Exploring small energy scales with x-ray absorption and dichroism

Soft x-ray linear and circular dichroism (XLD, XMCD) experiments at the Ce M$_{4,5}$ edges are being used to determine the energy scales characterizing the Ce $4f$ degrees of freedom in the ultrathin ordered surface intermetallic CeAg$_x$/Ag(111). We find that all relevant interactions, i. e. Kondo scattering, crystal field splitting and magnetic exchange coupling occur on small scales. Our study demonstrates the usefulness of combining x-ray absorption experiments probing linear and circular dichroism owing to their strong sensitivity for anisotropies in both charge distribution and paramagnetic response, respectively.Comment: 5 pages, 4 figure

Is There a Sex Difference in the Age of Elite Marathon Runners?

Purpose: The purposes of this study were to determine i) if there is a sex difference in the age of the elite marathon runners and ii) if the sex difference in performance altered across the years that women have participated in the marathon. Methods: Age at time of competition and running times of the first five placed male and female runners who competed in the seven marathons of the World Marathon Majors Series were analyzed. Data from as many years as was available online were retrieved so that 410 men and 410 women were included in the analysis. The marathons and years included the Berlin (1999–2009), Boston (2000–2009), Chicago (1997–2009), London (2001–2009), New York City (1990–2009), International Athletic Association Federation World Championship (1983, 1987, and every 2 yr from 1991), and Olympic (every 4 yr since 1984) marathons. Results: Women were older than men (mean ± SD = 29.8 ± 4.2 vs 28.9 ± 3.8 yr), but for only two of the seven marathons, the Chicago and the London marathons (P \u3c 0.05): the sex difference in age was not consistent across the years. There was no sex difference in age for the Berlin, Boston, New York City, World Championship, and Olympic marathons. Men were faster than women (11.6% ± 1.8%). The sex difference in running velocity varied across marathons (least for the World Championships, 10.2%) and also across years, but not systematically. This sex difference in running velocity increased from first to fifth place across all marathons. Conclusions: These data indicate that men and women physiologically peak at a similar age in marathon running performance. The sex difference in performance of elite marathon runners varied across years but has not systemically decreased or varied since the 1980s

THE ACUTE TIME COURSE OF CONCURRENT ACTIVATION POTENTIATION

This study evaluated the acute time course of the ergogenic effect of concurrent activation potentiation (CAP). Forty-two men and women, including CAP non-responders and responders, performed a 5 second isometric knee extension on a dynamometer with the use of remote voluntary contractions (RVC). Mean torque was assessed in seven 500 millisecond (ms) time periods. A two-way repeated measures ANOVA revealed significant main effects for time period (p ≤ 0.001), but no significant interaction between time period and CAP non-responders and responders (p > 0.05). The ergogenic effects of CAP are accrued during the first 1000ms. Concurrent activation potentiation responders produce greater initial force than the CAP non-responders, without a concomitant acceleration in force decay throughout the time course

ECCENTRIC MUSCLE ACTIONS PRODUCE 36% TO 154% LESS ACTIVATION THAN CONCENTRIC MUSCLE ACTIONS

This study evaluated the differences in eccentric and concentric phase muscle activation of variety of muscles during lower body resistance training exercises. Surface electromyography data (EMG) from 12 subjects was analyzed for the eccentric and concentric phases of the squat, deadlift, step-up, and lunge. Data from the test exercises were averaged for the eccentric and concentric phase for each muscle group to produce a comprehensive measure of activation differences between the eccentric and concentric phases. A paired samples t-test revealed differences between eccentric and concentric phase activation for all muscles assessed (p ≤ 0.05). Results demonstrated that during lower body multi-joint exercises the eccentric phase produced 36% to 154% less muscle activation that the concentric phase

THE EFFECT OF REMOTE VOLUNTARY CONTRACTIONS ON STRENGTH AND POWER TASKS OF WOMEN

This study evaluated the effect of remote voluntary contractions (RVC’s) on the performance of closed kinetic chain exercises. Subjects performed the squat and jump squat in a RVC condition and a condition without RVC’s (NO-RVC’s). Peak ground reaction force (GRF), rate of force development during the first 100 ms (RFD 100), RFD to peak GRF (RFD-P), and jump squat height (JH) were assessed with a force platform. Data were analyzed with a one way ANOVA. Results revealed there were no significant differences between RVC and NO-RVC conditions for peak GRF for either the squat (p = 0.11) or jump squat (p = 0.47), RFD 100 for either the squat (p = 0.25) or jump squat (p = 0.23), RFD-P for either the squat (p = 0.88) or jump squat (p = 0.38), or for JH for the jump squat (p = 0.68)

GENDER DIFFERENCES IN KNEE EXTENSOR AND FLEXOR PERFORMANCE

The purpose of this study was to evaluate gender differences in peak torque (PT), rate of torque development (RTD), power, and work during isometric (ISOM) knee extension and isokinetic (ISOK) knee extension and flexion. Forty-four university women and men volunteered to perform the test exercises on a computerized dynamometer. Data were reduced with manufacturer software and were analyzed with an independent-samples t-test in order to determine gender differences. Results revealed significant differences (P ≤ 0.001) for ISOM PT and ISOK PT, RTD, power, and work. Gender differences in knee extensor and flexor performance are present, with women demonstrating a range of 68.9 to 76.9% of their male counterparts. Conversely, the rate of force production is not gender specific during ISOM knee extension

GROUND REACTION FORCE AND RATE OF FORCE DEVELOPMENT DURING LOWER BODY RESISTANCE TRAINING EXERCISES

This study quantified the differences in the kinetic profiles of the back squat, deadlift, step-up, and lunge. Eleven subjects performed 2 repetitions of their 5 repetition maximum in each of the 4 exercises. Kinetic data were collected using a force platform. The exercises were compared based on their peak vertical ground reaction force (GRFP) and rate of force development (RFD) in both the eccentric and concentric phase. A repeated measures ANOVA indicated differences (p ≤ 0.001) in GRFP attained for the different exercises in both the eccentric and concentric phase. No significant differences (p ≥ 0.05) were found for RFD for any of the exercises in either the eccentric or concentric phase. Results can guide the development of training programs that are specific to strength, explosiveness, or osteogenesis

THE TIME COURSE OF RECOVERY FROM A MESOCYCLE OF PERIODIZED PLYOMETRIC TRAINING

This study evaluated the effectiveness of a mesocycle of periodized plyometric training and the influence of the duration of the post training recovery period. All subjects’ countermovement jump height, peak power, and body mass were assessed with a force platform prior to and 2, 4, 6, 8, and 10 days after training. Jump height was 25.0% greater (p ≤ 0.05) after training with no difference (p > 0.05) between the recovery periods of 2, 4, 6, 8, or 10 days. Peak power was 11.6 to 14.3 % greater (p ≤ 0.001) after training for the training group with no difference (p > 0.05) between recovery periods of 2, 4, 6, 8, or 10 days. Periodized plyometric programs with decreasing volume and increasing intensity improve jump performance without a need for a post training recovery period

KINETIC ANALYSIS OF LOWER BODY RESISTANCE TRAINING EXERCISES

This study evaluated and compared the peak vertical ground reaction force (GRF) and rate of force development (RFD) for the eccentric and concentric phases of 4 lower body resistance training exercises, including the back squat, deadlift, step-up, and forward lunge. Sixteen women performed 2 repetitions of each of the 4 exercises at a 6 repetition maximum load. Kinetic data were acquired using a force platform. A repeated measures ANOVA was used to evaluate the differences in GRF between the exercises. Results revealed significant main effects for GRF both the eccentric (p ≤ 0.001) and concentric (p ≤ 0.001) phases. Significant main effects were also found for RFD for the eccentric (p ≤ 0.001) and concentric phases (p ≤ 0.001). Force and power requirements and osteogenic potential differ between these resistance training exercises

ANTAGONIST CONDITIONING CONTRACTIONS IMPAIR AGONIST FUNCTIONING

This study assessed the effect of antagonist conditioning contractions (ACC) on the subsequent force and electromyography of an agonist. Twelve subjects performed isokinetic elbow flexion on a dynamometer in 4 test conditions including a baseline condition without, and 1, 3 and 6 seconds after, isometric triceps extension. Average peak torque (T), peak torque/body weight (T:BW), average power (P), and rate of torque development (RTD) were assessed. Electromyographic data were obtained from elbow extensors and flexors. A repeated measures ANOVA with post hoc analysis demonstrated that T, T:BW, P, and RTD were higher in the baseline, compared to the post ACC conditions (P ≤ 0.05), and appears to be due to higher brachioradialis activation in the baseline condition in compared to some post ACC conditions (P ≤ 0.05)