Epsilon-near-zero three-dimensional metamaterial for manipulation of terahertz beams.

Metamaterials offer the potential of unprecedented refractive indices and evolution into metadevices for the manipulation of electromagnetic waves. However, the potential of the epsilon-near-zero (ENZ) concept has not been fully demonstrated in the terahertz waveband. Most conventional ENZ lenses have a uniform distribution of refractive indices in spite of their three-dimensional structure. Here, inspired by the ENZ concept, we demonstrate the two-dimensional distribution of a three-dimensional ENZ lens realized by circular openings of varying diameters on metal plates and apply it to a metal-slit array lens with gradient indices of 0

Acute Handgrip Fatigue and Forearm Girth in Recreational Sport Rock Climbers.

Indoor sport rock climbing has been increasing in popularity both recreationally and competitively. Despite this increase in popularity, the physiological responses to sport climbing as an exercise to specific muscle groups are not well defined. The purpose of this study was to quantify the change in handgrip strength over a 30-minute bout of continuous climbing, specifically in intermediate-level sport climbers. Ten intermediate rock climbers (age = 27 ± 2 years; climbing experience: 7.3 ± 1.5 years) completed baseline handgrip strength and forearm girth measurements. Each participant ascended one of two 5.9 difficulty routes as many times as possible in 30 minutes. After each ascent, heart rate was obtained, and handgrip strength and forearm girth were measured. Data were analyzed using repeated-measures ANOVA with significance set at α < 0.05. Dominant arm handgrip strength decreased by 22%, and non-dominant handgrip strength reduced by 23%. Dominant and non-dominant forearm girth increased by 4.5% and 4.4%, respectively. Weak but significant negative correlations were observed between handgrip strength and forearm girth in dominant (r = -0.311, p = 0.001) and non-dominant limbs (r = -.491, p = 0.001). These results indicate a relationship between increased forearm girth and decreases in muscular strength. Since handgrip strength decreases substantially during a 30-min climb in intermediate rock climbers, this population would be advised to carefully monitor recovery time between bouts.

The effects of adding leucine to pre and postexercise carbohydrate beverages on acute muscle recovery from resistance training.

The present study examined the effects of adding leucine to pre and postexercise carbohydrate beverages on selected markers of muscle damage, delayed-onset muscle soreness (DOMS), and squat performance for up to 72 hours after lower-body resistance training. Seventeen resistance trained men (mean +/- SD age 22.9 +/- 2.9 years) and 3 resistance trained women (mean +/- SD age 21.6 +/- 2.6 years) performed 6 sets of squats to fatigue using 75% of the 1 repetition maximum. Each subject consumed a carbohydrate beverage 30 minutes before and immediately after exercise with or without the addition of 22.5 mgxkg (45 mgxkg total) of leucine in a randomized, double-blind fashion. Serum creatine kinase (CK), lactate dehydrogenase (LDH), and DOMS were analyzed immediately before (TIME1), 24 (TIME2), 48 (TIME3), and 72 (TIME4) hours after exercise. The subjects repeated the squat protocol at TIME4 to test recovery. No differences were observed between groups for squat performance, defined as the total number of repetitions performed during 6 sets of squats, for both TIME1 and TIME4. The addition of leucine did not significantly decrease CK and LDH activity or DOMS. These results suggested that adding leucine to carbohydrate beverages did not affect acute muscle recovery and squat performance during both initial testing and during a subsequent exercise bout 72 hours later in resistance trained subjects.

An Evaluation of Select Physical Activity Exercise Classes on Bone Metabolism.

Weight-bearing physical activity can optimize bone mass early in life and prevent the development of osteoporosis. However, less is known about the potential benefits of non-weight-bearing activities. The purpose of this study was to assess the efficacy of structured physical activity classes on bone metabolism. Twenty-eight premenopausal women, aged 18-35 years who were either enrolled in a yoga class (n=14) or cardio-kickboxing class (n=14) voluntarily consented to participate. Both classes were introductory classes meeting twice per week for 50 min per session for 12 weeks. Anteroposterior spine (L1-L4), hip (dual femur), and total body bone mineral density (BMD) was measured in both groups pre and post intervention using dual-energy X-ray absorptiometry (DXA). Pre and post blood samples were drawn for measurement of serum osteocalcin (OC) by enzyme-linked immunosorbent assay (ELISA) in each group. Baseline subject characteristics including age, height, weight, body fat percentage, and lean body mass did not differ between groups. BMD levels did not increase but were held stable over the course of the intervention. Yoga increased OC by 68% (P < 0.001) and cardio-kickboxing increased OC by 67% (P < 0.001) over the course of the 12-week classes. While 12 weeks of yoga and cardio-kickboxing were insufficient to induce BMD changes, OC levels reflect the bone formation process was initiated, but not yet complete. Increased OC levels suggest the selected physical activity classes provided enough of a stimulus to precipitate a future response of bone growth, assuming exercise training remains constant.

Running Economy While Running in Shoes Categorized as Maximal Cushioning.

The purpose of the study was to determine if running economy was influenced by wearing maximal cushioning shoes vs. control (neutral cushioning) shoes. Participants (n=10, age=28.2±6.1yrs; mass=68.1±10.2 kg; height=170±6.1 cm) completed two experiments. Each experiment included running conditions wearing control and maximal cushioning shoes. In Experiment 1, participants ran on a treadmill at three speeds in each shoe condition (6 total conditions). The speeds were: 1) preferred speed, 2) preferred speed + 0.447 m·s-1, and 3) preferred speed - 0.447 m·s-1. In Experiment 2, participants ran on a treadmill at two inclines (0%, 6%) in each shoe condition (4 total conditions) at preferred speed. Experiments were conducted on separate days with Experiment 1 first. For all conditions, participants ran for 8-10 minutes while rate of oxygen consumption (VO2) was recorded. Average VO2 during steady state for each running condition was calculated. For Experiment 1, a 2 (shoe) × 3 (speed) repeated measures ANOVA (α=0.05) was used. For Experiment 2, a 2 (shoe) × 2 (incline) repeated measures ANOVA (α=0.05) was used. Rate of oxygen consumption was not influenced by the interaction of speed and shoe (p=0.108); VO2 was different between speeds (p<0.001), but not between shoes (p=0.071). Rate of oxygen consumption was not influenced by the interaction of incline and shoe (p=0.191); VO2 was greater for incline vs. level (p<0.001), but not different between shoes (p=0.095). It is concluded that a maximal cushioning running shoe did not influence running economy when compared to a control shoe (neutral cushioning running shoe).

Reliability and Validation of the Hexoskin Wearable Bio-Collection Device During Walking Conditions.

To evaluate if the Hexoskin smart shirt (HxS) would produce valid and reliable measurements for heart rate (HR), respiratory rate (RR), minute ventilation (VE), step count (SC), and energy expenditure (EE) when compared to a Polar T-31 heart rate monitor, an Applied Electrochemistry Moxus Metabolic System, and a manual step count. A two-day walking treadmill protocol with participants walking for 3 minutes at 3 speeds (1.5mph, 2.5mph, 3.5mph, 0% grade) was performed. Forty-nine volunteers participated the first day, forty-six on the second, thirty-one were used for reliability. Values calculated for the HxS data used Pearson's product-moment correlation (p < 0.05; r ≥ 0.70) for validity and Cronbach's α (≥ 0.70) for reliability. HxS HR (1.5mph; p<0.01, r=0.86, α=0.86. 2.5mph; p<0.01, r=0.81, α=0.88. 3.5mph; p<0.01, r=0.85, α=0.85), HxS RR (1.5mph; p<0.01, r=0.87, α=0.93. 2.5mph; p<0.01, r=0.86, α=0.92. 3.5mph; p<0.01, r=0.71, α=0.76), HxS VE (1.5mph; p=0.66, r=0.11, α=0.70. 2.5mph; p=0.01, r=0.15, α=0.73. 3.5mph; p=0.31, r=0.08, α=0.14), HxS SC (1.5mph; p=0.90, r=-0.01, α=0.70. 2.5mph; p=0.22, r=0.13, α=0.86. 3.5mph; p<0.01, r=0.74, α=0.85), HxS EE (1.5mph; p<0.01, r=0.56, α=0.85. 2.5mph; p<0.01, r=0.50, α=0.83. 3.5mph; p<0.01, r=0.51, α=0.80). HxS HR and RR provided valid and reliable measures at all three speeds while VE, SC, and EE had a mixture of results based on speed. These results are important in the use of the Hexoskin in an accurate manner for athletes, coaches, and for the potential medical applications being advocated in the field of telemedicine procedures.

Sex and Age Differences in Trail Half Marathon Running.

Female participation is growing in trail running races. The purpose was to evaluate sex and age differences in top finishers of a trail running half marathon. Velocity differences between males (M) and females (F) were determined for the top 10 finishers of the Moab Trail Half Marathon from 2012 - 2015 across age, and by finishing place. Differences between age category and between sexes were determined through ANOVA with significance accepted at P < 0.05. A significant difference for running velocity was present between sexes at each age category (20-29 yr F = 2.9±0.3, M = 3.4±0.4 m·sec-1; 30-39 yr F = 2.8±0.3, M = 3.3±0.3; 40-49 yr F = 2.7±0.3, M = 3.0±0.5; 50-59 yr F = 2.3±0.2, M = 2.8±0.3; 60-69 yr F = 1.6±0.3, M = 2.2±0.4; P < 0.0001). Sex difference in trail running velocity was consistent (~13%) among all age categories with exception of the oldest group (33%, P = 0.0001). There were significantly greater female finishers in every age category (20 - 29 yr F = 107±18, M = 56±1;, 30 - 39 yr F = 150±34, M = 84±21; 40 - 49 yr F = 112±17, M = 64±16; P < 0.01) until 50 - 59 yr (F = 48±13, M = 41±14; P = 0.50). These data indicate that the widening gap in sex differences observed in road races are ameliorated in a trail running environment that has a larger number of female participants.

The effect of creatine supplementation on mass and performance of rat skeletal muscle.

This study investigated the effect of dietary creatine supplementation on hypertrophy and performance of rat skeletal muscle. Male Sprague-Dawley rats underwent either tibialis anterior ablation or partial ablation of the plantaris/gastrocnemius to induce compensatory hypertrophy of the extensor digitorum longus (EDL) or soleus respectively, or sham surgery. Creatine (300 mg/kg) was administered to one half of each group for 5 weeks, after which force production was measured. With the leg fixed at the knee and ankle, the distal tendon of the EDL or soleus was attached to a force transducer and the muscle was electrically stimulated via the sciatic nerve. Synergist ablation resulted in a significant increase in EDL mass and in soleus mass relative to control muscles. However, no effect of creatine supplementation on muscle mass or performance was found between control and either group of creatine-treated rats. Despite an apparent increase in muscle creatine content, creatine supplementation did not augment muscle hypertrophy or force production in rat EDL or soleus muscle, providing evidence that the potential benefits of creatine supplementation are not due to a direct effect on muscle but rather to an enhanced ability to train.

Examining the Impact of a University-driven Exercise Programming Event on End-of-semester Stress in Students.

Stress levels in university students peak during the final exam period. An inverse association exists between Physical Activity (PA) and poor mental health. UNLV has created Fitness4Finals (F4F), an event novel in its approach to academic stress reduction by incorporating both physical activity and mental relaxation. To our knowledge, a university-driven programming event aimed at reducing physiological and psychological stress among students approaching final exams had never been studied. Therefore, the aims of this research were to 1) examine the influence of F4F on physiological stress and perceived psychological stress (PPS) and 2) to examine the relationship between physiological stress and PPS. Fifteen full-time university students were recruited to participate in their choice of one of two groups: F4F or control (NonF4F). Pre-F4F and post-F4F measures of physiological stress, measured by salivary cortisol, and perceived psychological stress, measured by survey were collected. The F4F event was held the week prior to final examinations. Participants in the F4F group engaged in one F4F activity per day for the duration of the 3-day event. Results of the repeated measures MANOVA indicated nonsignificant interaction (p = .864) between F4F participation, physiological stress and PPS. PPS and cortisol were not correlated at the onset of the study (r = -0.18, p = 0.48) or at the last sampling period (r = 0.097, p = 0.73). Preemptive elevated levels of PA in the F4F group may have influenced results. Qualitative data indicates a unanimous perceived reduction in stress from F4F participation. While the physiological measures of stress in the present study were not significantly different, the perceived stress reduction reported by F4F participants is influential. Further investigation with improvements in timing and measurement tools is warranted.

The effect of moderate consumption of non-nutritive sweeteners on glucose tolerance and body composition in rats.

Glucose tolerance and body composition were determined in male rats given non-nutritive sweeteners (NNS) (aspartame or sucralose) in drinking water. Areas under the curve for glucose and insulin with NNS did not differ from control. NNS treatment had no effect on weight gain or percent body fat. Epididymal fat pad mass was higher with aspartame and the ratio of trunk to total fat was less with sucralose versus control, suggesting that NNS consumption altered body fat distribution.

Effect of a high protein diet on glucose tolerance in the rat model.

The purpose of this study was to determine the effects of a high protein diet on glucose tolerance. Nine Sprague Dawley rats received a high protein (HP) diet (65% protein, 35% fat) and eight rats consumed a standard chow (SC) diet over eight weeks. Oral glucose tolerance tests (OGTT) were performed at the end of the third and the seventh week. The diet did not effect glucose tolerance in the first (SC=10357+/-294 mg/dl/120 min; HP=9846+/-300 mg/dl/120 min) or the second OGTT (SC=10134+/-395 mg/dl/120 min; HP=10721+/-438 mg/dl/120 min) as reflected by the area under the glucose concentration curve. Similarly, the area under the insulin concentration curve was not effected by the high protein diet during the first (SC=49.21+/-8.46 ng/ml/120 min; HP=41.75+/-10.54 ng/ml/120 min) or the second OGTT (SC=96.63+/-13.68 ng/ml/120 min; HP=92.77+/-17.44 ng/ml/120 min). The high protein diet group experienced a delayed glucose response for the first (SC=30 min at 112+/-7 mg/dl; HP=60 min at 101+/-5 mg/dl) and second OGTT (SC=15 min at 117+/-5 mg/dl; HP=60 min at 95+/-7 mg/dl). Body mass increased to the same extent in each diet group from the initial to final weighing (SC=159+/-2 g to 254+/-7 g; HP=157+/-2 g to 242+/-7 g). Despite a delay in peak glucose response, these findings suggest that glucose tolerance and body mass were neither adversely nor positively affected by a high protein diet.

Using Hexoskin Wearable Technology to Obtain Body Metrics During Trail Hiking.

Use of wearable technology to obtain various body metrics appears to be a trending phenomenon. However there is very little literature supporting the notion that these apparatuses can be used for research purposes in the field. The purpose of this study was to utilize Hexoskin wearable technology shirts (HxS) to obtain data in a pilot study using a trail hiking situation. Ten individuals (male, n = 4, female n = 6) volunteered to participate. On the first day, volunteers completed two approximately flat trail hikes at a self-preferred pace with a 15-minute rest between trials. On the second day, participants completed a strenuous uphill hike (17.6% grade) with a 15-minute rest at the summit and then completed the downhill portion. Body metrics provided by the HxS were average heart rate (HR), maximal HR (MHR), total energy expenditure (EE), average respiratory rate (RR), maximal respiratory rate (MRR), total steps (SC), and cadence (CA). Other measurements obtained were systolic and diastolic blood pressure (SBP, DBP), and ratings of perceived exertion (RPE). Data were analyzed using both one-way repeated measures analysis of variance (ANOVA) with significance accepted at p≤0.05 and intraclass correlation coefficients (ICC) for each variable. Both were determined using Statistical Package for the Social Sciences software (SPSS). No significant differences for trail type were noted for MHR (p=0.38), RR (p=0.45) or MRR (p=0.31). The uphill trail elicited significantly elevated HR (up=154±24 bpm, easy=118±11 bpm, down=129±19 bpm; p=0.04) and EE (up=251±78 kcal, easy=124±38 kcal, down=171±52 kcal; p=0.02). Significant ICC were observed for DBP (r = 0.80, p = 0.02), RR (r = 0.98, p = 0.01), SC (r = 0.97, p = 0.01) and RPE (r = 0.94, p = 0.01). Non-significant correlation were noted for uphill RR vs CA (r=0.51, p=0.16) or RPE vs SBP (r=0.03, p=0.94), HR (r=0.60, p=0.12), and MHR (r=0.70, p=0.051). We utilized HxS to provide physiological data in an applied setting. It should be noted that HR did not register in 5 out of 10 subjects on the easy trail, and 8 of 10 participants during the uphill hike. Additionally, estimated EE appears to be linked to HR intensity. Future investigations taken in an outdoor environment should take these findings into consideration.

The effect of creatine supplementation on glucose uptake in rat skeletal muscle.

Glucose transport in muscle is a function of the muscle metabolic state, as evidenced by the increase in glucose transport which occurs with conditions of altered aerobic metabolism such as hypoxia or contractile activity. The energy state of the muscle can be determined by the muscle phosphocreatine concentration. Dietary supplementation of creatine has been shown to increase both phosphocreatine (PCr) and creatine (TCr) levels in muscle, although not in the same proportion, so that the PCr/TCr ratio falls suggesting an altered energy state in the cell. The purpose of this study was to determine the effect of increased creatine content on glucose uptake in muscle. PCr and TCr were determined in plantaris muscles from rats following five weeks of dietary supplementation of creatine monohydrate (300 mg/kg/day). (3)H-2-deoxyglucose uptake was measured in epitrochlearis muscles incubated in the presence or absence of a maximally stimulating dose of insulin. Despite a significant increase in creatine content in muscle, neither basal nor insulin-stimulated glucose uptake was altered in creatine supplemented rats. Since PCr levels were not increased with creatine supplementation, these results suggest that the actual concentration of PCr is a more important determinant of glucose uptake than the PCr/TCr ratio.

The effect of acute exercise on pistol shooting performance of police officers.

Previous studies indicate that rifle shooting performance while standing is compromised when fatigued. Apprehension of suspects by police officers may involve foot pursuit and firing a weapon from a standing position. The purpose of the current study was to investigate pistol shooting performance in police officers under similar conditions of physical fatigue. Participants (mean age: 30.1 years; 4.4 years of experience as police officer) completed two shooting trials separated by an acute bout of exercise on a cycle ergometer to voluntary exhaustion. Each trial consisted of three rounds of five rapid-fire shots at a target, each round separated by a 15-s rest. Participants' backs were turned to the target between rounds. Despite physical exertion, with an average heart rate of 164 bpm, shooting accuracy (mean distance of the closest 4 shots from the center of the target) and precision (diameter of the tightest 4-shot grouping) remained unchanged on postexercise trials relative to preexercise trials. This suggests that automatic shooting reactions override the adverse consequences of fatiguing exercise on shooting performance.

The effect of resistance exercise on the thermic effect of food.

PURPOSE: The thermic effect of food (TEF) is the increment in energy expenditure above resting metabolic rate associated with the cost of absorption and processing of food for storage. Previous studies have shown that TEF is enhanced by aerobic endurance exercise of sufficient duration and intensity. The purpose of this study was to determine if a similar effect occurs with a single bout of resistance exercise (weightlifting). METHODS: VO2 was measured in 9 healthy volunteers (3 males and 6 females) for 2 hours after ingestion of a 2760 kJ (660 kcal) carbohydrate meal with and without prior completion of a resistance training regimen (2 sets of 10 repetitions of 10 different exercises). RESULTS: The meal caused an immediate and persistent thermic effect in both the control and the exercise trial. Mean oxygen consumption over baseline increased 20% in the control trial and 34% in the exercise trial. TEF calculated from VO2 and RER (total area under the response curve above baseline) was 73% greater in the exercise trial compared with the control trial (159 +/- 18 vs. 92 +/- 14 KJ/2 hrs, p < .02). CONCLUSION: These results indicate that TEF in response to a carbohydrate meal is enhanced following a single bout of resistance exercise.