Generalized equations for predicting body density of men. 1978.

1. Skinfold thickness, body circumferences and body density were measured in samples of 308 and ninety-five adult men ranging in age from 18 to 61 years. 2. Using the sample of 308 men, multiple regression equations were calculated to estimate body density using either the quadratic or log form of the sum of skinfolds, in combination with age, waist and forearm circumference. 3. The multiple correlations for the equations exceeded 0.90 with standard errors of approximately +/-0.0073 g/ml. 4. The regression equations were cross validated on the second sample of ninety-five men. The correlations between predicted and laboratory-determined body density exceeded 0.90 with standard errors of approximately 0.0077 g/ml. 5. The regression equations were shown to be valid for adult men varying in age and fatness.

Concurrent improvements in cardiorespiratory and muscle fitness in response to total body recumbent stepping in humans.

A group of 26 sedentary adults [mean age 48.4 (SD 6.4) years] were allocated randomly into either a non-exercising control group (CON, n =9) or an exercise group (EX, n = 17) that trained 3 days a week for 12 weeks using a total body recumbent stepper (TBRS). Training intensity and duration progressed from 50% of heart rate reserve maximum (HRRmax) for 20 min to 75% HRRmax for 40 min. Maximal exercise responses were measured during incremental treadmill (TM) and TBRS tests to examine the specificity of the adaptations to training. Muscle strength was measured using a one repetition maximum (1 RM) test for the leg press (LP), chest press (CP), and seated row (SR). Muscle endurance (END) was evaluated for LP, CP, and SR as the number of repetitions achieved before failure when exercising at an intensity of 60% of baseline 1 RM. Body composition was estimated using the sum of seven skinfolds. After training, significant increases (P < 0.05) in maximal oxygen uptake and exercise time were observed in the EX group on both the TM (9.3% and 4.8%, respectively) and TBRS (18.2% and 70.5%, respectively). The TBRS training resulted in significant increases (P < 0.01) in 1 RM and END of the legs, chest, and back, with greater magnitude of improvements observed for END. Furthermore, TBRS training resulted in a significant increase in lean body mass and significant reductions in fat mass and percentage body fat (P<0.01). The CON did not show changes in any measurement (P>0.05). These data indicated concurrent improvements in both cardiovascular and muscle fitness. The greater improvements observed on the TBRS test and in muscle endurance suggest the adaptations are specific to the mode of training.

Effects of resistance training on insulin-like growth factor-I and IGF binding proteins.

PURPOSE: Our goal was to determine the effects resistance training on circulating IGF-I and on two of its major binding proteins, IGFBP-1 and IGFBP-3. Additional goals were to compare the time course of hormonal changes with the time course of strength changes and to determine the effect of training volume on the extent of hormonal changes. METHODS: Thirty-one men and women (mean age = 37 +/- 7 yr) completed a 25-wk, 3 d x wk(-1) program in which they performed single-set resistance training (1-SET, N = 11), multiple-set resistance training (3-SET, N = 11), or no exercise (Control, N = 9). Before training, and after 13 and 25 wk of training, blood hormones were analyzed and strength was assessed as the sum of one-repetition maximum (1-RM) for leg extension and chest press exercises. RESULTS: During the first 13 wk of resistance training, circulating IGF-I increased by approximately 20% in both the 1-SET and 3-SET groups (P = 0.041). No further increases occurred between 13 and 25 wk. In the 3-SET group, IGFBP-3 decreased 20% between 13 and 25 wk (P = 0.008). Training did not alter IGFBP-1. Increases in 1-RM strength occurred mainly during the first 13 wk of training and were significantly higher with 3-SET training compared to 1-SET. CONCLUSIONS: These findings indicate that increased circulating IGF-I may, at least in part, mediate increases in strength that result from resistance training.

Nurturing the transformation from staff nurse to leader.

A major component of nurse job satisfaction is autonomy of clinical practice, recognition by colleagues, and participation in decision making relative to patient outcomes. Shared governance provides the framework for autonomy and control of practice, yet implementation of this model implies staff participation as leaders. Staff nurses describe a transformation of perspective when adopting decision-making, leadership-oriented roles and recount the factors that influence and nurture their confidence and acceptance.

The effects of exercise training on the pharmacokinetics of digoxin.

BACKGROUND: Studies have shown that digoxin binds to the working muscles during an acute bout of exercise, with a concomitant decrease in serum digoxin concentration. This study investigated the effects of 16 weeks of endurance exercise training on the pharmacokinetics of digoxin in old and young adults. METHODS: Twelve subjects, aged 68.5 +/- 4.5 years, and six subjects, aged 30.3 +/- 3.8 years, completed the study. All subjects were healthy, sedentary, and taking no cardiovascular medications. After initial testing and maximum oxygen consumption (VO2max) measurements, subjects were hospitalized for 28 hours for renal function testing and digoxin clearance studies and then randomly assigned to an exercise (EG) or control (CG) group. The EG completed 16 weeks (three 1-hour bouts/week) of aerobic training at 75% to 85% of maximum capacity. The CG did not exercise. All tests were repeated at the end of the 16-week study period. RESULTS: In the older EG subjects, VO2max increased by 3.4 ml/kg/min, or approximately 16% (P = 0.0002). VO2max increased in the younger EG subjects by 1.1 ml/kg/min, but the increase was not significant (P > 0.05). There were no significant changes in body composition, renal function, or time of onset, peak concentration, or elimination phase half-life of digoxin in either the old or young exercise or control groups (P > 0.05 for all variables). CONCLUSION: Although 16 weeks of endurance exercise training improves cardiorespiratory fitness, the pharmacokinetics of digoxin are neither improved nor adversely affected in healthy old and young adults.

Time course for strength and muscle thickness changes following upper and lower body resistance training in men and women.

The purpose of this study was to investigate the time course of skeletal muscle adaptations resulting from high-intensity, upper and lower body dynamic resistance training (WT). A group of 17 men and 20 women were recruited for WT, and 6 men and 7 women served as a control group. The WT group performed six dynamic resistance exercises to fatigue using 8-12 repetition maximum (RM). The subjects trained 3 days a week for 12 weeks. One-RM knee extension (KE) and chest press (CP) exercises were measured at baseline and at weeks 2, 4, 6, 8, and 12 for the WT group. Muscle thickness (MTH) was measured by ultrasound at eight anatomical sites. One-RM CP and KE strength had increased significantly at week 4 for the female WT group. For the men in the WT group, 1 RM had increased significantly at week 2 for KE and at week 6 for CP. The mean relative increases in KE and CP strength were 19% and 19% for the men and 19% and 27% for the women, respectively, after 12 weeks of WT. Resistance training elicited a significant increase in MTH of the chest and triceps muscles at week 6 in both sexes. There were non-significant trends for increases in quadriceps MTH for the WT groups. The relative increases in upper and lower body MTH were 12%-21% and 7%-9% in the men and 10%-31% and 7%-8% in the women respectively, after 12 weeks of WT. These results would suggest that increases in MTH in the upper body are greater and occur earlier compared to the lower extremity, during the first 12 weeks of a total body WT programme. The time-course and proportions of the increase in strength and MTH were similar for both the men and the women.

Single versus multiple sets in long-term recreational weightlifters.

PURPOSE: The purpose of this study was to determine the effects of increasing training volume from one set to three sets on muscular strength, muscular endurance, and body composition in adult recreational weight lifters. METHODS: Forty-two adults (age 39.7 +/- 6.2 yr; 6.2 +/- 4.6 yr weight training experience) who had been performing one set using a nine-exercise resistance training circuit (RTC) for a minimum of 1 yr participated in this study. Subjects continued to perform one set (EX-1; N = 21) or performed three sets (EX-3; N = 21) of 8-12 repetitions to muscular failure 3 d x wk(-1) for 13 wk using RTC. One repetition maximums (1-RM) were measured for leg extension (LE), leg curl (LC), chest press (CP), overhead press (OP), and biceps curl (BC). Muscular endurance was evaluated for the CP and LE as the number of repetitions to failure using 75% of pretraining 1-RM. Body composition was estimated using the sum of seven skinfold measures. RESULTS: Both groups significantly improved muscular endurance and 1 RM strength (EX-1 by: 13.6% LE; 9.2% LC; 11.9% CP; 8.7% OP; 8.3% BC; and EX-3 by: 12.8% LE; 12.0% LC; 13.5% CP; 12.4% OP; 10.3% BC) (P < 0.05). Both groups significantly improved lean body mass (P < 0.05). No significant differences between groups were found for any of the test variables (P > 0.05). CONCLUSION: Both groups significantly improved muscular fitness and body composition as a result of the 13 wk of training. The results show that one-set programs are still effective even after a year of training and that increasing training volume over 13 wk does not lead to significantly greater improvements in fitness for adult recreational weight lifters.

Prescription of resistance training for health and disease.

When prescribed appropriately, resistance training is effective for developing fitness, health, and for the prevention and rehabilitation of orthopedic injuries. Because resistance training is an integral component in the comprehensive health program promoted by the major health organizations (e.g., American College of Sports Medicine, American Heart Association, American Association of Cardiovascular and Cardiopulmonary Rehabilitation, Surgeon General's Office), population-specific guidelines have recently been published. The current research indicates that, for healthy persons of all ages and many patients with chronic diseases, single set programs of up to 15 repetitions performed a minimum of 2 d x wk(-1) are recommended. Each workout session should consist of 8-10 different exercises that train the major muscle groups. Single set programs are less time consuming and more cost efficient, which generally translates into improved program compliance. Further, single set programs are recommended for the above-mentioned populations because they produce most of the health and fitness benefits of multiple set programs. The goal of this type of program is to develop and maintain a significant amount of muscle mass, endurance, and strength to contribute to overall fitness and health. Patients with chronic diseases (e.g., arthritis) may have to limit range of motion for some exercises and use lighter weights with more repetitions.

Quantification of full-range-of-motion unilateral and bilateral knee flexion and extension torque ratios.

OBJECTIVES: To evaluate the reliability and variability of repeated measurements of isometric knee flexion and extension strength, to quantify the extent of measurement error that may occur due to gravity, and to quantify isometric knee flexion/extension torque ratios at multiple angles through a full range of motion. DESIGN: Reliability assessment. SETTING: A university exercise center. PARTICIPANTS: Seventy-seven healthy men and women recruited from a university and surrounding community. INTERVENTION: Isometric knee flexion and extension strength tests. MAIN OUTCOME MEASURES: Knee flexion/extension strength was measured at 6 degrees, 24 degrees, 42 degrees, 60 degrees, 78 degrees, 96 degrees, and 108 of knee flexion. Before each contraction, subjects were instructed to completely relax the limbs to measure the mass of the lower leg. Torque values obtained during relaxation at each angle were added to or subtracted from "Total Torque" (TTQ) at peak exertion. The adjusted value was recorded as "Net Muscular Torque" (NMT). RESULTS: Reliability for the unilateral and bilateral tests was high (r =.88 to r=.98) and measurement variability low (SEM%=5.1% to 12.6%). There was a statistically significant difference at each angle of measurement between the TTQ and NMT values for both knee flexion and extension. Knee flexion/extension ratios were highly dependent on the angle tested, ranging from 1.30 (at 60) to .31 (at 1080). CONCLUSIONS: Isometric testing, using standardized angles, can reliably quantify knee flexion/extension strength. Furthermore, these findings emphasize the importance of correcting for the mass of the lower leg when assessing muscle function. Angle-specific knee flexion/extension torque ratios should provide clinicians with a more precise method of evaluating muscular balance (imbalance) throughout the range of motion.

Resistance exercise prevents glucocorticoid-induced myopathy in heart transplant recipients.

PURPOSE: To determine the effect of resistance exercise training (ET) on glucocorticoid-induced myopathy in heart transplant recipients (HTR), 14 male HTR were randomly assigned to a ET group that trained for 6 months (54 +/- 3 yr old; mean +/- SD) or a control group (51 +/- 8 yr old; mean +/- SD). METHODS: Fat mass, fat-free mass, and total body mass were measured by dual-energy x-ray absorptiometry before and 2 months after transplantation (Tx), and after 3 and 6 months of ET or control period. The exercise regimen consisted of lumbar extension (MedX) performed 1 d.wk-1 and variable resistance exercises (Nautilus) performed 2 d.wk-1. PreTx body composition did not differ between groups. RESULTS: At 2 months after Tx, fat-free mass was significantly decreased below baseline in both control (-3.4 +/- 2.1%) and ET groups (-4.3 +/- 2.4%). Fat mass was significantly increased at 2 months after Tx in both the control (+8.3 +/- 2.8%) and ET groups (+7.3 +/- 4.0%). Six months of ET restored fat-free mass to levels 3.9 +/- 2.1% greater (P < or = 0.05) than before Tx. Fat-free mass of the control group decreased progressively to levels that were 7 +/- 4.4% lower than preTx values (P < or = 0.05). Both groups increased knee extension, chest press, and lumbar extensor strength, but improvements in the ET group were four- to six-fold greater (P < or = 0.05). CONCLUSION: Our results demonstrate that glucocorticoid-induced changes in body composition in HTR occur early after Tx. However, 6 months of specific ET restores fat-free mass to levels greater than before Tx and dramatically increases skeletal muscle strength. Resistance exercise, as part of a strategy to prevent steroid-induced myopathy, appears to be safe and should be initiated early after heart Tx.

Plasma volume changes with an acute bout of high-intensity exercise in men with chronic congestive heart failure secondary to coronary artery disease.

We assessed plasma volume changes at peak exercise in 17 nonedematous men with chronic congestive heart failure due to coronary artery disease. Our findings suggest that acute exercise is associated with transient decreases in plasma and blood volume in these patients, similar in magnitude to those reported for healthy adults at peak exercise.

The effects of endurance exercise training on ambulatory blood pressure in normotensive older adults.

This study investigated the effects of 16-weeks of endurance exercise training (EET) on ambulatory blood pressure in older adults. Twenty-one men and women, 68.5 +/- 4.7 (mean +/- SD) years of age were randomly assigned to an exercise group (EG, n = 11) or to a control group (CG, n = 10). Subjects were normotensive (mean resting BP 132.0 +/- 8.6/80.1 +/- 6.6 mm Hg), free from overt cardiovascular or renal diseases, and were taking no vasoactive or diuretic medications. Maximal oxygen uptake (VO2max), body composition, resting BP, and 24-hr ambulatory systolic (ASBP) and diastolic (ADBP) blood pressures were measured in all subjects before and after the study period. The EG completed 16 weeks (3, 1-hour bouts/wk) of EET, progressing in intensity from 50% to 85% of maximal workload. The CG did not exercise. In the EG, although body composition and resting BP did not change (p > 0.05), VO2max increased by 14% (p = 0.001), mean 24-hr ASBP decreased 7.9 mm Hg (p = 0.0001), and mean 24-hr ADBP decreased 3.6 mm Hg (p = 0.002). In the CG, there were no significant changes in these variables (p > 0.05). These data suggest that EET can improve both aerobic fitness and "real-life" blood pressures in healthy older adults and may help inhibit increases in blood pressure associated with normal aging.

Effects of age, physical training, and physical fitness on coronary heart disease risk factors in older track athletes at twenty-year follow-up.

OBJECTIVE: To compare current coronary heart disease (CHD) risk factor values in older athletes with mid-life measures and to examine the associations between changes in CHD risk factors with aging, physical training, and physical fitness. DESIGN: Prospective study with three longitudinal evaluation points: initial (T1), 10-year (T2), and 20-year (T3). Subjects were selected because of their elite status in Masters track competition. SETTING: University and medical center laboratories. PARTICIPANTS: Participants were 60 to 92 years of age and included 21 of the initial 27 subjects. At T3, subjects were divided into three groups, based on physical activity levels: high intensity (H), remained elite in national and international competition (n = 9); moderate intensity (M) continued frequent rigorous endurance training but rarely competed (n = 10); and low intensity (L) greatly reduced their training volume and intensity (n = 2). MEASUREMENTS: Smoking history; family history of coronary or cerebrovascular disease; resting blood pressure; resting electrocardiogram (ECG); serum total cholesterol, plasma glucose; body weight, % body fat, body mass index, waist:hip ratio; training pace and mileage; maximal oxygen consumption VO2 max). MAIN RESULTS: Several risk factors (smoking, diabetes, obesity) were never present, and the prevalence of other risk factors (family history of cardiovascular disease, abnormal resting ECG) remained low through T3 (< or = 14% of subjects). Mean systolic and diastolic blood pressure remained low without medication, but diastolic blood pressure measurements had the greatest redistribution between evaluation periods of any risk factor (r = .16, P = .479, T1 to T2). Mean total cholesterol was lower at T2 (-13%, P = .005) and T3 (-14%, P = .019) compared with T1. Change in VO2 max was correlated with changes in body weight (r = -.44, P = .048) and % fat (r = -.52, P = .015) from T1 to T2, whereas age was correlated to changes in systolic blood pressure (r = -.61, P = .003) and total cholesterol (r = -.49, P = .023) from T2 to T3. CONCLUSIONS: The prevalence of CHD risk factors remained low, and mean risk factor values remained low and generally stable in older athletes who had maintained habitual exercise training.

Twenty-year follow-up of aerobic power and body composition of older track athletes.

The purpose was to determine the aerobic power (maximal oxygen uptake) and body composition of older track athletes after a 20-yr follow-up (T3). At 20 yr, 21 subjects [mean ages: 50.5 +/- 8.5 yr at initial evaluation (T1), 60.2 +/- 8.8 yr at 10-yr follow-up (T2), and 70.4 +/- 8.8 yr at 20-yr follow-up (T3)] were divided into three intensity groups: high (H; remained elite; n = 9); moderate (M; continued frequent moderate-to-rigorous endurance training; n = 10); and low (L; greatly reduced training; n = 2). All groups decreased in maximal oxygen uptake at each testing point (H, 8 and 15%; M, 13 and 14%; and L, 18 and 34% from T1 to T2 and T2 to T3, respectively). Maximal heart rate showed a linear decrease of approximately 5-7 beats.min-1.decade-1 and was independent of training status. Body weight remained stable for the H and M groups and percent fat increased approximately 2-2.5%/decade. Although fat-free weight decreased at each testing point, there was a trend for those who began weight-training exercise to better maintain it. Cross-sectional analysis at T3 showed that leg strength and bone mineral density were generally maintained from age 60 to 89 yr. Those who performed weight training had a greater arm region bone mineral density than those who did not. These longitudinal data show that the physiological capacities of older athletes are reduced despite continued vigorous endurance exercise over a 20-yr period (approximately 8-15%/decade). Changes in body composition appeared to be less than those shown for the healthy sedentary population and were related to changes in training habits.

Isometric torso rotation strength: effect of training frequency on its development.

OBJECTIVE: To examine training frequency's effect on torso rotation muscle strength. DESIGN: The study followed a pretest-posttest randomized-group design. SETTING: University laboratory. PATIENTS: Subjects, 33 men (age 30 +/- 11yr) and 25 women (age 28 +/- 10yr) with no history of low back pain, volunteered to participate in the study and were tested for isometric (IM) torso rotation strength before (T1) and after (T2) 12 weeks of training. Measurements of maximal voluntary IM torso rotation torque (N.m) were made through a 108 degrees range of motion (54 degrees, 36 degrees, 18 degrees, 0 degree, -18 degrees, -36 degrees, -54 degrees). Subjects were stratified by peak torque at T1, and randomized to a nonexercising control group (C, n = 10), or groups that trained once a week (1x/wk, n = 16), twice a week (2x/wk, n = 17), or three times a week (3x/wk, n = 15); and all groups were similar in strength. INTERVENTIONS: Training consisted of 8 to 12 repetitions of full range dynamic variable resistance exercise to volitional fatigue, for both left and right rotation. MAIN OUTCOME: To determine the best training frequency for the development of torso rotation strength. RESULTS: Relative improvements (average increase in strength gained at each angle) for the training groups were 4.9%, 16.3%, and 11.9% for the 1, 2, and 3x/wk groups, respectively. The 1x/wk group did not increase in IM torso rotation strength compared to the control group at any angle. Both the 2 and 3x/ wk groups increased their IM torso rotation strength compared to the control group at all but one angle. There were no significant differences in IM torso rotation strength between the groups that trained 2 or 3x/wk. During the training period, the 2 and 3x/wk groups increased their dynamic training load significantly more than the 1x/wk group. CONCLUSIONS: Posttraining dynamic strength was not different between training frequencies of 2 and 3x/wk. Therefore, training the rotary torso muscles 2x/wk is recommended.

Distribution of subcutaneous fat and muscle thicknesses in young and middle-aged women.

Thicknesses of subcutaneous fat tissue at 13 sites (triceps, biceps, forearm, subscapular, abdomen, suprailiac, axilla, chest, quadriceps, suprapatellar, hamstrings, posterior calf, medial calf), and muscle tissue at nine sites (triceps, biceps, forearm, subscapular, abdomen, quadriceps, suprapatellar, hamstrings, posterior calf) were determined by using the B-mode ultrasound technique. Subjects were 36 young (18-29 years) and 44 middle-aged women (45-64 years). Body density averaged 1.047 ± 0.007 g · ml-1 (SD) for the young, and 1.022 ± 0.005 g · ml-1 for the middle-aged women. The middle-aged women showed significantly thicker subcutaneous fat than the young at all sites, and the relative differences between the two groups were larger on the trunk and adjacent sites. Muscle thicknesses on the trunk and quadriceps were significantly higher in the young women than in the middle-aged, but values for the upper extremities and calf were not significant between the two groups. The sum of subcutaneous fat thicknesses at 13 sites was significantly correlated with fat mass relative to the second power of stature (FM · St-2 ) in both groups, r = 0.766 (P < 0.05) for the young and r = 0.803 (P < 0.05) for the middle aged women. For subcutaneous fat thickness per unit FM · St-2 , the young women showed significantly higher values than the middle-aged on both the upper and lower extremities. The sum of muscle thicknesses at nine sites was significantly correlated with fat-free mass per unit stature2 (FFM · St-2 ) in both groups, r = 0.764 (P < 0.05) for the young and r = 0.636 (P < 0.05) for the middle-aged. The relative values of muscle thicknesses to FFM · St-2 were significantly lower on the abdomen and quadriceps in the middle-aged women than in the young. Thus compared with the young, the middle-aged women have thicker subcutaneous fat thicknesses along the whole body and thinner muscle thicknesses on the trunk and quadriceps regions. Moreover, it appears that in middle-aged women, the relative distribution of subcutaneous fat and muscle thicknesses to FM and FFM, respectively, show disproportionately higher fat stores internally than subcutaneously, and more rapid atrophy of muscle tissues at the anterior sites of the trunk and thigh than at other body sites. Am. J. Hum. Biol. 9:247-255, 1997. © 1997 Wiley-Liss, Inc.

Strength training: rationale for current guidelines for adult fitness programs.

Strength training is an effective method for developing musculoskeletal strength and is often prescribed for fitness, health, and the prevention and rehabilitation of orthopedic injuries. Because strength training is an integral component in the comprehensive health program promoted by the major health organizations (eg, American College of Sports Medicine, American Heart Association, Centers for Disease Control and Prevention, US Surgeon General's Office), population-specific guidelines have recently been published. For the average adult beginning a strength training program, current research indicates that single-set programs performed a minimum of two times per week are recommended over multiple-set programs because they are less time-consuming, more cost-efficient, and produce most of the health and fitness benefits. The goal of this type of program is to develop and maintain a significant amount of muscle mass, endurance, and strength to contribute to overall fitness and health, not to optimize strength, power, and hypertrophy. By incorporating exercise prescription into patient counseling, clinicians can further increase their effectiveness as prevention-oriented healthcare providers.