Comparisons of the Metabolic Intensities at Heart Rate, Gas Exchange, and Ventilatory Thresholds

International Journal of Exercise Science 13(2): 455-469, 2020. PURPOSE: This study compared the O2corresponding to the critical heart rate (CHRO2) and the physical working capacity at the heart rate fatigue threshold (PWChrtO2) to the gas exchange threshold (GET), ventilatory threshold (VT), and respiratory compensation point (RCP). METHODS: Nine runners (mean ±SD, age 23 ±3 years) completed an incremental test on a treadmill to determine O2peak, GET, VT, and RCP. The CHRO2and PWChrtO2were determined from 4 separate constant velocity treadmill runs to exhaustion and HR and time to exhaustion were recorded. Differences among the thresholds were examined with a one-way repeated measures ANOVA (p≤ 0.05). RESULTS: The GET (38.44 mL×kg-1×min-1, 78%O2peak), VT (37.36 mL×kg-1×min-1, 76%O2peak), and PWChrtO2 (38.26 mL×kg-1×min-1, 77%O2peak) were not different, but were lower than the RCP (44.70 mL×kg-1×min-1, 90%O2peak;p= 0.010, p\u3c 0.001,p= 0.001, respectively). The CHRO2(40.09 mL×kg-1×min-1, 81%O2peak) was not different from the GET (p= 1.000), VT (p= 0.647), PWChrtO2(p =1.000), or RCP (p= 0.116). CONCLUSIONS: These results indicated that the initial metabolic intensities at CHR and PWChrtlie within the heavy and moderate intensity domains, respectively. Therefore, the PWChrtmay provide a relative intensity more appropriate for untrained populations, while the CHR may be more appropriate for more trained populations

Muscular Performance and Neuromuscular Fatigue are not Sex-Dependent During Low-Load Fatiguing Bilateral Leg Extension Exercise

Purpose. This study examined the sex-related differences in muscular performance and neuromuscular (electromyographic [EMG] and mechanomyographic [MMG] amplitude [AMP] and mean power frequency [MPF]) responses during fatiguing leg extension repetitions performed at the critical load (CL). Methods. Eleven men and nine women completed one-repetition maximum (1RM) testing, repetitions to failure at 50, 60, 70, and 80% 1RM to determine CL, and repetitions to failure at CL, on separate days. The EMG and MMG, AMP and MPF signals and number of repetitions completed were recorded. Results. There were no sex-dependent responses in the %1RM that corresponded to, the number of repetitions completed at, or the neuromuscular responses during repetitions performed to failure at CL. There were time-dependent responses in EMG AMP from 25-100% of total repetitions completed, respectively. The EMG MPF and MMG MPF demonstrated fatigue-induced decreases from 50-100% and at 100% of total repetitions completed, respectively. There was no change over time for MMG AMP. Conclusions. These findings indicated men and women responded similarly to leg extension exercise performed at the CL. Further, sex-dependent responses to fatiguing exercise may be related to the amount of active muscle mass engaged in exercise and the corresponding afferent feedback that influences peripheral fatigue and central drive during fatiguing tasks

A molten salt test loop for component and instrumentation testing

Molten salt is an effective coolant for a wide range of applications, including nuclear reactors, concentrated solar power, and other high temperature industrial heat transfer processes. The technical readiness level of components and instrumentation for high-temperature molten salt applications needs improvement for molten salt to be more widely adopted. A molten salt test loop was designed, built, and commissioned as a test bed to address these issues. The molten salt test loop at Abilene Christian University was built out of 316 stainless steel with a forced flow centrifugal-type pump, and was instrumented for remote operation. A low-temperature molten nitrate salt was used in this system, which was designed to operate at temperatures up to 300 ◦C and flow rates up to 90 liters per minute. This paper describes the loop design, computational fluid dynamics modeling, construction, and commissioning details. An outline of the data acquisition and control systems is presented. Salt samples were taken before and after introduction into the loop, and melting points were measured both before and after salt circulation. Performance of the system is discussed as well as improvements required for higher temperature loops envisioned for the future

Proceedings of the Thirteenth International Society of Sports Nutrition (ISSN) Conference and Expo

Meeting Abstracts: Proceedings of the Thirteenth International Society of Sports Nutrition (ISSN) Conference and Expo Clearwater Beach, FL, USA. 9-11 June 201

Sex Comparisons for Very Short-Term Dynamic Constant External Resistance Training

This study compared sex responses for strength and barbell velocity from very short-term resistance training (VST, consisting of 2–3 training sessions) for an upper body dynamic constant external resistance (DCER) exercise (bench press [BP]). Ten females (mean ± standard deviation (SD) age: 21.3 ± 3 years, height: 166.2 ± 6 cm, body mass: 71.4 ± 10.7 kg) and 10 males (mean ± SD age: 24.6 ± 4 years, height: 179.5 ± 8 cm, body mass: 88.6 ± 11 kg) completed a pre-test visit to determine the BP 1 repetition maximum (1RM) as well as the mean (BPMV) and peak (BPPV) barbell velocities from the BP 1RM. The VST involved three training visits where the participants performed 5 sets of 6 repetitions, at 65% of the 1RM. The post-test followed the same procedures as the pre-test visit. There were significant increases in 1RM strength for both the males (5.1%) and females (5.4%) between pre-test and post-test. There were no significance differences between sex for mean (BPMV) and peak (BPPV); however, overall there was a 32.7% increase in BPMV and a 29.8% increase in BPPV. These findings indicated an increase in strength and barbell velocity for both males and females as a result of VST upper body DCER exercise in untrained subjects

Effects of Very Short-Term Dynamic Constant External Resistance Exercise on Strength and Barbell Velocity in Untrained Individuals

International Journal of Exercise Science 11(1): 867-874, 2018.This study examined the effect of an upper body dynamic constant external resistance (DCER) exercise (barbell bench press [BP]), using the very short-term training (VST) model on strength and barbell velocity. Ten (5 females, 5 males) subjects (mean ± SD age: 21.4 ± 2.8 yrs; height: 1.75 ± 0.12 m; body mass: 83 ± 8.8 kg) completed two pre-test visits (pre-test 1 and pre-test 2) to serve as the within subjects control, three training visits, and one post-test visit. The subject’s 1 repetition maximum (1RM) for the BP as well as the mean (BPMV) and peak (BPPV) barbell velocities were determined during pre-test 1, pre-test 2 and post-test visits. The barbell bench press throw (BT) mean (BTMV) and peak (BTPV) velocities were also measured utilizing 35% of the subject’s BP 1RM as resistance. The three training visits consisted of 5 sets of 6 repetitions, at 65% of the subject’s 1RM. Statistical analyses included one-way repeated measures ANOVAs and paired samples t-tests (alpha level of p≤0.05). The post-test 1RM, BTMV, and BTPVwere all significantly greater than pre-test 1 (p=0.002, p=0.0001, and p=0.002) and pre-test 2 (p=0.008, p=0.034, and p=0.015), with no significant differences seen between pre-test 1 and pre-test 2 for any of the variables. The post-test BPMV and BPPVwere significantly greater than pre-test 1 (p=0.024 and p=0.005), but not pre-test 2 (p=0.131 and p=0.069). These findings showed the VST model, utilizing an upper body DCER exercise improved strength and barbell velocity in untrained subjects

The Effects of Pre-Workout Supplementation on Anaerobic Power and Maintenance of Power in College Students

International Journal of Exercise Science 12(2): 355-365, 2019. This study examined the effects of Assault™ pre-workout supplementation on peak power output (PP), mean power output (MP), and percent decline in power output (% decline) during repeated, Wingate anaerobic tests. Thirteen healthy, physically active participants (7 male, 6 female) completed the randomized, double-blind, placebo-controlled crossover design with two conditions, supplement and placebo. The participants visited the laboratory for a total of three visits, 2-7 days apart. During visit 1, the participants completed a 4-minute familiarization warm-up on the Monark cycle ergometer and performed one baseline, 30-second Wingate cycle ergometry test. During visits 2 and 3, the participants consumed either the pre-workout supplement or placebo flavored maltodextrin (randomized by a third party) and waited 20 minutes before beginning the test protocol. Each participant then completed a 4-minute warm-up on the Monark cycle ergometer followed by four, 30-second Wingate tests, with a 5-minute rest between each Wingate. There were no significant two-way condition x Wingate trial interactions for PP (F=0.713, p=0.566), MP (F=0.669, p-value=0.590), or % decline (F=0.398 p=0.540). There was a significant main effect for the Wingate trial for both PP (F=10.632, p=0.002) and MP (F=11.781, p =0.001), but there was no main effect for the Wingate trial for % decline. There were no main effects for condition for any of the variables. The pre-workout supplement examined in this study did not elicit ergogenic effects on anaerobic power output (PP or MP) or the maintenance (% decline) during multiple Wingate tests

Sex Comparisons for Very Short-Term Dynamic Constant External Resistance Training

This study compared sex responses for strength and barbell velocity from very short-term resistance training (VST, consisting of 2–3 training sessions) for an upper body dynamic constant external resistance (DCER) exercise (bench press [BP]). Ten females (mean ± standard deviation (SD) age: 21.3 ± 3 years, height: 166.2 ± 6 cm, body mass: 71.4 ± 10.7 kg) and 10 males (mean ± SD age: 24.6 ± 4 years, height: 179.5 ± 8 cm, body mass: 88.6 ± 11 kg) completed a pre-test visit to determine the BP 1 repetition maximum (1RM) as well as the mean (BPMV) and peak (BPPV) barbell velocities from the BP 1RM. The VST involved three training visits where the participants performed 5 sets of 6 repetitions, at 65% of the 1RM. The post-test followed the same procedures as the pre-test visit. There were significant increases in 1RM strength for both the males (5.1%) and females (5.4%) between pre-test and post-test. There were no significance differences between sex for mean (BPMV) and peak (BPPV); however, overall there was a 32.7% increase in BPMV and a 29.8% increase in BPPV. These findings indicated an increase in strength and barbell velocity for both males and females as a result of VST upper body DCER exercise in untrained subjects

Single-Cell Technologies to Study Phenotypic Heterogeneity and Bacterial Persisters

Antibiotic persistence is a phenomenon in which rare cells of a clonal bacterial population can survive antibiotic doses that kill their kin, even though the entire population is genetically susceptible. With antibiotic treatment failure on the rise, there is growing interest in understanding the molecular mechanisms underlying bacterial phenotypic heterogeneity and antibiotic persistence. However, elucidating these rare cell states can be technically challenging. The advent of single-cell techniques has enabled us to observe and quantitatively investigate individual cells in complex, phenotypically heterogeneous populations. In this review, we will discuss current technologies for studying persister phenotypes, including fluorescent tags and biosensors used to elucidate cellular processes; advances in flow cytometry, mass spectrometry, Raman spectroscopy, and microfluidics that contribute high-throughput and high-content information; and next-generation sequencing for powerful insights into genetic and transcriptomic programs. We will further discuss existing knowledge gaps, cutting-edge technologies that can address them, and how advances in single-cell microbiology can potentially improve infectious disease treatment outcomes

Single-Cell Technologies to Study Phenotypic Heterogeneity and Bacterial Persisters

Antibiotic persistence is a phenomenon in which rare cells of a clonal bacterial population can survive antibiotic doses that kill their kin, even though the entire population is genetically susceptible. With antibiotic treatment failure on the rise, there is growing interest in understanding the molecular mechanisms underlying bacterial phenotypic heterogeneity and antibiotic persistence. However, elucidating these rare cell states can be technically challenging. The advent of single-cell techniques has enabled us to observe and quantitatively investigate individual cells in complex, phenotypically heterogeneous populations. In this review, we will discuss current technologies for studying persister phenotypes, including fluorescent tags and biosensors used to elucidate cellular processes; advances in flow cytometry, mass spectrometry, Raman spectroscopy, and microfluidics that contribute high-throughput and high-content information; and next-generation sequencing for powerful insights into genetic and transcriptomic programs. We will further discuss existing knowledge gaps, cutting-edge technologies that can address them, and how advances in single-cell microbiology can potentially improve infectious disease treatment outcomes