Steven E. Gaskill

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.

Heart rate versus %VO2max: age, sex, race, initial fitness, and training response--HERITAGE.

PURPOSE In the HERITAGE Family Study, heart rate (HR) associated with various percentages of maximal oxygen intake (VO2max) was used to prescribe exercise intensity. When fitness improved, HR at the same power output (PO) decreased, and PO was increased to produce the prescribed HR. Although we assumed that subjects were again working at the same %VO2max, there were no studies with a large heterogeneous population to determine whether this was correct. METHODS Therefore, 653 subjects with complete data were classified by age, sex, race, initial VO2max, and VO2max response after 20 wk of training. RESULTS All groups had a significant increase in VO2max and a significant decrease in HR at the same absolute PO after training but no difference in HR at the same relative intensity. CONCLUSIONS Training does not affect HR at a given %VO2max in a heterogeneous population of men and women, blacks and whites aged 17-65 yr with different initial VO2max values and different responses to training.

The addition of fenugreek extract (Trigonella foenum-graecum) to glucose feeding increases muscle glycogen resynthesis after exercise

Summary.The purpose of this study was to determine the effects of ingesting an oral supplement containing 4-Hydroxyisoleucine (4-OH-Ile, isolated from fenugreek seeds [Trigonella foenum-graecum]) with a glucose beverage on rates of post-exercise muscle glycogen resynthesis in trained male cyclists. Following an overnight fast (12 hr), subjects completed a 90-minute glycogen depletion ride after which a muscle biopsy was obtained from the vastus lateralis. Immediately and 2 hours after the muscle biopsy, subjects ingested either an oral dose of dextrose (Glu) (1.8 g·kg BW−1) or 4-OH-Ile supplement (Glu+4-OH-Ile, including 2.0 mg·kg−1 4-OH-Ile with the same oral dose of dextrose) with a second muscle biopsy 4 hours after exercise. Post exercise muscle glycogen concentration was similar for both trials. Overall, there was a significant increase in glucose and insulin concentrations from time 0 throughout the majority of the 4-hour recovery period, with no significant differences between the two trials at any time point. Although muscle glycogen concentration significantly increased from immediately post exercise to 4 hr of recovery for both trials, the net rate of muscle glycogen resynthesis was 63% greater during Glu+4-OH-Ile (10.6±3.3 vs. 6.5±2.6 g·kg wet wt.−1·hr.−1 for the Glu+4-OH-Ile and Glu trials, respectively). These data demonstrate that when the fenugreek extract supplement (4-OH-Ile) is added to a high oral dose of dextrose, rates of post-exercise glycogen resynthesis are enhanced above dextrose alone.

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.

Familial resemblance in ventilatory threshold: The HERITAGE Family Study

PURPOSE This study investigates the familial resemblance of VO2 at the ventilatory threshold (VO2vt) from 199 nuclear families (100 White and 99 Black) participating in the HERITAGE Family Study. METHODS VO2vt (mL x min(-1)) was determined in the sedentary state and again after 20 wk of aerobic cycle ergometer exercise training in 339 individuals (131 parents and 228 of their offspring), aged between 17 and 65 yr. VO2vt was adjusted for weight, age, fat mass, and fat-free mass by using regression methods. RESULTS There was evidence for significant familial resemblance in the sedentary state for VO2vt (maximal heritability = 58% in White and 54% in Black families) and VO2vt/VO2max (maximal heritability = 38% in White and 39% in Black families). Spouse, sibling, and parent-offspring relationships for VO2vt were significant at baseline, suggesting that both genetic and shared environmental factors may contribute to the familial resemblance in the sedentary state. There was a moderate familial component in the response of VO2vt to aerobic exercise training in Whites (22%) and a larger component in Blacks (51%). In Blacks, the familial effect for VO2vt/VO2max appeared to be accounted for by fat and fat-free mass. CONCLUSION These results show a strong familial contribution to VO2vt in the sedentary state and to the response of VO2vt to aerobic exercise training.

Developing and Piloting the Journey to Native Youth Health Program in Northern Plains Indian Communities

Purpose The purpose of this study was to develop a lifestyle change program for Native American youth by modifying the Diabetes Prevention Program (DPP) and assess implementation indicators and short term behavioral and physiological outcomes of the intervention among a small pilot sample. Methods Community members and project staff modified the original DPP to be developmentally and culturally appropriate for youth targeting healthy weight maintenance, lowering fat intake, and increasing physical activity. Modifications included incorporating cultural aspects and delivering the program in small groups led by community members. Sixty-four Native American youth, aged 10-14 years old were recruited from 2 Montana Indian reservations to participate in the project, titled “Journey to Native Youth Health.” Participants were randomized to the Journey DPP or a health-oriented comparison condition. Pretest and posttest measures included body mass index (BMI), dietary intake, physical activity (PA), and nutrition knowledge, attitudes and beliefs (KAB). Results The target number of participants was recruited and 84% completed the program and final measures. Changes favoring the Journey DPP group were observed on measures of PA, KAB, and kilocalories from fat consumed. As expected given the short (3-month) duration of treatment, there was no overall effect on BMI at end of treatment. Among youth who were overweight or obese at baseline, however, the Journey DPP had lower BMI growth. Conclusions Results suggest the Journey DPP is feasible to implement and has the potential to impact behaviors and weight gain associated with risk for type-2 diabetes in Native American youth.

Physiological effects of technique and rolling resistance in uphill roller skiing.

OBJECTIVE The double pole technique (DP) has been shown to be more economical than the V1 skate technique (V1 ) on flat terrain. The objective of the present study was to compare these two techniques during uphill roller skiing. In addition, the physiological effects of changing roller ski rolling resistance was examined for V1. METHODS Five female and five male competitive cross-country skiers roller skied 4-min bouts on a 5.2% incline while physiological measurements were made. RESULTS Oxygen uptake (VO2) values averaged 8% greater (P = 0.0004) with V1, whereas rating of perceived exertion (RPE) and blood lactate concentrations were higher (P < or = 0.002) with DP. Doubling the dynamic friction coefficient of the roller skis, which increased external power output by 16-17%, resulted in VO2 values with V1 that averaged 13% higher (P = 0.0006). This magnitude of change in roller ski rolling resistance did not cause a statistical change in the relationship of VO2 with RPE. CONCLUSIONS These findings suggest that 1) grade has little effect on relative economies of DP and V1, possibly because of a lower effectiveness of force application with V1 when going uphill, and 2) large differences in roller ski rolling resistance should have no effect on the cardiovascular training adaptations that result from uphill roller skiing with V1.

No gender-specific differences in mechanical efficiency during arm or leg exercise relative to ventilatory threshold.

The purpose of this study was to determine economy and mechanical efficiency in men and women during both arm cranking (AC) and leg cycling (LC) at 70%, 85%, 100%, and 115% of mode‐specific ventilatory threshold (Tvent). Recreationally active men (n=9) and women (n=9) with similar values for %V̇O2peak at Tvent served as subjects. All subjects performed 5 min of exercise at each intensity of 70%, 85%, 100%, and 115% of Tvent for both AC and LC. Economy was expressed as W/L/min. Gross efficiency (GE) was determined as the ratio of work accomplished to total energy expended (%). Delta efficiency (DE) was determined as the ratio of delta work accomplished to delta energy expended (%). Economy and efficiency during LC were greater than during AC in men and women. During AC or LC exercise, no sex differences were found in either economy (P=0.93 for AC, 0.98 for LC), GE (P=0.88 for AC, 0.75 for LC), or DE (P=0.57 for AC, 0.51 for LC). These findings indicate that men and women show similar economy and efficiency during both AC and LC exercise when subjects have similar %V̇O2peak at Tvent.

Substrate oxidation during incremental arm and leg exercise in men and women matched for ventilatory threshold

Abstract The aim of this study was to determine the variations in substrate utilization between men and women matched for ventilatory threshold (T vent) during incremental arm cranking and leg cycling exercise at 70, 85, 100 and 115% of the mode-specific T vent. Recreationally active men (n = 12) and women (n = 10) with similar values for percentage of peak oxygen consumption at T vent participated in the study. Ventilatory equivalence, excess CO2 and modified V-slope methods were used concurrently to determine T vent. The participants performed 5 min of exercise at each of 70, 85, 100 and 115% T vent during both arm cranking and leg cycling exercise. The females were tested during the early follicular phase for all trials. A two-way mixed-design analysis of variance was performed to test for differences between the sexes. When carbohydrate and fat oxidation were expressed relative to total fat-free mass, carbohydrate oxidation during arm cranking and leg cycling was significantly higher in men than women at each percentage of T vent. In contrast, women showed significantly higher fat oxidation across intensities during both arm cranking and leg cycling. Our results suggest that when substrate utilization is expressed relative to total fat-free mass, women appear to maintain a higher rate of fat and lower rate of carbohydrate oxidation than men during both incremental arm cranking and leg cycling exercise relative to T vent.

Base Camp Personnel Exposure to Particulate Matter During Wildland Fire Suppression Activities

Wildland fire base camps commonly house thousands of support personnel for weeks at a time. The selection of the location of these base camps is largely a strategic decision that incorporates many factors, one of which is the potential impact of biomass smoke from the nearby fire event. Biomass smoke has many documented adverse health effects due, primarily, to high levels of fine particulate matter (PM2.5). Minimizing particulate matter exposure to potentially susceptible individuals working as support personnel in the base camp is vital. In addition to smoke from nearby wildland fires, base camp operations have the potential to generate particulate matter via vehicle emissions, dust, and generator use. We monitored particulate matter at three base camps during the fire season of 2009 in Washington, Oregon, and California. During the sampling events, 1-min time-weighted averages of PM2.5 and particle counts from three size fractions (0.3–0.5 microns, 0.5–1.0 microns, and 1.0–2.5 microns) were measured. Results showed that all PM size fractions (as well as overall PM2.5 concentrations) were higher during the overnight hours, a trend that was consistent at all camps. Our results provide evidence of camp-based, site-specific sources of PM2.5 that could potentially exceed the contributions from the nearby wildfire. These exposures could adversely impact wildland firefighters who sleep in the camp, as well as the camp support personnel, who could include susceptible individuals. A better understanding of the sources and patterns of poor air quality within base camps would help to inform prevention strategies to reduce personnel exposures.