College-age Subjects Research Articles

A Comparison Of The Traditional Vs The Unilateral Back Saver Sit And Reach Hamstring Stretch

The sit and reach position is used both as a stimulus for flexibility training and as a measure of lower back/hamstring flexibility. The traditional bilateral sit and reach (BSR) is common, however the unilateral back saver (USR) has gained popularity and is purported to improve hamstring flexibility. Purpose The purpose of this study is to evaluate flexibility training and measurement between the traditional BSR and the USR test on college aged students during an eight week trial. Methods Twenty-eight moderately active college age subjects (age 20.6 ± 2.2 yr; body mass 66.2 ± 12.3 kg, ht. 163 ± 7.8 cm) who participated in a supervised exercise program were matched and randomly assigned to either the BSR or USR protocols for sixteen sessions. Pre and post sit and reach assessments (BSR and USR) were obtained using a sit and reach box in a counterbalanced order. The BSR is performed as a seated hamstring stretch with both legs extended, while the USR holds one leg straight while the knee of the other leg flexed with the plantar surface of the foot on the flexed leg placed adjacent to the medial surface of the straight leg (modified hurdler stretch). In training, the BSR group completed 4 repetitions of 30 seconds while the USR group performed 3 repetitions of 20 seconds on each leg. Results Statistical analysis by t-test (p>.05) revealed no significant difference between BSR (pre: 46.89 ± 8.29cm, post: 46.79 ± 8.02 cm) and USR (pre: 48.57 ± 8.38 cm, post: 48.52 ± 8.97 cm). Statistical analysis by ANOVA (p>.05) found no significant difference within groups, however, 66% of the subjects reported the USR as more comfortable to perform. Conclusion College students, who possessed excellent flexibility prior to the intervention trial, did not improve flexibility with either protocol. In addition, both assessment techniques provided almost identical results. Two minutes of isolated flexibility training performed twice a week is insufficient to alter flexibility in young adults.

Plasma Erythropoietin Levels Are Elevated 24 H Following High Intensity Intermittent Exercise

Blood volume expansion during endurance exercise training is well documented. Factors contributing to a rapid increase in plasma volume during endurance exercise training are well documented, however, the physiological signals involved in stimulating an increase in red cell production are less clear. PURPOSE To examine the change in circulating levels of erythropoietin (EPO) following a high intensity intermittent exercise protocol (EX, 8 bouts of 4 min 85% followed by 5 min at 40%). This exercise protocol is known to induce significant plasma volume expansion within 24 h of exercise. METHODS Blood samples were collected at rest prior to EX and at 30 min, 2 h, and 24 h following EX for determination of EPO levels. 8 active collegeaged subjects (5 men, 3 female) participated in this study. RESULTS 24 hr following EX plasma volume increased 4.5 +/− 0.9 ml/kg or 10.9% (p<0.05) with a 0.11 +/− 0.05 g/kg increase in albumin content (p<0.05). EPO levels at baseline prior to EX averaged 16.5 +/− 2.4 mU/ml and were unchanged immediately following EX averaging 16.8 +/− 2.1 and 15.1 +/− 1.8 mU/ml at 30 and 120 min of recovery. EPO levels increased 37% to 22.5 +/− 4.6 mU/ml 24 h following EX (p<0.05). CONCLUSIONS These data indicate that this high intensity intermittent exercise protocol stimulates a small rise in EPO. It is uncertain if this increase in EPO is sufficient to contribute to the increase in red cell mass during training.

Plasma Erythropoietin Levels Are Elevated 24 H Following High Intensity Intermittent Exercise

Blood volume expansion during endurance exercise training is well documented. Factors contributing to a rapid increase in plasma volume during endurance exercise training are well documented, however, the physiological signals involved in stimulating an increase in red cell production are less clear. PURPOSE To examine the change in circulating levels of erythropoietin (EPO) following a high intensity intermittent exercise protocol (EX, 8 bouts of 4 min 85% followed by 5 min at 40%). This exercise protocol is known to induce significant plasma volume expansion within 24 h of exercise. METHODS Blood samples were collected at rest prior to EX and at 30 min, 2 h, and 24 h following EX for determination of EPO levels. 8 active collegeaged subjects (5 men, 3 female) participated in this study. RESULTS 24 hr following EX plasma volume increased 4.5 +/− 0.9 ml/kg or 10.9% (p<0.05) with a 0.11 +/− 0.05 g/kg increase in albumin content (p<0.05). EPO levels at baseline prior to EX averaged 16.5 +/− 2.4 mU/ml and were unchanged immediately following EX averaging 16.8 +/− 2.1 and 15.1 +/− 1.8 mU/ml at 30 and 120 min of recovery. EPO levels increased 37% to 22.5 +/− 4.6 mU/ml 24 h following EX (p<0.05). CONCLUSIONS These data indicate that this high intensity intermittent exercise protocol stimulates a small rise in EPO. It is uncertain if this increase in EPO is sufficient to contribute to the increase in red cell mass during training.

Comparison Of Tympanic And Rectal Temperatures In Adults At Rest And Exercise

Infrared tympanic thermometry (ITT) has been developed to measure tympanic temperature (Tty). However, ITT has not been extensively evaluated against rectal temperature (Tre). This study measured Tty and Tre in 13 college-aged subjects (5 men and 8 women) at rest and exercise in a thermoneutral environment (22–24°C). Subjects first performed 90-min steady state exercise at 55%VO2peak. This was followed by a 30-min time trial, which required subjects to perform the amount of work equivalent to 30 minutes at 60% of their VO2peak. Although a statistically Significant correlation was observed between Tty and Tre at rest or exercise, the variance in Tty accounted for only 36% of the total variance in Tre and the standard error of estimate was high (+0.48). Moreover, Tre was 0.9°C (P<0.05) higher than Tty at all time points for men and women combined, confirming that Tty and Tre do not agree. Tty was stable during steady state exercise and increased gradually during the time trial for both men and women. However, Tre increased during steady state exercise and then decreased slightly in men, but continued to increase for women during the time trial. These results demonstrate that Tty responses during exercise lag behind Tre responses.FigureIn conclusion, Tty is not a good predictor of Tre in adults at rest or during exercise. Supported by Campbell Soup Company, Inc.

The Effect of 4 Different Durations of Static Hamstring Stretching on Passive Knee-Extension Range of Motion

Design:Pretest–posttest.Objective:To determine the effect of 4 durations of static hamstring stretching on knee-extension passive range of motion (KE-PROM).Context:Effects of longer (90 and 120 seconds) static hamstring stretching on PROM have not been established relative to more typically recommended 30- or 60-second durations.Subjects:35 healthy college-age subjects with &gt;20° loss of KE-PROM.Outcome Measure:KE-PROM.Intervention:5-week program of single daily stretch for 30, 60, 90, or 120 seconds.Results:Static stretching was effective in increasing KE-PROM regardless of stretch duration (P &lt; .0001). A significant improvement was identified in mean PROM for each stretching group, but no difference existed among the 4 stretch-duration groups. The control group’s mean PROM decreased (mean = -3.2°, SD = 1.9), whereas each stretching group increased PROM (means 1.9° to 3.6°).Conclusions:Five weeks of daily static hamstring stretching for 30, 60, 90, or 120 seconds increase KE-PROM. Similar benefits were achieved regardless of stretch duration, suggesting that clinicians need not perform static hamstring stretches of more than 30 seconds.

RPE-lactate dissociation during extended cycling

This study examined the association of blood lactate concentration [La] and heart rate (HR) with ratings of perceived exertion (RPE) during 60 min of steady workload cycling. Physically active college-aged subjects (n = 14) completed an exhaustive cycling test to determine VO(2) (peak) and lactate threshold (2.5 mmol l(-1)). Subjects then cycled for 60 min at the power output associated with 2.5 mmol l(-1) [LA]. HR, [LA], RPE-overall, RPE-legs and RPE-chest were recorded at 5, 10, 20, 30, 40, 50 and 60 min. The 60-min trials were below maximal lactate steady state, with peak lactate concentration occurring at 20 min after which [LA] declined. The 20-min point was therefore considered pivotal, and data at other points were compared to this time point. Repeated measures ANOVA with simple contrasts (alpha = 0.05) showed (a) [LA] at 40, 50 and 60 min was significantly lower than at 20 min, (b) RPE-O and RPE-L were significantly greater at 30, 40, 50 and 60 min than at 20 min, (c) RPE-C was significantly greater at 40, 50 and 60 min than at 20 min, and (d) HR was significantly greater at 30, 40, 50 and 60 min than at 20 min. Significant (P < 0.05) positive correlations were found between HR and RPE-O (r = 0.43), RPE-L (r = 0.48) and RPE-C (r = 0.41) while correlations for [LA]-HR (r = 0.13) and [LA]-RPE (RPE-O: r = -0.11, RPE-L: r = 0.01, RPE-C: r = -0.06) were weak and non-significant. There is a dissociation of RPE and [LA] owing to RPE drift and lactate kinetics in longer duration sub-maximal exercise. Apparently, [LA] is not a strong RPE mediator during extended cycling.

オフィス空間における非等温気流タスク空調方式の有効性

Subjective experiments with a desktop based task conditioning system were carried out to investigate the benefits of system in an office like chamber. The experiments were conducted under three different combinations of ambient air temperature and relative humidity, (1) 27℃/40%RH, (2) 30℃/40%RH, and (3) 30℃/70%RH. Each of 16 college age subjects was exposed to the three different experimental room air conditions. There were six supply air flow patterns for task air conditioning, which parameters included isothermal air flow and non-isothermal airflow with three different air velocities. Setting of task condition was fixed at first, and then the subjects were allowed to control the environment freely after certain period in the subjective experiments. Thermal sensation, airflow sensation, and other variable were investigated. The way the subjects controlled the task system was also monitored. It was considered that the task conditioning system could keep subjects thermally comfortable with their ambient temperature higher than condition without it. Questionnaire responses under the 'preferred air' condition revealed the importance of adjustment of task conditioning.

Microbiological changes associated with dental prophylaxis

Despite the common application of dental prophylaxis as part of patient therapy, there is little reported that describes the microbiological impact of this treatment. The authors gave 20 healthy college-aged subjects three dental prophylaxes with a fluoride-containing prophylaxis paste during a two-week period and instructed them in oral hygiene. They evaluated the microbiological composition of dental plaque samples collected before and after treatment using DNA probe analysis. They analyzed 40 representative bacterial species in seven bacterial complexes by checkerboard DNA-DNA hybridization assay techniques. After three dental prophylaxes, the patients' mean Gingival Index score decreased from 0.82 to 0.77, the mean Plaque Index score decreased from 0.72 to zero, and the total number of bacteria per tooth decreased to approximately one-third of the original number. The authors computed two different measures of bacterial presence. The reduction in bacterial numbers was statistically significant and occurred in many species. Bacterial proportion (DNA percentage or percentage of the bacteria per tooth) did not change significantly. Greater reductions in bacterial count occurred in species that showed high numbers before treatment. The total bacterial count decreased by approximately 72 percent of its original level before prophylaxis was initiated. Professional dental prophylaxis did not target any particular bacteria or bacterial groups but removed bacteria nonspecifically and in proportion to their initial numbers. Repeated dental prophylaxes effect a reduction in bacterial amount that is commensurate with the initial amount, but they do does not alter composition. This suggests that mild gingivitis may be a bacterially nonspecific effect of plaque accumulation and emphasizes the need for regular plaque removal to maintain optimal gingival health.

The effects of gender on quadriceps muscle activation strategies during a maneuver that mimics a high ACL injury risk position

While the increased incidence of serious knee injuries in female athletes is well established, the underlying neuromuscular mechanisms related to the elevated ACL injury rate has yet to be delineated. Video analysis of ACL injury during competitive sports play indicates a common body position associated with non-contact ACL injury; the tibia is externally rotated, the knee is close to full extension, the foot is planted and as the limb is decelerated it collapses into valgus. The purpose of the current prospective study was to evaluate gender differences in quadriceps muscle activation strategies when performing a physically challenging, but reproducible maneuver that mimics the high ACL injury risk position (in the absence of high velocity and high loads). Twenty physically active college-aged subjects (10 male and 10 female) performed multiple sets of the prescribed exercise. EMG recordings were employed to measure the ratio of activation between the medial and lateral quadriceps during the 4, 8, 12, 16, and 20th sets of exercise. Females demonstrated decreased RMS medial-to-lateral quadriceps ratios compared to males ( F(1,18) = 5.88, p = 0.026). There was no main effect of set number on RMS quadriceps ratio ( p > 0.05). The results of this study suggest that females utilize neuromuscular activation strategies which may contribute to “dynamic valgus” and ACL rupture when performing high-risk maneuvers.

Physiologic Effects of Caffeine on Crosscountry Runners

Birnbaum, L.J., and J.D. Herbst. Physiologic effects of caffeine on cross-country runners. J. Strength Cond. Res. 18(3):463–465. 2004.—This study determined the physiological effects of caffeine on cross-country runners during submaximal exercise. Ten college-age subjects (5 women; 5 men) volunteered to participate in this study. After completing a SymbolO2max test, each subject completed 2 30-minute runs at 70% SymbolO2max on the treadmill, 1 after ingesting caffeine and the other after ingesting a placebo. A caffeine dosage of 7 mg·kg-1 of body weight was administered. The same dosage of vitamin C was used as a placebo. The order of treatments was randomly assigned, and the trials followed a double-blind format. The physiological data were analyzed using a repeated measures analysis of variance (SPSS). Tidal volume (TV), alveolar ventilation (VA), and rating of perceived exertion (RPE) were significantly different (p < 0.05) between treatment and control groups. The results suggest that the ingestion of caffeine at 7 mg·kg-1 of body weight prior to submaximal running might provide a modest ergogenic effect via improved respiratory efficiency and a psychological lift.Symbol

Postural Perturbation by Electric Stimulation has no Effect upon Anticipatory Postural Adjustment

0079 Anticipatory postural adjustments (APA) have been known to assist equilibrium maintenance in standing humans by adjusting muscle activation prior to a postural perturbation. Previous studies have focused primarily on APA accompanying the relocation of the center of mass (COM). However, few studies are available which examine the effect of APA on quiet standing during an expected postural perturbation. PURPOSE: To investigate whether APA's are utilized during quiet standing when a subject encounters a postural perturbation. METHODS: Subjects stood quietly on force platform and center of pressure recordings and EMG activity was monitored during each 20–30 second trial. Electrical stimulation was applied to either the peroneal (PNS) or tibial (TNS) nerve bilaterally in order to produce a postural perturbation. College-age subjects (N = 8, 5 males and 3 females) were examined under three conditions: PNS, TNS, and no stimulation (NS). Each condition was tested under a vision and a no-vision condition. Eight trials were recorded for each of the six conditions. In each condition, subjects were able to anticipate the type of perturbation. The perturbation was randomly delivered during the 20–30 second trial, but subjects were aware of which stimulus condition was being presented. Sway parameters and EMG activity (sample rate = 1 kHz) from the pre-perturbation phase were analyzed. RESULTS: No differences were observed between the no-vision and the vision conditions, and data were pooled. Lateral deviation (1.27±0.68 in PNS, 1.35±0.64 in NS, and 1.37±0.69 in TNS, mm), and sagital deviation (2.86±1.42 in PNS, 3.04±1.46 in NS, and 2.86±1.41 in TNS, mm), sway velocity (6.97±2.70 in PNS, 7.13±2.76 in NS, and 7.15±2.44 in TNS, mm/sec), sway area (128.98±121.91 in PNS, 124.60±106.10 in NS, and 138.08±99.72 in TNS, mm2), sway amplitude (2.98±1.37 in PNS, 2.94±1.35 in NS, and 3.23±1.39 in TNS, mm), and background EMG of the tibialis anterior muscle (7.03±2.60 in PNS, 8.61±5.46 in NS, and 6.72±1.84 in TNS) and the soleus muscle (22.92±13.12 in PNS, 25.51±14.86 in NS, and 26.11±14.77 in TNS) showed no significant difference among stimulation types. CONCLUSIONS: Perturbation via electrical stimulation which produces an anterior/posterior displacement of the body is not accompanied by anticipatory changes in subject behavior. The role of APA with elderly subjects and/or populations with balance deficits remains to be determined.

The Effects of Caffeine on Repeated Lower-Body Wingate Performance

1169 PURPOSE: This study examined the effects of caffeine supplementation on repeated lower-body Wingate performance. METHODS: Ten college-aged subjects (22.4 +/− 1.7 yrs) volunteered to participate in this study. The 5 men and 5 women were considered physically fit and athletic, but none were deemed to be a fit anaerobic athlete. The subjects performed three 30-second Wingate tests (using a Monark 824-E cycle ergometer) with 30 minutes of rest between tests. This sequence was performed on two separate days with either the caffeine treatment (7 mg/kg) or placebo control (vitamin C) ingested 30 minutes prior to the first test on each of the two days. The design of the study was double-blind and the samples for each subject were randomly assigned. The anaerobic indices of peak power (PP), mean power (MP), and fatigue index (FI) were measured during each of the six tests (3 caffeine and 3 placebo) for each subject. RESULTS: ANOVA with repeated measures revealed a significant increase (P<0.05) in MP from 547.9 W to 590.0 W during the third Wingate test under the influence of the treatment. No significance was found among the other 8 variables analyzed. CONCLUSIONS: While these results indicate that caffeine increases MP during a 30-second Wingate test, the lack of a conclusive mechanism highlights the need for additional studies related to caffeine and anaerobic performance. The conclusion is that caffeine may enhance performance in athletic events requiring multiple supramaximal efforts over a relatively short period of time.

Air Displacement Plethysmography Under Dehydrated And Hyperhydrated Conditions

0492 The sensitivity of air displacement plethysmography to changes in hydration has not been evaluated. PURPOSE: This study examined body composition assessment using air displacement plethysmography when subjects were dehydrated and hyperhydrated. METHODS: Twenty college-age subjects participated in two treatments of dehydration and hyperhydration each conducted on separate days. Dehydration required intermittent exercise and heat exposure. Hyperhydration was accomplished with glycerol supplementation. Body composition was measured twice before and after each treatment. RESULTS: A decrease and increase in body weight of ∼2% resulted from dehydration and hyperhydration, respectively. Percent body composition was reduced following the dehydration protocol compared to baseline (2.18 ± .25; p<0.05). Percent body fat for glycerol hyperhydration was greater than baseline values (1.71 ± .17; p<0.05). CONCLUSIONS: These results demonstrate that alterations in body composition values occur when hydration status deviates by approximately 2% of the individuals' body weight. When measuring body composition using air displacement plethysmography, special attention needs to be taken to ensure proper hydration status.

Air Displacement Plethysmography Under Dehydrated And Hyperhydrated Conditions

0492 The sensitivity of air displacement plethysmography to changes in hydration has not been evaluated. PURPOSE: This study examined body composition assessment using air displacement plethysmography when subjects were dehydrated and hyperhydrated. METHODS: Twenty college-age subjects participated in two treatments of dehydration and hyperhydration each conducted on separate days. Dehydration required intermittent exercise and heat exposure. Hyperhydration was accomplished with glycerol supplementation. Body composition was measured twice before and after each treatment. RESULTS: A decrease and increase in body weight of ∼2% resulted from dehydration and hyperhydration, respectively. Percent body composition was reduced following the dehydration protocol compared to baseline (2.18 ± .25; p<0.05). Percent body fat for glycerol hyperhydration was greater than baseline values (1.71 ± .17; p<0.05). CONCLUSIONS: These results demonstrate that alterations in body composition values occur when hydration status deviates by approximately 2% of the individuals' body weight. When measuring body composition using air displacement plethysmography, special attention needs to be taken to ensure proper hydration status.

Iron Status of Young Males and Females Performing Weight-Training Exercise

To determine the effect of weight training on measures of iron status in young males and females. Forty (27 female, 13 male) non-weight-trained college age subjects participated in a 12-wk weight-training program conducted 3 d.wk-1. Blood samples and food diaries were obtained pretraining and at 4-wk intervals. Blood was analyzed for hemoglobin, hematocrit, serum iron (SI), total iron binding capacity (TIBC), transferrin saturation (TS), serum ferritin (SF), soluble transferrin receptor (sTfR), and creatine kinase (CK). Subjects were grouped by SF level (FL, females < or = 20 microg.L-1; FN, females > 20 microg.L-1; ML, males < or = 45 microg.L-1; MN, males > or = 50 microg.L-1) to determine the impact of initial iron status on measured responses. Weight training increased strength and fat-free mass and decreased levels of percent body fat. Hemoglobin concentration declined after 12 wk of training (13.7 +/- 1.6 vs 13.2 +/- 1.7 g.dL-1), independent of gender or initial iron status. Only the MN group experienced a decline in SF level after 8 wk of training (129.7 +/- 77.9 vs 102.0 +/- 57.8 microg.L-1). No significant changes were observed for hematocrit, SI, TIBC, TS, sTfR, or CK measures. Total iron intake, but not heme or bioavailable iron intakes, declined at the 12th week of training compared with baseline (13.4 +/- 6.5 vs 10.7 +/- 4.8 mg.d-1) and was not significantly correlated with hematological or iron status measures. Hemoglobin concentration declines without alterations in SI, TIBC, TS, or sTfR after 12 wk of weight training. The SF level of males with adequate iron status is lowered with weight training but not among females or males with low iron status.

A diffusion model analysis of the effects of aging on recognition memory

The effects of aging on response time were examined in a recognition memory experiment with young, college age subjects and older, 60–75 year old subjects. The older subjects were slower than the young subjects but almost as accurate. Ratcliff’s (1978) diffusion model was fit to the data and it provided a good account of response times, their distributions, and accuracy values. The fits showed a 100 ms slowing of the nondecision components of response time for older subjects relative to young subjects, and roughly equal response criteria settings with accuracy instructions but more conservative settings for the older subjects with speed instructions. In the diffusion model, the decision process is driven by the rate of accumulation of evidence from the stimulus. We found that the rate of accumulation for older subjects was a non-significant 7% lower than the rate for young subjects, indicating that the output from recognition memory entering the decision process was not significantly worse for the older subjects. The results are compared to those obtained from letter discrimination, brightness discrimination, and signal detection-like tasks.

RELATIONSHIP OF LOWER EXTREMITY POWER AND STRENGTH TO VERTICAL JUMP PERFORMANCE IN MALES AND FEMALES

Currently, several prediction equations are employed to estimate power from a subject's vertical jump performance. How these predictions relate to actual leg strength and/or power has received little attention, especially in female subjects. PURPOSE The purpose of this study was to evaluate the relationship among lower extremity power and 1-RM strength on vertical jump performance and estimates of power predicted from vertical jump performance. METHODS Male (n=11) and female (n=17) college age subjects were evaluated for: 1) a counter-movement vertical jump (VJ) test (cm); 2) a lower extremity 1 repetition maximum (1-RM) and mean power output (Watts) derived from the Omnikinetic (Omk) closed chain, lower extremity dynamometer. Subjects mean powers from VJ performance were estimated from previously published equations by Lewis (Fox, Bowers & Foss, 1993), Johnson & Bahamonde (J. Strength Cond Res, 1996) and Harman et al. (J. Appl. Sport Sci. Res., 1991). Pearson product correlations were calculated among all variables and significance was set at p < 0.05. RESULTS For females, VJ was related (p > <0.05) to Omk mean power (r=0.58) but not to 1-RM (r = −0.26). Estimated power from the three VJ equations were related (p > <0.05) to 1-RM (r's = 0.52 – 0.59) but not to Omk mean power (r's = −0.06 – 0.10). For males, VJ was related (p > <0.05) to Omk mean power (r = 0.68) but not to 1-RM (r = 0.34). Estimated power from the three VJ equations were related (p > <0.05) to 1-RM (r's = 0.65– 0.71) and Omk mean power (r's = 0.74 – 0.83). CONCLUSION These results suggest that the present equations to predict mean power from VJ performance is appropriate for males, but do not appear to relate to lower extremity power in females. Additionally, lower extremity power appears to contribute more to VJ performance that 1-RM, and this observation is more prevalent in males than females. This may indicate that females depend more upon jumping technique than lower extremity strength when compared to their male counterparts.Table: No Caption Available

EFFECT OF ACTIVITY LEVEL, GENDER, AND EXERCISE DURATION ON SELF-SELECTED EXERCISE INTENSITIES

PURPOSE Allowing individuals to self-select their preferred exercise intensity may increase enjoyment and participation levels. An important consideration when using a self-selected exercise intensity is to ensure that the workrate elicits a physiologic response likely to improve cardiovascular health. This study compared percent VO2max (%VO2max), percent heart rate max (%HRM), overall rating of perceived exertion (RPE), and energy expenditure (EE) in young men and women of varying activity levels while exercising on a treadmill (TM) at their preferred intensity for different durations. METHODS 60 healthy, college-aged subjects (15 sedentary men, 15 sedentary women, 15 active men, and 15 active women) were recruited to take part in the study. Prior to testing, subjects underwent 3 familiarization sessions (20, 30, and 40-min of supervised self-selected TM exercise) and an incremental maximal TM test to determine VO2max. During the experimental sessions subjects exercised for 20, 30, or 40 min at a self-selected intensity while masked to the speed of the TM. The experimental sessions were presented in a counterbalanced order. Respiratory metabolic measures, RPE, and HR were determined continuously throughout each session. RESULTS RPE was similar (11–13 range) in active and sedentary men and women during each exercise bout. The RPE was associated with a significantly higher %VO2max and %HRM in active vs sedentary men during each exercise bout and during the 30 and 40 min exercise bout in active vs sedentary women. EE (kcal/min) and TM speed (mph) were significantly higher in active men and women compared to their sedentary counterparts during each exercise bout. CONCLUSION When allowed to self-select preferred TM exercise intensity, physically active and sedentary men and women work within a stimulus zone required to improve cardiovascular health.

RELIABILITY OF INTRA-SUBJECT BLOOD [NH3] ACROSS THREE HIGH-INTENSITY EXERCISE SESSIONS

Blood ammonia [NH3] concentration is a marker for the assessment of training status. However, concerns arise as to the intra-subject reproducibility of the blood [NH3] assay across high-intensity exercise sessions. Although an inverse relationship exists between blood [NH3] and training status (Graham et al. MSSE 29:646), the reproducibility of the ammonia assay is unknown. PURPOSE To investigate the reliability of the blood [NH3] assay across high-intensity exercise sessions. METHODS Fifteen recreationally upper body trained (e.g. weight training, surfing, swimming) college-age male (n = 11) and female (n = 4) students were ramp-tested via incremental (25W.30 second-1) arm ergometry to RPE 17 on three occasions (S1, S2, S3). Total time, power output, cadence (100rpm), and stage completion were constant per subject across sessions. A 48h-72h washout separated each session. Antecubital venous blood samples were drawn at 3-minutes postexercise (subject seated and resting), immediately chilled, centrifuged, with harvested serum frozen (−20 degrees C) immediately. Subsequent batch analysis for [NH3] used a multi-layered urease/colorimetric slide technique ([email protected] Ektachem DT Analyzer). RESULTS One-way repeated measures ANOVA revealed no significant (p > .05) differences (x ± SE) in blood ammonia [uM/L] across S1 (180 ±13), S2 (190 ±14), and S3 (184 ±13). Secondly, the intraclass correlation coefficient was highly significant, r = .92, p < .0000, as were the correlations between the individual sessions (S1 vs. S2, r =.94, p < .0000; S2 vs. S3, r =.90, p < .0000; S1 vs. S3, r = .90, p < .0000). CONCLUSION These results suggest that blood [NH3] post-exercise is highly reliable in moderately trained college age subjects. However, additional work is needed to ascertain whether the effects of 1) training status (e.g. in-season training, progression, and taper) and 2) arm vs. leg activity can influence the reliability of blood [NH3].

THE EFFECT OF ANALYSIS METHOD IN DETERMINING CHANGE IN POST EXERCISE OXYGEN CONSUMPTION

PURPOSE To determine if the method of calculating EPOC yields different results prior to and after 9 months of aerobic training in previously sedentary overweight adults. METHODS Forty-three moderate obese college-aged subjects, 26 women (age=24.1±5.5, wt=76.2±10.6kg) and 17 men (age=22.2±4.4, wt=95.0±12.9kg). Exercise progressed from 3d/wk, 30min/session at 60% of heart rate reserve (HRR) to 5d/wk, 45 min/session at 75% of HRR at 4 months and then was maintained until 9 months. Three hour post exercise oxygen consumption was measured baseline and again at 9 months. At baseline subjects walked on a treadmill for 35 min at 65% of HRR. At 9 months subjects walked for 45 min at 75% of HRR. Oxygen consumption was measured 15 min prior to, during, and 15 min subsequent to the exercise bout. In addition, oxygen consumption was measured for 15 min at 60, 120 and 180 min post-exercise. Incremental area under the curve was determined by subtracting the area under the curve at baseline from the total area under the curve. Positive incremental area was calculated the same way as incremental area with negative values being set to zero. RESULTS For women, area under the curve increased 4.61±9.20L, 2.24±6.32L and 1.51±6.32L for the total, positive incremental and incremental methods respectively, while men increased 6.50±13.30L, 2.06±9.47L, 2.08±10.82L. There was no significant main effect for method of analysis and change in post-exercise oxygen consumption after controlling for change in exercise intensity. CONCLUSION The use of total area under the curve instead of incremental or positive incremental area under the curve may be a more sensitive method of detecting change in post-exercise oxygen consumption. This is especially important when attempting to determine the effect of exercise training over time on energy balance, where how much the person changes total energy expenditure may be more important than how much they expended above some baseline value that may or may not reflect a true resting state. Supported by NIH DK49181 and M01 RR00051