Neuromuscular adaptations during bilateral versus unilateral strength training in middle-aged and elderly men and women

Twelve middle-aged men and 12 middle-aged women in the 50-year-old age group (M50; range 44–57 years; W50; 43–57), and 12 elderly men and 12 elderly women in the 70-year-old age group (M70; 59–75; W70; 62–75) volunteered as subjects in order to examine effects of 12-week progressive heavy resistance strength training on electromyographic activity (EMG), muscle cross-sectional area (CSA) of the quadriceps femoris and maximal concentric force in a one repetition maximum (1 RM) test of the knee extensor muscles. One half of the subjects in each group performed the knee extension (and flexion) exercises only bilaterally (BIL), while another half performed the exercises only unilaterally (UNIL). None of the subject groups demonstrated statistically significant changes in any of the 1 RM values during the 2 week control period with no training (between week -2 and 0) preceding the actual experimental training. However, the 12-week training resulted in increases (P<0.05–0.001) in 1 RM values in each group so that the average relative increase of 19±12% (P<0.001) in bilateral 1 RM in all BIL trained subjects was greater (P<0.05) than that of 13±8% (P<0.001) recorded for all UNIL trained subjects. The average relative increases of 17±11% (P<0.001) and 14±14% (P<0.001) in unilateral 1 RM values of the right and left leg in all UNIL trained subjects were greater (P<0.05) than those of 10±18% (P<0.001) and 11±11% (P<0.001) recorded for all BIL trained subjects, respectively. The relative average increase of 19±19% (P<0.001) observed in the maximum averaged IEMG of both legs during the bilateral actions in all BIL trained subjects was greater (P<0.05) than that of 10±17% (P<0.05) recorded for all UNIL trained subjects. The relative increases of 14±12% (P<0.001) and 11±6% (P<0.001) recorded for the CSA in all BIL and UNIL trained subjects did not differ significantly from each others. The present findings suggest that progressive heavy resistance strength training leads to great increases in maximal dynamic strength of the trained subjects accompanied by both considerable neural adaptations and muscular hypertrophy not only in middle-aged but also in elderly men and women. Both bilateral and unilateral exercises are effective to produce functional and structural adaptations in the neuromuscular system, although the magnitude of functional strength increase seems to be specific to the type of exercise used, further supporting the principle of specificity in the design of strength programmes.     

Gonadal steroids and salivary IgA in healthy young women and men

Empirical evidence from clinical, nonhuman animal, and in vitro studies point to links between immune function and gonadal steroids, including potential androgenic immunosuppression and estrogenic immunoenhancement. This study was designed to test links between steroids and one marker of mucosal humoral immunity—immunoglobulin A (IgA) in healthy individuals, to facilitate comparisons with other species and clinical populations, as there are few existing studies with healthy humans that also allow gender/sex investigations. Participants (86 women, 91 men) provided a saliva sample for measurement of testosterone (T), estradiol (E₂), and IgA. Results showed that E₂ was significantly and positively correlated with IgA in women, and group analyses by E₂ quartile showed that this association was linear. No significant correlations or nonlinear associations were seen between T and IgA in men or women, or E₂ and IgA in men. Evidence from this study indicates that IgA and E₂ are significantly associated in healthy premenopausal women. Am. J. Hum. Biol. 2010. © 2009 Wiley‐Liss, Inc.     

Hip bone mineral density is improved by high-impact aerobic exercise in postmenopausal women and men over 50 years

Fifteen men and women (six men) between the ages of 50 and 73 years were recruited to begin keep-fit classes. They were matched for sex, age, menopausal status and mass to 15 non-exercising controls. The keepfit classes were two to three times a week and included high-impact exercise, including step and jumping exercises specifically to load the proximal femur and spine. Proximal femur, lumbar spine and total body bone mineral density (BMD) were measured at 0 and 12 months. Urinary pyridinoline (Pyr) and deoxypyridinoline (dPyr) crosslinks were measured every 6 months to assess bone resorption. Quadriceps isometric strength was measured every 6 months. BMD increased non-significantly at the femoral neck [1.57 (0.8%] and Wards triangle [1.97 (1.4%], and significantly at the greater trochanter 2.21 (0.9)% (P=0.02) in the exercise group. Femoral neck BMD decreased by −1.9(0.8)% (P=0.049) in the control group, which was significantly different from the change in the exercise group (P=0.009). BMD did not change at the Wards triangle or trochanter in the controls. Lumbar spine BMD did not change in either group. Total body BMD did not change in the exercise group, but decreased by −0.79 (0.3)% (P=0.02) in the controls. Follwing 6 months of the exercise classes, Pyr and dPyr crosslinks were significantly reduced [−19.0 (7.2)%;P=0.0019 and −20.0 (7.7)%;P=0.021 respectively]. There was no significant change in crosslinks after 1 year, and no change at any time in the controls. Quadriceps strength changed by 5.4 (3.7)% in the exercise group and by −6.9 (2.5)% (P=0.01) in the control group after 12 months, being significant between groups (P=0.008). This study suggests that high-impact, aerobic exercise in postmenopausal women and men over 50 years old is feasible and effective at maintaining muscle strength and increasing proximal femur BMD but not spine or total body BMD.     

Telomere length versus hormonal and bone mineral status in healthy elderly men

Telomeres, the termini of linear chromosomes, exert a key role in the process of cellular ageing. Progressive telomere shortening is implicated in senescence in vitro and ample evidence exists to support the hypothesis that telomere length is correlated with chronological age and ageing phenotypes in vivo. In this study, we assessed whether mean telomere length of peripheral blood leukocytes predicts age-associated bone loss and/or is related to sex steroid status in an elderly healthy male population (71-86 years). Out of this population, we selected 110 samples for telomere restriction fragment (TRF) length analysis. Fasting blood was analysed for testosterone, estradiol, sex hormone binding globulin and biochemical markers of bone turnover. Also, the bioavailable fractions of sex steroids were calculated. Bone mineral density was measured at baseline and longitudinal follow-up was available for 84 men. We found that mean TRF length was inversely correlated with age (r=-0.19; P=0.049). Although no correlations were found with sex steroids or BMD at baseline, age corrected mean TRF length was associated with longitudinal bone loss for different distal forearm sites (P<0.05). Further studies are required to confirm our results, yet in this study, the predictive value of telomere length for bone loss appears to be substantial, hence underscoring the role of telomere length as a biomarker of ageing phenotypes.     

Association between depression and bone mineral density in community-dwelling older men and women in Korea

Objectives

Previous research suggested a significant correlation between depression and osteoporosis, but little is known for the elderly Asian population. We investigated an association between depression and bone mineral density (BMD) in the Korean elderly.

Study design

Cross-sectional data analysis of a community-based study, Kangwha Island, South Korea.

Main outcome measures

BMD, measured at the os calcis using a quantitative ultrasound device, was expressed as stiffness index and T-score. Depressive symptoms were evaluated by the Korean version of Beck Depression Inventory (K-BDI). Depression was defined as a K-BDI score of 16 or higher. Participants also completed a questionnaire, including demographic factors, metabolic abnormalities, and health-related lifestyle factors.

Results

A total of 932 local residents (422 men and 510 women) aged 60–80 years completed the questionnaires and baseline BMD evaluation. Men with depression had a significantly lower stiffness index compared to those without depression in an age-adjusted (77.2 ± 5.2 vs. 86.0 ± 1.5, p = 0.002) and a multivariate-adjusted model (78.5 ± 5.2 vs. 85. 9 ± 1.5, p = 0.007). Correspondingly, men with depression had an increased probability of having an osteoporosis (T-score ≤ −2.5) compared to those without depression; the age-adjusted odds ratio was 2.86 (95% CI, 1.36–6.01) and the multivariate-adjusted odds ratio was 2.69 (95% CI, 1.26–5.76). However, no significant association was observed in older women.

Conclusions

Depression was significantly associated with lower BMD in Korean older men, but not in women.     

Skeletal muscle satellite cell populations in healthy young and older men and women

The purpose of the present investigation was to assess satellite cell populations and morphology in m. vastus lateralis biopsies obtained from young (20-30 years) and older (65-75 years) healthy, sedentary men and women. Multiple muscle biopsies were obtained from 14 young individuals (men, n = 7; women, n = 7) and 15 older individuals (men, n = 8; women, n = 7). Muscle fibers were viewed longitudinally using a Zeiss EM 10 CA electron microscope. All myonuclei and satellite cells were counted and satellite cells were photographed for morphological analysis. The proportion of satellite cells [satellite cells/(myonuclei + satellite cells)] did not differ among the four subject groups (1.7-2.8%), nor did proportions differ when subject groups were combined for age and gender comparisons. Few morphological differences were noted between groups; however, lipofuscin granules were more prominent in satellite cells from older subjects and women demonstrated significantly larger satellite cell and satellite cell nucleus areas than men. Mitochondria from satellite cells (regardless of group) were more pallid and exhibited fewer cristae than mitochondria located in the adjacent muscle fiber. The results of the current investigation suggest that, despite findings in animal models, satellite cell populations are not significantly lower in healthy, sedentary older compared to young adult men and women.     

无锡地区0-3个月足月健康婴儿骨骼强度的测定

目的了解无锡地区0-3个月婴儿骨骼强度的状况。方法共检测3370例0-3个月健康婴儿,测定婴儿胫骨中段的SOS值,以Sunlight系统内提供的亚洲婴儿数据库SOS值作为参照标准;对不同季节、不同性别SOS值进行分组分析。结果得出不同季节、性别无锡地区0-3个月健康婴儿骨骼SOS值。结论不同地区、性别、季节的婴儿骨骼SOS测量结果不同。     

Estrogen receptor-1 genotype is associated with bone structure in premenopausal obese women

Estrogen action in bone is mediated mainly by estrogen receptor alpha (ESR1). Bone mineral content of the lumbar spine and left proximal femur and the femoral neck structure was measured with DXA, and the structure of the radius and tibia were assessed with pQCT in 75 premenopausal obese (BMI>30) women. The number of women in the ESR1 Pvu II genotype groups was 26 in TT, 37 in TC and 12 in CC. The CC genotype group had 7.8% (CI 3.3% to 12.6%) and 5.4% (CI 0.8% to 10.4%) narrower neck width than the TC and the TT groups, respectively. Cortical density at the tibial shaft among the CC genotype carriers was 1.5% (CI 0.0% to 3.0%) and 1.4% (CI 0.0% to 2.8%) higher than among the TC or TT carriers, respectively. Other bone traits did not show significant differences. Our results suggest that the less frequent CC genotype in obese premenopausal women is related to narrower femoral neck and higher cortical density at the tibial shaft compared to the TC and TT genotypes. Thus, this gene polymorphism seems to be associated specifically with bone structural traits rather than bone mass.     

Relations between anthropometric characteristics and androgen hormone levels in healthy young men

Inter-individual correlations between androgen hormone levels and anthropometric features were computed using data from a sample of 110 healthy young men. Radioimmunoassays were used to determine the total testosterone and dihydrotestosterone in the serum and the free testosterone in the saliva. The 58 body measures encompassed the head, trunk and extremities in terms of their length, breadth and circumference. In addition, skin-fold thicknesses were also measured. This set of features was also subjected to factor analysis; the correlations of the resulting individual factor scores with the body measurements were also determined. The total testosterone and dihydrotestosterone were found to have a number of significant correlations with the various body measures and factors, while the free testosterone did not yield any significant findings. These correlations indicate in particular that there is a relation between the serum androgens and leptomorphism (especially negative correlations to indicators of the fat development), whereas a connection between the serum androgens and masculinity is only hinted at.     

Resistance training increases in vivo quadriceps femoris muscle specific tension in young men

Aim: The present study investigated whether in vivo human quadriceps femoris (QF) muscle specific tension changed following strength training by systematically determining QF maximal force and physiological cross-sectional area (PCSA). Methods: Seventeen untrained men (20 ± 2 years) performed high-intensity leg-extension training three times a week for 9 weeks. Maximum tendon force (F_t) was calculated from maximum voluntary contraction (MVC) torque, corrected for agonist and antagonist muscle activation, and moment arm length (d_PT) before and after training. QF PCSA was calculated as the sum of the four component muscle volumes, each divided by its fascicle length. Dividing F_t by the sum of the component muscle PCSAs, each multiplied by the cosine of the respective fascicle pennation angle, provided QF specific tension. Results: MVC torque and QF activation increased by 31% (P < 0.01) and 3% (P < 0.05), respectively, but there was no change in antagonist co-activation or d_PT. Subsequently, F_t increased by 27% (P < 0.01). QF volume increased by 6% but fascicle length did not change in any of the component muscles, leading to a 6% increase in QF PCSA (P < 0.05). Fascicle pennation angle increased by 5% (P < 0.01) but only in the vastus lateralis muscle. Consequently, QF specific tension increased by 20% (P < 0.01). Conclusion: An increase in human muscle specific tension appears to be a real consequence of resistance training rather than being an artefact of measuring errors but the underlying cause of this phenomenon remains to be determined.     

Neuromuscular performance in voluntary bilateral and unilateral contraction and during electrical stimulation in men at different ages

A group of 33 men divided into three different age groups, M30 years (n = 11), M50 years (n = 12) and M70 years (n = 10) volunteered as subjects for examination of their maximal voluntary isometric bilateral and unilateral forces and force-time curves of the knee extensor muscle group as well as electromyogram activity of the vastus lateralis, vastus medialis and rectus femoris muscles of the right and/or left leg contractions. Electrical stimulation (ES) of 50 Hz was also given by two surface tin electrodes for each subject and each leg separately with the maximal tolerable intensity for recording the isometric force evoked. The maximal force produced by the voluntary isometric unilateral knee extension combined with ES was also measured. Maximal voluntary bilateral force of 1142 (SD 82) N in M30 was greater (P < 0.001) and the force of 1094 (SD 228) N in M50 was also greater (P < 0.05) than that of 962 (SD 70) N recorded for M70. The shapes of the isometric force-time curves, especially in absolute values, differed also among the groups so that the force produced during the early positions of the curve were in M30 greater (P < 0.05-0.001) than the force produced M50 and in M70. Neither the maximal voluntary bilateral force per the summed unilateral force nor the average integrated EMG between the bilateral and unilateral conditions differed significantly from each other either in M30, M50 or in M70. The force produced by pure ES was significantly greater in M30 (P < 0.05) than in M50 and M70, but the latter two groups were not significantly different. When ES was combined with the voluntary contractions, the absolute force values declined (P < 0.05-0.001) with increasing age similarly to those forces produced by the voluntary contractions alone. The present results suggest that increasing age results in great decreases both in the maximal voluntary strength and explosive force characteristics of the neuromuscular system but no bilateral deficit may necessarily be observed either in neural activation or in force production in a simple single joint isometric force production task of the knee extensors. The finding that no difference was observed between M50 and M70 in the force caused by ES alone despite the difference in maximal voluntary force indicated that in addition to the well-known age-related peripheral decrease in muscle mass, maximal voluntary neural activation of these muscles may also decrease to some extent contributing in part to the decrease in strength, especially at older ages.     

Sleep-facilitating effect of exogenous melatonin in healthy young men and women is circadian-phase dependent

STUDY OBJECTIVES: To investigate the effects of a physiologic and a pharmacologic dose of exogenous melatonin on sleep latency and sleep efficiency in sleep episodes initiated across a full range of circadian phases. DESIGN: Double-blind placebo-controlled parallel-group design in a 27-day forced desynchrony paradigm with a 20-hour scheduled sleep-wake cycle. SETTING: Private suite of a general clinical research center, in the absence of time-of-day information. Subjects: Thirty-six healthy, 18- to 30-year-old, men (n = 21) and women (n = 15). INTERVENTIONS: Oral melatonin (0.3 mg or 5.0 mg) or identical-appearing placebo was administered 30 minutes prior to each 6.67-hour sleep episode during forced desynchrony. MEASUREMENTS AND RESULTS: Both doses of melatonin improved polysomnographically determined sleep efficiency from 77% in the placebo group to 83% for sleep episodes occurring during circadian phases when endogenous melatonin was absent. However, this remained below the average sleep efficiency of 88% observed during sleep episodes scheduled during the circadian night, when endogenous melatonin was present. Melatonin did not significantly affect sleep initiation or core body temperature. Melatonin appeared to maintain efficacy across the study and did not significantly affect percentages of slow-wave sleep or rapid eye movement sleep. CONCLUSIONS: Exogenous melatonin administration possesses circadian-phase-dependent hypnotic properties, allowing for improved consolidation of sleep that occurs out of phase with endogenous melatonin secretion during the circadian night. The results support the hypothesis that both exogenous and endogenous melatonin attenuate the wake-promoting drive from the circadian system.     

Bigger is better! Hippocampal volume and declarative memory performance in healthy young men

The importance of the hippocampus for declarative memory processes is firmly established. Nevertheless, the issue of a correlation between declarative memory performance and hippocampal volume in healthy subjects still remains controversial. The aim of the present study was to investigate this relationship in more detail. For this purpose, 50 healthy young male participants performed the California Verbal Learning Test. Hippocampal volume was assessed by manual segmentation of high-resolution 3D magnetic resonance images. We found a significant positive correlation between putatively hippocampus-dependent memory measures like short-delay retention, long-delay retention and discriminability and percent hippocampal volume. No significant correlation with measures related to executive processes was found. In addition, percent amygdala volume was not related to any of these measures. Our data advance previous findings reported in studies of brain-damaged individuals in a large and homogeneous young healthy sample and are important for theories on the neural basis of episodic memory.     

Serum leptin levels,bone mineral density and osteoblast alkaline phosphatase activity in elderly men and women

Although primarily secreted by adipose cells, leptin, a polypeptide hormone that influences body weight, satiety and lipid metabolism, and its receptor are also expressed in human osteoblasts. Leptin plays a role in the central, hypothalamic modulation of bone formation, as well as locally within the skeleton by enhancing differentiation of bone marrow stroma into osteoblasts and inhibiting its differentiation into osteoclasts and adipocytes. The purpose of this investigation was to compare serum leptin values in 100 postmenopausal women (age 62-97) and 31 men (age 72-92) to bone mineral density (BMD) measurements made by dual X-ray absorptiometry and additionally to biochemical markers of bone resorption and formation, including crosslinked collagen N-telopeptides (NTx), aminoterminal extension procollagen propeptides (PINP) and bone-specific alkaline phosphatase (bAP). The circulating level of leptin directly correlated with body mass index (BMI) (r=0.61-0.78, P<0.001) and was modestly, but significantly and positively associated with bAP activity (r=0.24-0.33, P<0.01) in the sera of men and women after adjustment for BMD, age and BMI. The association of circulating leptin levels with bAP, a specific marker of osteoblast activity suggests that leptin levels influence osteoblast activity in vivo in elderly women and men.     

Creatine supplementation does not enhance submaximal aerobic training adaptations in healthy young men and women

The benefits of dietary creatine supplementation on muscle performance are generally related to an increase in muscle phosphocreatine content. However, creatine supplementation may benefit endurance sports through increased glycogen re-synthesis following exercise. This study investigated the effect of creatine supplementation on muscle glycogen content, submaximal exercise fuel utilisation and endurance performance following 4 weeks of endurance training. Thirteen healthy, physically active, non-vegetarian subjects volunteered to take part and completed the study. Subjects were supplemented with either creatine monohydrate (CREAT, n = 7) or placebo-maltodextrin (CON, n = 6). Submaximal fuel utilisation and endurance performance were assessed before and after a 4 week endurance training program. Muscle biopsies were also collected before and following training for assessment of muscle creatine and glycogen content. Training increased quadriceps glycogen content to the same degree (∼20%) in both groups (P = 0.04). There was a significant training effect on submaximal fuel utilisation and improved endurance performance. However, there was no significant treatment effect of creatine supplementation. Creatine supplementation does not effect metabolic adaptations to endurance training.     

乌鲁木齐市维吾尔族青年与老年女性血清微量元素及骨密度的对比

 背景：雌激素通过影响骨骼细胞的新陈代谢而促进微量元素在骨骼中的储存,影响骨密度的变化。 目的：比较乌鲁木齐市维吾尔族青年女性与老年女性骨密度及血清中微量元素的差异。 方法：使用MEDILINK生产的双能X射线骨密度测量仪对乌鲁木齐市维吾尔族30-40岁(青年女性组)与60-70岁(老年女性组)女性各30人进行骨密度测定;使用美国贝克曼库尔特生产的Unicel Dxc 800 Synchron生化检验仪查血清中的微量元素钙、磷、镁、铁、铜、锌含量。比较不同年龄段女性血清中微量元素及骨密度水平。 结果与结论：维吾尔族青年女性组骨密度显著高于老年女性组(P < 0.001);维吾尔族青年女性组血清微量元素锌显著低于老年女性组(P < 0.001);其余的血清微量元素钙、磷、镁、铁、铜两组之间差异无显著性意义(P > 0.05)。结果表明维吾尔族女性不同年龄段骨密度随体内血清中部分离子元素的改变有较大的改变。 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

Neuromuscular fatigue in young and older men using constant or variable resistance

The purpose of the present study was to determine: (1) if different acute neuromuscular responses occur between constant versus variable external resistance machines, two commonly used resistance machines and (2) whether the potential differences in fatigability between young and older men influence the magnitude of acute response between these resistance machines. Twelve young men (28 ± 5 year) and 13 older men (65.4 ± 4 year) performed 15 × 1 repetition maximum and 5 × 10 repetitions isotonic knee extension resistance loadings with both constant and variable resistance (four loadings in total). Maximum isometric knee extension torque, superimposed twitch, resting twitch torque, maximal M wave properties, electromyograph, and blood lactate concentration measured the effects of loading. Concentric torque reduced to a greater extent during variable 15 × 1 versus constant loading in young men only (P < 0.05). While three out of the four loadings caused decreased voluntary activation in young men, only 15 × 1 using variable resistance caused reductions in older men (P < 0.05). 5 × 10 variable resistance loading significantly increased M wave duration and decreased EMG median frequency, which was not observed following constant resistance loading in both age groups. Acute decreases in force production were significantly greater in young men following all loading protocols (P < 0.05). Both young and older men showed indications of greater fatigue from variable resistance loadings. Differing muscle properties may have led to different magnitudes of fatigue between groups, and older subjects may benefit from specifically tailored training programs.     

Association between bone mineral density and LDL receptor-related protein 5 gene polymorphisms in young Korean men

Recently, It has been reported that the LDL receptor-related protein 5 (LRP5) regulates bone formation, and that mutations of the gene cause osteoporosis-pseudoglioma syndrome or high bone mass phenotypes. However, the mutations cannot explain a genetic trait for osteoporosis in the general population because of their rarity. From 219 Korean men aged 20-34 yr, we looked for six known polymorphisms causing amino acid changes in the LRP5 coding region, and investigated their association with bone mineral density (BMD) at the following anatomical sites: lumbar spine (L2-L4) and the left proximal femur (femoral neck, Ward's triangle, trochanter and shaft). We found that the Q89R polymorphism was significantly associated with BMD at the femoral neck and Ward's triangle (p=0.004 and <0.001, respectively). However, after adjusting for age, weight and height, a statistically significant association only occurred at the Ward's triangle (p=0.043), and a marginal association was observed at the femoral neck (p=0.098). No A400V, V667M, R1036Q and A1525V polymorphisms were found, and no statistically significant association was found between the A1330V polymorphism and BMD at any sites. Although we failed to demonstrate a clear association between the LRP5 polymorphism and peak bone mass in young men, the present study suggests that larger-scale studies on the Q89R polymorphism need to be performed.