Transcranial Direct Current Stimulation of Primary Motor Cortex over Multiple Days Improves Motor Learning of a Complex Overhand Throwing Task.

Transcranial direct current stimulation (tDCS) applied to the primary motor cortex (M1) improves motor learning in relatively simple motor tasks performed with the hand and arm. However, it is unknown if tDCS can improve motor learning in complex motor tasks involving whole-body coordination with significant endpoint accuracy requirements. The primary purpose was to determine the influence of tDCS on motor learning over multiple days in a complex over-hand throwing task. This study utilized a double-blind, randomized, SHAM-controlled, between-subjects experimental design. Forty-six young adults were allocated to either a tDCS group or a SHAM group and completed three experimental sessions on three consecutive days at the same time of day. Each experimental session was identical and consisted of overhand throwing trials to a target in a pre-test block, five practice blocks performed simultaneously with 20 min of tDCS, and a post-test block. Overhand throwing performance was quantified as the endpoint error. Transcranial magnetic stimulation was used to obtain motor-evoked potentials (MEPs) from the first dorsal interosseus muscle to quantify changes in M1 excitability due to tDCS. Endpoint error significantly decreased over the three days of practice in the tDCS group but not in the SHAM group. MEP amplitude significantly increased in the tDCS group, but the MEP increases were not associated with increases in motor learning. These findings indicate that tDCS applied over multiple days can improve motor learning in a complex motor tasks in healthy young adults.

An acute application of transcranial random noise stimulation does not enhance motor skill acquisition or retention in a golf putting task.

Transcranial random noise stimulation (tRNS) is a brain stimulation technique that has been shown to increase motor performance in simple motor tasks. The purpose was to determine the influence of tRNS on motor skill acquisition and retention in a complex golf putting task. Thirty-four young adults were randomly assigned to a tRNS group or a SHAM stimulation group. Each subject completed a practice session followed by a retention session. In the practice session, subjects performed golf putting trials in a baseline test block, four practice blocks, and a post test block. Twenty-four hours later subjects completed the retention test block. The golf putting task involved performing putts to a small target located 3 m away. tRNS or SHAM was applied during the practice blocks concurrently with the golf putting task. tRNS was applied over the first dorsal interosseus muscle representation area of the motor cortex for 20 min at a current strength of 2 mA. Endpoint error and endpoint variance were reduced across the both the practice blocks and the test blocks, but these reductions were not different between groups. These findings suggest that an acute application of tRNS failed to enhance skill acquisition or retention in a golf putting task.

Cerebellar Transcranial Direct Current Stimulation Enhances Motor Learning in a Complex Overhand Throwing Task.

Cerebellar transcranial direct current stimulation (c-tDCS) enhances motor adaptation, skill acquisition, and learning in relatively simple motor tasks. The purpose was to examine the influence of c-tDCS on motor learning in a complex overhand throwing task. Forty-two young adults were randomized to a c-tDCS group or a SHAM group and completed a practice session and a retention session. The practice session involved an overhand throwing task to a small target (6 m away) in a pre-test block, 6 practice blocks, a post-test block, and a retention-test block (24 h later). c-tDCS or SHAM was applied during overhand throwing in the practice blocks. The decline in endpoint error was greater for the tDCS group compared to SHAM at the end of practice (P = 0.019) and at retention (P = 0.003). The findings indicate that a single application of c-tDCS enhances motor learning in a complex overhand throwing task.

A novel mechanical mitral valve replacement using Sapien XT.

PATIENT PRESENTATION: We report the case of a 66 year old female who presented to our institution fourteen years after receiving a St. Jude Mechanical Mitral Valve Replacement. She presented in refractory NYHA class IV congestive heart failure with comorbidities of acute renal failure, liver failure, and mental status changes. She was found to have immobility of one of the mitral valve disks with resultant severe mitral stenosis with a mean pressure gradient of 12 mmHg. EVALUATION AND MANAGEMENT: The patient was found to have an STS predicted mortality of 39% with redo surgical MVR, and evaluation by the valve team led to a recommendation of a hybrid surgical and transcatheter procedure. The patient underwent femoral bypass and hypothermia with a sternotomy and left atrial approach. The mechanical discs were removed utilizing needle drivers without removal of the St. Jude ring. Subsequently, a 26 mm Edwards Sapien XT valve was deployed under direct and fluoroscopic visualization. The patient had an event free post-operative course, and one year following the procedure has had an outstanding clinical response with NYHA class II congestive heart failure. Her echocardiogram reveals normal valve function with a MPG of 4 mmHg without mitral regurgitation. CONCLUSION: Transatrial hybrid TMVR within the ring of a St. Jude mechanical mitral valve appears to be a feasible procedure which may be used in the future to decrease morbidity and mortality associated with high-risk redo-MVR in patients with mechanical mitral valve prostheses.

The application of the challenge point framework in medical education.

OBJECTIVES: The current paper describes a model of learning that has been used to produce efficient learning, thus yielding greater retention of information and superior performance under stress. In this paper, the model is applied to the learning of technical skills. STRUCTURE: After a brief review of the learning-performance paradox and other relevant literature from the field of movement science, the benefits of challenge and adversity for learning are discussed in the context of a framework for learning known as the challenge point framework (CPF). The framework is based on laboratory and field studies of methods that have been shown to consistently enhance learning, and is used to model and generate insight into the relationships between practice protocols and the learning that results from them. APPLICATION: The practical application of the CPF to simulation-based medical education and training is described. Firstly, a simple conceptual model that utilises three key elements to adjust the functional difficulty of the tasks to be learned is outlined. Secondly, a number of assessment strategies that may be necessary to ensure that the trainee remains in the optimal learning zone are proposed. Thirdly, a practical example is used to demonstrate how to utilise this conceptual model to design simulation environments suitable for teaching an endotracheal intubation task to beginners and more advanced trainees.

The magnitude of tissue cooling during cryotherapy with varied types of compression.

CONTEXT: Certified athletic trainers can choose different types of external compression (none, Flex-i-Wrap, and elastic wrap) when applying an ice bag to the body. However, which type facilitates the greatest magnitude of tissue cooling is unclear. OBJECTIVE: To compare the effects of 2 common types of external compression on the magnitude of surface and intramuscular cooling during an ice-bag treatment. DESIGN: Randomized controlled trial. SETTING: University research laboratory. PATIENTS OR OTHER PARTICIPANTS: Fourteen college students (10 women, 4 men; age = 22.4 +/- 1.8 years, height = 169.1 +/- 8.2 cm, mass = 73.3 +/- 18.5 kg, skinfold = 13.14 +/- 1.61 mm) with previous cryotherapy experience and a posterior lower leg skinfold equal to or less than 15 mm. INTERVENTION(S): On 3 different days separated by 24 to 48 hours, an ice bag was applied to the posterior lower leg surface of each participant for 30 minutes with no compression, with elastic wrap, or with Flex-i-Wrap. MAIN OUTCOME MEASURE(S): Posterior lower leg surface and intramuscular (2 cm) temperatures were recorded for 95 minutes. RESULTS: At 15 minutes, the elastic wrap produced greater surface temperature reduction than no compression (P = .03); this difference remained throughout the protocol (P range, .03 to .04). At 30 minutes, surface temperatures were 14.95 degrees C, 11.55 degrees C, and 9.49 degrees C when an ice bag was applied with no external compression, Flex-i-Wrap, and elastic wrap, respectively. Surface temperatures between Flex-i-Wrap and elastic wrap and between Flex-i-Wrap and no compression were never different. At 10 minutes, Flex-i-Wrap (P = .006) and elastic wrap (P < .001) produced greater intramuscular temperature reduction than no compression produced; these differences remained throughout the protocol. At 10 minutes, no compression, Flex-i-Wrap, and elastic wrap decreased intramuscular temperature by 1.34 degrees C, 2.46 degrees C, and 2.73 degrees C, respectively. At 25 minutes, elastic wrap (8.03 degrees C) produced greater temperature reduction than Flex-i-Wrap (6.65 degrees C) (P = .03) or no compression (4.63 degrees C) (P < .001 ). These differences remained throughout ice application and until 50 minutes after ice-bag removal. CONCLUSIONS: During an ice-bag application, external compression with elastic wrap was more effective than Flex-i-Wrap at reducing intramuscular tissue temperature. Elastic wraps should be used for acute injury care.

Acute effects of static and ballistic stretching on measures of strength and power.

Preactivity stretching is commonly performed by athletes as part of their warm-up routine. However, the most recent literature questions the effectiveness of preactivity stretching. One limitation of this research is that the stretching duration is not realistic for most athletes. Therefore, the purpose of this study was to determine the effects of a practical duration of acute static and ballistic stretching on vertical jump (VJ), lower-extremity power, and quadriceps and hamstring torque. Twenty-four subjects performed a 5-minute warm-up followed by each of the following three conditions on separate days with order counterbalanced: static stretching, ballistic stretching, or no-stretch control condition. Vertical jump was determined with the Vertec VJ system and was also calculated from the ground-reaction forces collected from a Kistler force plate, which also were used to calculate power. Torque output of the quadriceps and hamstrings was measured through knee extension and flexion on the Biodex System 3 Dynamometer at 60 degrees x s(-1). Data normalized for body weight were analyzed using five separate, 3 (stretch condition) x 2 (gender) analysis-of-variance procedures with repeated measures on the factor of stretch condition. The gender x stretch interaction was not significant for any of the four measures, suggesting that the stretching conditions did not affect men and women differently. The results of this study reveal that static and ballistic stretching did not affect VJ, or torque output for the quadriceps and hamstrings. Despite no adverse effect on VJ, stretching did cause a decrease in lower-extremity power, which was surprising. Because of the mixed results, strength coaches would be better served to use dynamic stretching before activity; this has been consistently supported by the literature.

Effect of hamstring-emphasized resistance training on hamstring:quadriceps strength ratios.

A decreased hamstring:quadriceps (H:Q) ratio may put the hamstrings and anterior cruciate ligament (ACL) at increased risk of injury. Therefore, the purpose of this study was to evaluate H:Q ratios of 12 female National Collegiate Athletic Association soccer players, and to test the effects of a 6-week strength training program on these ratios. Each subject completed 2 practice sessions before a pretest. Subjects then completed 6 weeks of strength training that included the addition of 2 hamstring specific exercises, followed by a posttest. Peak torque during concentric and eccentric actions for both hamstrings and quadriceps was measured with an isokinetic dynamometer. Each muscle action was tested at 3 angular velocities in the following order: concentric 240, 180, and 60 degrees x s(-1) and eccentric 60, 180, and 240 degrees x s(-1). The H:Q strength ratio was evaluated using concentric muscle actions (concentric hamstrings:concentric quadriceps). This method is commonly used and is thus called the conventional ratio. Because concentric actions do not occur simultaneously in opposing muscles, a more functional assessment compares eccentric hamstring actions to concentric quadriceps actions. This functional ratio was also analyzed. Mean conventional and functional H:Q ratio data were analyzed using separate analysis of variance procedures with repeated measures on all factors (2 [Test] x 2 [Leg] x 3 [Angular Velocity]). The results revealed a significant main effect for factor (F test) with the functional ratio (p < 0.05) but not for the conventional ratio. The mean functional ratio increased from 0.96 +/- 0.09 in pretest to 1.08 +/- 0.11 in posttest. These results suggest that 6 weeks of strength training that emphasizes hamstrings is sufficient to significantly increase the functional ratio. The functional ratio after training exceeded 1.0, which is specifically recommended for prevention of ACL injuries.

The acute effects of mechanical vibration on power output in the bench press.

This study was designed to investigate the effect of mechanical vibration on acute power output in the bench press exercise. Ten male subjects who were experienced in resistance training participated in this study. Each subject performed 3 sets of 3 repetitions in the bench press exercise using a load equal to 70% of 1 repetition maximum in each of 2 sessions separated by 3 days. One session served as the experimental (vibration) condition, whereas the other session served as the control (no vibration) condition. The intervention (vibration or control) was applied between sets 2 and 3. The vibration was applied by a vibrating barbell apparatus held by the subjects while lying supine on a bench. The only difference between the 2 conditions was the vibration of the barbell apparatus during the vibration condition. Peak and average power were calculated during each bench press set to determine whether power output differed following vibration compared to control. Average power was significantly higher for the vibration condition compared to the control (525 +/- 74 vs. 499 +/- 71 W; p = 0.01). There was also a trend toward an increase in peak power in the vibration condition (846 +/- 168 by vs. 799 +/- 149 W; p = 0.06). In general, peak and average power output were higher following the vibration intervention compared to control. However, the sets prior to vibration application during the vibration condition also demonstrated higher power outputs compared with the control condition, which contributed to the main effect for the vibration condition. These results suggest that factors other than the vibration intervention influenced task performance during the vibration condition. We suggest that psychological factors related to the novelty of the vibration intervention were involved. These factors may partially explain the conflicting results of previous investigations that examined vibration as an exercise intervention.

Effects of information processing load in abstinent and nonabstinent smokers' psychomotor task performance.

Recent evidence has indicated that nicotine, the active agent in tobacco, may affect mental abilities of smokers. To better understand the effects of nicotine on central processing, we used a basic chronometric approach to studying information processing. This chronometric approach allowed for the independent examination of nicotine's effects on two theoretically nonoverlapping information-processing stages, stimulus identification and response programming. Two stimulus intensity and four distance traversed conditions were used to affect the stimulus identification and response programming stages, respectively. The 11 subjects completed two experimental sessions (nicotinized and denicotinized), which were conducted 1 week apart. Each experimental session comprised two tests. The first test consisted of abstinent baseline measures, and the second test was administered after subjects smoked an investigator-supplied nicotinized or denicotinized cigarette. Data analysis revealed that the higher intensity stimulus elicited faster reaction times, as did the shorter movement distances, thus confirming successful manipulation of both the stimulus identification and response programming stages of the information-processing model. Furthermore, the significant improvement in reaction-time performance over baseline abstinent levels was consistent despite the manipulations made within the stimulus identification stage of processing, demonstrating that no interaction existed between stimulus intensity and the administration of nicotine. Interestingly, these data provide initial evidence that although nicotine may not affect the programming of very simple movements, it has a more pronounced effect on more complex movements. Although distance traversed had a reliable effect on movement time, nicotine had no observable effect.

Reciprocal influences of attentional focus on postural and suprapostural task performance.

The authors examined the influence that attentional focus on either a postural or a suprapostural task had on the performance of each task. Participants (N = 32) stood on an inflated rubber disk and held a pole horizontally. All participants performed under 4 attentional focus conditions: external (disk) or internal (feet) focus on the postural task, and external (pole) or internal (hands) focus on the suprapostural task. Compared with internal focuses, external focuses on either task resulted in similar and reduced postural sway. Response frequency on each task increased when participants focused on the respective task. Finally, an external focus on either task produced higher frequencies of responding on the suprapostural task. The authors conclude that suprapostural task goals have a stronger influence on postural control than vice versa, reflecting the propensity of the motor system to optimize control processes on the basis of the desired movement effect.

Challenge point: a framework for conceptualizing the effects of various practice conditions in motor learning.

The authors describe the effects of practice conditions in motor learning (e.g., contextual interference, knowledge of results) within the constraints of 2 experimental variables: skill level and task difficulty. They use a research framework to conceptualize the interaction of those variables on the basis of concepts from information theory and information processing. The fundamental idea is that motor tasks represent different challenges for performers of different abilities. The authors propose that learning is related to the information arising from performance, which should be optimized along functions relating the difficulty of the task to the skill level of the performer. Specific testable hypotheses arising from the framework are also described.

The relationship between knowledge of results and motor learning in Parkinsonian patients.

A simple timing movement was used to investigate augmented feedback on motor learning in Parkinson's disease (PD) patients and controls. During acquisition, participants received knowledge of results (KR) about their errors after every trial (100%) or every fifth trial (20%). Participants then performed a retention test without KR. Controls performed better on the retention test after having had 20% KR during acquisition. PDs showed superior retention with 100% KR. This suggests that the PD patients are more reliant on KR for learning motor skills; a difference that may be attributable to reduced proprioceptive acuity in PD patients.