Aging and the Restructuring of Precued Movements

A precue paradigm was used to examine the time it takes to restructure a planned motor response. Two groups of subjects, a young group, and an elderly group, performed an aiming task in which 75% of the trials involved no change of movement parameters. On remaining trials, subjects had to change one or more of the movement parameters. Elderly subjects had slower reaction times (RTs), movement times, and made more errors in both conditions. Elderly subjects had proportionally longer RTs overall, independent of restructuring a movement plan. Preparation of arm and direction also exhibited a proportional increase in RT. However, differential aging effects were found for preparation of extent. Elderly subjects were slower preparing short movements compared with long movements, whereas young subjects showed the opposite trend. These results suggest that with advancing age, operations concerned with movement-plan restructuring for arm and direction undergo a change in processing rate, whereas operations for extent undergo more extensive alteration

Age Differences in the Maintenance and Restructuring of Movement Preparation

In 2 experiments, 56 elderly (aged 65–78 yrs) and young Ss (aged 20–28 yrs) performed simple reaction time (RT), choice RT, and movement plan restructuring tasks, using a stimulus precuing paradigm. In Exp 1, the precue display (200 ms) and preparation interval (250, 500, 750, or 1,000 ms) were experimentally determined. In Exp 2, the precue display interval was S determined. For the restructuring task, the precue specified the response on 75% of the trials, enabling movement plan preparation with respect to movement parameters of arm and direction. On remaining trials, the precue incorrectly specified the response, requiring movement plan restructuring. Elderly, but not young, Ss restructured a movement plan for direction more quickly than for arm or for both parameters. These findings indicate that elderly individuals have poorer movement plan maintenance for direction than for arm and thus exhibit functional change in movement preparation processes relative to young individuals

Age Differences in Bimanual Coordination

A bimanual coordination experiment was conducted in which two groups of 10 male and female participants, elderly (67 to 75 years of age) and young (21 to 25 years of age), produced unimanual, bimanual symmetrical (equal extent amplitude), and bimanual asymmetrical (unequal extent amplitude) movements. In addition to an overall increase in performance latency, the elderly group exhibited a linear increase in response initiation (RT) with increases in task complexity similar to that of the young group. However, the elderly participants showed a proportional increase over the young participants in response execution latency (MT). Further, the elderly group had a slower RT for short movements than long movements, an effect not found in the young group. Compared with the young participants, the elderly participants showed greater asynchrony in response initiation of bimanual movements; increased inability to subsequently compensate during response execution also resulted in a greater asynchrony in response termination. These results suggest specific aging deficits in bimanual coordination processes

Effects of Age on Motor Preparation and Restructuring

Age-related decrements in motor plan restructuring were investigated. In this experiment, older and younger adults performed a discrete aiming task that involved responses that were precued and responses that were modified at the time of an imperative signal. On 75% of the trials, the precue specified the response-stimulus (valid trials) with respect to the movement parameters of the arm (left or right) and direction (toward or away). On the remaining 25% of the trials, the response-stimulus was different from the precue (invalid trials) in that the subject was required to modify a planned movement by changing the arm to be used and/or the direction of movement. The older subjects were slower than the younger in both the valid and invalid trials. Across preparatory intervals (PI) of 500, 1,000, 1,500, and 2,000 msec, older, but not younger subjects exhibited less reaction time cost for restructuring the motor plan for the direction-change condition than for the other parameter change conditions. Since there was little apparent cost of restructuring, these findings suggest that older adults did not prepare the direction of movement, and thus found it temporally more efficient to alter direction than arm or arm and direction combined

Effect of Using a Counter-balanced Smith Machine on Performance Measurements for Concentric-Only Bench Press Throws

Bench press throws using a Smith machine are often used for assessment and training of upper body power. Concentric only bench press throws (CON-BT) provide important information on an individual’s ability to produce force from a static start. Smith machines often utilize a counter-balance weight system to reduce the net load on the barbell; however, it is not known how counter-balance weight affects measurements of performance during a CON-BT. PURPOSE: To examine the effect of a counter-balance weight on CON-BT performance measurements. METHODS: 24 men (age: 23 ± 3 years, height: 179 ± 6 cm, mass: 91 ± 17 kg, bench press 1-repetition maximum [1RM]: 107 ± 18 kg) performed 2 sets of 2 repetitions of CON-BT at 30% of their 1RM using a no counter-balanced (NCB) and a counter-balanced (CB) Smith machine. Total duration, peak power, peak force, and peak velocity were measured using a linear accelerometer attached to the barbell; peak ground reaction force (GRF) was measured using a force plate. For each condition, data from the repetition with the highest peak power was used for further analyses. Peak EMG was measured for the right pectoral, deltoid and triceps muscles and normalized using peak EMG in the 1RM. RESULTS: Measurements for peak barbell power (NCB: 1169 ± 260 W, CB: 938 ± 262 W) and force (NCB: 695 ± 129 N, CB: 577 ± 134 N) were significantly greater (p\u3c0.05) for NCB compared to CB. The total duration of CON-BT was shorter for NCB (0.62 ± 0.41 s) compared to CB (0.78 ± 0.50 s). The peak GRF showed a trend (p\u3c0.10) for being lower for NCB (884 ± 213 N] compared to CB [912 ± 190 N). Peak EMG and peak velocity were unaffected by the use of counter-balance weight. CONCLUSION: The use of a CB Smith machine reduced barbell performance measurements (peak power and peak force) but increased the peak GRF during a CON-BT. A counter-balance weight becomes ineffective and the net external load increases during the CON-BT when the barbell accelerates faster than the gravitational constant pulls on the counter weight, thus explaining the lower performance measurements found for CB

Use of Counter-balanced Smith Machine Affects Performance Measurements for Rebound Bench Press Throws

Rebound bench presses throws (RBT), often performed on a Smith machine, are used for assessment and training of upper body power. During a RBT, the stretch-shortening cycle potentiates performance in the concentric movement. Smith machines frequently utilize a counter-balance weight to reduce the net load on the barbell; however, the use of counter-balance weight affects measures of performance for RBT. PURPOSE: To evaluate how the use of a counter-balanced Smith machine affects performance measures for RBT. METHODS: Performance measures for the no counter-balanced (NCB) and counter-balanced (CB) RBT were assessed for 24 men (age: 23 ± 3 years, height: 179 ± 6 cm, mass: 91 ± 17 kg, bench press 1-repetition maximum [1RM]: 107 ± 18 kg). Each participant performed 2 sets of 2 repetitions of RBT for each condition at 30 % of their 1RM. Peak power, peak force, peak concentric and eccentric velocities, and duration of eccentric and concentric phases were measured using a linear accelerometer attached to the barbell; peak ground reaction force (GRF) was measured using a force plate. For each condition, data from the repetition with the highest peak power was used in further analyses. Peak EMG was measured for the right pectoral, deltoid and triceps muscles and normalized using peak EMG in the 1RM. RESULTS: Peak barbell measurements for power (NCB: 1220 ± 269 W, CB: 1069 ± 255 W), force (NCB: 906 ± 252 N, CB: 713 ± 143 N), and concentric (NCB: 2.54 ± 0.27 m•s-1, CB: 2.24 ± 0.32 m•s-1) and eccentric (NCB: -1.19 ± 0.46 m•s-1, CB: -0.95 ± 0.29 m•s-1) velocities were significantly (p\u3c0.05) higher for NCB compared to CB. The durations for the eccentric (NCB: 0.53 ± 0.16 s, CB: 0.64 ± 0.12 s) and concentric phases (NCB: 0.58 ± 0.58 s, CB: 0.77 ± 0.82 s), and peak pectoral EMG (NCB: 91 ± 21 % of 1RM, CB: 101 ± 24 % of 1RM) were lower for NCB compared to CB. Peak EMG for deltoid and triceps and peak GRF were unaffected by the use of counter-balance weights. CONCLUSION: The use of CB equipment resulted in reduced performance measurements (peak power, peak force, and peak eccentric and concentric velocities) for the RBT compared to NCB equipment. The lower peak eccentric stretch velocity likely resulted in a less effective stretch-shortening cycle for CB compared to NCB and thus helps explain the lower performance measurements found for CB

APPROVED: OXYGEN UPTAKE KINETICS IN SEVERE INTENSITY EXERCISE

titles. The purpose of this study was to describe mathematically the oxygen uptake kinetics during cycle ergometry, and to examine the effect of intensity on the kinetic responses within the severe domain. Sixteen volunteers performed a series of exercise tests at a range of intensities selected to elicit fatigue in ~3 to 10 min. A simple monoexponential model effectively described the response across all intensities. There was a positive correlation between the response time and the time to fatigue, demonstrating that the maximal oxygen uptake was achieved faster at higher intensities within the severe domain. Models incorporating two components effectively described the responses only in tests lasting 8 min or more. It was concluded that there is a second, slow component in the oxygen uptake response only at the lower intensities within the severe domain

First-in-class thyrotropin-releasing hormone (TRH)-based compound binds to a pharmacologically distinct TRH receptor subtype in human brain and is effective in neurodegenerative models

JAK4D, a first-in-class thyrotropin-releasing hormone (TRH)-based compound, is a prospective therapeutic candidate offering a multifaceted approach to treating neurodegeneration and other CNS conditions. The purpose of these studies was to determine the ability of JAK4D to bind to TRH receptors in human brain and to evaluate its neuropharmacological effects in neurodegenerative animal models. Additionally, JAK4D brain permeation was examined in mouse, and initial toxicology was assessed in vivo and in vitro. We report that JAK4D bound selectively with nanomolar affinity to native TRH receptors in human hippocampal tissue and showed for the first time that these receptors are pharmacologically distinct from TRH receptors in human pituitary, thus revealing a new TRH receptor subtype which represents a promising neurotherapeutic target in human brain. Systemic administration of JAK4D elicited statistically significant and clinically-relevant neuroprotective effects in three established neurodegenerative animal models: JAK4D reduced cognitive deficits when administered post-insult in a kainate (KA)-induced rat model of neurodegeneration; it protected against free radical release and neuronal damage evoked by intrastriatal microdialysis of KA in rat; and it reduced motor decline, weight loss, and lumbar spinal cord neuronal loss in G93A-SOD1 transgenic Amyotrophic Lateral Sclerosis mice. Ability to cross the blood–brain barrier and a clean initial toxicology profile were also shown. In light of these findings, JAK4D is an important tool for investigating the hitherto-unidentified central TRH receptor subtype reported herein and an attractive therapeutic candidate for neurodegenerative disorders. •First-in-class TRH-based compound JAK4D detects new receptor subtype in human brain.•JAK4D elicits statistically significant effects in neurodegenerative animal models.•JAK4D crosses the blood–brain barrier and has a clean initial toxicology profile.•JAK4D is a tool to study central pharmacologically-distinct TRH receptor subtype.•JAK4D is an attractive therapeutic candidate for neurodegenerative diseases