The purpose of this study was to develop a simple and convenient indirect method for estimating maximal oxygen uptake (VO2max) and oxygen uptake at the anaerobic threshold (VO2AT) by using workrate and a rating of perceived exertion (RPE) during a submaximal graded cycling test (GCTsubmax). One hundred and fifty-four healthy Japanese men, aged 20 to 64 years, volunteered to participate in the study. The subjects were randomly divided into two groups, a validation (V) group (n=100) and a cross-validation (CV) group (n=54). The V and CV groups performed a maximal cycling test and the GCTsubmax. The GCTsubmax was conducted with documentation of three categories (overall, chest, legs) of RPE, up to a rating of 15. Prediction equations of VO2max and VO 2AT were developed by multiple regression analysis using data of the V group. The mean VO2max and VO2AT of the V group were 2462 ± 484 ml·min-1 and 1349 ± 334 ml·min-1, respectively. Correlational analyses indicated that the workrate (W) at which the legs RPE (RPElegs) reached 15 or higher was evaluated first (W RPE legs 15) together with W RPE legs 14 both yielded the highest correlation coefficients (r) with VO2max (r=0.781) and VO2AT (r=0.790), respectively. The developed prediction equations of VO2max and VO2AT were VO2max (ml·min -1) =1.19WRPE legs 15 (kgm·min-1) - 15.84age (yr) + 13.06 weight (kg) + 1365 (R=0.849, SEE=261 ml·min -1) VO2AT (ml·min-1) = 1.34WRPE legs 14 (kgm·min-1) -5.49 age (yr) + 665 (R=0.816, SEE=195 ml·min-1) Results of a cross-validation analysis indicated a similar estimation (r=0.793 and 0.853, and SEE=240 ml·min-1 and 183 ml·min-1) compared with the above equations developed from data of the V group. Reliability coefficients of VO2max (r=0.891) and VO2AT (r=0.870) respectively were significant and there was no difference in the mean value between trials 1 and 2. The "RPE method" developed for estimating cardiorespiratory fitness is not only a unique indirect method but also a valid and useful tool in various settings of exercise prescription.
This project examined the effects of repeated, resting cold-water immersion on metabolic heat production and core temperature defence during subsequent rest and exercising immersions. Seven males undertook 15 days of cold-water adaptation, immersed to the fourth intercostal space, with cold-water stress tests (CWST) on days 1, 8 and 15 (18.1 SD 0.1°C: 60 min seated, followed by 30 min cycling (1 W·kg-1)), and 90-min resting immersions (18.4 SD 0.4°C) on each of the intervening days. Adaptation elicited an habituated thermogenic response during the rest phase of CWST3 beyond 20 min, compared to CWST1 (P<0.05), with oxygen consumption averaging 11.15 (± 0.25) ml·kg-1·min-1 and 8.61 (± 0.90) ml·kg-1·min-1 by 50 min, for CWST1 and CWST3, respectively. During exercise, this metabolic blunting was only apparent over the first 10-min period (60-70 min). No significant differences were observed during either the rest or exercise phases of the CWSTs for oesophageal temperature (Tes). While repeated cold-water exposures produced an habituated-thermogenic response, for an equivalent drop in Tes during rest, neither this response, nor an elevated thermogenesis, were apparent during subsequent cold-water exercise.
The purpose of the present study was to determine whether or not the exercise intensity of water-walking for elderly women could be accurately prescribed by heart rate data obtained during treadmill exercise on land. Six healthy female volunteers, with a mean age of 62.2 ± 4.2 years, took part in this study. Walking on land was performed on a treadmill. Each subject completed three consecutive 4-minute walks at a progressively increasing velocity (40, 60 and 80 m·min-1), with a 1-minute rest after both the first and second walks. The room temperature and relative humidity were 24.5 ± 0.2°C and 54.8 ± 4.0%, respectively. Walking in water was performed in a Flowmill, which is a treadmill positioned at the base of a water flume. Each subject completed three consecutive 4-minute walks at a progressively increasing belt and water-flow velocity (20, 30 and 40 m·min-1), with a 1-minute rest after both the first and second walks. The water depth was at the level of the xiphoid process of each subject. The water temperature was 30.7 ± 0.1°C. The exercise intensity at the highest workrate was equivalent to 44.2 ± 10.3% of the heart rate reserve (HRR) during water-walking and 38.4 ± 4.7% of the HRR during land-walking. There was a highly significant linear relationship between heart rate (HR) and oxygen uptake (VO2) during both water-walking and land-walking. The relationship between HR and VO2 in both exercise modes was similar. Thus, the relationship of HR to VO2 derived from a treadmill-graded walking test on land may be used to prescribe exercise intensity for water-walking in thermoneutral water.
The age dependence of human gastrocnemius Mg2+ concentration is demonstrated. To quantitate Mg2+ concentration, an original and accurate fitting algorithm using quantum mechanics-based prior knowledge is detailed. In a group of 28 volunteers (14 females) in the age range 5-80 years, pH, PCr/ATP and Pi/ATP values in the gastrocnemius were 7.02 ± 0.02 pH, 4.16 ± 0.33 and 0.13 ± 0.02, respectively and independent of age and sex. By contrast, intracellular Mg2+ concentration (mM) decreased linearly (p<0.05) with age (Mg2+ = 0.7803 ± 0.0247-0.0027 ± 0.0005 * age). No difference was found between sexes. From these results, it follows that care must be taken when comparing muscle Mg2+ data from subjects of different age. The hypothesis can be put forward that during aging insufficient intake and/or increased depletion of Mg2+ (e.g., intestinal hypoabsorption or urinary leakage) may affect the musculoskeletal system.
This study was designed to determine whether combined treatments with genistein dosage and moderate resistance exercise would exhibit synergistically preventive effects on bone loss following the onset of menopause. Forty-one 12 wk-old female SD rats were assigned to five groups: 1) Sham operated (Sham); 2) ovariectomized (OVX-Cont); 3) OVX received genistein (OVX-GEN); 4) OVX exercised (OVX-EXE); and 5) OVX treated with both genistein and exercise (OVX-GEN-EXE). All rats were fed a low Ca (0.1%) diet ad libitum. Daily genistein dosage was 12 mg/kg body weight. Exercising rats took 40 sets of 1-min run interspersed with 1-min rest with a 100 g weight on the back on an uphill treadmill at 20 m/min. The experimental duration consisted of the adaptation and treatment periods of 4 weeks each. Uterine weight in OVX-Cont, OVX-GEN, OVX-EXE and OVX-GEN-EXE decreased to about 15% of that in Sham (p<0.001). The femoral BMD (mg/cm2; mean ± SE), assessed by DEXA (Lunar), of OVX-Cont was significantly lowered to 206 ± 5 by -9%, as compared to 226 ± 2 of Sham (p<0.001). The BMD of OVX-GEN, OVX-EXE and OVX-GEN-EXE were 217 ± 2, 217 ± 2 and 222 ± 2, respectively, and genistein dosage and resistance exercise equally increased the BMD of OVX rats by 5% (p<0.01). Combined treatment of genistein and exercise more successfully recovered their decreased BMD by 8% (p<0.001). BMD of the fourth lumbar vertebrae in OVX-Cont was declined to 191 ± 7 by -15%, as compared to 225 ± 4 in Sham (p<0.001). OVX-EXE and OVX-GEN-EXE gained the BMD by 6% to 205 ± 4 and 203 ± 3, respectively, as compared to that of OVX-Cont (p<0.01). These results suggest the possibility that the combined treatment of genistein dosage and resistance exercise have more beneficial effects by acting rather independently than their separate trials on the prevention of ovx-induced bone loss in femurs.
The aim of the present study was to quantify changes in human skeletal muscle pennation angle (Fθ) values during growth and adult life. The human gastrocnemius medialis muscle of 162 subjects (96 males and 66 females) in the age range 0-70 years was scanned with ultrasonography. The subjects were laying prone, at rest, with the ankle maintained at 90° with all muscles relaxed. Fθ increased monotonically starting from birth (0 years) and reached a stable value after the adolescent growth spurt. There was a significant (p<0.05) linear relationship between Fθ and muscle thickness (TK). Fθ = 0.84 (± 0.09) * TK + 3.15 (± 1.13). Human gastrocnemius medialis F θ and TK data found in the literature seem to fit the Fθ-TK plot in a coherent manner, independent of the physiological or anatomical characteristics of the subject. The present findings indicate that Fθ is not a constant parameter but evolves, as is the case for bone length and height, as a function of age.