Intensity-dependent effect of body tilt angle on calf muscle fatigue in humans

Body tilt angle affects the fatigue of human calf muscle at a high contractile force (i.e. 70 %MVC); but the range of forces across which this effect occurs is not known and we sought to determine this in the present study. Fourteen men performed intermittent calf muscle contractions at either 30, 40, 50 and 60 %MVC (Group 1 n = 7) or at 80 and 90 %MVC (Group 2 n = 7). Two tests were performed at each intensity in the supine (tilt angle = 0°) and inclined head-up position (tilt angle = 67°). MVC was measured prior to and during each calf exercise test, and the linear rate of decline in MVC during each test was used to estimate muscle fatigue. MVC prior to each test was unaffected by body tilt angle in Groups 1 and 2. In Group 1 muscle fatigue was significantly lower in the inclined than supine position at 50 %MVC (0.10 ± 0.05 vs. 0.19 ± 0.10 N s⁻¹) and 60 %MVC (0.22 ± 0.20 vs. 0.36 ± 0.33 N s⁻¹); but there was no significant difference in fatigue at 30 %MVC (0.07 ± 0.06 vs. 0.07 ± 0.07 N s⁻¹) and 40 %MVC (0.12 ± 0.07 vs. 0.18 ± 0.08 N s⁻¹). In Group 2, muscle fatigue was significantly lower in the inclined compared with the supine position at 80 %MVC (0.90 ± 0.50 vs. 1.49 ± 0.87 N s⁻¹) and 90 %MVC (1.19 ± 0.47 vs. 1.79 ± 0.78 N s⁻¹). These data demonstrate that the postural effect on calf muscle fatigue during intermittent contractions is manifest at moderate to very high forces, but that it does not occur at low forces.     

Strength recovery after anterior cruciate ligament reconstruction with quadriceps tendon versus hamstring tendon autografts in soccer players: A randomized controlled trial

Background

The comparison between HT and QT grafts in strength recovery and function after an ACLR is scarce in the literature.

Short-term functional advantages after medial unicompartmental versus total knee arthroplasty

Background

There are many uncertainties about the advantages and disadvantages of using unicompartmental (UKA) versus total knee arthroplasty (TKA) to treat patients with knee osteoarthritis. It is important to have sufficient early postoperative quadriceps strength for long-term, self-reported and gait-related outcomes after knee arthroplasty, but very limited comparative data exist regarding UKA and TKA patients.

ICU老年机械通气患者握力现状与影响因素分析

目的 调查ICU老年机械通气患者握力现状,并探讨其影响因素。 方法 便利选取2020年1月—12月浙江省某三级甲等医院ICU收治的218例老年机械通气患者作为调查对象,采用一般资料调查表、电子握力器、营养风险评估量表2002对其进行横断面调查。采用多元线性回归分析老年机械通气患者握力的影响因素。 结果 ICU老年机械通气患者的握力为（13.8±4.7） kg。多元线性回归分析显示,性别、年龄、运动方式、镇静药物使用时间、营养风险评估量表2002评分是影响其握力的主要因素（P<0.05）。 结论 ICU老年机械通气患者的握力较低,女性、高龄、既往不运动、镇静药物使用时间>5 d、营养风险评估量表2002评分≥3分的机械通气患者握力较低。护理人员应加强其握力的动态评估,控制相关影响因素。     

Hand Grip and Leg Muscle Strength in Hemodialysis Patients and Its Determinants

BackgroundChronic kidney disease is associated with chronic inflammation and progressive loss of peripheral muscle strength and the ability to exercise, and these changes are highly pronounced in patients receiving hemodialysis (HD). We evaluated hand grip strength (HGS) and leg muscle strength (LMS) in patients receiving HD and attempted to identify factors associated with muscle strength.MethodsWe screened HGS (opposite the fistula side) and LMS (both sides) in HD patients at a single center (n = 112) by using digital hand and leg dynamometers (T.K.K. 5401 and 5710e/5715, Takei Scientific Instruments Co. Ltd., Niigata, Japan).ResultsThe mean age of patients was 62.6 years, and 73.2% of the patients were male. Diabetes was the cause of kidney failure in 50% of the patients, and the median HD vintage was 34 months. A total of 77.7% of patients reported that they participated in regular home-based exercise, and 29.5% of patients regularly participated in hospital-based resistance exercise. HGS and LMS showed good correlation (r = 0.715, P < 0.001). HGS (25.1 vs. 17.0 kg) and LMS (30.1 vs. 20.4 kg) were greater in males (P < 0.001 and P < 0.001, respectively) than in females. Older patients (≥ 60 years) showed less LMS than younger patients in both males and females (P = 0.012 and P = 0.037, respectively), but HGS did not differ according to age. Patients performing regular home- or hospital-based exercise showed higher HGS than those who did not exercise (24.2 vs. 18.6 kg, P = 0.011), but LMS was not significantly different (29.3 vs. 23.6 kg, P = 0.185). Multiple linear regression analysis proved that male sex, younger age, and any type of exercise were factors associated with improved HGS and LMS. Groups of older age (≥ 60 years), male sex, and shorter duration of HD (< median) benefitted more from exercise.ConclusionSex, age, and exercise were the most important determinants of muscle strength in HD patients. We need to encourage patients to engage in regular home or group exercise from the beginning of dialysis and introduce new feasible forms of exercise for HD patients.     

Association between muscle strength and the cardiopulmonary status of individuals living with HIV/AIDS

OBJECTIVE:

The purpose of this study was to compare aerobic function [anaerobic threshold (%V˙O₂-AT), respiratory compensation point (%V˙O₂-RCP) and peak oxygen uptake (V˙O_2peak)] between physically active patients with HIV/AIDS and matched controls and to examine associations between disease status, poor muscle strength, depression (as estimated by the profile of mood states questionnaire) and the aerobic performance of patients.

METHODS:

Progressive treadmill test data for %V˙O₂-AT (V-slope method), RCP and (V˙O_2peak) were compared between 39 male patients with HIV/AIDS (age 40.6±1.4 years) and 28 male controls (age 44.4±2.1 years) drawn from the same community and matched for habitual physical activity. Within-patient data were also examined in relation to CD4⁺ counts (nadir and current data) and peak isokinetic knee torque.

RESULTS:

AT, RCP and (V˙O_2peak) values were generally similar for patients and controls. Within the patient sample, binary classification suggested that AT, RCP and (V˙O_2peak) values were not associated with either the nadir or current CD4⁺ count, but treadmill test variables were positively associated with peak isokinetic knee torque.

CONCLUSION:

The aerobic performance of physically active patients with HIV/AIDS is generally well conserved. Nevertheless, poor muscle strength is observed in some HIV/AIDS patients, which is associated with lower anaerobic power and (V˙O_2peak), suggesting the possibility of enhancing the aerobic performance of patients with weak muscles through appropriate muscle-strengthening activities.     

Remineralising fluorine containing bioactive glass composites

ObjectivesThe objective was to investigate the mechanical properties, fluoride release and apatite formation of resin based dental composites based on a fluoride containing Bioactive Glass (BG) with and without a silylating agent.MethodsA SiO₂–P₂O₅–CaO–SrO–Na₂O–CaF₂ BG was synthesized by the melt quench route. This glass and a commercially available inert glass (IG) were incorporated into a light cured BisGMA-TEGMA resin. The composite resins were then evaluated in terms of their ability to form apatite by Fourier Transform Infrared spectroscopy (FTIR) and by scanning electron microscopy (SEM) following immersion in artificial saliva at pH 4 (AS4) and pH 7 (AS7). The experiments were performed with and without silylation of the BG. The compressive strength and flexural strength were determined after 1, 28 and 84 days of immersion in the AS4 and AS7 immersion media.ResultsThe FTIR spectra of the BG composites exhibited split bands at approximately 560 and 600 cm^?1 corresponding to a apatite formation in the surface or on the surface under all immersion conditions. SEM showed the presence of a reacted layer of glass particles in the composite surface and the presence of a surface layer of apatite in AS7.The compressive strength and flexural strength were significantly higher for the silylated BG composites. The strengths of both silylated and non silylated BG composites and IG composites decreased upon immersion.SignificanceBG composites exhibit reduced strengths upon immersion but still exhibit strengths comparable to existing composites after 84 days of immersion.     

Damage sensitivity of dental zirconias to simulated occlusal contact

ObjectiveMechanical damages can occur from dental restoration processing and fitting, or while it is in-service. This study evaluates the damage sensitivity of translucent zirconia (5Y-PSZ) relative to conventional 3Y-PSZ following mouth-motion simulations at various loads.Methods5Y-PSZ and 3Y-PSZ discs were adhesively bonded to a dentin-like substrate and divided into groups according to the load (50 N or 200 N) and number of cycles (up to 10⁶) used in the chewing simulation. Specimens were mounted with 30° inclination in an electrodynamic mouth-motion simulator, and subjected to contact-slide-liftoff cyclic loading in water. Surface and sub-surface damages were analyzed using a sectioning technique. After the simulation, specimens were removed from the substrate and loaded with the damaged surface in tension for biaxial strength testing to assess their damage tolerance.ResultsThe strength of both ceramics underwent significant degradation after mouth-motion simulations. For 5Y-PSZ, the strength degradation was greater (～60%) and occurred at a lower number of cycles than 3Y-PSZ. Herringbone cracks emerged on 3Y-PSZ and 5Y-PSZ surfaces under a 200-N load after 50 and 10 cycles, respectively. Meanwhile at a 50-N load, cracks formed at ～1000 cycles in both ceramics. Further increasing the number of cycles only had moderate effects on the strength of both ceramics, despite an increase in surface and sub-surface damage. More significantly, a 50-N occlusal load can debase the zirconia strengths as much as a 200-N load.SignificanceSurface flaws produced during the chewing simulation are capable of significant strength degradation in zirconia, even after a small number of low-load cycles.     

A Comparison of Maxillary Basal length in a Group of Skeletal III Cases,with a Control Group

Abstract

Skeletal III malocclusions may be due to mandibular prognathism or maxillary retrognathism or any combination of these features. It had been the impression that the maxilla was shorter in Class III cases with a high maxillary-mandibular planes angle and so a comparison was made between skeletal III cases with high maxillary-mandibular planes angle and a control group. The results showed a significant shortening in the Class III group.