Prospects for Ductility and Toughness Enhancement of Nial by Ductile Phase Reinforcement

The use of NiAl as a structural material has been hindered by the fact that this ordered intermetallic does not exhibit significant tensile ductility or toughness at room temperature. A critical review of the operative flow and fracture mechanisms in monolithic NiAl has thus established the need for ductile phase toughening in this order system. Progress in ductile phase reinforced intermetallic systems in general and specifically NiAl-based materials has been reviewed. In addition, further clarification of the primary mechanisms involved in the flow and fracture of ductile phase reinforced alloys has evolved from ongoing investigations of several model NiAl-based materials. The mechanical behavior of these model directionally-solidified alloys (Ni-30Al and Ni-30Fe-20Al) are discussed. Finally, the prospects for developing a ductile phase toughened NiAl-based alloy and the shortcomings presently inherent in these systems are analyzed

Simple Bodyweight Training Improves Cardiorespiratory Fitness With Minimal Time Commitment: A Contemporary Application of the 5BX Approach

International Journal of Exercise Science 14(3): 93-100, 2021. Bodyweight training (BWT) is a style of interval exercise based on classic principles of physical education. Limited research, however, has examined the efficacy of BWT on cardiorespiratory fitness. This is especially true for simple BWT protocols that do not require extraordinarily high levels of effort. We examined the effect of a BWT protocol, modelled after the original “Five Basic Exercises” (5BX) plan, on peak oxygen uptake (VO2peak) in healthy, inactive adults (20 ± 1 y; body mass index: 20 ± 5 kg/m2; mean ± SD). Participants were randomized to a training group that performed 18 sessions over six weeks (n=9), or a non-training control group (n = 10). The 11-minute session involved five exercises (burpees, high knees, split squat jumps, high knees, squat jumps), each performed for 60-seconds at a self-selected “challenging” pace, interspersed with active recovery periods (walking). Mean intensity during training was 82 ± 5% of maximal heart rate, rating of perceived exertion was 14 ± 3 out of 20, and compliance was 100%. ANCOVA revealed a significant difference between groups after the intervention, such that VO2peak was higher in the training group compared to control (34.2 ± 6.4 vs 30.3 ± 11.1 ml/kg/min; p = 0.03). Peak power output during the VO2peak test was also higher after training compared to control (211 ± 43 vs 191 ±50 W, p = 0.004). There were no changes in leg muscular endurance, handgrip strength or vertical jump height in either group. We conclude that simple BWT— requiring minimal time commitment and no specialized equipment — can enhance cardiorespiratory fitness in inactive adults. These findings have relevance for individuals seeking practical, time-efficient approaches to exercise

Stress asymmetry in cyclic deformation of b.c.c. metals

Asymmetric slip in b.c.c. metals is related to both the symmetry about screw dislocations and elastic anisotropy. The elastic anisotropy differs quite substantially from one b.c.c. metal to the next and this anisotropy has been observed in measurements of asymmetric stresses in plastic deformation experiments. In this paper, data from cyclic deformation of b.c.c. metals, with special emphasis on tungsten which is elastically isotropic, are used to demonstrate the role of screw dislocation geometry and elastic anisotropy on stress asymmetry. The interaction of dislocation geometry and thermal activation of screw dislocation motion is discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30320/1/0000722.pd

Application of the speed-duration relationship to normalize the intensity of high-intensity interval training

The tolerable duration of continuous high-intensity exercise is determined by the hyperbolic Speed-tolerable duration (S-tLIM) relationship. However, application of the S-tLIM relationship to normalize the intensity of High-Intensity Interval Training (HIIT) has yet to be considered, with this the aim of present study. Subjects completed a ramp-incremental test, and series of 4 constant-speed tests to determine the S-tLIM relationship. A sub-group of subjects (n = 8) then repeated 4 min bouts of exercise at the speeds predicted to induce intolerance at 4 min (WR4), 6 min (WR6) and 8 min (WR8), interspersed with bouts of 4 min recovery, to the point of exercise intolerance (fixed WR HIIT) on different days, with the aim of establishing the work rate that could be sustained for 960 s (i.e. 4×4 min). A sub-group of subjects (n = 6) also completed 4 bouts of exercise interspersed with 4 min recovery, with each bout continued to the point of exercise intolerance (maximal HIIT) to determine the appropriate protocol for maximizing the amount of high-intensity work that can be completed during 4×4 min HIIT. For fixed WR HIIT tLIM of HIIT sessions was 399±81 s for WR4, 892±181 s for WR6 and 1517±346 s for WR8, with total exercise durations all significantly different from each other (P<0.050). For maximal HIIT, there was no difference in tLIM of each of the 4 bouts (Bout 1: 229±27 s; Bout 2: 262±37 s; Bout 3: 235±49 s; Bout 4: 235±53 s; P>0.050). However, there was significantly less high-intensity work completed during bouts 2 (153.5±40. 9 m), 3 (136.9±38.9 m), and 4 (136.7±39.3 m), compared with bout 1 (264.9±58.7 m; P>0.050). These data establish that WR6 provides the appropriate work rate to normalize the intensity of HIIT between subjects. Maximal HIIT provides a protocol which allows the relative contribution of the work rate profile to physiological adaptations to be considered during alternative intensity-matched HIIT protocols

Tapering practices of New Zealand's elite raw powerlifters

Pritchard, HJ, Tod, DA, Barnes, MJ, Keogh, JW, and McGuigan, MR. Tapering practices of New Zealand's elite raw powerlifters. J Strength Cond Res 30(7): 1796-1804, 2016-The major aim of this study was to determine tapering strategies of elite powerlifters. Eleven New Zealand powerlifters (28.4 ± 7.0 years, best Wilks score of 431.9 ± 43.9 points) classified as elite were interviewed, using semistructured interviews, about their tapering strategies. Interviews were transcribed verbatim and content analyzed. Total training volume peaked 5.2 ± 1.7 weeks from competition while average training intensity (of 1 repetition maximum) peaked 1.9 ± 0.8 weeks from competition. During tapering, volume was reduced by 58.9 ± 8.4% while intensity was maintained (or slightly reduced) and the final weight training session was performed 3.7 ± 1.6 days out from competition. Participants generally stated that tapering was performed to achieve full recovery; that accessory work was removed around 2 weeks out from competition; and deadlifting takes longer to recover from than other lifts. Typically participants stated that trial and error, and changes based on "feel" were the sources of tapering strategies; equipment used and movements performed during tapering are the same as in competition; nutrition was manipulated during the taper (for weight cutting or performance aims); and poor tapering occurred when too long (1 week or more) was taken off training. These results suggest that athletes may benefit from continuing to strength train before important events with reduced volume and maintained intensity. Only exercises that directly assist sports performance should remain in the strength program during tapering, to assist with reductions in fatigue while maintaining/improving strength expression and performance

Short Fiber Reinforced Thermoplastics: Prediction of Stiffness in Injection Molded PS-PPO Blends

The prediction of stiffness in short fiber reinforced thermoplastics is stud ied as a function of fiber length using injection molded blends of PS and PPO. The theoret ical models for predicting composite stiffness are reviewed. The results are first compared with the theoretical models advanced for uniaxially aligned composites. These models predict higher than experimental values. However, agreement between the predictions and experimental values improves when the effect of fiber orientation distribution in the injec tion molded samples is taken into account and as the ductility (or the PPO content) of the matrix increases. Cox's model when used with the "laminate analogy" gives the closest prediction to the experimental stiffness. Reinforcement efficiency factor for stiffness is a strong function of retained fiber lengths. The dependence of composite stiffness on the matrix ductility and the effects of compatibility on the mechanical properties of PS-PPO blend system are also discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68613/2/10.1177_089270579100400205.pd

Surface film effects during cyclic deformation of dislocation-mobility-limited materials

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30047/1/0000415.pd

No effect of glutamine supplementation and hyperoxia on oxidative metabolism and performance during high-intensity exercise.

addresses: Health and Biology, Liverpool Hope University, Liverpool, UK. [email protected]: Comparative Study; Journal ArticleThis is an Author's Accepted Manuscript of an article published in Journal of Sports Sciences, 2008, Vol. 26, Issue 10, pp. 1081 – 1090 © 2008 copyright Taylor & Francis, available online at: http://www.tandfonline.com/doi/abs/10.1080/02640410801930200Glutamine enhances the exercise-induced expansion of the tricarboxylic acid intermediate pool. The aim of the present study was to determine whether oral glutamine, alone or in combination with hyperoxia, influenced oxidative metabolism and cycle time-trial performance. Eight participants consumed either placebo or 0.125 g kg body mass(-1) of glutamine in 5 ml kg body mass(-1) placebo 1 h before exercise in normoxic (control and glutamine respectively) or hyperoxic (FiO(2) = 50%; hyperoxia and hyperoxia + glutamine respectively) conditions. Participants then cycled for 6 min at 70% maximal oxygen uptake (VO(2max)) immediately before completing a brief high-intensity time-trial (approximately 4 min) during which a pre-determined volume of work was completed as fast as possible. The increment in pulmonary oxygen uptake during the performance test (DeltaVO(2max), P = 0.02) and exercise performance (control: 243 s, s(x) = 7; glutamine: 242 s, s(x) = 3; hyperoxia: 231 s, s(x) = 3; hyperoxia + glutamine: 228 s, s(x) = 5; P < 0.01) were significantly improved in hyperoxic conditions. There was some evidence that glutamine ingestion increased DeltaVO(2max) in normoxia, but not hyperoxia (interaction drink/FiO(2), P = 0.04), but there was no main effect or impact on performance. Overall, the data show no effect of glutamine ingestion either alone or in combination with hyperoxia, and thus no limiting effect of the tricarboxylic acid intermediate pool size, on oxidative metabolism and performance during maximal exercise

Appetite and gut hormone responses to moderate-intensity continuous exercise versus high-intensity interval exercise, in normoxic and hypoxic conditions.

This study investigated the effects of continuous moderate-intensity exercise (MIE) and high-intensity interval exercise (HIIE) in combination with short exposure to hypoxia on appetite and plasma concentrations of acylated ghrelin, peptide YY (PYY), and glucagon-like peptide-1 (GLP-1). Twelve healthy males completed four, 2.6 h trials in a random order: 1) MIE-normoxia, 2) MIE-hypoxia, 3) HIIE-normoxia, and 4) HIIE-hypoxia. Exercise took place in an environmental chamber. During MIE, participants ran for 50 min at 70% of altitude-specific maximal oxygen uptake ( 2max) and during HIIE performed 6 x 3 min running at 90% 2max interspersed with 6 x 3 min active recovery at 50% 2max with a 7 min warm-up and cool-down at 70% 2max (50 min total). In hypoxic trials, exercise was performed at a simulated altitude of 2,980 m (14.5% O2). Exercise was completed after a standardised breakfast. A second meal standardised to 30% of participants’ daily energy requirements was provided 45 min after exercise. Appetite was suppressed more in hypoxia than normoxia during exercise, post-exercise, and for the full 2.6 h trial period (linear mixed modelling, p 0.05). These findings demonstrate that short exposure to hypoxia causes suppressions in appetite and plasma acylated ghrelin concentrations. Furthermore, appetite responses to exercise do not appear to be influenced by exercise modality