Electromyographical Analysis of Lower Extremity Muscle Activation During Variations of the Loaded Step-Up Exercise

The loaded step-up exercise allows strength and conditioning practitioners to incorporate a unilateral resistance for athletes while performing extension at the hip, knee, and plantar flexion at the ankle. This study evaluated the activation of the biceps femoris (BF), gluteus maximus (GMx), gluteus medius (GMe), rectus femoris, semitendinosus (ST), vastus lateralis, and vastus medialis during 4 variations of the step-up exercise to assess the specific muscle training stimulus of each exercise variation. The exercises included the step-up, crossover step-up, diagonal step-up, and lateral step-up. Fifteen women who regularly engaged in lower body resistance training performed the 4 exercises with 6 repetition maximum loads on a 45.72-cm (18-in.) plyometric box. Data were collected with a telemetered electromyography (EMG) system, and root mean square values were calculated for EMG data for eccentric and concentric phases. Results of a repeated-measures analysis of variance revealed a variety of differences in muscle activation between the exercises (

SP Equity Case Study

This case involves an entrepreneur who raises a search fund to pursue the acquisition of a software firm. It is intended for the deal structure segment of an entrepreneurial finance course, as it illustrates stages of financing, returns to investors, layering of debt and equity, and valuation, as well as the search/acquisition process. The case is positioned with the entrepreneur having found an “ideal” company to acquire; however, three days prior to closing, he has uncovered some information the seller had been trying to hide. He now needs to decide whether he should continue with the deal

Cash Conversion Cycle Management in Small Firms Relationships with Liquidity, Invested Capital, and Firm Performance

This study investigated the relationship between cash conversion cycle and levels of liquidity, invested capital, and performance in small firms over time. In a sample of 879 small U.S. manufacturing firms and 833 small U.S. retail firms, cash conversion cycle was found to be significantly related to all three of these aspects. Firms with more efficient cash conversion cycles were more liquid, required less debt and equity financing, and had higher returns. The results also indicate that small firm owners/managers may be reactive in managing cash conversion cycle. The study highlights the importance of cash conversion cycle as a proactive management tool for small firm owners

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 EFFECT OF PLYOMETRIC TRAINING VOLUME ON JUMPING PERFORMANCE

This study compared high and low daily volume periodized plyometric training programs and their effect on countermovement jump (CMJ) performance over a 2 week testing time course after training. Thirty-five male subjects participated. Subjects CMJ was tested on a force platform prior to and at 2, 6, 10 and 14 days post training. Peak vertical ground reaction force (GRF), reactive strength index-modified (RSI mod), jump height (JH), and body mass were assessed. No differences were found between the high and low volume training groups. Subjects GRF, RSI mod, and JH performance was improved in a range of 6 to 14 days post- training. Low and high volume periodized plyometric training programs produced equal results. Six to 14 days of recovery post training was required to accrue the training benefit

Aversive Stimuli Drive Drug Seeking in a State of Low Dopamine Tone

Background Stressors negatively impact emotional state and drive drug seeking, in part, by modulating the activity of the mesolimbic dopamine system. Unfortunately, the rapid regulation of dopamine signaling by the aversive stimuli that cause drug seeking is not well characterized. In a series of experiments, we scrutinized the subsecond regulation of dopamine signaling by the aversive stimulus, quinine, and tested its ability to cause cocaine seeking. Additionally, we examined the midbrain regulation of both dopamine signaling and cocaine seeking by the stress-sensitive peptide, corticotropin releasing factor (CRF). Methods Combining fast-scan cyclic voltammetry with behavioral pharmacology, we examined the effect of intraoral quinine administration on nucleus accumbens dopamine signaling and hedonic expression in 21 male Sprague-Dawley rats. We tested the role of CRF in modulating aversion-induced changes in dopamine concentration and cocaine seeking by bilaterally infusing the CRF antagonist, CP-376395, into the ventral tegmental area (VTA). Results We found that quinine rapidly reduced dopamine signaling on two distinct time scales. We determined that CRF acted in the VTA to mediate this reduction on only one of these time scales. Further, we found that the reduction of dopamine tone and quinine-induced cocaine seeking were eliminated by blocking the actions of CRF in the VTA during the experience of the aversive stimulus. Conclusions These data demonstrate that stress-induced drug seeking can occur in a terminal environment of low dopamine tone that is dependent on a CRF-induced decrease in midbrain dopamine activity

GROUND REACTION FORCES OF VARIATIONS OF PLYOMETRIC EXERCISES ON HARD SURFACES, PADDED SURFACES AND IN WATER

Subjects performed drop jumps from 46 cm, a single leg jump, counter movement jump, and squat jump on a hard surface, wrestling mat and in water. Ground reaction force data obtained via a force platform were used to determine the time to takeoff, takeoff peak ground reaction force, power, jump height, and landing peak ground reaction force. A one way repeated measures ANOVA demonstrated differences between plyometic exercises assessed for all of the variables assessed (P ≤ 0.05), with post hoc analysis demonstrating the specific differences. Results indicate that the hard surface and mat conditions were similar for almost all of the plyometric exercises assessed for most outcome variables whereas the plyometric exercises performed in water were different than those performed on the hard surface or mat in most cases

BIOMECHANICAL ANALYSIS OF THE FASTBALL THROWN FROM THE WIND-UP AND THE STRETCH

This study assessed the biomechanics associated with the fastball thrown in two conditions. Fifteen men pitched from the wind-up and stretch beginning and landing on force platforms. Doppler radar was used to assess ball velocity. A paired samples t-test was used to determine differences in ball velocity, propulsive and landing phase kinetics, as well as time, distance, and subject velocity from the propulsive to landing phase. The stretch produced 5.55% more horizontal ground reaction force, a higher horizontal to vertical force ratio, 35.05% greater vertical rate of force development (RFD) in the propulsive phase, and 8.85% higher horizontal and 24.65% vertical RFD upon landing (p ≤ 0.05). The wind-up produced 39.49% greater horizontal RFD in the propulsive phase (p ≤ 0.05). These variations of the fastball use different mechanisms to achieve similar (p = 0.77) ball velocities

KINETIC ANALYSIS OF HORIZONTAL PLYOMETRIC EXERCISE INTENSITY

This study assessed the multi-planar kinetic characteristics of a variety of plyometric exercises that have a horizontal component. Ten men and ten women performed a variety of plyometric exercises including the double leg hop, standing long jump, single leg standing long jump, bounding, skipping, power skipping, cone hops and the hurdle hop (45.72 cm). Subjects also performed the countermovement jump. All plyometric exercises were performed on a force platform. Landing peak ground reaction forces (GRF) and rate of force development (RFD) were analyzed for three planes of movement. A number of differences were found between plyometric exercises. Quantification of plyometric exercises based on the analysis of GRF and RFD assists practitioners in the design of programs based on known intensity of these exercise

THE EFFECT OF REACHING TO AN OVERHEAD GOAL WHILE PERFORMING THE COUNTERMOVEMENT JUMP

One potentially simple way to maximize jumping effort and thus intensity is to have athletes jump to and attempt to touch challenging overhead goals during training. The purpose of this study was to compare the effect of jumping with and without the use of an overhead goal. Subjects performed 3 countermovement jumps in conditions with and without an overhead goal. Jump performance was evaluated using a force platform to determine peak ground reaction force, time to takeoff, power, and jump height. Data were evaluated with a two way ANOVA with results demonstrating no significant (p > 0.05) difference between goal conditions for any of the variables assessed and no interaction between goal condition and gender (p > 0.05)