Additional therapy promotes a continued pattern of improvement in upper-limb function and independence post-stroke.

BACKGROUND: Upper-limb motor impairment after stroke is common and disabling. Growing evidence suggests that rehabilitation is effective in the chronic period. However, there is limited knowledge on the effects of ongoing targeted rehabilitation programs on patient outcomes. OBJECTIVES: This study investigated the effects of delivering two programs of dose-matched evidence-based upper-limb rehabilitation to community-dwelling post-acute stroke patients with low, moderate and high motor-function. MATERIALS AND METHODS: 12 patients (2 female) aged 50.5±18.2 years and 13.8±10.8 months post-stroke completed 2-weeks of modified-Constraint-Induced Movement Therapy followed by 2-weeks of Wii-based Movement Therapy after a mean interval of 9.6±1.1 months (range 6-19months). Function was assessed at 6 time points (i.e. before and after each therapy program and 6-month follow-up after each program). Primary outcome measures were the Wolf Motor Function Test timed-tasks (WMFT-tt), upper-limb Fugl-Meyer Assessment (F-M) and the Motor Activity Log Quality of Movement Scale (MALQOM). Improvement and maintenance was analyzed using Paired T-Tests and Wilcoxon Signed Rank Tests. RESULTS: Upper-limb function significantly improved on all primary outcome measures with the first therapy program (WMFT-tt p=0.008, F-M p=0.007 and MALQOM p<0.0001). All scores continued to improve with the second therapy program with significant improvements in the F-M (p=0.048) and the MALQOM (p=0.001). CONCLUSIONS: All patients showed a pattern of continued improvement in upper-limb motor-function and independence in activities of daily living. These improvements demonstrate the benefit of ongoing post-stroke rehabilitation for community-dwelling stroke survivors for individuals of varying baseline functional status.

Changes in measures of motor axon excitability with age.

OBJECTIVE: Threshold tracking is a novel technique that permits examination of the excitability of human axons in vivo. Protocols have been validated for sensory and motor axons, but there are limited data on the changes in the excitability of motor axons with age. This study aimed to determine such changes from the third to the eighth decades. METHODS: Sixty healthy subjects aged 22-79, 10 per decade, were studied using the TRONDXM4 protocol of the QTRAC threshold-tracking program to assess motor axon function. The median nerve was stimulated at the wrist and the compound muscle action potential was recorded from the thenar muscles. RESULTS: There was an increase in threshold in elderly subjects, associated with a decrease in slope of the stimulus-response curves. Strength-duration time constant and threshold electrotonus to depolarising and hyperpolarising currents of up to 40% did not change significantly with aging. The current-threshold relationship was similar across all decades for subthreshold depolarising currents, but the slope of the current-threshold relationship was significantly steeper the older the subjects for hyperpolarising currents, particularly those greater than 40% of threshold. There was also a significant decrease in supernormality in the recovery cycle with increasing age. CONCLUSIONS: The threshold of axons increases with age and the extent of supernormality decreases. There may also be greater inward rectification in motor axons, perhaps due to greater activity of I(H), the hyperpolarisation-activated conductance, though this is only significant with hyperpolarising currents greater than 40% of the threshold current. SIGNIFICANCE: Many indices of axonal excitability, such as strength-duration time constant, the relative refractory period, late subnormality, threshold electrotonus and the depolarising side of the current-threshold relationship, do not change significantly with age. For other indices, age-related changes may be due to a combination of non-neural factors that alter current access to the node of Ranvier, changes in the axon and its myelination and, possibly, changes in channel activity and/or changes in extracellular [K(+)](o).

Recruitment of single human low-threshold motor units with increasing loads at different muscle lengths.

We investigated the recruitment behaviour of low threshold motor units in flexor digitorum superficialis by altering two biomechanical constraints: the load against which the muscle worked and the initial muscle length. The load was increased using isotonic (low load), loaded dynamic (intermediate load) and isometric (high load) contractions in two studies. The initial muscle position reflected resting muscle length in series A, and a longer length with digit III fully extended in series B. Intramuscular EMG was recorded from 48 single motor units in 10 experiments on five healthy subjects, 21 units in series A and 27 in series B, while subjects performed ramp up, hold and ramp down contractions. Increasing the load on the muscle decreased the force, displacement and firing rate of single motor units at recruitment at shorter muscle lengths (P<0.001, dependent t-test). At longer muscle lengths this recruitment pattern was observed between loaded dynamic and isotonic contractions, but not between isometric and loaded dynamic contractions. Thus, the recruitment properties of single motor units in human flexor digitorum superficialis are sensitive to changes in both imposed external loads and the initial length of the muscle.

Prevalence and contributing factors of eating disorder behaviors in active duty service women in the Army, Navy, Air Force, and Marines.

Eating disorders continue to be studied among civilian women. Gross disturbances in eating behaviors characterize the condition of anorexia nervosa (AN), currently seen among 1 to 2% of non-active duty women. Bulimia nervosa (BN) is prevalent among 2% of the female population, and both disorders have a female-to-male ratios of 10:1. Another category of eating disorders known as not otherwise specified (NOS) occurs in 3 to 35% of individuals in the reported literature. This study examined the prevalence of AN, BN, and NOS among a large sample of active duty women currently serving in the Army, Navy, Air Force, and Marines. Multiple military, professional, and behavioral variables were analyzed to provide an increased understanding and awareness of these disorders among all active duty service women. This descriptive, correlational study of 3,613 service women targeted females from the total population of three major medical centers (Army, Navy, and Air Force) and the total population of Marine women serving in Okinawa, Japan, at the time of the study. Anonymous survey return was obtained at 34% (N = 1,278). The study revealed an overall prevalence of 1.1% for AN, 8.1% for BN, and 62.8% for NOS among all service women. However, AN, BN, and NOS were found at significantly higher rates (p = 0.000) among women in the Marines, who reported AN at 4.9%, BN at 15.9%, and NOS at 76.7%. Use of laxatives, diuretics, diet pills, vomiting, and fasting for standards increased during the body measurement and fitness periods for all services, but year-round use of many of these behaviors occurred at significantly higher rates among Marines (p = 0.000). Multiple logistic regression analysis predicted several factors associated with the manifestation of eating disorders in this population of active duty women.

Prevalence and contributing factors of eating disorder behaviors in a population of female Navy nurses.

Eating disorders continue to be reported at a steady rate among lay women. The disorders of anorexia nervosa (AN), bulimia nervosa (BN), and eating disorders not otherwise specified (NOS) have only been reported in a military population in isolated case reports. The military lifestyle and the nursing profession mimic the environment that appears to prevail among women with eating disorders who have been previously studied in civilian populations. A total of 706 active duty female Navy nurses returned an anonymous mailed survey that was developed to correlate military and professional demographics and variables with current and past eating disorder behaviors. Responses were analyzed using the criteria established by the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders Third Edition, Revised; for AN, BN, and NOS eating disorders. Nurses who fit the criteria for AN were 1.1%, and 12.5% met the criteria for BN. NOS was seen in 36% of those sampled, and those classified as normal by exclusion were 50.4%. The Navy provides an environment in which eating disorder behaviors thrive and survive due to many reported military and professional factors.

Prevalence and contributing factors of eating disorder behaviors in active duty Navy men.

Eating disorders have been widely studied among civilian women and among select groups of men (athletes and wrestlers). Gross disturbances in eating behaviors characterize the conditions of anorexia nervosa (AN), currently seen among 1 to 2% of non-active duty women. Bulimia nervosa (BN) is prevalent among 2% of the female population, and both disorders have a female-to-male ratio of 10:1. Another category of eating disorders known as not otherwise specified (NOS) occurs in between 3 and 35% of the population according to the reported literature. This study examined the prevalence of AN, BN, and NOS among a large sample of active duty Navy men. Multiple military, professional, and behavioral were analyzed to promote an increased understanding and awareness of these disorders among active duty men. This was a descriptive, correlational study among 4,800 Navy men targeted from hospitals, clinics, and ships at sea. Anonymous surveys were returned by 28% of prospective subjects (N = 1,425). The study revealed a prevalence of 2.5% for AN, 6.8% for BN, and 40.8% for NOS among active duty Navy men. AN and BN existed without difference among all active duty men regardless of rank/rate, job assignment, or age. Use of laxatives, diuretics, diet pills, vomiting, and fasting for standards increased during the body measurement and fitness periods, but year-round use of these methods existed at disturbing rates. Multiple logistic regression analysis predicted several factors that might predict the manifestation of eating disorders in this population of active duty members.

Mapping the motor point in the human tibialis anterior muscle.

OBJECTIVE: Percutaneous electrical stimulation of the motor point permits selective activation of a muscle. However, the definition and number of motor points reported for a given muscle varies. Our goal was to address these problems. METHODS: The area, location and number of motor points in human tibialis anterior were examined, using isometric dorsiflexion torque responses to electrical stimuli. Three methods were used: lowest electrical threshold, maximum muscle response, and approximate motor point. RESULTS: A single motor point was identified in 39/40 subjects regardless of method. The area of the site of lowest electrical threshold was smaller (median, 35 mm(2)) than those using the maximum muscle response (144 mm(2)) and approximate motor point (132 mm(2)). There was substantial, but not significant, between-subject variation in motor point location. Fifty three percent of motor points would have been missed if located only by reference to anatomical landmarks. CONCLUSIONS: These results suggested that the motor point's location cannot be determined a priori and that the identification method will affect both area and location. SIGNIFICANCE: If it is important to maximally activate a single muscle in isolation, the motor point is best represented by the site producing a maximal but isolated muscle response at the lowest stimulation intensity.

Modulation of ongoing EMG by different classes of low-threshold mechanoreceptors in the human hand.

1. We have previously demonstrated that the input from single FA I and SA II cutaneous mechanoreceptors in the glabrous skin of the human hand is sufficiently strong to modulate ongoing EMG of muscles acting on the digits. Some unresolved issues have now been addressed. 2. Single cutaneous (n = 60), joint (n = 2) and muscle spindle (n = 34) afferents were recorded via tungsten microelectrodes inserted into the median and ulnar nerves at the wrist. Spike-triggered averaging was used to investigate synaptic coupling between these afferents and muscles acting on the digits. The activity of 37 % of FA I (7/19), 20 % of FA II (1/5) and 52 % of SA II afferents (11/21) evoked a reflex response. The discharge from muscle spindles, 15 SA I and two joint afferents did not modulate EMG activity. 3. Two types of reflex responses were encountered: a single excitatory response produced by irregularly firing afferents, or a cyclic modulation evoked by regularly discharging afferents. Rhythmic stimulation of one FA I afferent generated regularly occurring bursts which corresponded to the associated cyclic EMG response. 4. Selectively triggering from the first or last spike of each burst of one FA I afferent altered the averaged EMG profile, suggesting that afferent input modulates the associated EMG and not vice versa. 5. The discharge from single FA I, FA II and SA II afferents can modify ongoing voluntary EMG in muscles of the human hand, presumably via a spinally mediated oligosynaptic pathway. Conversely, we saw no evidence of such modulation by SA I, muscle spindle or joint afferents.

Comparison of contractile properties of single motor units in human intrinsic and extrinsic finger muscles.

1. The purpose of the present study was to compare the contractile properties of single motor units in the intrinsic (short) and extrinsic (long) finger muscles in awake human subjects using intraneural motor axon stimulation. 2. Twitch properties were measured for 17 intrinsic and 11 extrinsic motor units by selective stimulation of a single motor axon in the ulnar or the median nerve. Force was measured from the appropriate digit, just distal to the muscle's point of insertion and single unit EMG was recorded with surface electrodes. Force-frequency relationships (2-100 Hz) were established for 16 of these units (7 intrinsic, 9 extrinsic). Across the 16 motor units for which force-frequency data were obtained, twitch contraction time (63.7 +/- 6.0 ms, mean +/- s.e.m.) was inversely correlated with the frequency required to generate half-maximum tetanic force (12.0 +/- 1.1 Hz). 3. We found no systematic differences between the contractile properties of intrinsic and extrinsic motor units. There was no evidence of a bimodal distribution into large/small or fast/slow units based on maximum force or contraction times, although both fast and slow motor units were encountered. 4. The peak slope of the sigmoidal force-frequency relationship for intrinsic motor units (9.1 and 4.4-12.9 mN Hz-1, median and interquartile range) was significantly higher than that for extrinsic motor units (2.9 and 2.3-3.1 mN Hz-1; P = 0.028), i.e. greater force steps were produced by the intrinsic motor units for a given change in stimulation frequency. This difference suggests that motor units in the intrinsic muscles of the hand are more sensitive to modulating force output by changes in motoneurone firing rates than are those in the extrinsic muscles. This reflects the important role of the intrinsic hand muscles in the fine manipulation of objects.

Evidence for strong synaptic coupling between single tactile afferents and motoneurones supplying the human hand.

1. Electrical stimulation of digital nerves elicits short-latency excitatory and inhibitory spinal reflex responses in ongoing EMG in muscles acting on the fingers and thumb. Similar responses are elicited by stimulating a population of muscle spindles but not when a single muscle spindle is activated. The current study investigated whether short-latency EMG responses could be evoked from the discharge of a single cutaneous afferent. 2. Thirty-three tactile afferents were recorded via tungsten microelectrodes in the median nerve of awake humans. Spike-triggered averaging revealed EMG events time-locked to the afferent discharge. The afferents were activated by an external probe and the EMG was elicited by a weak voluntary contraction. 3. Eleven cutaneous afferents (33 %) showed a short-latency response in the ongoing EMG. Overt increases or decreases in EMG were observed for seven afferents (onset latency 20.0-41.1 ms). For four slowly adapting (SA) type II afferents, EMG showed a periodicity that was correlated to the afferent interspike interval (r = 0.99). 4. The EMG associated with two rapidly adapting (FA) type I afferents (29 %) showed a short-latency excitation while five showed neither excitation nor inhibition. Seven SA II afferents (39 %) showed excitation and 11 no response; and none of the six SA I afferents showed any response. 5. We conclude that, unlike muscle spindle afferents, the input from a single cutaneous afferent is strong enough to drive, via interneurones, motoneurones supplying muscles acting on the digits. The potent short-latency response we found supports the important role of cutaneous mechanoreceptors in fine motor control of the human hand.

Cortically evoked neural volleys to the human hand are increased during ischaemic block of the forearm.

Reorganisation of the motor cortex may occur after limb amputation or spinal cord injury. In humans, transcranial magnetic stimulation (TMS) shows expansion of motor cortical representations of muscles proximal to the injury. Similarly, ischaemic block of the hand can increase acutely the representation of the biceps muscle, measured by increased biceps motor potentials evoked by TMS. It is thought that this increase occurs at the expense of the cortical representation of the paralysed and deafferented hand muscles but this has never been investigated. To study what changes occur in the cortical representation of the hand muscles during ischaemic block, a tungsten microelectrode was inserted into the ulnar or median nerve above the elbow and the size of the neural potential elicited by TMS in fascicles supplying the hand was measured in seven subjects. Prior to ischaemia, TMS evoked EMG responses in the intrinsic hand muscles. In the nerve, a brief motor potential preceded the response in the muscle and was followed by a contraction-induced sensory potential. During 40 min of ischaemia produced by a blood pressure cuff inflated around the forearm to 210 mmHg, the EMG response to TMS and the sensory potential from the hand were progressively blocked. However, the motor neural evoked potential showed a significant increase in amplitude during the ischaemic period (30.5 %, P = 0.005). The increase in the neural potential suggests that output to the hand evoked from the cortex by TMS was not decreased by ischaemic block. Thus, we conclude that the increased response of biceps to TMS during distal ischaemia is not accompanied by a corresponding decrease in the motor cortical representation of the hand.