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

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)

High Resolution Spectroscopy of CF3Br by Diode Laser in the Frequency Range 1070–1090 cm−1

The IR absorption spectra of gaseous CF3Br expanded in a molecular jet have been recorded with a linewidth of about 0.002 cm−1. The rotational K-structure of the ν1 fundamental has been resolved and the molecular constants ΔB and ΔA have been determined with an accuracy better than 5 x 10−6 cm−1. Spectral features belonging to the ν6- and ν3-hotbands have been identified. For CF3B79r (CF3B81r) improved values of the vibrational origins for the fundamental ν1 = 1084.768(2) cm−1 (1084.520(2) cm−1) and for its hotbands ν3+ν1←ν3 = 1081.709(80) cm−1 (1081.065(40) cm−1) and ν6+ν1←ν6 = 1083.533(4) cm-1 (1083.288(4) cm-1) have been determined

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

Drug Predictive Cues Activate Aversion-Sensitive Striatal Neurons That Encode Drug Seeking

Drug-associated cues have profound effects on an addict’s emotional state and drug-seeking behavior. Although this influence must involve the motivational neural system that initiates and encodes the drug-seeking act, surprisingly little is known about the nature of such physiological events and their motivational consequences. Three experiments investigated the effect of a cocaine-predictive stimulus on dopamine signaling, neuronal activity, and reinstatement of cocaine seeking. In all experiments, rats were divided into two groups (paired and unpaired), and trained to self-administer cocaine in the presence of a tone that signaled the immediate availability of the drug. For rats in the paired group, self-administration sessions were preceded by a taste cue that signaled delayed drug availability. Assessments of hedonic responses indicated that this delay cue became aversive during training. Both the self-administration behavior and the immediate cue were subsequently extinguished in the absence of cocaine. After extinction of self-administration behavior, the presentation of the aversive delay cue reinstated drug seeking. In vivo electrophysiology and voltammetry recordings in the nucleus accumbens measured the neural responses to both the delay and immediate drug cues after extinction. Interestingly, the presentation of the delay cue simultaneously decreased dopamine signaling and increased excitatory encoding of the immediate cue. Most importantly, the delay cue selectively enhanced the baseline activity of neurons that would later encode drug seeking. Together these observations reveal how cocaine cues can modulate not only affective state, but also the neurochemical and downstream neurophysiological environment of striatal circuits in a manner that promotes drug seeking

THE OPTIMAL PLYOMETRIC EXERCISE HORIZONTAL TO VERTICAL FORCE RATIO FOR SPRINTING

This study determined the horizontal to vertical force ratio (H:V) of two types of sprint starts and a variety of plyometric exercise, for the purpose of determining the exercises which are most biomechanically specific to sprinting. Subjects included 15 men. All subjects’ performed the sprinter start, the standing sprint start, the CMJ, 18 inch hurdle hop, bounding, power skipping, standing long jump, and multiple hops, starting on a force platform. A repeated measures ANOVA was used to determine differences in H:V between the sprinter start, the standing start, and the plyometric exercises. Results reveal significant main effects for sprint start H:V and standing start H:V, and the plyometric exercises H:V (p ≤ 0.001). Post-hoc analyses revealed that bounding and standing long jumps are the most biomechanically for training athletes for sprint starts

THE ROLE OF WALKING AND RUNNING VELOCITY ON OSTEOGENIC POTENTIAL

This study assessed the ground reaction forces (GRF) associated with walking and running at a variety of speeds and compared these kinetic values to the landing after a maximum counter-movement jump in order to understand the osteogenic potential for these activities. Twenty-four women walked and ran over a force platform at slow, medium, and fast walking and running speeds, which were assessed using Doppler radar. Landing vertical peak GRF and rate of force development (RFD) were analyzed for all movements using a force platform. In almost all cases, higher walking or running speeds resulted in statistically significant increases in GRF and RFD. Based on the findings of this study, moderate to fast sprints should be prescribed in the training programs for those who seek to maximize their bone health

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

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