carried out to evaluate biological risk indicators for recurrent non-specific low back pain in adolescents. METHODS: Adolescents with recurrent non-specific low back pain (symptomatic; n = 28; mean (SD) age 14.9 (0.7) years) and matched controls (asymptomatic; n = 28; age 14.9 (0.7) years) with no history of non-specific low back pain participated. Measures of stature, mass, sitting height, sexual maturity (Tanner self assessment), lateral flexion of the spine, lumbar sagittal plane mobility (modified Schober), hip range of motion (Leighton flexometer), back and hamstring flexibility (sit and reach), and trunk muscle endurance (number of sit ups) were performed using standardised procedures with established reliability. Backward stepwise logistic regression analysis was performed, with the presence/absence of recurrent low back pain as the dependent variable and the biological measures as the independent variables. RESULTS: Hip range of motion, trunk muscle endurance, lumbar sagittal plane mobility, and lateral flexion of the spine were identified as significant risk indicators of recurrent low back pain (p<0.05). Follow up analysis indicated that symptomatic subjects had significantly reduced lateral flexion of the spine, lumbar sagittal plane mobility, and trunk muscle endurance (p<0.05). CONCLUSIONS: Hip range of motion, abdominal muscle endurance, lumbar flexibility, and lateral flexion of the spine were risk indicators for recurrent non-specific low back pain in a group of adolescents. These risk indicators identify the potential for exercise as a primary or secondary prevention method.

Adolescent↗

PubMed1992

Application of a programmable dual-channel adaptive electrical stimulation system for the control and analysis of gait.

A dual-channel electrical stimulation system with a stimulator and a programmer/stride analyzer was designed for clinical rehabilitation of gait and for subsequent daily use as an orthotic aid. The stimulator, with controls to adjust amplitude only (50 mA), adapts chosen stimulation sequences to the walking rate of a patient. Pulse duration (50-500 microseconds), frequency (5-120 Hz), shape (symmetrical biphasic, monophasic), stimulation sequences (16 stride segments) and their cycle (2-12 sec), and right/left foot-switch choices are selected for each patient and programmed into a separate unit. The programming unit also statistically processes the foot-switch data collected by the stimulator. The device was evaluated with regard to the programmable parameters, effectiveness during gait, and feasibility in clinical use. It was applied to 11 stroke patients and 10 brain injury patients during gait, stimulating 22 combinations of peroneal nerve and hamstring, quadriceps, triceps brachii, and gluteus maximus muscles. Forces on both feet, equinovarus, knee extension and hyperextension, elbow flexion, and hip extension were corrected. Selection of the stimulation sequences, their adaptation, range of pulse duration, and valid statistics were verified. Improved forces and joint angles were recorded together with significant changes in the stride time, length, and velocity by the stimulation.

Adult↗

PubMed1991

Rehabilitation concerns following anterior cruciate ligament reconstruction.

Rehabilitation following anterior cruciate ligament reconstruction is a subject of controversy in the orthopaedic and rehabilitation literature. With an increasing number of these operations currently being performed and with the advent of arthroscopically assisted ACL reconstruction over the past several years, particular rehabilitation needs and problems have been identified in association with these patients. Various authors have stressed one or a combination of a few basic themes which outline the basic rehabilitation concerns following ACL reconstruction. The most fundamental concern is the need to initiate motion very soon after surgery. Prolonged postoperative immobilisation is known to cause serious complications after ACL reconstruction which can be avoided by early motion. Positions or activities which may apply excessive stress to a newly reconstructed ACL must also be considered. The amount of protection required by the graft will vary depending upon the type of graft used and the quality of fixation obtained intraoperatively. Most authors agree that nonweightbearing, active resistive quadriceps exercises should be avoided for an extended period, while closed chain exercises may be initiated much earlier. Strength recovery is obviously important for the quadriceps postoperatively, but maximal strength returns of all of the muscles about the knee must be pursued. Hamstring strength is of particular concern as this may provide an active support to the reconstructed ACL. Sensory loss in the knee after ACL disruption should also be addressed during rehabilitation, prior to a patient's return to full athletic activity. Progressive neuromuscular re-education exercises which rely on sensory input from intact pericapsular structures are encouraged. A final concern is the role of bracing after ACL reconstruction.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗

PubMed1983

[Electromyographical study of the straight leg raising test in lumbar disc herniation].

The straight leg raising test is one of the most reliable test for the diagnosis of the disc herniation. It is well known that the pain is produced by the increased tension of the affected root. However, the patient's response to the pain evoked by the straight leg raising test is not uniform. In some patients the leg is raised beyond the straight leg raising positive angle without resistance and some young patients show the tight hamstrings phenomenon. To elucidate these phenomena, the muscle action of erector spinae, gluteus maximus and biceps femoris evoked by this test was studied electromyographically. The results are as follows: 1) The muscle action patterns in the patients of disc herniation which are not observed in normal group are classified into four groups, namely LGB type (erector spinae, gluteus maximus and biceps femoris act), GB type (gluteus maximus and biceps femoris act), G type (gluteus maximus only acts), B type (biceps femoris only act). These abnormal muscle actions disappear under general anesthesia and are different from the actions which are recorded when the patients resist passive straight leg raising intentionally. 2) In the case of L4-5 intervertebral disc herniation mainly gluteus maximus acts as the resisting force against the passive straight leg raising. On the other hand, biceps femoris acts mainly in the case of L5-S1 disc herniation. 3) The group of younger age and less degenerated disc shows more resistance against straight leg raising and records the action potential of resisting muscles in earlier stage of the leg raising test.

Adolescent↗

PubMed2005

Elucidation of a potentially destabilizing control strategy in ACL deficient non-copers.

PURPOSE: The purpose was to differentiate the dynamic knee stabilization strategies of potential copers (individuals who have the potential to compensate for the absence of an ACL without episodes of giving way after return to pre-injury activities) and non-copers (those who have knee instability following ACL rupture with return to pre-injury activities). METHODS: Twenty subjects with ACL rupture were assigned to potential coper (n=10) and non-coper (n=10) groups via a screening examination. Ten active people without lower extremity injury were also tested. Knee angle, tibial position and muscle activity data were collected while subjects stood in unilateral stance on a platform that moved horizontally in an anterior direction. Analysis included the preparation for platform movement; and monosynaptic, intermediate reflex and voluntary response intervals after platform movement. RESULTS: Non-copers showed greater knee flexion than uninjured subjects, and had a posterior tibial position and altered hamstring recruitment compared to the other groups. Potential copers demonstrated greater medial quadriceps activity while maintaining knee kinematics similar to uninjured subjects. Both potential copers and non-copers had greater co-contraction between medial hamstrings and quadriceps than uninjured subjects. All excitatory muscle activation occurred in the intermediate reflex interval. DISCUSSION AND CONCLUSIONS: Non-copers displayed aberrant muscle recruitment that may contribute to knee instability. Potential copers maintained normal tibial position using a strategy that permits quadriceps activation without excessive anterior tibial translation. Muscle recruitment in the intermediate reflex interval suggests neuromuscular training may influence the strategies.

Adaptation, Physiological↗

PubMedDate not supplied

Strain within the anterior cruciate ligament during hamstring and quadriceps activity.

The objectives of this study were to measure strain in the ACL during simulated: hamstring activity alone, quadriceps activity alone, and simultaneous quadriceps and hamstring activity. Seven knee specimens removed from cadavers were studied. Heavy sutures applied to load cells were attached to the hamstring and quadriceps tendons. Loads were then applied manually (hamstrings) and/or with an Instron testing machine (quadriceps) to simulate isometric contractions of the various muscle groups. Strain was measured using a Hall effect transducer. Acting alone, the isometric hamstring activity decreased ACL strain relative to the passive normal strain at all positions tested. Thus, hamstring exercises are not detrimental to ACL repairs or reconstruction and can be included early in the rehabilitation program after ACL surgery. Acting alone, at flexion angles of 0 degree to 45 degrees, the quadriceps significantly increased the strain within the ACL relative to the passive normal strain. Strain in the ACL during simultaneous hamstring and quadriceps activity was significantly higher than that during passive normal motion from full extension to 30 degrees of flexion. The hamstrings are not capable of masking the potentially harmful effects of simultaneous quadriceps contraction on freshly repaired or reconstructed ACLs unless the knee flexion angle exceeds 30 degrees.

Adult↗

PubMed1990

Isokinetic evaluation of quadriceps and hamstrings symmetry following anterior cruciate ligament reconstruction.

After anterior cruciate ligament (ACL) reconstruction, isokinetic muscle parameters are commonly measured to assess the dynamic status of the knee and to monitor progress in rehabilitation. This study evaluated the symmetry of the quadriceps and hamstrings musculature in postsurgical and contralateral normal limbs of subjects who had undergone one of two types of ACL reconstruction. Subjects were also evaluated for differences on selected isokinetic parameters between types of surgery and lengths of postoperative periods. Postsurgical and normal contralateral limbs of 46 subjects aged 18 to 49 years (mean, 23.7 years) were divided into groups according to type of autogenous intraarticular ACL substitute and length of postoperative period. Results of paired t-tests and analyses of variance indicated significant asymmetries between limbs for all measures of quadriceps and hamstrings musculature strength and endurance (p less than .001) irrespective of the type of reconstruction technique. Average surgical knee deficits in hamstrings endurance were significantly less for the long-term (41 to 101 months) follow-up group (1.9%) than for the intermediate (24 to 40 months) group (12.1%). The results suggest that extended periods of time are required to approximate hamstrings endurance symmetry after ACL reconstruction. Asymmetries between postsurgical and contralateral normal limbs in these subjects may reflect either incomplete rehabilitation or an inability to regain full isokinetic strength and endurance after ACL reconstruction.

Adult↗

PubMed2001

Inhibition of dynamic thigh muscle contraction by electrical stimulation of the posterior cruciate ligament in humans.

We investigated the influence of electrical stimulation of the posterior cruciate ligament (PCL) on the motoneuron pool of the thigh muscle during voluntary static and dynamic muscle contraction. The study group comprised nine young men with no history of injury to the knee joints. Multistranded Teflon-insulated stainless-steel wires were inserted into the PCL guided by ultrasound. In three subjects wires were also inserted into the fat pad of the knee. The PCL was electrically stimulated during static, concentric, or eccentric muscle contraction with a constant load of 20% of the maximal voluntary contraction of either the quadriceps or the hamstrings. Electromyographic signals were recorded with bipolar surface electrodes placed over the vastus medialis, rectus femoris, vastus lateralis, biceps femoris caput longum, and semitendinosus muscles. The stimuli consisted of four pulses delivered at 200 HZ; the stimulus amplitude was two to three times the sensory threshold. The electrical stimulation of the PCL inhibited the ongoing muscle activity in both the quadriceps and hamstrings with latencies of 114-150 ms and 99-130 ms, respectively. Stimulation of the fat pad of the knee did not influence the muscle activity. The study suggests that the mechanoreceptors in the PCL are involved in controlling muscle activity during both static and active muscle contractions. The relative long latency of the reflex makes it unlikely that it can serve as a directly protective reflex for the cruciate ligaments.

Adult↗

PubMed2000

Effect of short-duration spaceflight on thigh and leg muscle volume.

PURPOSE: Human skeletal muscle probably atrophies as a result of spaceflight, but few studies have examined this issue. Thus, little is known about the influence of microgravity upon human skeletal muscle, nor is it possible to assess the validity of ground based models of spaceflight. This study tested the hypothesis that the magnitude of spaceflight induced muscle atrophy would be a function of flight duration and greater than that of bed rest. METHODS: Three astronauts flew 9, 15, and 16 d in space. Volume of the knee extensor (quadriceps femoris), knee flexor (hamstrings, sartorius, and gracilis), and plantar flexor (triceps surae) muscle groups was measured using magnetic resonance imaging before and after spaceflight and during recovery. The volume of each muscle group in each image was determined by multiplying cross-sectional area by slice thickness. These values were subsequently summed to calculate muscle volume. RESULTS: Volume changes in the knee extensor, knee flexor, and plantar flexor muscle groups ranged from -15.4 to -5.5, -14.1 to -5.6, and -8.8 to -15.9%, respectively. Muscle volume decreases normalized by flight duration ranged from 0.62 to 1.04% x d(-1). These relative changes appeared to be greater than those that we have reported previously for bed rest (Akima et al., J. Gravitat. Physiol. 4:15-22, 1997). CONCLUSIONS: These results suggest that atrophy as a result of at least 2 wk of spaceflight varied among individuals and muscle groups and that the degree of atrophy appeared to be greater than that induced by 20 d of bed rest.

Astronauts↗

PubMed1996

Electromyographic identification of spinal oscillator patterns and recouplings in a patient with incomplete spinal cord lesion: oscillator formation training as a method to improve motor activities.

A patient with a strongly lesioned spinal cord, sub C5, relearned running, besides improving other movements, by an oscillator formation training (rhythmic, dynamic, stereotyped exercise). After 45 days of jumping on a springboard and other rhythm trainings, the patient was able to run 90 m in 41 s (7.9 km/h) (even 9.3 km/h 3 years after the lesion) besides marching (5.7 km/h), cycling, playing tennis and skiing. FF-type (alpha 1) (f = 8.3-11.4 Hz) and FR-type (alpha 2) (f = 6.7 Hz) motor unit firings were identified by electromyography (EMG) with surface electrodes by their oscillatory firing patterns in this patient. In EMG literature, the alpha 2-oscillatory firing is called "myokymic discharging". Alternating long and short oscillation periods were measured in FF-type motor units, with changing focus (change from long/short to short/long oscillation periods). The alternating mean period durations differed by approximately 10 ms. Transient synchronization of oscillatory firing FF-type motor units was observed with up to two phase relations per oscillation cycle. In recumbent position, the phase change in synchronization of two oscillatory firing motor units in the soleus muscle of one leg correlated with the change from alternating to symmetrical oscillatory firing of a third motor unit in the soleus muscle of the other leg. This measurement indicates that the alternating oscillatory firing of premotor neuronal networks is correlated with synchronization of oscillatory firing neuronal subnetworks, i.e., with coupling changes of oscillators, and is not due to reciprocal inhibition of half-centre oscillators as suggested by the change from alternating to symmetrical oscillatory firing. Coupling changes of oscillatory firing subnetworks to generate macroscopic (integrative) network functions are therefore a general organization form of the central nervous system (CNS), and are not related to rhythmic movements like walking or running only. It is proposed that synchronization of spinal oscillators, phase changes in synchronization, changes from alternating to symmetrical firing and backwards, and changes in the focus of alternating oscillatory firing are, among others, physiologic coupling rules of the human CNS to generate, by ongoing coupling changes of oscillatory firing subnetworks, integrative functions such as rhythmic and non-rhythmic movements. One phase relation between two oscillatory firing alpha 1-motor units was preserved from one volitional leg muscle activation (isometric contraction) to the subsequent one. Since running times improved upon successive runs for 90 m, the spinal cord seems to be able to store pattern organization for seconds up to minutes. Controlled and uncontrolled oscillatory firing of alpha 1-motor units in volitionally activated leg muscles were observed in this patient, which indicated that there still were pathologic recruitments of subnetworks after re-learning running and other movements. During walking, running, and jumping on a springboard, the activation patterns of the vastus lateralis, hamstrings, tibialis anterior, peronaeus longus, peronaeus brevis and soleus muscles were recorded (surface electromyography) to be still pathologic in accordance with partly still pathologic joint rotation angles measured kinematically. Especially upon running, the left knee joint flexion was reduced in swing by a rather permanent activity of the rectus femoris combined with an extra burst of the vastus lateralis in mid-swing. The recorded abnormalities are due to modification of the motor program rather than to muscle weakness per se. A further improvement of the movements of the patient seems possible by improving the motor program, i.e., by improving the functioning of the spinal pattern generators.(ABSTRACT TRUNCATED)

Accidents, Traffic↗

PubMed1995

Body fat and muscle thickness distributions in untrained young females.

Brightness-mode (B-mode) ultrasound was used to measure fat and muscle thicknesses on 44 untrained females (age = 18-29 yr, body density = 1.050 +/- 0.009 (SD)g.ml-1, %fat = 21.5 +/- 4.1%) at eight sites (triceps, biceps, forearm, subscapular, abdomen, quadriceps, hamstrings, and posterior calf). The correlation coefficients between fat and muscle thickness were not significant at any measurement site except for the triceps (r = -0.32, P < 0.05). Intercorrelation analyses among the eight sites were significant (P < 0.05) in almost all cases for fat thickness, while mainly between adjoining sites for muscle thickness. However, both tissues had a low degree of generality in thickness among sites. Fat thickness at all measurement sites was significantly correlated with body density except for the posterior calf; the best correlation was found with the quadriceps (r = -0.73). On the other hand, for muscle thickness, only the forearm and triceps were significantly correlated with body density. These results show 1) the extent of muscled and fat thicknesses are independent each of other within the same region, 2) fat and muscle thicknesses have a high degree of specificity in site distribution, and 3) fat thickness measurements determined from B-mode ultrasound may be of significant value assessing total body composition.

Adipose Tissue↗

PubMed2006

Analysis of EMG patterns of control subjects and subjects with ACL deficiency during an unanticipated walking cut task.

PURPOSE: The purpose of this study was to describe the muscle activation patterns of the vastus lateralis (VL), medial hamstrings (MH) and lateral hamstrings (LH) associated with subjects that were anterior cruciate ligament (ACL) deficient and controls. METHODS: A total of 54 subjects participated in this study including 25 ACL deficient subjects subdivided into copers (n=9) and non-copers (n=16) using clinical criteria. Muscle activation patterns were recorded at 1000 Hz during an unanticipated side step cut task. The root mean square processed data (time constant 11 ms) were ensemble averaged from 20% of stance before heel strike to toe off. Using the first five harmonics of the Fourier Coefficients as features, muscle activation patterns were divided using a cluster analysis algorithm. RESULTS: A majority (76-93%) of control subjects used three muscle activation patterns for each muscle. The coper group preferentially used a particular VL and MH activation pattern >2 times more frequently than controls. The non-coper group also preferentially used a MH activation pattern >2 times more frequently than controls and utilized a unique MH and LH activation pattern, distinct from the copers and controls. CONCLUSIONS: Specific muscle activation patterns distinguish subsets of subjects that are healthy and injured, suggesting possible patterns of muscle activation that contribute to coping status.

Adaptation, Physiological↗

PubMed1976

Electromyographic temporal analysis of gait: normal human locomotion.

The telemetered electromyographic (EMG) activity of pretibial muscles (tibialis anterior), triceps surae (lateral gastrocnemius), medial hamstring group and quadriceps (vastus lateralis) of 20 normal subjects was examined during locomotion. The ages of the subjects ranged from 8 to 72 years (mean, 37 years). A microswitch shoe was used to correlate the EMG activity with eight specific components of the gait cycle. Tibialis anterior showed two peaks of activity, the first at the swing-stance transition, the second at the stance-swing transition. Gastrocnemius showed a single peak of activity recorded during push-off. The medial hamstring showed its greatest activity during deceleration in the swing phase. Vastus lateralis demonstrated peak activity at the transition from swing to stance. The mean cadence was 106 steps per minute. Swing phase occupied 39.6% and stance phase 60.4% of the gait cycle.

Adolescent↗

PubMed1982

Architecture of the hind limb muscles of cats: functional significance.

Force, velocity, and displacement properties of a muscle are determined in large part by its architectural design. The relative effect of muscle architecture on these physiological variables was studied by determining muscle weight, fiber length, average sarcomere length, and approximate angle of pinnation of 24 cat hind limb muscles. Muscle lengths ranged from 28.3 to 144 mm, whereas fiber lengths ranged from 8.4 to 105.5 mm. Generally, fiber to muscle length ratios were similar throughout a muscle. Estimated angles of pinnation of muscle fibers varied from 0 to 21 degrees with most having an angle of less than 10 degrees. The cross-sectional area of the knee extensors was similar to the knee flexors (16.43 vs. 16.83 cm2) whereas the cross-sectional area of the ankle extensors was more than six times greater than the ankle flexors (18.59 vs. 2.83 cm2). There was a 6.7-fold difference in the maximal force between muscles, when normalized to a constant weight, that could be attributed to architectural features. Ratios of wet weight to predicted maximal tetanic tension for each muscle and muscle group were calculated to compare the relative priority of muscle force versus muscle length-velocity for a given mass of muscle. These ratios varied from 0.4 to 4.84. The ratios suggest that velocity and/or displacement is a priority for the hamstrings, whereas force is a priority for the quadriceps and lower leg muscles. As much as a 12.6-fold difference in maximal velocity between muscles can be attributed to differences in fiber lengths. This can be compared to approximately a 2.5-fold difference in maximal velocity reported to occur as a result of biochemical (intrinsic) differences.

Animals↗

PubMedDate not supplied

Thigh musculature in relation to chronic anterior cruciate ligament tear: muscle size, morphology, and mechanical output before reconstruction.

Eighteen male patients who had untreated chronic ACL rupture were studied in order to evaluate thigh muscle size, morphology, and isokinetic performance of the quadriceps muscle. Computed tomography disclosed a 5.1% mean atrophy of the quadriceps (P less than 0.05), 2.1% slight hypertrophy of the hamstrings (P less than 0.05), and also nonsignificant changes of all other muscle areas of the injured thigh. Muscle morphology (m. vastus lateralis) was normal in 11 biopsy specimens, whereas minor abnormalities (irregular shape or hypotrophy) could be seen in the rest. Isokinetic mechanical output of the knee extensors was 71% to 87% of that of the noninjured limb (P less than 0.01), and the mechanical output corrected for differences in quadriceps cross-sectional area was significantly lower in the injured than the uninjured limb. As there were no significant correlations between isokinetic performance and muscle size or qualitative morphology or morphometric data, the strength decrease cannot be explained by muscle atrophy or structural changes per se. We conclude that nonoptimal activation of the muscles during voluntary contractions is probably the most important causative mechanism of the strength decrease found in patients who have chronic symptomatic ACL tear.

Adult↗

PubMed1988

Nitrogen and energy relationships in malnourished patients with emphysema.

The purpose of this study was to examine the impact of nutritional support on nitrogen-energy relationships and functional parameters in malnourished patients with emphysema. Malnourished patients without lung disease served as the control group. Ten ambulatory, stable patients with emphysema and six patients without lung disease received an infusion of 5% dextrose (baseline) plus electrolytes (D5W) for two days, which was followed by an enteral or a parenteral infusion of either a carbohydrate-based (CB, 53% carbohydrate) or a fat-based diet (FB, 55% fat) for 1 wk each, in a randomized cross-over design. All patients had greater than 10% weight loss. Caloric intake was set at 1.7 times the resting energy expenditure (REE) as measured during the baseline period. The REE of patients with emphysema was 23 and 27% above that of the control group during baseline and refeeding periods, respectively. The increased REE was met primarily by an increased carbohydrate oxidation. During the infusion of D5W, N balance was lower in patients with emphysema, but during repletion N balance was similar in both groups of patients. Two weeks of nutritional support with either a CB or a FB diet increased body weight, N balance, and arm muscle area and improved maximal inspiratory pressure, skeletal muscle strength, and endurance-strength (using quadriceps, hamstring, and handgrip) to a similar degree in malnourished patients with and without lung disease. In other stress states, such as infection, it has been shown that hypermetabolism, hypercatabolism, and preferential fat oxidation occur concomitantly. Patients with emphysema are unusual because, although they are hypermetabolic, they are not hypercatabolic and do not demonstrate preferential fat oxidation.

Aged↗