Robert C. Serfass

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 years 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.

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.

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 years 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.

The Effects of Rapid Weight Loss and Attempted Rehydration on Strength and Endurance of the Handgripping Muscles in College Wrestlers

Abstract Eleven university wrestlers were tested on three occasions in a 6-min fatigue bout during which the subject squeezed a hand dynamometer maximally and then relaxed every other second until a total of 180 contractions had been completed. Testing was administered (1) following a 5% body weight loss within a 3-day period just prior to testing, (2) after a 5% body weight loss followed by an attempt to rehydrate to the original weight, and (3) under a control condition with no weight loss. All subjects were tested under all conditions with the order of testing assigned at random. One-way ANOVA failed to reveal any effects of the rapid weight loss or attempted rehydration on initial strength, final strength, or the force-time integrals. In addition, a 3 × 13 ANOVA for hydration level across the 13 observation times failed to reveal any interaction between the two factors. A mathematical analysis of the force-time values revealed that fatigue progressed in an exponential pattern described by a curve with...

The effect of wearing the complete Lenox Hill Derotation Brace on energy expenditure during horizontal treadmill running at 161 meters per minute

Ten volunteer subjects (x age = 26.6 ± 4.9 years, x height = 177.9 ± 5.6 cm, and x weight = 76.9 ± 11.2 kg) who had been wearing the Lenox Hill Derotation Brace (LHB) for a mean time of 23.9 ± 28.0 months were familiarized with horizontal treadmill running at 161 m/min with and without the LHB. They were then tested randomly for four runs, two with the LHB and two without the LHB. Metabolic measurements using a device that counted footstrikes on the treadmill were taken during the 3rd and 6th minutes of each run. Regardless of sampling time, wearing the LHB pro duced significantly higher values for VO2 (4.58%, P < 0.025) and heart rate (5.10%, P < 0.004) compared to the no brace condition. Regardless of whether or not the subjects were wearing the LHB, 6 minute values were significantly higher than 3 minute values for VO2 (5.89%, P < 0.0004), VE (10.08%, P < 0.004), heart rate (5.35%, P < 0.0000), and R (2.17%, P < 0.038). The mean 6 minute values of VO2 with (37.42 ± 3.55 ml/kg/min) and without (35.54 ± 2.17 ml/kg/min) the brace fall within the range of expected values of 28.1 to 39.3 ml/kg/min derived from regression equations from the literature which predict VO2 response to hori zontal treadmill running. Mean stride lengths while wearing the LHB (97.85 cm) were not significantly different from mean stride lengths without the LHB (98.56 cm). It is concluded that wearing the LHB pro duces a 4.58% increase in energy expenditure during horizontal treadmill running at 161 m/min which cannot be attributed to changes in stride length or to time of sampling during the run.

Effect of endurance exercise on myosin heavy chain isoform expression in diabetic rats with peripheral neuropathy.

Snow LM, Sanchez OA, McLoon LK, Serfass RC, Thompson LV: Effect of endurance exercise on myosin heavy chain isoform expression in diabetic rats with peripheral neuropathy. Am J Phys Med Rehabil 2005;84:770–779. Objective:This study evaluated the effect of endurance exercise on myosin heavy chain (MHC) isoform expression in soleus muscle of diabetic rats with peripheral neuropathy Design:Male Sprague Dawley rats were randomly divided into four groups: control sedentary, diabetic sedentary, control exercise, and diabetic exercise. The exercised animals performed treadmill running five times per week. After 12 wks, electrophysiologic testing documented peripheral neuropathy in the diabetic rats. The soleus muscles were then excised and quick-frozen. Cross-sections were immunohistochemically stained for slow, fast, developmental, and neonatal MHCs. Fiber-type composition and fiber cross-sectional areas were then determined. Results:The diabetic groups showed a significantly greater percentage of fast MHC than did the control groups, regardless of exercise status (diabetic sedentary, 22.6%; diabetic exercise, 25.2%; control sedentary, 13.5%; control exercise, 13.1%). The diabetics also showed a significantly lower percentage of slow-only MHC than controls (diabetic sedentary, 77.1%; diabetic exercise, 74.3%; control sedentary, 86.2%; control exercise, 86.1%). No differences in muscle fiber cross-sectional area existed between the groups. The exercised animals showed greater expression of developmental MHC than did the sedentary animals (diabetic sedentary, 1.6%; diabetic exercise, 3.8%; control sedentary, 0.8%; control exercise, 2.0%). Conclusion:The altered slow and fast MHC expression in the diabetic muscle is similar to MHC expression in several other conditions, including decreased neuromuscular activity and denervation. Mechanisms of this MHC expression shift are unknown. Chronic endurance training does not alter adult MHC expression in the diabetic animals. The developmental MHC expression is likely a manifestation of uphill treadmill running due to eccentric contractions in the soleus resulting in myofiber injury and regeneration.

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

Abstract 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.

Effect of Stride Length Variation on Oxygen Uptake during Level and Positive Grade Treadmill Running.

Abstract Sixteen men were studied during 6-min bouts of motorized treadmill running at 230 m · min–1 and 0% and 4% grade to compare [Vdot]O2 while using freely chosen stride lengths (CSL) and stride lengths approximately 8% shorter (SSL) and longer (LSL) than CSL. The study also attempted to determine whether stride length variations of these proportions altered [Vdot]O2 differently at the two grades. CSL were greater (p<.05) at 0% than 4% with mean values of 133.5 and 131.5 cm, respectively. Two-way ANOVA (Stride x Grade) with repeated measures yielded significant F values (p<.05) for the main effects of both stride length and grade but not for interaction between the two factors. Mean [Vdot]O2 values were 44.95 and 56.80 ml · kg1 · min–1 at 0% and 4% grade, respectively. The Tukey w procedure was used for comparing the main effect means across both grades for the three stride lengths. These means were 50.94, 49.88, and 51.80 ml · kg1 · min–1 for SSL, CSL, and LSL, respectively, with the CSL mean signifi...

Elicitation of Maximal Oxygen Uptake from Standing Bicycle Ergometry

Abstract Twelve male university students were tested twice on each of three continuous max [Vdot]RO2 protocols for treadmill running, pedaling on a bicycle ergometer while seated, and pedaling on a bicycle ergometer while standing. A comparison of the results failed to reveal any differences among protocols for pulmonary ventilation (max [Vdot]RE). For max [Vdot]RO2 (both liters [mdot] minute-1 and ml [mdot] minute-1. kg-1) all differences were significant with the highest value associated with treadmill running, the intermediate with cycling in the standing position, and the lowest with cycling while seated. Max heart rate (HR) was significantly higher on the treadmill than on either bicycle protocol, and the respiratory exchange ratio (R) was higher on the sitting bicycle task than on the standing bicycle task. No other differences among protocols were significant. Although the reliability coefficients for all protocols (range was from r = .95 to r = .97) and the intercorrelation coefficients among prot...

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.