Legs and Trunk Muscle Hypertrophy Following Walk Training with Restricted Leg Muscle Blood Flow

We examined the effect of walk training combined with blood flow restriction (BFR) on the size of blood flow-restricted distal muscles, as well as, on the size of non-restricted muscles in the proximal limb and trunk. Nine men performed walk training with BFR and 8 men performed walk training alone. Training was conducted two times a day, 6 days/wk, for 3 wk using five sets of 2-min bouts (treadmill speed at 50 m/min), with a 1-min rest between bouts. After walk training with BFR, MRI-measured upper (3.8%, P < 0.05) and lower leg (3.2%, P < 0. 05) muscle volume increased significantly, whereas the muscle volume of the gluteus maximus (-0.6%) and iliopsoas (1.8%) and the muscle CSA of the lumber L4-L5 (-1.0) did not change. There was no significant change in muscle volume in the walk training alone. Our results suggest that the combination of leg muscle blood flow restriction with slow walk training elicits hypertrophy only in the distal blood flow restricted leg muscles. Exercise intensity may be too low during BFR walk training to increase muscle mass in the non- blood flow restricted muscles (gluteus maximus and other trunk muscles).

Key points

• Previous studies of blood flow restricted walk training have focused solely on thigh muscles distal to pressure cuffs placed on the upper most portion of the proximal thigh.
• In the current study, both proximal and distal muscles were evaluated following the combination of walk training with leg blood flow restriction (BFR). Muscle hypertrophy only occurred in the thigh and lower leg, which were the blood flow restricted muscles examined.
• No significant change was observed in the non-restricted trunk muscles following 3 weeks of twice-daily BFR walk training.

     

Metabolic and Cardiovascular Responses to Upright Cycle Exercise with Leg Blood Flow Reduction

The purpose of this study was to examine the metabolic and cardiovascular response to exercise without (CON) or with (BFR) restricted blood flow to the muscles. Ten young men performed upright cycle exercise at 20, 40, and 60% of maximal oxygen uptake, VO₂max in both conditions while metabolic and cardiovascular parameters were determined. Pre-exercise VO₂ was not different between CON and BFR. Cardiac output (Q) was similar between the two conditions as a 25% reduction in stroke volume (SV) observed in BFR was associated with a 23% higher heart rate (HR) in BFR compared to CON. As a result rate-pressure product (RPP) was higher in the BFR but there was no difference in mean arterial pressure (MAP) or total peripheral resistance (TPR). During exercise, VO₂ tended to increase with BFR (~10%) at each workload. Q increased in proportion to exercise intensity and there were no differences between conditions. The increase in SV with exercise was impaired during BFR; being ~20% lower in BFR at each workload. Both HR and RPP were significantly greater at each workload with BFR. MAP and TPR were greater with BFR at 40 and 60% VO₂max. In conclusion, the BFR employed impairs exercise SV but central cardiovascular function is maintained by an increased HR. BFR appears to result in a greater energy demand during continuous exercise between 20 and 60% of control VO₂max; probably indicated by a higher energy supply and RPP. When incorporating BFR, HR and RPP may not be valid or reliable indicators of exercise intensity.

Key points

• Blood flow reduction (BFR) employed impairs stroke volume (SV) during exercise, but central cardiovascular function is maintained by an increased heart rate (HR).
• BFR appears to result in a greater energy demand during continuous exercise between 20 and 60% of control VO₂max;
• Probably indicated by a higher energy supply (VO₂) and rate-pressure product (HR x systolic blood pressure).

Key words: Aerobic exercise, doppler echocardiography, apparent exercise intensity, occlusion     

Effects of High versus Low-Intensity Resistance Training on Bone Mineral Density in Young Males

The purpose of this study was to investigate the effect of high-intensity and low-intensity resistance training upon bone mineral density (BMD) by comparing the BMD of young male powerlifters (n = 5), recreational trainees (n = 5), and controls (n = 5). Lumbar spine (L2-L4), proximal femur, and whole body BMDs were measured using dual-energy X-ray absorptiometry (DXA). The high-intensity group showed a significantly greater BMD when the whole body and trochanter regions were measured than the low-intensity and control group. The BMD of the lumbar spine, femoral neck, and Ward's triangle was greater in the high-intensity group compared with the control group. There was no significant BMD difference between the low-intensity and control group except at the trochanter region. These results suggest that high-intensity resistance training is effective for increasing BMD, but low-intensity resistance training is not.     

Effects of Hypothyroidism on the Skeletal Muscle Blood Flow Response to Contractions

Hypothyroidism is associated with impaired blood flow to skeletal muscle under whole body exercise conditions. It is unclear whether poor cardiac and/or vascular function account for blunted muscle blood flow. Our experiment isolated a small group of hindlimb muscles and simulated exercise via tetanic contractions. We hypothesized that muscle blood flow would be attenuated in hypothyroid rats (HYPO) compared with euthyroid rats (EUT). Rats were made hypothyroid by mixing propylthiouracil in their drinking water (2.35 × 10⁻³ mol/l). Treatment efficacy was evidenced by lower serum T₃ concentrations and resting heart rates in HYPO (both P<0.05). In the experimental preparation, isometric contractions of the lower right hindlimb muscles at a rate of 30 tetani/min were induced via sciatic nerve stimulation. Regional blood flows were determined by the radiolabelled microsphere method at three time points: rest, 2 min of contractions and 10 min of contractions. Muscle blood flow generally increased from rest (∼5–10 ml/min per 100 g) through contractions for both groups. Further, blood flow during contractions did not differ between groups for any muscle (eg. red section of gastrocnemius muscle; EUT, 59.9 ± 14.1; HYPO, 61.1 ± 15.0; NS between groups). These findings indicate that hypothyroidism does not significantly impair skeletal muscle blood flow when only a small muscle mass is contracting. Our findings suggest that impaired blood flow under whole body exercise is accounted for by inadequate cardiac function rather than abnormal vascular function.     

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     

The Effects of a Single Session of High Intensity Functional Training on Energy Expenditure,VO2, and Blood Lactate

High intensity functional training (HIFT) provides a potential option to meet public exercise recommendations for both cardiorespiratory and strength outcomes in a time efficient manner. To better understand the potential for HIFT as an exercise approach, energy expenditure (EE) and relative intensity need quantifying. In thirteen sedentary men and women with metabolic syndrome (MetS), we used both indirect calorimetry and blood lactate levels to calculate EE of a single session of HIFT. The HIFT session included four, 6-minute sets of consecutive functional exercises. Examples of the exercises involved were squats, deadlifts, suspension rows, suspension chest press, and planks. Intensity is described relative to individual ventilatory thresholds. The total group EE was 270.3 ± 77.3 kcal with approximately 5% attributed anaerobic energy production. VO₂ ranged between 88.8 ± 12.3% and 99 ± 12% of the second ventilatory threshold (VT2), indicating a vigorous effort. After each work interval, peak blood lactate ranged between 7.9 ± 1.9 and 9.3 ± 2.9 mmol, and rate of perceived exertion between 6.9 ± 1.0 and 8.7 ± 0.8 arbitrary units from 1-10. These were achieved in approximately 46 minutes of exercise per participant. In conclusion, HIFT elicits the energy expenditure and effort requisite to result in the adaptive responses to produce the known suite of benefits of exercise for individuals with MetS. Key points

• Mean energy expenditure for a 46-minute session of high intensity functional training was 270 kcal.
• VO₂ during the work intervals fell at or very near to the second ventilatory threshold indicating a vigorous effort.
• Peak blood lactate ranged between 7.9 and 9.3 mmol, contributing to approximately 5% of total energy expenditure.

Key words: Acute exercise, ventilatory threshold, metabolic syndrome     

Effect of Moderate Altitude on Peripheral Muscle Oxygenation During Leg Resistance Exercise in Young Males

Training at moderate altitude (~1800m) is often used by athletes to stimulate muscle hypoxia. However, limited date is available on peripheral muscle oxidative metabolism at this altitude (1800AL). The purpose of this study was to determine whether acute exposure to 1800AL alters muscle oxygenation in the vastus lateralis muscle during resistance exercise. Twenty young active male subjects (aged 16 – 21 yr) performed up to 50 repetitions of the parallel squat at 1800AL and near sea level (SL). They performed the exercise protocol within 3 h after arrival at 1800 AL. During the exercise, the changes in oxygenated hemoglobin (OxyHb) in the vastus lateralis muscle, arterial oxygen saturation (SpO₂), and heart rate were measured using near infrared continuous wave spectroscopy (NIRcws) and pulse oximetry, respectively. Changes in OxyHb were expressed by D_eff defined as the relative index of the maximum change ratio (%) from the resting level. OxyHb in the vastus lateralis muscle decreased dramatically from the resting level immediately after the start of exercise at both altitudes. The D_eff during exercise was significantly (p < 0.001) lower at 1800AL (60.4 ± 6.2 %) than at near SL (74.4 ± 7.6 %). SpO₂ during exercise was significantly (p < 0.001) lower at 1800AL (92.0 ± 1.7 %) than at near SL (96.7 ± 1.2 %). Differences (SL – 1800AL) in D_eff during exercise correlated fairly strongly with differences in SpO₂ during exercise (r = 0.660). These results suggested that acute exposure to moderate altitude caused a more dramatical decrease in peripheral muscle oxygenation during leg resistance exercise. It is salient to note, therefore, that peripheral muscle oxygenation status at moderate altitude could be evaluated using NIRcws and that moderate altitudes might be effectively used to apply hypoxic stress on peripheral muscles.

Key Points

• The change in muscle oxygenation during the parallel squat at 1800 altitude and near sea level was investigated using near infrared continuous wave spectroscopy (NIRcws)
• The muscle oxygenation during exercise at 1800 altitude decreased more dramatically compared to sea level.
• NIRcws could help to provide a better understanding of exercising muscle metabolism at moderate altitude.

Key words: NIRcws, muscle oxygenation, moderate altitude, parallel squat, SpO₂     

Effects of Subanesthetic Doses of Ketamine on Regional Cerebral Blood Flow, Oxygen Consumption, and Blood Volume in Humans

Background: Animal experiments have demonstrated neuroprotection by ketamine. However, because of its propensity to increase cerebral blood flow, metabolism, and intracranial pressure, its use in neurosurgery or trauma patients has been questioned.

Methods: 15O-labeled water, oxygen, and carbon monoxide were used as positron emission tomography tracers to determine quantitative regional cerebral blood flow (rCBF), metabolic rate of oxygen (rCMRO2), and blood volume (rCBV), respectively, on selected regions of interest of nine healthy male volunteers at baseline and during three escalating concentrations of ketamine (targeted to 30, 100, and 300 ng/ml). In addition, voxel-based analysis for relative changes in rCBF and rCMRO2 was performed using statistical parametric mapping.

Results: The mean +/- SD measured ketamine serum concentrations were 37 +/- 8, 132 +/- 19, and 411 +/- 71 ng/ml. Mean arterial pressure was slightly elevated (maximally by 15.3%, P < 0.001) during ketamine infusion. Ketamine increased rCBF in a concentration-dependent manner. In the region-of-interest analysis, the greatest absolute changes were detected at the highest ketamine concentration level in the anterior cingulate (38.2% increase from baseline, P < 0.001), thalamus (28.5%, P < 0.001), putamen (26.8%, P < 0.001), and frontal cortex (25.4%, P < 0.001). Voxel-based analysis revealed marked relative rCBF increases in the anterior cingulate, frontal cortex, and insula. Although absolute rCMRO2 was not changed in the region-of-interest analysis, subtle relative increases in the frontal, parietal, and occipital cortices and decreases predominantly in the cerebellum were detected in the voxel-based analysis. rCBV increased only in the frontal cortex (4%, P = 0.022).     

Effects of Lithotomy Position and External Compression on Lower Leg Muscle Compartment Pressure

Background: Case reports have suggested that externally applied pressure from antithrombosis devices may contribute to the development of compartment syndromes during extended surgery in the lithotomy position. The purpose of this study was to assess the effects of a pneumatic compression device on directly measured intracompartment pressure in the lower leg with the leg positioned in the lithotomy position.

Methods: In 25 conscious, healthy men and women, the authors measured pressure within the tibialis anterior muscle compartment with the leg supine and in the lithotomy position with and without intermittent compression. Three different devices were used to keep the leg in the lithotomy position, supporting the leg either behind the knee, under the calf, or at the ankle.

Results: The lithotomy position with support behind the calf or knee increased intracompartment pressure to 16.5 +/- 3.4 versus 10.7 +/- 5.8 mmHg supine (mean +/- SD;P < 0.05). The addition of intermittent compression decreased pressure to 13.4 +/- 5.1 mmHg during lithotomy (P < 0.05) and to 9.1 +/- 7.0 mmHg in the supine position (P < 0.05). In contrast, the lithotomy position with support near the ankle decreased intracompartment pressure to 8.7 +/- 5.6 versus 13.3 +/- 5.1 mmHg supine (P < 0.05). The addition of intermittent compression decreased pressure to 6.5 +/- 5.4 mmHg during lithotomy (P < 0.05) and to 10.3 +/- 4.7 mmHg in the supine position (P < 0.05).     

Blood Flow After Peripheral Arterial Reconstruction:V. Effect of Body Position on Leg Blood Flow at Rest and during Exercise

Common iliac arterial blood flow was measured with implanted electromagnetic flow probes in 6 patients after reconstruction of the aorto-iliac-femoral region. On the 3rd, 4th or 5th day after operation heart rate, oxygen uptake and local leg blood flow were studied at rest and during exercise on a bicycle ergometer in supine and sitting position. Heart rate at rest was 10 beats/min higher in sitting than in supine position. During exercise there was no significant difference in heart rate between the two postures. Oxygen uptake was 8% higher in sitting than in supine position at rest. During exercise oxygen uptake did not differ significantly between the two postures. Local leg blood flow was significantly lower in sitting position both at rest and during exercise.     

Bone Mineral Density and Muscle Strength in Young Men with Mental Retardation (With and Without Down Syndrome)

The objective of this study was to compare the bone mineral density (BMD) of men with Down syndrome (DS) to otherwise mentally retarded (MR) men and to investigate whether leg muscle strength of these patients is related to BMD. Two groups with MR (with and without DS) participated in the study, having met the following criteria: similar age, moderate to mild mental retardation, Tanner stage V of sexual development, similar age of beginning to walk, and equal motor activities. The DS group consisted of 8 men 23.9 ± 4.2 years, and the MR group without DS consisted of 8 men 23.5 ± 3.6 years. The two groups were compared with 10 sedentary students of the same age range (25.9 ± 2.9 years) attending our University. The BMD of the 2^nd to 4^th lumbar vertebrae was measured in the PA projection and the mean density was expressed as g/cm². The isokinetic muscle strength of the right quadriceps femoris and hamstrings muscles was measured on a Cybex II isokinetic dynamometer. The value measured was peak torque at angular velocities at 60, 120, and 300°.sec⁻¹. The results showed that BMD in DS individuals versus young adults (reference group of the scanner) was lower at the 26% level (T-score − 2.66 ± 0.29) and significantly lower (P= 0.002) than that of the MR group. Significantly different muscle strength was observed between the DS and non-DS MR group (in quadriceps at 300°.s⁻¹: P < 0.01, at 120 and 60°.s⁻¹: P < 0.05; in hamstrings at 300°.s⁻¹: P < 0.05). Higher differences in muscle strength were found between MR and control men, but no significant difference existed in BMD between them. Bivariate correlation showed that quadriceps strength significantly predicted the BMD in the DS patients. Active lifestyle and increased physical exercise to improve muscular strength should be instituted to avoid the development of osteoporosis in DS patients. Received: 22 July 1998 / Accepted: 30 September 1999     

Effects of Sevoflurane, Propofol, and Adjunct Nitrous Oxide on Regional Cerebral Blood Flow, Oxygen Consumption, and Blood Volume in Humans

Background: Anesthetic agents, especially volatile anesthetics and nitrous oxide (N2O), are suspected to perturb cerebral homeostasis and vascular reactivity. The authors quantified the effects of sevoflurane and propofol as sole anesthetics and in combination with N2O on regional cerebral blood flow (rCBF), metabolic rate of oxygen (rCMRO2), and blood volume (rCBV) in the living human brain using positron emission tomography.

Methods: 15O-labeled water, oxygen, and carbon monoxide were used as positron emission tomography tracers to determine rCBF, rCMRO2 and rCBV, respectively, in eight healthy male subjects during the awake state (baseline) and at four different anesthetic regimens: (1) sevoflurane alone, (2) sevoflurane plus 70% N2O (S+N), (3) propofol alone, and (4) propofol plus 70% N2O (P+N). Sevoflurane and propofol were titrated to keep a constant hypnotic depth (Bispectral Index 40) throughout anesthesia. End-tidal carbon dioxide was strictly kept at preinduction level.

Results: The mean +/- SD end-tidal concentration of sevoflurane was 1.5 +/- 0.3% during sevoflurane alone and 1.2 +/- 0.3% during S+N (P < 0.001). The measured propofol concentration was 3.7 +/- 0.7 [mu]g/ml during propofol alone and 3.5 +/- 0.7 [mu]g/ml during P+N (not significant). Sevoflurane alone decreased rCBF in some (to 73-80% of baseline, P < 0.01), and propofol in all brain structures (to 53-70%, P < 0.001). Only propofol reduced also rCBV (in the cortex and cerebellum to 83-86% of baseline, P < 0.05). Both sevoflurane and propofol similarly reduced rCMRO2 in all brain areas to 56-70% and 50-68% of baseline, respectively (P < 0.05). The adjunct N2O counteracted some of the rCMRO2 and rCBF reductions caused by drugs alone, and especially during S+N, a widespread reduction (P < 0.05 for all cortex and cerebellum vs. awake) in the oxygen extraction fraction was seen. Adding of N2O did not alter the rCBV effects of sevoflurane and propofol alone.     

CO2气腹对动脉粥样硬化兔颈动脉血流量的影响

目的探讨CO2气腹对动脉粥样硬化兔颈动脉血流量的影响及其机理.方法将50只日本大耳白兔按随机数字表法分为正常对照组(n=13)和动脉粥样硬化组(n=37), 后者根据气腹压的不同[0、10及15 mm Hg(1 mm Hg=0.133 kPa)]分为3个亚组,n分别为12、12及13.通过高脂饮食制作兔动脉粥样硬化模型.采用电磁流量计检测实验兔颈动脉血流量变化,生化分析仪行血气分析.结果建立气腹后(10及15 mm Hg)各时点兔颈动脉血流量均明显高于0 mm Hg组及正常对照组(P＜0.05),且随气腹持续时间延长而增加,均明显高于气腹前(P＜0.05),解除气腹后30 min虽有下降,但仍高于气腹前(P＜0.05); 其中15 mm Hg组颈动脉血流量明显高于10 mm Hg组(P＜0.05); 0 mm Hg组与正常对照组颈动脉血流量差异无统计学意义(P>0.05).建立气腹后(10及15 mm Hg)各时点,动脉血PaCO2逐渐升高,pH值逐渐下降,均明显高于或低于气腹前、0 mm Hg组及正常对照组(P＜0.05); 各时点0 mm Hg组及正常对照组 pH值及PaCO2差异无统计学意义(P>0.05); 各组间及各时点间血HCO3-含量差异无统计学意义(P>0.05).结论动脉粥样硬化状态下,CO2气腹可引起颈动脉血流量增加,其机理可能与腹内压增高、CO2通过腹膜吸收导致PaCO2升高、pH降低、造成高碳酸血症等原因有关.     

Comparison of VO2 Peak during Treadmill and Cycle Ergometry in Severely Overweight Youth

The purpose of this study was to compare peak cardiorespiratory parameters during treadmill and cycle ergometry in severely overweight youth. Twenty-one participants from the Committed to Kids Pediatric Weight Management program at the Louisiana State University Health Sciences Center volunteered. Participants completed peak treadmill and cycle ergometer tests on separate days. In order to examine reliability, six subjects completed a second treadmill test and seven subjects a second cycle test. Physical characteristics included the following: Age (yrs) 12.5 ± 2.8; Body weight (BW) (kg) 78.5 ± 27.0, Height (m) 1.56 ± 0.13; and % fat 42.8 ± 7.5. No statistical significant differences (p ≤ 0.05) were found between treadmill and cycle peak tests. Treadmill VO₂ peak (l·min^-1) averaged 1.57 ± 0.40 and cycle 1.46 ± 0.30 and VO₂ peak relative to BW 21.5 ± 4.1 and 20.3 ± 5.5 for treadmill and cycle ergometry, respectively. Therefore treadmill values were 7.0% and 5.6% higher than cycle values. In normal weight or children and adolescents at risk for overweight, treadmill values typically average from 7 to 12% higher than cycle values. Reliability of VO₂ peak as indicated by intraclass correlation coefficients ranged from 0.70 to 0.96 for a single or repeated tests. Intra individual variability averaged 0.5% for VO₂ peak (l·min^-1) during treadmill ergometry and 5.7% for cycle ergometry. Also, standard errors of measurement were low (40 to 90 ml min or 1.0 to 1.7 ml.kg^-1. min^-1) for the peak treadmill or cycle tests. In summary, our data suggest that both treadmill and cycle ergometry provide reliable methods for determining VO₂ peak in overweight youth.

Key Points

• Treadmill peak VO₂ higher than cycle ergometry in severely overweight youth.
• VO₂peak test-retest or single trial reliability high in both treadmill and cycle VO₂ peak.
• Standard errors of measure low for both treadmill and cycle VO₂peak.

Key Words: VO₂peak, severely overweight youth, treadmill, cycle ergometry     

Investigating the Effects of Motion Streaks on pQCT-Derived Leg Muscle Density and Its Association With Fractures

Lower peripheral quantitative computed tomography (pQCT)-derived leg muscle density has been associated with fragility fractures in postmenopausal women. Limb movement during image acquisition may result in motion streaks in muscle that could dilute this relationship. This cross-sectional study examined a subset of women from the Canadian Multicentre Osteoporosis Study. pQCT leg scans were qualitatively graded (1–5) for motion severity. Muscle and motion streak were segmented using semi-automated (watershed) and fully automated (threshold-based) methods, computing area, and density. Binary logistic regression evaluated odds ratios (ORs) for fragility or all-cause fractures related to each of these measures with covariate adjustment. Among the 223 women examined (mean age: 72.7?±?7.1 years, body mass index: 26.30?±?4.97?kg/m²), muscle density was significantly lower after removing motion (p?<?0.001) for both methods. Motion streak areas segmented using the semi-automated method correlated better with visual motion grades (rho?=?0.90, p?<?0.01) compared to the fully automated method (rho?=?0.65, p?<?0.01). Although the analysis-reanalysis precision of motion streak area segmentation using the semi-automated method is above 5% error (6.44%), motion-corrected muscle density measures remained well within 2% analytical error. The effect of motion-correction on strengthening the association between muscle density and fragility fractures was significant when motion grade was?≥3 (p interaction <0.05). This observation was most dramatic for the semi-automated algorithm (OR: 1.62 [0.82,3.17] before to 2.19 [1.05,4.59] after correction). Although muscle density showed an overall association with all-cause fractures (OR: 1.49 [1.05,2.12]), the effect of motion-correction was again, most impactful within individuals with scans showing grade 3 or above motion. Correcting for motion in pQCT leg scans strengthened the relationship between muscle density and fragility fractures, particularly in scans with motion grades of 3 or above. Motion streaks are not confounders to the relationship between pQCT-derived leg muscle density and fractures, but may introduce heterogeneity in muscle density measurements, rendering associations with fractures to be weaker.     

High Intensity Resistance Training: Effects on Bone in Older Men and Women

There is evidence that high intensity resistance training promotes bone maintenance in older women, however, the effect of high intensity free weight training has not been investigated in older men or women. Furthermore, little is known about the chronic effect of weight training on serum insulin growth factor-I (IGF-I) in this population. We compared the effects of a moderate intensity seated resistance-training program with a high intensity standing free weight exercise program on bone mass and serum levels of IGF-I and IGFBP3 in healthy older men and women. Twenty-eight men (54.6 ± 3.2 years) and 26 nonestrogen-replaced women (52.8 ± 3.3 years) served as their own controls for 12 weeks, then were randomly assigned to a moderate or high intensity training group and trained three times/week for 24 weeks. Prior to and after the control period and at the end of training, bone mass and body composition were assessed by dual energy X-ray absorptiometry (DXA), muscle strength by isokinetic dynamometry, muscular power by Wingate Anaerobic Power Test, and IGF-I by radioimmunoassay (RIA). A repeated measures analysis of covariance (ANCOVA) revealed that high intensity training resulted in a gain in spine BMD in men (1.9%), P < 0.05, but not in women, whereas moderate intensity training produced no changes in either gender at this site. Increases were observed at the greater trochanter, P < 0.03, in men regardless of training intensity, but not in women at any hip site. However, when compared with zero, both men and women in the high intensity group demonstrated significant increases in trochanteric BMD (1.3% and 2.0%, respectively) and a decrease in femoral BMD (−1.8%). Neither circulating serum IGF-I nor IGFBP3 were altered by either training regimen, but both training programs resulted in improvements in total body strength (37.62%) and lean mass (males 4.1%, females 3.1%). We conclude that although resistance training of moderate to high intensity produced similar muscle changes in older adults, a higher magnitude is necessary to stimulate osteogenesis at the spine. However, at the spine, intensity was not sufficient to offset low levels of estrogen in early postmenopausal women. Furthermore, bone changes were not accompanied by changes in circulating serum levels of IGF-I or IGFBP3. Received: 21 July 1999 / Accepted: 11 January 2000     

老年ED病人阴茎背动脉横切面积和血流量研究

目的 :探讨老年人血流动力学因素在勃起功能障碍 (ED)中的作用。　方法 :随机抽取 40例勃起功能正常和 5 9例老年ED病人 ,先以脉冲超声波多普勒探测阴茎背动脉横切面图形和平均流速时间积分 ,再用微机图像扫描仪自动测量图形面积 ,最后计算出阴茎背动脉每分血流量。　结果 :勃起功能正常不同年龄组间阴茎背动脉横切面积和血流量均无显著性差异 (P >0 0 5 ) ;勃起功能正常与ED相同年龄两组间阴茎背动脉横切面积有显著性差异 (P <0 0 5 ) ,血流量有非常显著性差异 (P <0 0 1)。　结论 :血管横切面积缩小及血流量降低在老年ED流行病学中起重要作用。     

Effects of Morphine and Halothane Anesthesia on Coronary Blood Flow

This study was undertaken to determine the relative effects of morphine and halothane anesthesia on coronary blood flow. Right heart bypass was instituted in 20 dogs by draining the vena cava blood into a cardiotomy reservoir and returning it to the main pulmonary artery. Coronary sinus drainage was measured by a right ventricular cannula. Group I (10 dogs) was sequentially given 0.5, 1, 1.5, 2.0, and 2.5% halothane. Group II (10 dogs) was given 1, 2, 3, 4, and 5 mg per kilogram of morphine intravenously. Arterial pressure, coronary sinus blood flow, cardiac output, arterial pH, Pco₂, and Po₂ were determined and repeated at each dose level of anesthesia and compared to the control values.Morphine significantly increased coronary flow at 3, 4, and 5 mg/kg without pressure adjustment and at 2 mg/kg after pressure adjustment. Coronary flow with halothane was unchanged from control values except for a decrease at 2.5%. Coronary flow was significantly greater with 3, 4, and 5 mg/kg of morphine than with 1.0 and 1.5% halothane.