Skeletal muscle sorbitol levels in diabetic rats with and without insulin therapy and endurance exercise training.

Sorbitol accumulation is postulated to play a role in skeletal muscle dysfunction associated with diabetes. The purpose of this study was to determine the effects of insulin and of endurance exercise on skeletal muscle sorbitol levels in streptozotocin-induced diabetic rats. Rats were assigned to one experimental group (control sedentary, control exercise, diabetic sedentary, diabetic exercise, diabetic sedentary no-insulin). Diabetic rats received daily subcutaneous insulin. The exercise-trained rats ran on a treadmill (1 hour, 5X/wk, for 12 weeks). Skeletal muscle sorbitol levels were the highest in the diabetic sedentary no-insulin group. Diabetic sedentary rats receiving insulin had similar sorbitol levels to control sedentary rats. Endurance exercise did not significantly affect sorbitol levels. These results indicate that insulin treatment lowers sorbitol in skeletal muscle; therefore sorbitol accumulation is probably not related to muscle dysfunction in insulin-treated diabetic individuals. Endurance exercise did not influence intramuscular sorbitol values as strongly as insulin.

Sports and recreational injuries: regional rural injury study-II: impact on agricultural households and operations.

OBJECTIVES: To identify the incidence, severity, and potential risk factors for sports/recreational injuries incurred by children and adults in a five state, rural, Midwest, agricultural household population. METHODS: Computer assisted telephone interviews that included questions about all injuries were completed for eligible, participating households for 1999; 16,538 people participated, including 8488 children less than 20 years of age. Rates and 95% confidence intervals were calculated, and causal models guided multivariate models. RESULTS: Of a total of 2586 injuries, 1301 (50%) were not related to agricultural activity. Among these, 733 (28%) were associated with sports/recreational activities including multiple person sports (64%), general play activities (19%), and single person sports (14%). The overall rate was 46.4 injury events per 1000 persons per year. Rates for children were 99.4 for boys and 64.3 for girls. For adults (aged 20 and above), rates were 11.9 for men and 4.8 for women. For children, 93% received health care, 44% were restricted for seven or more days, and 18% lost agricultural work time of seven or more days; the respective proportions for adults were 88%, 45%, and 17%. Multivariate analysis for children showed increased risks for Nebraska residents, males, and those 10-14 or 15-19 years. For adults, increased risks were identified for males and those 20-24 years; decreased risks were observed for Nebraska residents and those 45-54 years. CONCLUSIONS: Sports/recreational activities are an important source of injury with relevant consequences for this population, including significant restricted daily activity and lost agricultural work time. Key findings provide a basis for further study to address these burdens.

Validity and reliability of combining three methods to determine ventilatory threshold.

PURPOSE: This research was undertaken to validate a combination of methodologies to determine ventilatory threshold (VT). METHODS: Three methods were used individually and then combined to determine VT as follows: 1) ventilatory equivalencies, 2) excess CO2 production, and 3) a modified V-slope method. Three groups of participants-endurance athletes (N = 132), healthy, aerobically active adults (N = 31), and healthy, sedentary/low-active adults (N = 22)-were independently evaluated for VT and compared with the criterion standard lactate threshold (LT) defined as the first rise in blood lactate with increasing intensity of exercise. RESULTS: VT and LT were significantly correlated using the combined VT method within each study group (r = 0.98, 0.97, and 0.95, respectively; P < 0.001). Mean VO2 values at VT and LT were not significantly different between the three groups (P > 0.20). The combined method improved the determination rate of VT and reduced the standard deviation of the LT - VT difference by 80-170% over the individual methods. During test-retest procedures VO2lt and VO2vt determined by the combined method met criteria demonstrating further reliability. CONCLUSION: The combined method to determine VT is valid and reliable across a wide fitness range in healthy individuals and improves the determination rate and accuracy of VT determination over the use of single methods.

Changes in ventilatory threshold with exercise training in a sedentary population: the HERITAGE Family Study.

UNLABELLED: The purpose of this study was to evaluate the effect of exercise training intensity relative to the ventilatory threshold (VT) on changes in work (watts) and VO2 at the ventilatory threshold and at maximal exercise in previously sedentary participants in the HERITAGE Family Study. We hypothesized that those who exercised below their VT would improve less in VO2 at the ventilatory threshold (VO2vt) and VO2max than those who trained at an intensity greater than their VT. Supervised cycle ergometer training was performed at the 4 participating clinical centers, 3 times a week for 20 weeks. Exercise training progressed from the HR corresponding to 55% VO2max for 30 minutes to the HR associated with 75% VO2max for 50 minutes for the final 6 weeks. VT was determined at baseline and after exercise training using standardized methods. 432 sedentary white and black men (n = 224) and women (n = 208), aged 17 to 65 years, were retrospectively divided into groups based on whether exercise training was initiated below, at, or above VT. RESULTS: 1) Training intensity (relative to VT) accounting for about 26% of the improvement in VO2vt (R2 = 0.26, p < 0.0001). 2) The absolute intensity of training in watts (W) accounted for approximately 56% of the training effect at VT (R2 = 0.56, p < 0.0001) with post-training watts at VT (VT(watts)) being not significantly different than W during training (p > 0.70). 3) Training intensity (relative to VT) had no effect on DeltaVO2max. These data clearly show that as a result of aerobic training both the VO2 and W associated with VT respond and become similar to the absolute intensity of sustained (3 x /week for 50 min) aerobic exercise training. Higher intensities of exercise, relative to VT, result in larger gains in VO2vt but not in VO2max.

Cardiac troponin T alterations in myocardium and serum of rats after stressful, prolonged intense exercise.

The goal of this study was to determine whether the stress of forced exercise would result in injury to the myocardium. Male rats with 8% of body weight attached to the tail were forced to swim 3.5 h (3.5S), forced to swim 5 h (5S), or pretrained for 8 days and then forced to swim 5 h (T5S). Rats were killed immediately after they swam (0 h PS) and at 3 h (3 h PS), 24 h (24 h PS), and 48 h after they swam (48 h PS). Tissue homogenates of the left ventricle were analyzed by Western blot analysis for cardiac troponin T (cTnT). Serum cTnT was quantified by immunoassay. Results indicated that, in the 3.5S, 5S, and T5S groups, serum cTnT was significantly (P < 0.01) increased at 0 and 3 h PS. The 5S group demonstrated a greater increase in serum cTnT than the 3.5S group (P < 0.01) and the T5S group (P < 0.01) at 0 h PS. Western blot analysis indicated significant decreases (P < 0. 01) in myocardial cTnT in the 5S group only at 0 h PS (P < 0.01) and 3 h PS (P < 0.05). Histological evidence of localized myocyte damage demonstrated by interstitial inflammatory infiltrates consisting of neutrophils, lymphocytes, and histiocytes, as well as vesicular nuclei-enlarged chromatin patterns, was observed in left ventricle specimens from the 5S group at 24 and 48 h PS. Our findings demonstrate that stressful, forced exercise induces alterations in myocardial cTnT and that training before exercise attenuates the exercise-induced heart damage.

Use of a 13C tracer to quantify the plasma appearance of a physiological dose of lutein in humans.

Increased intake of lutein from vegetables promotes increased density of the macular pigment and therefore may protect against age-related macular degeneration. Our objective was to use a 13C tracer and high-precision gas chromatography-combustion interfaced-isotope ratio mass spectrometry (GC-C-IRMS) to investigate metabolism of a lutein dose equivalent to that absorbed from vegetables. Biosynthetic per-labeled (>99% 13C) lutein was purified from a commercially available extract of algal biomass. Subjects (n = 4) ingested 3 mg of [13C]lutein with a standardized low-carotenoid breakfast. Blood samples were collected at baseline and then hourly for 12 h; additional blood samples were drawn at 16, 24, 48, 72, 96, 192, 360, and 528 h. To produce perhydro-beta-carotene suitable for analysis by GC-C-IRMS, the plasma lutein fraction was hydrogenated on palladium-on-carbon catalyst with acid-catalyzed hydrogenolysis. The stable carbon isotope (13C/12C) ratio measured by GC-C-IRMS was used to calculate the plasma concentration of [13C]lutein. There was a rapid increase in [13C]lutein in plasma until peak enrichment at 16 h followed by a decline to the next measurement at 24 h. At 528 h, small changes in 13C enrichment from baseline could still be measured in plasma lutein. High-precision GC-C-IRMS enables complete definition of the appearance and disappearance of [13C]lutein in plasma after ingestion of a dose similar to that absorbed from foods.

Time course of and effect of dietary iron level on iron incorporation into erythrocytes by infants.

As a part of our effort to explore various aspects of ferrokinetics in infancy, the present study was designed to determine the timing of entry of an orally ingested iron isotope into circulating erythrocytes, and the effect of the level of dietary iron [0.3 mg/100 kcal (418.4 kJ) vs. 1.8 mg/100 kcal] after isotope administration on erythrocyte incorporation of the isotope. We administered the stable isotope, (58)Fe, orally to 56-d-old and 168-d-old infants. All infants were fed a low-iron formula (LF) before and until 5 h after isotope administration. Thereafter, half the infants were fed a formula high in iron (HF group) while the remaining infants continued to receive the LF (LF group) for an additional 28 d. The quantity of (58)Fe in circulating erythrocytes increased from 14 to 28 d after isotope administration was nearly constant from 28 through 84 d of age (plateau value) and decreased between 84 and 112 d. Erythrocyte incorporation of (58)Fe was greater by the 168-d-old infants than by the 56-d-old infants, presumably because of the lesser iron stores of the older infants. In the 56-d-old infants, erythrocyte incorporation of (58)Fe was greater by the LF than by the HF group, but this difference was not significant in the 168-d-old infants. Thus, at least in younger infants, the level of iron intake after administration of an iron isotope affects erythrocyte incorporation of the isotope. The fact that less isotope was present in erythrocytes 112 d than 84 d after administration indicates that the life span of erythrocytes of infants, even beyond the immediate newborn period, is less than the 120-d life span of erythrocytes in the adult.

Loss of myocardial CK-MB into the circulation following 3.5 hours of swimming in a rat model.

The purpose of this study was to document alterations of creatine kinase-B (CK-B) in the left and right ventricles of rats and CK-MB release into the circulation following a single bout of stressful prolonged intense exercise. Male Sprague-Dawley rats, with 8% bodyweight attached to each tail, were forced to swim 3.5 hours and were then sacrificed immediately (0 h PS), 3 hours (3 h PS), 24 hours (24 h PS), and 48 hours (48 h PS) post swimming, respectively. Sedentary (control) rats were sacrificed at rest. Serum CK-MB mass increased 2.1 times (8.9 microg/L; p < 0.01 vs. controls of 4.3 microg/L) and 1.4 times (6.0 microg/L; P < 0.01 vs. controls) at 0 h PS, and 3 h PS, respectively, and returned to baseline at 24 h PS. Western blot analysis indicated that CK-B of the right ventricle decreased 14% (p < 0.05), 20% (p < 0.01), and 12% (p < 0.05) at 3h PS, 24h PS and 48h PS, respectively. The CK-B of the left ventricles decreased 34% (p < 0.05) at 0 h PS, returned to baseline at 3 h PS, and was increased 39% (P < 0.01) at 48 h PS. Our findings demonstrate that a single bout of stressful, prolonged, intense exercise resulted in CK-B subunit loss from the myocardium, resulting in increased serum CK-MB concentrations, an indication of myocardial injury.

Alterations in the expression and activity of creatine kinase-M and mitochondrial creatine kinase subunits in skeletal muscle following prolonged intense exercise in rats.

Creatine kinase (CK) isoenzymes are important structural and energy metabolism components in skeletal muscle. In this study, CK isoenzyme alterations were examined in male rats, with an 8% body mass weight attached to their tail. The rats were either forced to swim for 5 h (5S, n = 51), or were pre-trained for 8 days and then forced to swim for 5 h (T5S, n = 48). Rats were sacrificed either immediately (0 h PS), 3 h (3 h PS), or 48 h post-swimming (48 h PS). Serum CK was increased significantly (P < 0.01) 6.2- and 2.0-fold at 0 h PS following the 5S and T5S protocols, respectively. However, training (T5S protocol) significantly (P < 0.01) decreased CK release. Soleus and white gastrocnemius (WG) CK activity was significantly decreased following the 5S protocol (P < 0.05), but not following the T5S protocol. The CK-M activity of the soleus muscle was significantly (P < 0.05) decreased at 0 h PS following both the 5S and T5S protocols, and returned to control values at 3 h PS. The CK-M activity of the WG was significantly (P < 0.05) decreased at 0 h PS following the 5S protocol. Sarcomeric mitochondrial CK (sCK-Mit) was decreased significantly (P < 0.01) at 0 h PS (20%), 3 h PS (14%), 24 h PS (22%), and 48 h PS (15%) following the 5S protocol. However, sCK-Mit was decreased significantly (P < 0.01) only at 0 h PS (7%) following the T5S. The results of this study demonstrate that prolonged intense exercise causes a loss of skeletal muscle CK-M and sCK-Mit activity and that training prior to the prolonged intense exercise attenuates the exercise-induced CK-M and sCK-Mit loss in both red and white skeletal muscles.

Less than 80% of absorbed iron is promptly incorporated into erythrocytes of infants.

Erythrocyte incorporation of an administered iron isotope has been used as a surrogate for iron retention on the assumption (validated in normal and iron-deficient adults) that 80-100% of the retained isotope is promptly incorporated into circulating erythrocytes. This assumption has not been validated in infants or children. The purpose of our study was to determine concurrently in normal infants absorption and erythrocyte incorporation of the stable isotope, (58)Fe. In a preliminary study (Study 1), we demonstrated that fecal excretion of ingested isotope occurs predominantly during the first 4 d after administration but continues beyond 7 d after ingestion, that is, beyond the point at which isotope in feces can be explained either by excretion of isotope that failed to enter enterocytes or by exfoliation of isotope-enriched enterocytes. In Study 2, we administered (58)Fe to nine younger (age 20-69 d) and nine older (age 165-215 d) term infants and collected feces for 11 d. Geometric mean retention of (58)Fe by the younger infants was 31.2% of intake at 4 d and 26.9% at 11 d, and by the older infants, 35.0% at 4 d and 32.5% at 11 d. Erythrocyte incorporation of (58)Fe 14 d after ingestion was 5.2% of the dose by the younger infants and 12.5% by the older infants. Utilization of retained (11 d) isotope thus was 19.8% by the younger infants and 38.3% by the older infants. We conclude that far less than 80% of retained isotope is promptly incorporated into erythrocytes (utilized) by infants.

Upper body power comparison between groups of cross-country skiers and runners.

The purpose of this study was to evaluate relationships between upper body power (UBP) and cross-country ski skating race velocity (R) in a cross sectional representation of cross-country skiers. Additionally, cross-country skiers' UBP was compared to UBP of distance runners. Participants (n = 195) were tested on a Street Arm Ergometer for UBP using a ramped maximal UBP test simulating a double poling motion. A strong relationship (r = 0.89) between UBP and RV in skiers was determined. High school skiers were separated into slow and fast groups based on reported RV; significant differences (p < 0.05) in both UBP was found to be an effective partial predictor of RV, independent of gender. Mean UBP for the cross-country runners was 46% of mean UBP for the cross-country skiers. With UBP contributing so much to performance in cross-country ski racing, it is recommended that cross-country skiers focus a large portion of their training on the specific development of that fitness component.

Responses to training in cross-country skiers.

PURPOSE: This study evaluated whether cross-country skiers who did not respond positively to a training program consisting of high volume and low intensity would improve if high-intensity training volume was doubled during a subsequent training year. METHODS: During the first year of the study, cross-country skiers (N = 14) were evaluated for VO2max, VO2threshold, lactate response, max arm power, and competitive results after a standard training program. During the second year, the athletes were divided into a control group (athletes who had responded well to the training) and a treatment group (athletes who had responded poorly to the training). The control group (N = 7) repeated the previous year's training program. The treatment group (N = 7) was given a modified training program which increased high-intensity training time as a percentage of total training from < 17% to > 35% and decreased low-intensity training volume 22%. RESULTS: The treatment group, using the high-intensity training program, demonstrated significantly improved VO2max, VO2threshold, max arm power, and competitive results (P < 0.05). CONCLUSIONS: Increased volume of high-intensity training may improve competitive results in cross-country skiers who fail to respond to increased volume of low-intensity training.

Elevated intakes of zinc in infant formulas don not interfere with iron absorption in premature infants.

BACKGROUND: Zinc and iron may share common pathways for absorption and compete for uptake into mucosal cells. We determined whether elevated ratios of zinc to iron would interfere with erythrocyte incorporation of iron in premature infants both during and between feeds. METHODS: In the first experiment, five premature infants (<2500 g birth weight) were enrolled, once receiving full oral feeds by nasogastric tube. They received either high (1200 microg/kg, ratio 4:1) or low (300 microg/kg, ratio 1:1) doses of oral zinc sulfate, together with 300 microg/kg oral 58Fe as chloride in saline with 10 mg/kg vitamin C, between designated feeding periods. Each infant served as its own control and randomly received either high or low doses of zinc or iron and then the alternate dose after 2 weeks. In the second experiment, nine additional premature infants were assigned to the same zinc:iron intake protocol except zinc and iron were given with usual oral feeds (premature formula or human milk) equilibrated before feeding. Iron absorption was measured by the erythrocyte incorporation of 58Fe. RESULTS: High doses of zinc given between feeds significantly inhibited erythrocyte incorporation of iron. 58Fe incorporation (%) with the 1:1 ratio of zinc:iron intake was 7.5 (5.7, 10; geometric mean, -I SD, +1 SD). The percentage of 58Fe incorporation on the 4:1 ratio of zinc:iron intake was 3.6 (2.6, 5.1). Given with feeds, the percentage of 58Fe incorporation on low zinc:iron intake was 7.0 (2.6, 19). Finally, the percentage of 58Fe incorporation on high zinc:iron intake was 6.7 (2.5, 19). CONCLUSION: Elevated intakes of zinc do not interfere with erythrocyte incorporation of iron in premature formulas.

Use of high-precision gas isotope ratio mass spectrometry to determine natural abundance 13C in lutein isolated from C3 and C4 plant sources.

A method was developed for high-precision stable carbon isotope ratio analysis of lutein isolated from a C3 (marigold flower) and a C4 (corn gluten meal) plant source using gas chromatography-combustion interfaced isotope ratio mass spectrometry. The natural abundance of 13C (expressed as delta 13C versus the international standard, Pee Dee Belemnite, in per mil units, denoted /1000) in lutein isolated from marigold flower and corn gluten meal was determined to be -29.90 +/- 0.20/1000 and -19.77 +/- 0.27/1000 (mean +/- S.D.), respectively. The high precision of gas isotope ratio mass spectrometry is potentially applicable to detect differences of isotopic composition of lutein in the blood, tissues, or excreta of animal models or humans that result from differences in the natural abundance of 13C in C3 and C4 plant foods.

Erythrocyte incorporation and absorption of 58Fe in premature infants treated with erythropoietin.

We hypothesized that treatment of very low birth weight premature infants with r-HuEPO would increase erythrocyte incorporation and gastrointestinal absorption of iron. Infants with birth weights < or = 1.25 kg and gestational ages < 31 wk were randomized to receive 6 wk of 500 U of r-HuEPO/kg/wk (epo group, n = 7) or placebo (placebo group, n = 7). All infants received daily enteral supplementation with 6 mg of elemental iron per kg. An enteral test dose of a stable iron isotope, 58Fe, was administered after the 1st ("early dosing") and 4th ("late dosing") wk of treatment. Mean (+/-SD) erythrocyte incorporation of the dose of 58Fe administered determined 2 wk after early dosing was significantly greater in the epo group compared with the placebo group (4.4% +/- 1.6 versus 2.0 +/- 1.4%, p = 0.013). In contrast, after late 58Fe dosing, there was no difference between groups in incorporation (3.8 +/- 1.6% versus 5.5 +/- 2.7%). Within the epo group, percentage erythrocyte incorporation of 58Fe did not differ between early and late dosing, whereas in the placebo group it increased 3-fold (p < 0.01). Percentage absorption of 58Fe was not different between the epo and placebo groups after both early dosing (30 +/- 22% versus 34 +/- 8%) and late dosing (32 +/- 9% versus 31 +/- 6%). Absorption of nonlabeled elemental iron and 58Fe were significantly correlated with one another. The percentage of the absorbed 58Fe dose incorporated into Hb was not different between groups. We conclude that, although erythropoietin treatment stimulates erythrocyte iron incorporation in premature infants, it has no effect on iron absorption at the r-HuEPO dose studied.

Erythrocyte incorporation of iron is similar in infants fed formulas fortified with 12 mg/L or 8 mg/L of iron.

Although feeding of formulas with iron concentration of 215 mumol/L (12 mg/L) is a reliable means of preventing iron deficiency, high intakes of iron may adversely affect absorption of copper and zinc. Because data are not available to establish whether fortification at a lower level would result in equivalent iron absorption, we tested the hypothesis that iron absorption is greater by infants fed formulas with an iron concentration of 215 mumol/L (12 mg/L) than by those fed formulas with an iron concentration of 143 mumol/L (8 mg/L). Fifty-two normal infants entered the study at 112 +/- 4 d of age, and 46 of these were successfully studied until 196 d of age. Using the stable isotope 58Fe, we determined erythrocyte incorporation of iron by infants fed Formula 8 [iron approximately 143 mumol/L (8 mg/L)] and by infants fed Similac with Iron [iron approximately 215 mumol/L (12 mg/L)]. On each of three test days beginning at 154 d of age, a major portion of the formula was labeled with 58Fe. Geometric mean erythrocyte incorporation of iron adjusted for plasma ferritin concentration at 168 d of age was 4.82 mumol/d (0.269 mg/d) by infants fed Formula 8 and 5.21 mumol/d (0.291 mg/d) by infants fed Similac with Iron. Corresponding values at 196 d of age were 5.12 and 5.41 mumol/d (0.286 and 0.302 mg/d). The differences in quantity of iron incorporated into erythrocytes by infants fed Formula 8 and Similac with Iron were not statistically significant (P = 0.66 at 168 d of age, P = 0.75 at 196 d of age) and were judged to be nutritionally trivial. Because we were unable to provide support for our hypothesis that iron absorption is greater by infants fed formulas providing 215 mumol (12 mg) of iron per liter than by those fed formulas providing 143 mumol (8 mg) of iron per liter, we conclude that, pending the results of further studies, It is reasonable to decrease the iron concentration of iron-fortified infant formulas.

Failure of 40 weeks of brisk walking to alter blood lipids in normolipemic women.

Sedentary, eumenorrheic women (N = 27) 22 to 40 years of age, with high baseline levels of plasma high-density lipoprotein cholesterol, were randomly assigned to a walking (n = 16) or a control group (n = 11). The training program involved treadmill walking 4.8 km (3.0 miles) four times a week for 40 weeks at a mean intensity of 72% maximal heart rate. Aerobic power (VO2max) was improved by 22%, but no training effect was observed in body composition variables or blood lipid/lipoprotein levels. Despite additional increments in exercise intensity over the final 20 weeks of training, most of the improvement in VO2max was observed over the first 20 weeks of the study. Exercising subjects' baseline levels of plasma HDL-C were found to be inversely associated with the change (delta) scores in the lipoprotein (r = -0.51, p < or = .05).

Erythrocyte incorporation of iron by 56-day-old infants fed a 58Fe-labeled supplement.

In an effort to obtain information about absorption of supplemental iron by breast-fed infants during the early months of life, we determined erythrocyte incorporation of a stable iron isotope, administered to 56-d-old breast-fed infants in the form of a 58Fe-labeled vitamin-iron supplement. Infants of similar age fed a milk-based formula low in iron (approximately 4 mg/L) were also studied. The 58Fe-labeled vitamin-iron supplement was given between feedings. Fourteen days after administration of 58Fe, mean erythrocyte incorporation of the isotope was 7.8% of the dose by breast-fed infants and 4.4% of the dose by formula-fed infants. The feeding-related difference was statistically significant, probably reflecting the greater quantities of inhibitors of iron absorption in the intestines of formula-fed infants. With mean iron intake from the 58Fe-labeled vitamin-iron supplement of 7.99 mg for the breast-fed infants, erythrocyte incorporation of 7.8% of the dose corresponded to 0.62 mg, a value in the range of the estimated requirement for absorbed iron. We conclude that 2-mo-old breast-fed infants are able to absorb nutritionally significant amounts of iron from an iron supplement.

Ability of the Caltrac accelerometer to assess daily physical activity levels.

PURPOSE: The purpose of this study was to determine the ability of the Caltrac accelerometer to assess habitual daily physical activity levels. METHODS: The ability of the Caltrac accelerometer to assess 24-hour physical activity (PA) levels was studied in 28 men and 50 women, age 20 to 59 years, with varying levels of self-reported PA. Twelve days of Caltrac readings obtained over 1 year's duration were compared to simultaneously recorded 48-hour PA records. Additionally, 28 days of Caltrac readings obtained over 1 year's duration were compared to mean values of the following validation measures assessed repeatedly over a 1-year period: a 4-week version of the Minnesota Leisure Time Physical Activity Questionnaire (FWH); VO2peak; and percent body fat. RESULTS: The Caltrac measurements of movement (in MET minutes per day-1) were significantly associated with the following: PA record indices of total (r = .51) and heavy (r = .34) and PA; FWH indices of total (r = .30), heavy R = .36) and moderate (r = .23) PA;, and VO2peak (r = .24). However, the Caltrac measurements of caloric PA record and FWH indices of PA, although there were directly associated with percent body fat (r = .50) and inversely associated with VO2peak (r = -.26). CONCLUSIONS: Caltrac measurements of movement exhibited a moderate associated with several criterion measures related to habitual PA, whereas Caltrac measurements of total energy expenditure, were not reflective of varying levels of PA.

Comprehensive evaluation of the Minnesota Leisure Time Physical Activity Questionnaire.

The accuracy of the Minnesota Leisure Time Physical Activity (LTPA) Questionnaire (a 1-year survey of non-occupational activity used in MRFIT) was studied in 78 men and women, age 20-59 years, by comparing survey results to the following measures obtained over a year's duration: six 48-hour physical activity records; fourteen 48-hour Caltrac accelerometer readings (Caltrac); 14 administrations of a 4-week version of the LTPA Questionnaire (FWH); 3 VO2peak determinations and percent body fat (% BF). The LTPA Questionnaire demonstrated: weak to moderate associations with % BF (r = -0.24) and with VO2peak (r = 0.47); a weak association with Caltrac readings expressed as MET.minutes.day-1 (r = 0.23); strong associations with corresponding activities reported on the FWH; and moderate associations with total and heavy activities reported in the physical activity record, but no associations with moderate and light activities. Furthermore, several types of LTPA were found to be either under-represented or not currently included in the Minnesota LTPA Questionnaire. It is concluded that although validation results were found to be quite good, several possible refinements were identified, which should improve the accuracy of the Minnesota LTPA Questionnaire in assessing habitual physical activity.