Effects of Vibration Training and Detraining on Balance and Muscle Strength in Older Adults

The purpose of this study was to analyze the effects of 2 days/week versus 4 days/week of Whole Body Vibration (WBV) during eight weeks of WBV training on health-related quality of life (SF-36), balance and lower body strength, as well as short-term detraining (3 weeks) on balance and lower body strength among older adults. Thirty-four older adults were randomly assigned to a control group (Control; n = 11) or to one of the vibration training groups: WBV 2 days/week (WBV_2d; n = 11) or WBV 4 days/week (WBV_4d; n = 12). The WBV groups exercised for 8 weeks, following 3 weeks of detraining. Lower body strength increased significantly (p < 0.05) for both groups, WBV_2d and WBV_4d, after 8-week training. A significant reduction in strength was observed following 3 weeks of detraining only in WBV_2d group (p < 0.05). All variables of the SF-36 and the balance test did not change after intervention in any group. 2 days/week and 4 days/week of WBV during 8 weeks showed the same improvements on muscle strength. 3 weeks of detraining did not reverse the gains in strength made during 32 sessions of WBV.

Key points

• 2 days and 4 days per week of WBV training during 8 weeks showed the same improvements on muscle strength.
• 3 weeks of detraining did not reverse the gains in strength made during 32 sessions of WBV exercise.
• 3 weeks of detraining did reverse the gains in strength made during 16 sessions of WBV exercise.

Key words: Whole-body vibrations, posturography, dose-response, equilibrium     

Saturated and Unsaturated Bone Marrow Lipids Have Distinct Effects on Bone Density and Fracture Risk in Older Adults

Greater bone marrow adiposity (BMAT) is associated with lower bone mineral density (BMD) and vertebral fractures; less is known about BMAT composition and bone. We studied BMAT composition and bone outcomes in 465 participants from the Age Gene/Environment Susceptibility (AGES)-Reykjavik study. BMAT saturation and unsaturation, measured with magnetic resonance spectroscopy, were defined as the ratio of saturated (1.3 ppm peak) or unsaturated (5.3 ppm peak) lipid to total marrow contents, respectively. At baseline and follow-up visits, spine and hip BMD were assessed with quantitative computed tomography (QCT) and dual-energy X-ray absorptiometry (DXA) and vertebral fractures were identified with DXA. Incident clinical fractures were identified through medical records for up to 8.8 years of follow-up. Associations between BMAT composition and BMD, bone loss, and fractures were evaluated in adjusted regression models. At baseline, mean ± standard deviation (SD) participant age was 81.7 ± 4.3 years, mean BMAT unsaturation was 3.5% ± 1.0%, and mean saturation was 46.3% ± 7.2% in the full cohort (47.7% women). Each SD increase in BMAT saturation was associated with lower trabecular BMD: −23.6% (spine) and −13.0% (total hip) (all p < 0.0001). Conversely, BMAT unsaturation (per SD increase) was associated with higher trabecular BMD: +17.5% (spine) and +11.5% (total hip) (all p < 0.001). BMAT saturation (per SD increase) was associated with greater risk for prevalent (odds ratio [OR] 1.46; 95% confidence interval [CI], 1.11–1.92) and incident (OR 1.55; 95% CI, 1.03–2.34) vertebral fracture. BMAT unsaturation (per SD increase) was associated with lower risk for incident vertebral fracture (OR 0.58; 95% CI, 0.38–0.89). In gender stratified analyses, BMAT saturation and unsaturation had opposite associations with incident clinical fracture among men. In general, saturated marrow lipids were associated with worse skeletal outcomes, whereas unsaturated lipids were associated with better outcomes. We recommend that future studies of marrow fat and skeletal health report measurements of saturated and unsaturated marrow lipids, rather than total marrow fat content alone. © 2022 American Society for Bone and Mineral Research (ASBMR).     

老年人握力与身高、体质量及蛋白含量的相关性研究

目的 探讨老年人手部握力与身高、体质量、蛋白含量的相关性,寻找初级评估老年人营养状况的快捷方式.方法 选取86名年龄>65岁老年人,分别测量其身高、体质量及左、右手握力,同时抽取晨空腹血检查血清总蛋白、白蛋白含量.结果 老年人左、右手握力与身高、体质量,血清白蛋白、总白蛋白含量呈正相关(P<0.01,P<0.05).结论 老年人手部握力与身高、体质量及蛋白含量存在内在联系,能够在一定程度上反应老年人体内总蛋白、白蛋白含量,可作为一种初级评价老年人营养状况的快捷方式.     

Effects of Whole-Body Vibration Training on Bone-Free Lean Body Mass and Muscle Strength in Young Adults

Resistance training with whole-body vibration (WBV) is becoming increasingly popular as an alternative to conventional resistance training or as supplementary training. Despite its growing popularity, the specific effects of WBV training on muscle morphology, strength, and endurance are not well understood, particularly in young adults. The aim of this study was to determine the effects of WBV training on bone-free lean body mass (BFLBM), and maximal muscle strength and endurance in healthy, untrained, young individuals. Eighteen healthy men and women (21-39 years) were randomly assigned to either a body-weight exercise with WBV (VT) group or a control exercise group without WBV (CON). Participants performed eight exercises per 40- min session on a vibration platform (VT group, frequency = 30-40 Hz; amplitude = 2 mm) twice weekly for 12 weeks. Anthropometry, total and regional BFLBM (trunks, legs, and arms) measured by dual- energy X-ray absorptiometry, and muscle strength and endurance measured by maximal isometric lumbar extension strength, maximal isokinetic knee extension and flexion strength, and the number of sit- ups performed were recorded and compared. Two-way repeated-measures ANOVA revealed no significant changes between the groups in any of the measured variables. We conclude that 12 weeks of body weight vibration exercise compared to body weight exercise alone does not provide meaningful changes to BFLBM or muscle performance in healthy young adults.

Key points

• A randomized controlled trial was conducted to investigate the effects of body-weight exercise combined with whole-body vibration on bone-free lean body mass and maximal muscle strength and endurance in healthy young individuals.
• Body-weight exercises for lower extremities and trunk muscles were performed twice weekly for 12 weeks.
• Participants in the exercise with whole-body vibration group increased the vibration frequency from 30, 35, to 40 Hz at a constant amplitude of 2 mm during the trial.
• A 12-week body-weight exercise program with whole-body vibration did not significantly increase bone-free lean body mass in healthy young individuals, and no additional increases in maximal muscle strength and endurance were observed.

Key words: vibration, exercise, lean body mass, young, untrained     

Effects of High-Dose Creatine Supplementation on Kidney and Liver Responses In Sedentary and Exercised Rats

This study evaluated the effects of high-dose of short-term creatine supplementation (5g.kg^-1.day^-1 to 1 week) and long-term creatine supplementation (1g.kg^-1. day^-1 to 4-8 weeks) on kidney and liver structure and function of sedentary and exercised Wistar rats (Exercise sessions consisted of swimming at 80% of maximal work load supported during 5 days per week with daily sessions of 60 minutes throughout the duration of the supplementation). Seventy- two animals (245 ± 5g) were divided into four groups (n = 18): control diet Sedentary (SED), Creatine diet Sedentary (CRE), control diet Exercised (EXE), and Creatine diet Exercised (EXECRE). Histological and blood biochemical studies were performed after one, four, and eight weeks of creatine supplementation and exercise (n = 6). No differences were found when comparing SED, EXE and EXECRE groups for kidney and liver structure and function at one, four and eight weeks. However, the CRE group showed higher levels of creatinine (1.1 ± 0.2 vs. 0.4 ± 0.1 mg.dl^-1; p < 0.05), and urea (37 ± 3 vs. 19 ± 1 mg.dl^-1; p < 0.05) when compared with all others groups at four and eight weeks. At eight weeks, the CRE group presented increased levels of ALT (41 ± 7 vs. 23 ± 7 U.L^-1; p < 0.05), AST (89 ± 6 vs. 62 ± 5 U.L^-1; p < 0.05), GGT (8.0 ± 0.9 vs. 3.9 ± 1.0 U.L^-1; p < 0.05), and AP (125 ± 10 vs. 69 ± 9 U.L^-1; p < 0.05) also when compared with all others groups. Moreover, the CRE group demonstrated some structural alterations indicating renal and hepatic damage at four and eight weeks, respectively. These results suggest that long-term creatine supplementation (up to 4-8 weeks) may adversely affect kidney and liver structure and function of sedentary but not of exercised rats.

Key points

• Creatine supplementation is an established ergogenic aid in sports and is now claimed to have therapeutical applications in a variety of diseases.
• Although acknowledged, this nutritional supplement is rarely monitored precisely about their possible side effects.
• Previous studies indicated that short-term creatine supplementation associate with the physical exercise may be safe, but the effect of long-term creatine supplementation is still unknown.
• There is a need for further research to elucidate the controversial points refers to renal and hepatic function after creatine supplementation.
• The results of the current study indicate that supraphysiological long-term creatine supplementation (up to 4-8 weeks) may adversely affect kidney and liver structure and function of sedentary but not of exercised rats.

Key words: Creatine monohydrate, hepatic metabolism, kidney metabolism, swimming training, sports supplements, toxicology.     

Leukocyte Telomere Length Is Not Associated With BMD,Osteoporosis, or Fracture in Older Adults: Results From the Health,Aging and Body Composition Study

Short leukocyte telomere length (TL), low BMD, and osteoporosis have been associated with increased inflammation. Previous reports suggest an association between TL, BMD, and osteoporosis in women. We sought to verify these associations and to determine whether TL is related to fracture in a cohort of older men and women. Participants included 2750 community‐dwelling older persons from the longitudinal Health, Aging, and Body Composition Study (Health ABC) in who average leukocyte TL was measured at baseline using qPCR. We used unconditional logistic regression to determine the association of TL with prevalent fracture, Cox proportional hazards regression for the association with 7‐yr incident fracture, and mixed linear models for the association with BMD, change in BMD, and the number of incident fractures. TL was negatively correlated with age, weight, fasting insulin, and fasting glucose in men and women, and additionally, with C‐reactive protein and IL‐6 in men. TL was not associated with BMD; change in BMD over 1, 3, or 5 yr; osteoporosis; baseline fracture; or 7‐yr incident fracture, before or after adjustment for age, race, smoking, and health characteristics. TL is not associated with BMD, osteoporosis, or fracture in older men or women in this sample.     

Computer Simulation of the Effects of Alterations in Blood Flows and Body Composition on Thiopental Pharmacokinetics in Humans

Background: Understanding the influence of physiological variables on thiopental pharmacokinetics would enhance the scientific basis for the clinical usage of this anesthetic.

Methods: A physiological pharmacokinetic model for thiopental previously developed in rats was scaled to humans by substituting human values for tissue blood flows, tissue masses, and elimination clearance in place of respective rat values. The model was validated with published serum concentration data from 64 subjects. The model was simulated after intravenous thiopental administration, 250 mg, over 1 min, to predict arterial plasma concentrations under conditions of different cardiac outputs, degrees of obesity, gender, or age.

Results: The human pharmacokinetic model is characterized by a steady state volume of distribution of 2.2 l/kg, an elimination clearance of 0.22 l/min, and a terminal half-life of 9 h. Measured thiopental concentrations are predicted with an accuracy of 6 +/- 37% (SD). Greater peak arterial concentrations are predicted in subjects with a low versus a high cardiac output (3.1 and 9.4 l/min), and in subjects who are lean versus obese (56 and 135 kg). Acutely, obesity influences concentrations because it affects cardiac output. Prolonged changes are due to differences in fat mass. Changes with gender and age are relatively minor.     

Relationships Among Bone Mineral Density,Body Composition,and Isokinetic Strength in Young Women

The purpose of this study was to examine the relationships among bone mineral density (BMD), body composition, and isokinetic strength in young women. Subjects were 76 women (age: 20 ± 2 yr, height: 164 ± 6 cm, weight: 57 ± 6 kg, body fat: 27 ± 4%) with a normal body mass index (18–25 kg/m²). Total body, nondominant proximal femur, and nondominant distal forearm BMD were measured with dual-energy x-ray absorptiometry. Isokinetic concentric (CON) and eccentric (ECC) strength of the nondominant thigh and upper arm were measured at 60 deg/sec. Fat-free mass (FFM) correlated (P < 0.001) with BMD of the total body (r = 0.56) and femoral neck (r = 0.52), whereas fat mass (FM) did not relate to BMD at any site. Leg FFM, but not FM, correlated with BMD in all regions of interest at the proximal femur. Weak associations were observed between arm FFM and forearm BMD. Isokinetic strength did not relate to BMD at any site after correcting for regional FFM. In conclusion, strong, independent associations exist between BMD and FFM, but not FM or isokinetic strength, in young women.     

Muscle Strength and Body Composition Are Clinical Indicators of Osteoporosis

We examined the role of muscle strength, lean tissue distribution, and overall body composition as indicators of osteoporosis (OP) in a pooled sample of 979 Finnish postmenopausal women (mean age 68.1 years) from the Kuopio Osteoporosis Risk Factor and Prevention study. Bone mineral density (BMD) at the femoral neck (FN) and total body composition were assessed by dual-energy X-ray absorptiometry scans. The women (n = 979) were divided into three groups according to WHO criteria, based on FN BMD T score: normal (n = 474), osteopenia (n = 468), and OP (n = 37). Soft tissue proportions, fat mass index (FMI, fat/height2), lean mass index (LMI, lean/height2), and appendicular skeletal muscle mass (ASM, (arms + legs)/height2) were calculated. Handgrip and knee extension strength measurements were made. OP subjects had significantly smaller LMI (p = 0.001), ASM (p = 0.001), grip strength (p < 0.0001), and knee extension strength (p < 0.05) but not FMI (p > 0.05) compared to other subjects. Grip and knee extension strength were 19 and 16 % weaker in OP women compared to others, respectively. The area under the receiver operating characteristic curve was 69 % for grip and 71 % for knee extension strength. In tissue proportions only LMI showed predictive power (63 %, p = 0.016). An overall linear association of LMI (R2 = 0.007, p = 0.01) and FMI (R2 = 0.028, p < 0.001) with FN BMD remained significant. In the multivariate model, after adjusting for age, grip strength, leg extension strength, FMI, LMI, number of medications, alcohol consumption, current smoking, dietary calcium intake, and hormone therapy, grip strength (adjusted OR = 0.899, 95 % CI 0.84-0.97, p < 0.01), leg extension strength (OR = 0.998, 95 % CI 0.99-1, p < 0.05), and years of hormone therapy (OR = 0.905, 95 % CI 0.82-1, p < 0.05) remained as significant determinants of OP. Muscle strength tests, especially grip strength, serve as an independent and useful tool for postmenopausal OP risk assessment. In addition, lean mass contributes to OP in this age group. Muscle strength and lean mass should be considered separately since both are independently associated with postmenopausal BMD.     

Relationships Between Body Composition, Muscular Strength, and Bone Mineral Density in Estrogen-Deficient Postmenopausal Women

The purpose of this study was to examine relationships between muscular strength, body composition, and bone mineral density (BMD) in untrained postmenopausal women who are not on hormone replacement therapy (HRT). Fifty-five women (age: 63.3 ± 0.6 yr) completed menstrual history, physical activity, and calcium intake questionnaires. Total and regional body composition and total body, anteroposterior lumbar spine, nondominant forearm, and right proximal femur BMD were measured using dual-energy X-ray absorptiometry (DXA) (GE Lunar Prodigy, Prodigy enCORE software version 10.50.086, Madison, WI). Participants performed strength tests for 3 upper body and 5 lower body resistance exercises. Women with a relative skeletal muscle mass index (RSMI) value less than 5.45 kg/m² were defined as a sarcopenia group (SAR). SAR had significantly (p < 0.05) lower total body and forearm BMD compared with those who were not sarcopenic. BMD sites were significantly correlated with upper body strength (UBS) and lower body strength (LBS) (r = 0.28–0.50, p < 0.01), with the strength of relationship being site specific. Strength and fat mass (FM) significantly predicted total body BMD (R² = 0.232–0.241, p < 0.05), FM variables predicted spine BMD (R² = 0.109–0.140, p < 0.05), and LBS and RSMI predicted hip BMD sites (R² = 0.073–0.237, p < 0.05). Body composition variables failed to significantly predict LBS. In conclusion, the contribution of body composition and strength variables to BMD varied by site as FM was more important for total body, forearm and spine BMD, and LBS exerted greater influence on the hip sites.     

Effects of Exercise Training on Blood Lipids and Lipoproteins in Children and Adolescents

The following review aims to describe what is known about the effects of exercise training in children and adolescents on the following blood lipids and lipoproteins: total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), and triglycerides (TG). Only studies that described mode, frequency, duration and intensity of the exercise were included in the review. The results of the studies reviewed were equivocal. Clearly the effects of exercise training on the blood lipid and lipoprotein levels of normolipidemic children and adolescents are equivocal. Of the 14 studies reviewed, six observed a positive alteration in the blood lipid and lipoprotein profile, four of the studies observed no alteration in the blood lipid and lipoprotein profile and one study observed a negative effect on HDL-C but an overall improvement in the lipid and lipoprotein profile due to the decrease in the TC/HDL ratio. It appears that methodological problems present in the majority of the exercise training studies limits the ability to make a conclusive, evidence based statement regarding the effect exercise training has on blood lipid levels in normolipidemic children. Most of the research design flaws can be linked to one or more of the following: small numbers of subjects in each study, low or no representation of girls, inclusion of both boys and girls in the subject pool, inclusion of boys and girls at different maturational stages in the subject pool, exercise training regimes that do not adequately control for exercise intensity, exercise training regimes that do not last longer than 8 weeks and exercise training studies that do not have an adequate exercise volume to elicit a change. Ideally, future research should focus on longitudinal studies which examine the effects of exercise training from the primary school years through adulthood.

Key points

• Exercise training has limited to no effect on blood lipid levels in children and adolescents.
• Few well controlled studies have been done to examine the effect exercise training has on selected cardiovascular risk factors and those studies that have been completed contain methodological flaws which makes interpretation of the results difficult.
• More studies, particularly those of a longitudinal design, are required before a conclusion can be drawn regarding the effects exercise training has on selected cardiovascular risk factors in children and adolescents.

Key words: Cardiovascular risk factors, children, adolescents, aerobic exercise training     

The Association of Flexibility,Balance, and Lumbar Strength with Balance Ability: Risk of Falls in Older Adults

The purpose of the present study was to determine the effects of a proprioceptive training program on older adults, as well as to analyze the association between flexibility, balance and lumbar strength (physical fitness test) with balance ability and fall risk (functional balance tests). This study was a controlled, longitudinal trial with a 12-week follow-up period. Subjects from a population of older adults were allocated to the intervention group (n = 28) or to the usual care (control) group (n = 26). Subjects performed proprioceptive training twice weekly (6 specific exercises with Swiss ball and BOSU). Each session included 50 minutes (10 minutes of warm-up with slow walk, 10 minutes of mobility and stretching exercises, 30 minutes of proprioceptive exercises). The outcome variables were physical fitness (lower-body flexibility, hip-joint mobility, dynamic balance, static balance, and lumbar strength) and functional balance (Berg scale and Tinetti test). The experimental group obtained significantly higher values than the control group in lower-body flexibility, dynamic balance, and lumbar strength (p = 0.019, p < 0.001, and p = 0.034 respectively). Hip-joint mobility, dynamic balance, and lumbar strength were positively associated with balance ability (p < 0.001, p < 0.001, and p = 0.014, respectively) and the prevention of falls (p = 0.001, p < 0.001, and p = 0.017 respectively). These findings suggest that a 12-week proprioception program intervention (twice a week) significantly improves flexibility, balance, and lumbar strength in older adults. Hip-joint mobility, dynamic balance and lumbar strength are positively associated to balance ability and the risk of falls in older adults. This proprioceptive training does not show a significant improvement in hip-joint mobility or static balance.

Key points

• A 12-week proprioceptive intervention program (two times per week) significantly improves flexibility, balance, and lumbar strength in older adults.
• The risk of falls and balance ability are significantly improved after a training program with Bosu and Swiss ball in older adults.
• An improvement in joint mobility, dynamic balance and lumbar strength is positively associated with balance ability and improved fall risk in older adults.
• A 12-week proprioceptive intervention program (two times per week) does not show a significant improvement in hip-joint mobility and static balance.

Key words: Proprioception, physical condition, training, physical qualities, swiss ball     

The Kinetics and Stiffness Characteristics of the Lower Extremity in Older Adults During Vertical Jumping

The purpose of this study was to examine the modulating effects of age on lower limb stiffness and net muscle joint activity degeneration when performing a functional activity involving SSC. Seven young males and seven older males were recruited as subjects for this study. A high-speed camera and a force plate were synchronized to collect the biomechanical parameters. The kinetic parameters were calculated with the inverse dynamics process. The stiffness of lower limbs was calculated with the spring-mass model. The Student’s t-test was used to test the differences of two age groups. Statistical significance was set at α = 0.05. The present research showed that the older group produced a smaller peak net muscle joint moment at hip and knee. There were no differences in leg stiffness, hip stiffness, and ankle stiffness between the two age groups. Knee stiffness was smaller in the older group. In elderly adults, reduced muscle strength in the lower limbs, especially in the hip and knee, and reduced stiffness of the knee, influence the basic functions of human life and increase the risk of injury. Differences in lower extremity kinetics and stiffness in elderly adults during SSC movement may have implications for new preventive measures.

Key points

• The present research showed that the older group reduced muscle strength in the lower limbs, especially in the hip and knee, and reduced stiffness of the knee, influence the basic functions of human life and increase the risk of injury.
• There were no differences in leg stiffness, hip stiffness, and ankle stiffness between the two age groups.
• Older subjects maintain hip angular stiffness by decreasing joint angles in order to protect the joint and to increase stability during movement.
• In elderly adults, insufficient angular stiffness of the knee joint may increase the risk of knee injury during a functional activity involving SSC.

Key words: Aging, biomechanics, inverse dynamic, spring-mass model     

Effects of Hallux Valgus Surgery on Balance and Gait in Middle Aged and Older Adults

Hallux valgus is associated with balance deficits, and has been implicated as an independent risk factor for falls in older adults. However, it is unknown what effect hallux valgus surgery has on static and dynamic (i.e., while walking) balance in older adults. We enrolled 13 middle-aged and older aged adults (mean age 54.3 ± 12.7 years, range 47 to 70) who underwent isolated hallux valgus surgery and followed them for 12 months. Preoperative and postoperative gait and balance performance was assessed using non-invasive body worn sensors with standardized and validated testing protocols. Visual analog scale (VAS) for pain and radiographic angles were also assessed. All subjects reported improvements in pain (VAS mean change -38.3 ± 10.3 mm), and all subjects demonstrated improvements in their hallux valgus angles and first/second intermetatarsal angles (mean change 16.3 ± 8.8°, and 5.5 ± 3.0°, respectively). While standing in full tandem, center of mass (COM) sway was improved upon by 59% at 1 year postoperative (p < .05, paired t-test). While most gait parameters demonstrated little change postoperatively, patients tended to spend less time in double support (p = .08, paired t-test), while gait variability increased by 55% (p = .03, paired t-test) and medial-lateral sway while walking increased by 43% (p = .08, paired t-test) 12 months postoperatively. Balance improved after hallux valgus surgery in our population, particularly when subjects were forced to rely on their operative foot for support (e.g., full tandem). Patients also seemed to walk with greater variability in stride velocity and with greater medial-lateral sway postoperatively, suggesting perhaps increased ambulatory confidence after successful hallux valgus surgery.     

Effects of Circuit Resistance Training and Timely Protein Supplementation on Exercise-Induced Fat Oxidation in Tetraplegic Adults

Background:

Substrate utilization during exercise in persons with spinal cord injury (SCI) remains poorly defined.

Purpose:

To investigate effects of circuit resistance training (CRT) and timing of protein supplementation (PS) on fuel utilization in persons with tetraplegia.

Methods:

Eleven individuals with chronic tetraplegia underwent 6 months of CRT 3 times weekly. Five randomly assigned participants received immediate PS (iPS) administered in split doses prior to and following all exercise sessions. Other participants consumed a matched dose of PS that was delayed until 24 hours post-exercise (dPS). Participants underwent a maximal graded exercise test (GXT) to volitional exhaustion at 4 conditioning time points: 3 months before (-3mo), at the beginning of (0mo), 3 months into (3mo), and 6 months following (6mo) the CRT conditioning program. Respiratory measures were continuously obtained throughout the GXT via open-circuit spirometry. Fuel utilization and energy expenditure were computed from the respiratory data.

Results:

The differences in changes in substrate utilization between the PS groups were not significant as determined by the interaction of PS group and conditioning time point, F (3, 27) = 2.32, P = .098, η²_P = .205. Maximal absolute fat oxidation did not change significantly from 0 to 6mo (mean difference, 0.014 ± 0.031 g/min; P = .170), and fat oxidation remained low never exceeding an average of 0.10 ± 0.09 g/min for any given exercise intensity.

Conclusion:

Maximum fat utilization during exercise and fat utilization at matched exercise intensities were not increased in persons with tetraplegia, independent of PS, and levels of fat oxidation remained low after training.Key words: carbohydrate, fat, oxidationCnsiderable evidence documents a disturbing prevalence of overweight and obesity in persons with spinal cord injury (SCI). Combined prevalence rates for conditions of overweight and obesity in persons with chronic SCI are daunting; depending on the definition used for classification, they range from 55%¹ to 95.7%² of the population. Accretion of body fat is most common within 2 to 7 months of injury after SCI and is likely caused by physical deconditioning, loss of metabolically active muscle mass, reduced whole body energy expenditure, and a hypercaloric diet whose macronutrient composition is excessive in saturated fat.Fat oxidation plays an important role in daily energy homeostasis and the etiology of obesity, and numerous studies have reported a reduced ability to oxidize fat in obese individuals at rest and during exercise.^3–8 It is known that persons with physical disability have a 1.2- to 3.9-fold higher prevalence of obesity than those without disability,⁹ yet little is known about their substrate partitioning at rest or during physical activity. When compared to nondisabled controls performing voluntary exercise, persons with SCI have markedly reduced mobilization, delivery, and limb uptake of free fatty acids (FFA) during electrically stimulated leg exercise.¹⁰ This is most likely the result of reduced sympathoadrenal ß-adrenergic stimulation and/or limited neural activity in motor centers and afferent nerves from working muscle, depending on the level of injury.¹⁰ The limited FFA availability during exercise leads to heavy reliance on carbohydrates (CHO) and the limited contribution of fats as a fuel source.^11–15Knowledge of training-induced adaptations in substrate use after SCI represents an important step in evaluating exercise as a legitimate intervention to reduce the prevalence and severity of cardioendocrine diseases such as obesity; these adaptations have received limited research attention. A majority of studies on substrate partitioning after SCI have involved subjects who were already well-trained.^11–15 Otherwise, functional electrical stimulation (FES) training for 1 year shifted muscle fiber type distribution toward fatigue resistance and increased the activity of mitochondrial enzymes citrate synthase and ß-hydroxyacyl-CoA-dehydrogenase.^16,17 Although these adaptations provide indirect evidence for higher rates of maximal whole body fat oxidation, their effects on substrate oxidation and partitioning during more common volitional arm exercise were not examined.We have previously reported that 6 months of circuit resistance training (CRT) performed by persons with chronic SCI improves fitness measures of peak cardiorespiratory (CR) capacity (VO_2peak), time to fatigue, peak and average anaerobic power output, and isokinetic and isoinertial strength.^18,19 Recent data from our laboratory²⁰ also show that the addition of an optimally timed protein supplementation (PS) to a CRT conditioning program by persons with chronic tetraplegia augments gains made in CR fitness and anaerobic power, although it is not known whether these fitness gains translate into increased fat oxidation during exercise. As improvements in CR fitness have long been associated with an enhanced ability to utilize fat as a fuel source,^21–23 this investigation analyzed changes on substrate utilization following 6 months of CRT in persons with tetraplegia and examined whether these changes were affected by timely PS. It was hypothesized that conditioning exercise would be associated with greater amounts and proportions of fat utilization measured during matched intensities of subpeak work and that timely PS would further enhance these beneficial conditioning adaptations.     

The effects of Creatine Long-Term Supplementation on Muscle Morphology and Swimming Performance in Rats

Creatine (Cr) has been shown to increase the total muscle mass. The purpose of this study was to investigate the effect of Cr supplementation on muscle morphology and swimming performance, using an animal model. Each rat was subjected to exercise 15-minute period daily for the 12 weeks. The rats were randomly divided into four groups: no Cr supplementation (CON), no Cr supplementation and incomplete food intake (lacking lysine and methionine in diet for rats) (INCO), Cr supplementation 1 g·kg^-1·day^-1 (CREAT-I) and Cr supplementation 2 g·kg^-1·day^-1 (CREAT-II). Three months later, all groups adult rats exercised in swimming pool chambers. Swimming time was recorded as minute for each rat. Following swimming performance period, the animals were killed by cervical dislocation and the gastrocnemius and diaphragm muscles were dissected. Serial slices of 5-7 μm were allocated paraffin wax and histochemical staining procedure of cross-sections was carried out with heamatoxylin-eosin technics. All groups gained body weight at the end of 12 weeks but there was no statistical difference among them. Swimming time values were statistical difference between CREAT-II and CON group as well as between CREAT-I and CON group (p < 0.05). In the INCO group was determined increased connective tissue cell of the muscle sample. In contrast, in the CREAT-I and CREAT-II group, the basic histological changes were large-scale muscle fibers and hypertrophic muscle cells. These results suggest that long-term creatine supplementation increased the number of muscle fibers and enhanced endurance swimming performance in rats.

Key points

• There is no study about the effects of creatine long-term supplementation on muscle morphology and swimming performance in rats.
• Long-term creatine supplementation increase muscle hypertrophy (but not body weight) and enhance endurance swimming performance in rats.
• The quantitative analysis indicated that the number of muscle fibers per defined area increased in creatine supplementation groups.

Key words: Creatine, muscle hyprtrophy, muscle morphology, exercise, swimming performance     

Dose-Dependent Effects of Milk Lipids on Sex Hormone and Blood Lipid Levels in Male Mice

Dosisabhängige Einflusse von Milchlipiden auf Sexualhormon- und Blutlipid-Werte bei männlichen Mäusen
Im Tierexperiment wurde 21 Tage alten männlichen Mäusen eine Kost zugeführt, die aus Vollmilchpulver bestand; diese Kost führte zu einem dosisabhängigen Anstieg des Samenblasengewichtes. In dem Maße, wie die Lipide in der Kost anstiegen, stieg der Blutcholesterinwert. Die Triglyceride waren hoch und umgekehrt verwandt zur Lipid-aufnahme. Die peripheren Androgenkonzentrationen fielen mit steigender Lipidauf-nahme und einem Anstieg des Gewichtes der Samenblasen ab; das bedeutet nach Meinung der Autoren möglicherweise eine Verschiebung des Hormons zum Targetorgan-Gewebe.