Memory for fingertip forces: passive hand muscle vibration interferes with predictive grip force scaling

When subjects repetitively lift an object, the grip force they select is influenced by the mechanical object properties of the preceding lift. Similar effects on grip force scaling are observed whether the subsequent lift is performed with the same hand or the hand contralateral to the preceding lift. Here we demonstrate that passive vibration of the hand muscles involved in the generation of grip force in the interval between two blocks of lifting trials interferes with predictive grip force scaling. Following ten trials in which subjects lifted an object with constant mechanical properties with the dominant hand, muscle vibration was given to the first interosseus and adductor pollicis muscles of the dominant hand during a 10-min rest period. Compared with the last lift preceding vibration, peak rates of grip force increase and peak grip forces were scaled too high during the first lift following vibration whether the lift was made with the dominant or non-dominant hand. Subjects scaled grip force accurately to the object properties within three lifts following vibration. If subjects rested for 10 min after the first ten trials and received no vibration, then there was no significant difference in the peak grip force or its rate of increase between the last lift preceding rest and the first lift following it. We suggest that vibration impairs the memory processes responsible for predictive grip force scaling. Our data are consistent with the recent suggestion that these memory processes are neither specific for a certain motor action nor do they reflect internal representations of mechanical object properties.     

上海市50岁及以上人群维生素D水平与握力的关联研究

目的 探讨上海市≥50岁人群维生素D水平与握力的关系。方法 数据来源于WHO全球老龄化与成人健康研究我国上海市2018-2019年数据,采用logistic回归模型分析维生素D水平与握力的关系,进一步按照性别、年龄及乳制品摄入情况进行分层;采用限制性立方样条曲线绘制维生素D水平与低握力的剂量-反应曲线。结果 共4 391人纳入研究,其中男性2 054人（46.8%）;年龄（67.02±8.81）岁;低握力1 421人（32.4%）;维生素D不足及缺乏分别为1 533人（34.9%）和401人（9.1%）。在调整相关混杂因素后,logistic回归分析结果显示,维生素D缺乏的人群发生低握力的风险更高（OR=1.41,95%CI：1.09~1.83）;在男性中,调整相关混杂因素后,维生素D缺乏与低握力发生风险呈显著正相关（OR=1.67,95%CI：1.12~2.50）,而女性中两者之间无关联（OR=1.30,95%CI：0.97~1.74）;在60~69岁及≥80岁年龄组中,调整相关混杂因素后,维生素D缺乏与低握力发生风险呈显著正相关（OR=1.57,95%CI：1.05~2.35;OR=2.40,95%CI：1.08~5.31）,在乳制品摄入<250 ml/d的人群中,调整相关混杂因素后,二者之间呈显著正相关（OR=1.57,95%CI：1.17~2.09）,而在乳制品摄入≥250 ml/d的人群中无明显关联。限制性立方条样图显示,低握力的发生风险可能随维生素D含量的上升而降低,但差异无统计学意义（P>0.05）。结论 维生素D水平与握力存在一定的关系,维生素D缺乏人群出现低握力的风险更高。     

Influence of Grip Strength on Metacarpal Bone Mineral Density in Postmenopausal Japanese Women: A Cross-Sectional Study

Most published studies on the role of muscle strength in the maintenance of bone mineral density (BMD) focused on the relationship between specific muscle groups and adjacent bones, mostly in young and premenopausal women. This study examined the influence of grip strength on BMD of the metacarpal index in postmenopausal Japanese women. Subjects included 1168 postmenopausal women aged 40–70 years. BMD measurement was done with computed X-ray densitometry (CXD) by analyzing X-ray films of the right second metacarpal index. Grip strength was measured in both the dominant and nondominant hands using a squeeze dynamometer. Grip strength (r = 0.2474; P= 0.0001) and age (r =−0.5443; P= 0.0001) significantly correlated positively and negatively, respectively, with BMD. Physical activity (r = 0.1318; P= 0.0001) also correlated positively with BMD. Breastfeeding (r =−0.1658; P= 0.0001), however, correlated negatively with BMD. Subjects with a history of regular physical activity had higher grip strengths and BMD, than those with no physical activity. Adjustment for age, physical activity, calcium intake, BMI, breastfeeding, testing site, and menopausal type indicated a significant (P for trend = 0.0013) positive association of grip strength with BMD. Subjects with stronger grip strengths had a decreased risk for low BMD. Received: 24 February 1998 / Accepted: 7 August 1998     

CT评价腹股沟疝患者肌肉质量方法的前瞻性研究

目的　应用CT技术评价老年腹股沟疝患者的肌肉质量。方法　拟接受腹股沟疝手术、年龄在70~90岁的男性住院患者30例为研究对象,40~50岁10名男性健康受试者为成人对照组,10名同年龄段接受健康查体老年人为老年对照组,记录一般资料,应用CT技术扫描腹部和大腿,通过专用软件计算相应肌肉面积。结果　研究组握力（36.44±14.15）kg明显少于成人对照组（77.30±22.69）kg （P=0.001）,研究组小腿围（25.18±2.31）cm 明显少于成人对照组（27.62±2.33）cm （P=0.006）。CT扫描显示研究组与成人对照组L3（第3腰椎）平面腹部面积、皮下脂肪面积、腹腔脂肪面积和竖脊肌总面积相近,研究组腹部肌肉面积（12 094.23±1 970.30）mm2和竖脊肌肌肉面积（1 642.60±266.90）mm2明显少于成人对照组的（17 462.00±1 600.58）mm2和（2 003.50±350.91）mm2（P=0.001, P=0.007）。L3骨骼肌指数为50.64±7.52,存在肌肉减少症（≤52.4）为66.7 %（20/30）。与同年龄正常查体老人腹部肌肉CT结果相似。研究组下肢骨骼肌面积明显少于成人对照组（P=0.001）,下肢脂肪和股骨面积两组比较差异无统计学意义（P＞0.05）。结论　老年腹股沟疝患者肌肉质量和力量明显低于成人对照组,CT技术可作为评价工具。     

Midlife muscle strength and human longevity up to age 100 years: a 44-year prospective study among a decedent cohort

We studied prospectively the midlife handgrip strength, living habits, and parents’ longevity as predictors of length of life up to becoming a centenarian. The participants were 2,239 men from the Honolulu Heart Program/Honolulu–Asia Aging Study who were born before the end of June 1909 and who took part in baseline physical assessment in 1965–1968, when they were 56–68 years old. Deaths were followed until the end of June 2009 for 44 years with complete ascertainment. Longevity was categorized as centenarian (≥100 years, n = 47), nonagenarian (90–99 years, n = 545), octogenarian (80–89 years, n = 847), and ≤79 years (n = 801, reference). The average survival after baseline was 20.8 years (SD = 9.62). Compared with people who died at the age of ≤79 years, centenarians belonged 2.5 times (odds ratio (OR) = 2.52, 95% confidence interval (CI) = 1.23–5.10) more often to the highest third of grip strength in midlife, were never smokers (OR = 5.75 95% CI = 3.06–10.80), had participated in physical activity outside work (OR = 1.13 per daily hour, 95% CI = 1.02–1.25), and had a long-lived mother (≥80 vs. ≤60 years, OR = 2.3, 95% CI = 1.06–5.01). Associations for nonagenarians and octogenarians were parallel, but weaker. Multivariate modeling showed that mother’s longevity and offspring’s grip strength operated through the same or overlapping pathway to longevity. High midlife grip strength and long-lived mother may indicate resilience to aging, which, combined with healthy lifestyle, increases the probability of extreme longevity.     

中国老年人心血管代谢性共病与握力和步速关系的队列研究

目的 探索中国老年人心血管代谢性共病与握力和步速之间的关系。方法 采用2011-2015年中国健康与退休追踪调查数据,纳入 ≥ 60岁的老年人进行分析。采用广义估计方程分析心血管代谢性共病与握力和步速之间的相关性。结果 共纳入测量握力的研究对象6 357名,测量步速的研究对象6 250名。与未患心血管代谢疾病组相比,患有1种(β=-0.018,95%CI:-0.026~-0.010)、2种(β=-0.029,95%CI:-0.041~-0.018)、≥ 3种(β=-0.050,95%CI:-0.063~-0.037)心血管代谢性疾病的研究对象握力下降的风险增加。心血管代谢性疾病数量(1种:β=-0.052,95%CI:-0.326~0.222;2种:β=-0.083,95%CI:-0.506~0.340; ≥ 3种:β=-0.186,95%CI:-0.730~0.358)与步速的关联无统计学意义。未患心血管代谢性疾病以及患有1种、2种、≥ 3种心血管代谢性疾病的研究对象步速预测值分别为1.98(95%CI:1.38~2.58)、1.93(95%CI:1.34~2.51)、1.89(95%CI:1.18~2.61)和1.79(95%CI:1.10~2.48)m/s,其下降幅度有临床意义。具有较高的握力降低、步速减慢风险的心血管性代谢性疾病组合大多包含糖尿病。结论 心血管代谢性疾病数量和组合与握力降低和步速减慢的风险增加有关。握力和步速可推荐为评估心血管代谢性共病严重程度的测量指标。     

The effect of externally generated loading on predictive grip force modulation

A characteristic of skilled movement is the ability of the CNS to predict the consequences of motor commands. When we lift an object there is an anticipatory increase in grip force that prevents a grasped object from slipping. When an object is pulled from our grasp by an external force, a reflexive modulation in grip force prevents slippage. Here we examine how external perturbations to a grasped object influence anticipatory grip force during object manipulation using a bimanual task, with each hand holding a computer-controlled object. Subjects were instructed to maintain the position of the object held in the right hand. Loading was applied to this restrained object: either self-generated by the action of their left hand or externally generated by a motor. The magnitude of the grip force response to self-generated loading increased after the object was loaded, and the latency of this response remained predictive of load force. This implies that external and self-generated loading increase the anticipatory grip force response. Unlinked trials, where the subject's moved their left hand but no loading was generated on the right-hand object were used to assess the presence of purely predictive control of grip force. External loading soon after self-generated loading maintained an existing predictive response once the linkage between the subject's action and object loading had been removed. However, external loading had no influence as the existing prediction decays. Therefore, the predictive grip force response during object manipulation can be significantly modified by object loading from an external source.     

Treadmill walking effects on grip strength in young men with Down syndrome

This study was aimed at investigating the relation between grip strength and anthropometric factors and the impact of an aerobic exercise on grip strength in young men with Down syndrome (DS). This study was a pre-post design. Twelve males with DS were assigned to an exercise group, who walked using an incremental protocol on a treadmill for 20 min at aerobic levels. Eight additional persons with DS were assigned to an attentional control group, who watched a video. Measure of grip strength was tested pre- and post-interventions. The results showed positively significant relationship among grip strength and age (r = .74, p < .01), weight (r = .52, p = .02), body mass index (r = .61, p = .01) and waist circumference (r = .54, p = .02). In addition, Grip strength was slightly improved after exercise (p = .03) but decreased after control condition. The results showed that anthropometric factors, such as age, weight, body mass index and waist circumference, were positively correlated with grip strength in young men with DS. Further, improvement in grip strength can be found even after a single exercise session. This finding emphasizes the importance of maintaining an active lifestyle in persons with DS for performing activities of daily living.