METHODS: Twenty participants (13 men and 7 women; age: 23.0 ± 3.1 y; body mass index: 24.7 ± 2.8 kg·m-2) completed two testing protocols on a cycle ergometer. Maximal heart rate was recorded during each two-minute stage of a GXT and HRDP was calculated by determining the maximal distance (D MAX) between the linear regression line formed by heart rate values from the lowest and highest stages and the exponential plus constant regression model for values ≥ 140 bpm. CP was calculated as the average power output from the final 30s during a 3MT using a pedaling rate dependent linear mode with an individualized linear factor (α = power/cadence 2) determined from the GXT performance. 95% confidence intervals, linear regression, and limits of agreement were utilized to compare CP and HRDP. RESULTS: Mean ± confidence intervals for CP (185.6 ± 11.0 W) and HRDP (179.9 ± 9.6 W) were found to be comparable with CP representing ~79 ± 1.7% and HRDP ~76 ± 1.0% of peak power output from the GXT. Furthermore, these fatigue thresholds were highly related (y = 1.019x + 2.248; R² = 0.7944; SEE = 22.8 W). However, despite limited bias in this relationship (CPHRDP Δ: 5.7 ± 5.0 W), broad limits of agreement were identified (-37.8 W to 49.3 W). CONCLUSION: Groupwise data for CP and HRDP appear to be equivalent, but large individual variability suggests that these two thresholds are not interchangeable. The use of staged incremental (GXT) versus fatigue-based decremental (3MT) testing protocols as well as the particular modeling approach for HRDP may have played a role in these discrepancies. 447 Board #298 May 27, 11:00 AM - 12:30 PM Effect Of Age On Peak Jump Performance In Volleyball Players Satoru Tanigawa1, Hirotaka Yamanaka1, Kenichi Okano1, Nakaba Akiyama1, David H. Fukuda2, Jeffrey R. Stout2, Jay R. Hoffman, FACSM2. 1University of Tsukuba, Ibaraki, Japan. 2University of Central Florida, Orlando, FL. (Sponsor: Jay Hoffman, FACSM) Email: firstname.lastname@example.org (No relationships reported) Knowledge of age at peak performance in competitive sport informs decisions about selection and preparation of athletes for specific events. PURPOSE: To estimate performance differences between college and professional volleyball players, and to investigate age-related changes in jump performance in professional volleyball players. METHODS: 124 DivisionIJapanese college players (age: 19.79±1.23 yrs) and 58 Japanese professional volleyball players (age: 25.90±3.19 yrs) were examined in this study.Professional volleyball players were separated into three age groups (young [YG] ≤ 24 yrs; middle [MG] 25-27 yrs; older [OG] ≥28 yrs). All performance assessments were part of the athletes’ normal preseason training camp testing routine, which included height, standing reach height, body mass, squat jump (SJ), countermovement jump (CMJ), countermovement jump with arms (CMJA) performed on a contact mat, spike jump reach height (SPJh) with one step (SPJ1h) and three steps (SPJ3h) performed with a jumping device. Relative jump heights (relative spike height: RS1h and RS3h) were calculated by absolute jump height (SPJ1h and SPJ3h) minus standing reach height. The stretch-shortening cycle efficiency (SSCE) was assessed as the percent differences between CMJ and SJ (CMJ-SJ/SJ: EI), RS1h and CMJA (RS1h-CMJA/CMJA: RS1I) and RS3h and CMJA (RS3h-CMJA/CMJA: RS3I). RESULTS: SJ (45.5±5.6cm vs. 42.6±5.7cm: p<0.01) and CMJ (48.5±5.6cm vs. 46.63±5.5cm: p<0.05) was significantly higher in college players than the professional players. Standing reach height (233.5±11.3cm vs. 245.0±10.5cm), SPJ3h (316.6±11.4cm vs. 329.2±9.56cm), RS1h (76.3±7.9cm vs. 79.2±7.9cm) and SSCE were significantly higher in the professional players compared to the college players, respectively (p<0.01). Comparisons between age groups in the professional players revealed no differences in either SJ and CMJ, however RS1I and RS3hI were better (p<0.05) in YG than in OG. CONCLUSION: Anthropometric and SSCE differences exist between playing levels, and SSCE differences exist between age groups within the professional athletes. These results provide support to the importance of maintaining SSCE and SPJh through appropriately designed training programs for athletes to maintain their level of performance in elite levels of volleyball. 448 Board #299 May 27, 11:00 AM - 12:30 PM Oxygen Uptake Efficiency Slope (oues): A New Index Of Performance Evaluation? Andrea Di Castro1, Sabrina Demarie2, Carlo Minganti2, Claudio Gallozzi1, Roberto Tamburri3, Antonio Gianfelici1. 1Institute of Medicine and Science in Sports “CONI Servizi”, Rome, Italy. 2University of Rome “ Foro Italico”, Rome, Italy. 3Italian Triathlon Federation, Rome, Italy. Email: email@example.com (No relationships reported) VO2max obtained by a maximal effort is historically an important predictor of endurance performance. However, exercise testing protocol and subjective factors affect the measurement of this value, which is seldom attained. The oxygen uptake efficiency slope (OUES), which relates oxygen uptake to total ventilation during exercise, was proposed as alternative submaximal index of cardiorespiratory functional reserve in pediatric cardiac patients. No previous studies have investigated if OUES could be a good predictor also in highly trained athletes. PURPOSE: Our objective was to investigate OUES in comparison with VO2max in triathletes and its correlation to performance. METHODS: 13 high level young triathletes free of clinically recognized cardiovascular disease (7 males, 6 females, respectively age 18.1±0.90 and 16.8±0.98 years; height 179.6±6.4 and 162.8±2.64 cm; weight 65.0±3.53 and 53.5±4.2 kg) participated to the study. After giving written informed consent, they performed a treadmill exhaustive incremental test to determine their OUES that was calculated from data taken from the first 75%, 90% and 100% of the exercise duration in those subjects who were considered to have achieved a maximal effort. OUES was used to correlate either VO2max or 10 km running performance took a week later. Differences in the mean values were analyzed by the analysis of variance (ANOVA). The correlations between VO2max, OUES and running performance were assessed by linear regression analysis. RESULTS: VO2max resulted highly correlated either to OUES 75 (r 0.91) or OUES 90 (r 0.93) or OUES 100 (r 0.92) p<0.05. Also the running time performance was correlated to OUES either to OUES 75 (r 0.89) or OUES 90 (r 0.91) or OUES 100 (r 0.88) p<0.05. Finally, the running time performance was correlated to VO2max (r -0.98) p<0.05. CONCLUSION: The main findings of this study indicate that OUES in triathletes is independent of exercise intensity, that OUES 75 and OUES 90 are valid to determine VO2peak without achieving the maximal efforts and that it shows a valid correlation with running performance, as the VO2max. Results confirm that OUES is reproducible and reliable, supporting its validity to estimate the fitness state of athlete. 449 Board #300 May 27, 11:00 AM - 12:30 PM Regression of Peak Oxygen Uptake and Knee Extension Torque Predicts Difference in Body Fat Values Between Skinfold and Hydrostatic Weighing Techniques William R. Lunn, Maria Zenoni, Ian Crandall, Michelle Berglund, Ashley Dress, Robert Axtell, FACSM. Southern Connecticut State University, New Haven, CT. (Sponsor: Robert Axtell, FACSM) Email: firstname.lastname@example.org (No relationships reported) Regression of Peak Oxygen Uptake and Knee Extension Torque Predicts Difference in Body Fat Values Between Skinfold and Hydrostatic Weighing Techniques William R. Lunn, Maria Zenoni, Ian Crandall, Michelle Berglund, Ashley Dress, Robert Axtell, FACSM. Exercise Science Dept., Southern Connecticut State University, New Haven, CT Skinfold thickness determination and hydrostatic weighing are common, two-component techniques of body composition estimation. Despite test familiarization, difference in the percent body fat result between the two techniques can be observed in certain individuals, while precision is achieved in others. PURPOSE: The aim of the study was to use regression analysis to determine if the difference in body fat result (BF_diff) can be predicted by each of peak oxygen uptake (VO2peak) and peak isokinetic torque of knee extension (TORQ). METHODS: Healthy adult males (n = 51) completed two trials (one familiarization, one data collection) of each of isokinetic dynamometry of knee extension and a treadmill running VO2peak test on separate days. Isokinetic knee extension was evaluated at 180ºs-1. A common graded exercise test protocol with constant treadmill speed and gradually increasing incline and indirect calorimetry was used to determine VO2peak. Standard skinfold calipers and underwater weighing with vital capacity determination were used for body fat estimation. 120 Copyright © 2015 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.