Effects of closed versus open kinetic chain knee extensor resistance training on knee laxity and leg function in patients during the 8- to 14-week post-operative period after anterior cruciate ligament reconstruction

Open kinetic chain (OKC) knee extensor resistance training has lost favour in ACLR rehabilitation due to concerns that this exercise is harmful to the graft and will be less effective in improving function. In this randomized, single-blind clinical trial OKC and closed kinetic chain (CKC) knee extensor training were compared for their effects on knee laxity and function in the middle period of ACLR rehabilitation. The study subjects were 49 patients recovering from ACLR surgery (37 M, 12 F; mean age=33 years). Tests were carried out at 8 and 14 weeks after ACLR with knee laxity measured using a ligament arthrometer and function with the Hughston Clinic knee self-assessment questionnaire and single leg, maximal effort jump testing (post-test only). Between tests, subjects trained using either OKC or CKC resistance of their knee and hip extensors as part of formal physical therapy sessions three times per week. No statistically significant (one-way ANOVA, p>0.05) differences were found between the treatment groups in knee laxity or leg function. OKC and CKC knee extensor training in the middle period of rehabilitation after ACLR surgery do not differ in their effects on knee laxity or leg function. Exercise dosages are described in this study and further research is required to assess whether the findings in this study are dosage specific.     

试论医院的成本管理

文章对医院成本管理的意义、内容和基本要求进行了详述,指出医院成本管理应处理好的几个关系及医疗机构成本管理的发展趋势,认为加强成本管理对提高两个效益、提升竞争实力有重要意义。     

Oral contraceptive use and exercise-induced muscle damage and recovery

Endogenous estrogen appears to attenuate muscle damage in animals; however, similar evidence in humans is not as strong. This investigation tested the hypothesis that women taking oral contraceptives, thereby having higher exogenous estrogen levels, would be more susceptible to damage or have an attenuated recovery from exercise-induced muscle damage. Muscle damage in women taking combined estrogen and progesterone oral contraceptives (OC) were compared to noncontraceptive users (NOC) after 50 eccentric muscle contractions of the elbow flexors. Measures of maximal isometric strength (MIS), range of motion (ROM), arm circumference (CIR), soreness (SOR), and serum creatine kinase (CK) activity were taken pre- and for 5 days post-exercise. All measures following exercises were similar between groups with the exception of MIS. Force recovery began 2 days post-exercise in the NOC group, while in the OC group strength did not start to return to normal until 4 days post-exercise (p < 0.05). Women taking oral contraceptives had a delayed strength recovery after eccentric exercise.     

The effects of plasma cortisol elevation on total and differential leukocyte counts in response to heavy-resistance exercise

The purpose of this study was to examine the impact of heavy-resistance exercise-induced elevations of plasma cortisol on circulating leukocyte counts. Nine healthy, recreationally weight-trained men volunteered for this investigation. Two exercise protocols were employed. Protocol 1 (P-1) consisted of eight sets of ten-repetition maximum leg-press exercise with 1-min rest periods between sets. Protocol 2 (P-2) was identical except for 3-min rest periods. A non-exercise protocol was used as a control treatment (C). Venous blood samples, heart rates and ratings of perceived exertion were obtained pre-, mid- and 5 min post-exercise. In order to examine the maximal influence of cortisol on leukocyte counts, we placed the subject's highest magnitude of cortisol change in response to one of the heavy-resistance exercise protocols in what we designated as the response protocol (R) and the other value was placed into what was designated as the non-response protocol (NR) for analysis. Significant increases in cortisol occurred from pre- to post-exercise for P-1 [mean (SD) 241.4 (25.0) to 302.0 (60.0) nmol · 1^–1] and in the R conditions pre- to mid- and pre- to post-exercise [218.0(0.0) to 302.4(37.1) to 326.8 (51.9) nmol · 1^–1]. No significant changes in cortisol occurred for P-2, NR or the control conditions. Significant increases in total leukocyte counts occurred from pre- to mid- and pre- to post-exercise both for R [5.6 (0.4) to 7.4 (0.3) to 7.3 (0.3) cells · 10⁹ · 1^–1] and NR [5.7 (0.3) to 6.9 (0.4) to 7.1 (0.4) cells · 10⁹ · 1^–1]. No significant changes in differential leukocyte counts occurred. In addition, no significant correlations between cortisol and total or differential leukocyte counts were observed. These data indicate that acute increases in total leukocytes along with no changes in differential leukocyte counts can occur in response to heavy-resistance exercise that does not significantly elevate plasma cortisol concentrations.     

Heart Rate Regulation as Skill Learning: Strength-Endurance versus Cardiac Reaction Time

Fleishman's (1966) model of complex motor skill learning is applied to viscera) self-regulation. Five different underlying abilities are illustrated: strength, endurance, steadiness, control precision, and reaction time. In the experiment, 16 subjects were pre and post tested with instructions alone for degree of cardiac Strength and Endurance control (SE) (maximally increase or decrease heart rate and sustain it for a minute) and degree of cardiac Reaction Time control (RT) (produce a small, 3 sec burst of increased or decreased heart rate as quickly as possible to the onset of a trial). All subjects received heart rate biofeedback during training, but half practiced SE while the other practiced RT. It was predicted that cardiac learning would be specific to the skill practiced during biofeedback, with little transfer to the other task. The data indicated that SE training led to improved SE control (30%) accompanied by a slight decrement in RT control (-5%). Conversely, RT training led to markedly improved RT control (120%)H accompanied by a small decrement in SE control(18%). The value of conceptualizing complex visceral skills as reflecting learned patterns of underlying neurophysiological abilities is illustrated.     

Eccentric and posteccentric contractile behaviour of skeletal muscle a comparative study in frog single fibres and in humans

Summary Eccentric and posteccentric force behaviour in human skeletal muscle and in isolated frog muscle fibres was studied by imposing stretch-and-hold loading conditions during contractions with maximal voluntary effort or under tetanic stimulation in the isolated preparations. The investigations on human muscle were made on the forearm flexors of a group of kayak racers (n = 16; age: 17–22 years) and of schoolgirls (n = 15; age: 17–18 years) with both groups participating in a strength-training programme over 4 (kayak racers) or 3 (girls) months. Half of the training regime consisted of eccentric elements. In the isolated muscle fibres, it could be shown that in the posteccentric hold phase the enhanced force decayed exponentially to the original isometric value with a mean time-constant of 0.35 s (10°C) and of 0.23 (20°C). In the forearm flexor of human subjects similar results were obtained not only qualitatively but even quantitatively (time constant of posteccentric force decay: 0.25–0.37 s). Strength training in both groups did not lead to an enhancement in maximal isometric force alone [mean increase in force 17 (SD 10)%], a well-known and generally accepted fact, but also to a parallel shift in eccentric [21 (SD 10)%] and posteccentric force level. The close similarity between the findings in isolated muscle fibres and in human muscle in situ suggests that the eccentric and posteccentric behaviour must be primarily ascribed to the contractile properties of the muscle fibres themselves. A three-element muscle model with variable visco-elastic properties would appear to be most suitable for simulating the experimental findings.     

Comparison of pressure pain threshold, grip strength,dexterity and touch pressure of dominant and non-dominant hands within and between right-and left-handed subjects

This study was done to evaluate differences in pressure pain threshold, grip strength, manual dexterity and touch pressure threshold in the dominant and non-dominant hands of right- and left-handed subjects, and to compare findings within and between these groups. Thirty-nine right-handed and twenty-one left-handed subjects participated in the study. Pressure pain threshold was assessed using a dolorimeter, grip strength was assessed with a hand-grip dynamometer, manual dexterity was evaluated using the VALPAR Component Work Sample-4 system, and touch pressure threshold was determined using Semmes Weinstein monofilaments. Results for the dominant and non-dominant hands were compared within and between the groups. In the right-handed subjects, the dominant hand was significantly faster with the VALPAR Component Work Sample-4, showed significantly greater grip strength, and had a significantly higher pressure pain threshold than the non-dominant hand. The corresponding results for the two hands were similar in the left-handed subjects. The study revealed asymmetrical manual performance in grip strength, manual dexterity and pressure pain threshold in right-handed subjects, but no such asymmetries in left-handed subjects.     

Effect of strength training on the relationship between magnetic resonance relaxation time and muscle fibre composition

Summary The effect of muscle hypertrophy on the relationship between magnetic resonance (MR) relaxation time and muscle fibre composition was investigated. Relaxation time and muscle fibre composition were measured in five subjects before and after a 20-week period of strength training. Muscle fibre composition in all subjects exhibited a significant shift to a predominance of fast-twitch (FT) fibres as a result of 20-week strength training (% area FT fibres: mean values from 49.8%, SD 17.9% to 57%, SD 5.6%; P<0.05). Longitudinal relaxation time (T₁) and transverse relaxation time (T₂) were prolonged significantly after strength training (T₁ mean values from 334.9 ms, SD 13.6 to 359.0 ms, SD 9.0, P<0.001; T₂ from 27.5 ms, SD 0.9 to 30.8 ms, SD 2.3, P<0.05). A constant relationship was observed in changes caused by strength training in muscle fibre composition (% area FT) and relaxation time, with a high correlation obtained between both parameters. These results indicate that MR relaxation time can be used for non-invasive estimation of muscle fibre composition.     

Effect of very low calorie diet on body composition and exercise response in sedentary women

Summary The effect of very low calorie diet (VLCD) on fat-free mass (FFM) and physiological response to exercise is a topic of current interest. Ten moderately obese women (aged 23–57 years) received VLCD (1695 kJ·day^–1) for 6 weeks. FFM, estimated by four conventional techniques, and heart rate (f _c), blood lactate (la_b), mean arterial pressure (MAP), respiratory exchange ratio (R) and rating of perceived exertion (RPE) were measured during a submaximal cycle ergometry test 1 week bevore, in the 2nd and 6th week, and 1 week after VLCD treatment. Strength and muscular endurance of the quadriceps and hamstrings were tested by isokinetic dynamometry. The 11.5-kg reduction in body mass was approximately 63% fat and 37% FFM. The latter was attributed largely to the loss of water associated with glycogen. Whilst exercise f _c increased by 9–14 beats·min^–1 (P<0.01), there were substantial decreases (P<0.01) in submaximal MAP (1.07–1.73 kPa), lab (0.75–1.00 mmol·1^–1 and R (0.07–0.09) during VLCD. R and f _c returned to normal levels after VLCD. Gross strength decreased (P<0.01) by 9 and 13% at 1.05 rad·s^–1 and 3.14 rad·s^s–1, respectively. Strength expressed relative to body mass (Nm·kg^–1) increased (P<0.01) at the lower contraction velocity, but there was no change at the faster velocity. Muscular endurance also decreased (P<0.01) by 62 and 82% for the hamstrings and quadriceps, respectively: We concluded that the strength decrease was a natural adaptation to the reduction in body mass as the ratio of strength to FFM was maintained. Despite the physiological alterations, subjects could tolerate short-term, steady-state exercise during VLCD, with only slight increases in RPE. However, greater fatigue is associated with long duration strength training exercises during VLCD.