Impact of a Carbohydrate Mouth Rinse on Corticomotor Excitability after Mental Fatigue in Healthy College-Aged Subjects.

Mental Fatigue (MF) has been associated with reduced physical performance but the mechanisms underlying this result are unclear. A reduction in excitability of the corticomotor system is a way mental fatigue could negatively impact physical performance. Carbohydrate (CHO) mouth rinse (MR) has been shown to increase corticomotor excitability. PURPOSE: The purpose of this study was to determine if CHO MR impacts corticomotor excitability after MF. METHODS: Fifteen subjects (nine females, six males; age = 23 ± 1 years; height = 171 ± 2 cm; body mass = 69 ± 3 kg; BMI = 23.8 ± 0.7) completed two sessions under different MR conditions (Placebo (PLAC), 6.4% glucose (CHO)) separated by at least 48 h and applied in a double-blinded randomized fashion. Motor-evoked potential (MEP) of the left first dorsal interosseous (FDI) was determined by transcranial magnetic stimulation (TMS) before and after MF. Perceived MF was recorded before and after the MF task using a 100 mm visual analog scale (VAS). RESULTS: MF was greater following PLAC (+30.4 ± 4.0 mm) than CHO (+19.4 ± 3.9 mm) (p = 0.005). MEP was reduced more following PLAC (-16.6 ± 4.4%) than CHO (-3.7 ± 4.7%) (p < 0.001). CONCLUSIONS: CHO MR was successful at attenuating the reduction in corticomotor excitability after MF. Carbohydrate mouth rinse may be a valuable tool at combating the negative consequences of mental fatigue.

Carbohydrate mouth rinsing does not affect 6-min walk test performance and blood glucose responses in older adults.

PURPOSE: Carbohydrate (CHO) mouth rinsing (MR) prior to exercise has been shown to elicit enhanced performance and energy availability in some studies. Previous literature has concentrated on examining CHO MR strategies for improving aerobic endurance performance in younger athletic adults. Knowledge of the impact of CHO MR on functional performance in older adults is scarce. The purpose of this investigation was to determine if CHO MR would improve 6-min walk test (6MWT) performance, perceived exertion, and blood glucose responses in older adults. METHOD: Thirty-three individuals (16 males, 17 females), age ≥ 70 years performed two 6MWT trials, one of which utilized a 6.4% maltodextrin CHO MR and one of which utilized a placebo MR. Participants held the MR in their mouth for 20 s prior to the 6MWT, and trials occurred in a counterbalanced fashion. Total distance walked and rating of perceived exertion (RPE) were recorded upon completion of each 6MWT. Heart rate (HR), peripheral blood oxygen saturation (SpO2), systolic and diastolic blood pressures (BP), blood glucose, and blood lactate were measured before and after each 6MWT. RESULT: CHO MR did not alter the response of any study parameter compared to the placebo MR (p = 0.13-0.94). HR, systolic BP, and blood lactate increased and SpO2 decreased across time (p < 0.01). CONCLUSION: A 6.4% maltodextrin CHO MR did not alter total distance walked, perceived exertion, or other physiological responses elicited by the 6MWT in older adults.

Evaluation of cognitive performance and neurophysiological function during repeated immersion in cold water.

Exposure to cold causes disturbances in cognitive performance that can have a profound impact on the safety, performance, and success of populations that frequent cold environments. It has recently been suggested that repeated cold stress, resulting in cold acclimation, may be a potential strategy to mitigate the cognitive impairments frequently seen upon exposure to cold temperatures. The purpose of this study, therefore, was to examine cognitive and neurophysiological function during repeated cold water immersion. Twelve healthy participants consisting of 8 males and 4 females (mean ±â€¯SD age: 26 ±â€¯5 years, height: 174.0 ±â€¯8.9 cm, weight: 75.6 ±â€¯13.1 kg) completed seven 90-minute immersions in 10 °C water, each separated by 24 h. During immersions 1, 4, and 7, a double-digit addition task and a computer-based psychomotor vigilance task (PVT) were administered to assess cognitive performance, while neurophysiological function was assessed using electroencephalography (EEG) measurements collected during the PVT. Findings suggest that participants experienced an insulative type of cold acclimation, evidenced by greater heat retention and less shivering, with possible improvements in cognitive performance. Participants had more correct responses on the double-digit addition task on Immersion 7 (39 ±â€¯5) compared with Immersion 1 (33 ±â€¯6); p < 0.001, yet no differences were observed for reaction time between Immersion 7 (286 ±â€¯31 ms) and Immersion 1 (281 ±â€¯19 ms); p = 0.59. Additionally, EEG analyses indicate no beneficial changes in neurophysiological function. Results demonstrate that individuals who are frequently exposed to cold water may be more suited to handle certain cognitive challenges after several exposures, although additional investigations are needed to provide neurophysiological support for this.

Impact of a Carbohydrate Mouth Rinse on Quadriceps Muscle Function and Corticomotor Excitability.

PURPOSE: The purpose of this investigation is to determine the effects of different forms of a CHO MR on quadriceps muscle performance and corticospinal motor excitability. METHODS: Ten subjects (5 females, 5 males; 25±1 years; 1.71±0.03 m 73±5 kg) completed 4 trials. A different MR condition was applied during each trial (Placebo (PLA), 6.4% glucose (GLU), 6.4% maltose (MAL), 6.4% maltodextrin (MDX)). Maximal voluntary contraction (MVIC) of the right quadriceps and motor-evoked potential (MEP) of the right rectus femoris was determined pre (10 min), immediately after, and post (10 min) MR. MEP was precipitated by transcranial magnetic stimulation (TMS) during muscle contraction (50% of MVIC). MR was held in the mouth for 20 s and treatments were applied using a Latin square design. The relative change in MEP from pre-measures was different across treatments (p=0.025) but was not different across time (p=0.357). RESULTS: Relative change in MEP was greater for all CHO conditions immediately after (GLU=2.58±5.33%; MAL=3.92±3.90%; MDX=18.28±5.57%) and 10 min after (GLU=14.09±13.96%; MAL=8.64±8.67%; MDX=31.54±12.77%) MR compared to PLA (Immediately after=-2.19±4.25%, 10 min=-13.41±7.46%). The relative change in MVC was greater for CHO conditions immediately (GLU=3.98±2.49%; MAL=5.89±2.29.90%; MDX=7.66±1.93%) and 10 min after (GLU=7.22±2.77%; MAL=10.26±4.22%; MDX=10.18±1.50%) MR compared to PLA (Immediately after=-3.24±1.50%, 10 min=-6.46±2.22%). CONCLUSIONS: CHO MR increased corticospinal motor excitability and quadriceps muscle performance immediately and 10 min after application; however, the form of CHO used did not influence this response.

Brain Activity During Unilateral Physical and Imagined Isometric Contractions.

By convention, it is believed that the ipsilateral side of the body is controlled by the contralateral side of the brain. Past studies measuring brain activity primarily recorded changes before and after an intervention is performed on one side of the body within one hemisphere (usually the contralateral) of the brain. The purpose of this investigation was to observe the brain activity within the left and right hemispheres of the prefrontal and sensorimotor cortices during physical and imagined, dominant and non-dominant unilateral isometric elbow flexion. Fifteen right hand dominant individuals (six males and nine females) between the ages of 18 and 21 performed four different isometric contractions of their biceps brachii at a preacher curl bench: dominant physical contraction (DomCon), non-dominant physical contraction (NonCon), dominant imagined contraction (DomImagine), and non-dominant imagined contraction (NonImagine). Each contraction was sustained for 5 s followed by 30 s of rest. Motor activity-related cortical potential (MRCP) and event-related spectral perturbation (ERSP) within the right and left hemispheres of the sensorimotor and prefrontal cortices were determined for each condition at 500-1,000 ms and 2,000-2,500 ms after initiation of contraction. MRCP and ERSP were both changed at the 500-1,000 ms time window for all conditions. Changes in the 2,000-2,500 ms window were most consistently observed during physical contractions. While the changes during DomCon occurred in the left (contralateral) side of the brain, the greatest changes observed in MRCP and ERSP occurred in both sides of the brain during the NonCon condition. Further understanding of bilateral changes in brain activity during unilateral tasks is valuable for improving rehabilitation practices through mental and physical exercise.

Impairment of exercise performance following cold water immersion is not attenuated after 7 days of cold acclimation.

PURPOSE: It is well-documented that severe cold stress impairs exercise performance. Repeated immersion in cold water induces an insulative type of cold acclimation, wherein enhanced vasoconstriction leads to greater body heat retention, which may attenuate cold-induced exercise impairments. The purpose of this study, therefore, was to investigate changes in exercise performance during a 7-day insulative type of cold acclimation. METHODS: Twelve healthy participants consisting of eight males and four females (mean ± SD age: 25.6 ± 5.2 years, height: 174.0 ± 8.9 cm, weight: 75.6 ± 13.1 kg) performed a 20 min self-paced cycling test in 23 °C, 40% humidity without prior cold exposure. Twenty-four hours later they began a 7-day cold acclimation protocol (daily 90 min immersion in 10 °C water). On days one, four, and seven of cold acclimation, participants completed the same cycling test. Measurements of work completed, core and skin temperatures, heart rate, skin blood flow, perceived exertion, and thermal sensation were measured during each cycling test. RESULTS: Successful insulative cold acclimation was observed. Work produced during the baseline cycling test (220 ± 70 kJ) was greater (p < 0.001) than all three tests that were performed following immersions (195 ± 58, 197 ± 60, and 194 ± 62 kJ) despite similar ratings of perceived exertion during each test, suggesting that cold exposure impaired cycling performance. This impairment, however, was not attenuated over the cold acclimation period. CONCLUSIONS: Results suggest that insulative cold acclimation does not attenuate impairments in exercise performance that were observed following acute cold water immersion.

Cold acclimation and cognitive performance: A review.

Athletes, occupational workers, and military personnel experience cold temperatures through cold air exposure or cold water immersion, both of which impair cognitive performance. Prior work has shown that neurophysiological pathways may be sensitive to the effects of temperature acclimation and, therefore, cold acclimation may be a potential strategy to attenuate cold-induced cognitive impairments for populations that are frequently exposed to cold environments. This review provides an overview of studies that examine repeated cold stress, cold acclimation, and measurements of cognitive performance to determine whether or not cold acclimation provides beneficial protection against cold-induced cognitive performance decrements. Studies included in this review assessed cognitive measures of reaction time, attention, logical reasoning, information processing, and memory. Repeated cold stress, with or without evidence of cold acclimation, appears to offer no added benefit of improving cognitive performance. However, research in this area is greatly lacking and, therefore, it is difficult to draw any definitive conclusions regarding the use of cold acclimation to improve cognitive performance during subsequent cold exposures. Given the current state of minimal knowledge on this topic, athletes, occupational workers, and military commands looking to specifically enhance cognitive performance in cold environments would likely not be advised to spend the time and effort required to become acclimated to cold. However, as more knowledge becomes available in this area, recommendations may change.

Cold Acclimation Does Not Alter Physiological or Perceptual Responses During Subsequent Exercise in the Heat.

INTRODUCTION: Warfighters often train and conduct operations in cold environments. Specifically, military trainees and divers that are repeatedly exposed to cold water may experience inadvertent cold acclimatization, which results in body heat retention. These same warfighters can quickly switch between environments (cold to hot or hot to cold) given the nature of their work. This may present a risk of early onset of hyperthermia when cold-acclimatized warfighters are subsequently exposed to physiological insults that increase body temperature, such as exercise and heat stress. However, there is currently no evidence that suggests this is the case. The purpose of this work, therefore, is to determine what impact, if any, repeated immersion in cold water has on subsequent exercise in the heat. MATERIALS AND METHODS: Twelve healthy subjects (values in mean ± SD: age, 25.6 ± 5.2 years; height, 174.0 ± 8.9 cm; weight, 75.6 ± 13.1 kg) voluntarily provided written informed consent in accordance with the San Diego State University Institutional Review Board. They first completed 120 minutes of moderate treadmill walking in 40°C and 40% relative humidity. During this trial, subjects' physiological and perceptual responses were recorded. Twenty-four hours later, subjects began a cold acclimation protocol, which consisted of seven, 90-minute immersions in cold water (10°C, water level to chest). Each immersion was also separated by 24 hours. Subjects then repeated a subsequent trial of exercise in the heat 24 hours after the final immersion of the cold acclimation protocol. RESULTS: Results from cold acclimation revealed no change in core temperature, a decrease in skin temperature, and attenuated shivering and lactate responses, which supports a successful insulative-hypothermic cold acclimation response. This type of cold acclimation response primarily results in heat retention with associated energy conservation. Findings for heat trials (pre-cold acclimation and post-cold acclimation) revealed no differences between trials for all measurements, suggesting that cold acclimation did not influence physiological or perceptual responses during exercise in the heat. CONCLUSION: Our findings indicate that military divers or trainees that are frequently exposed to cold water, and hence have the ability to experience cold acclimatization, will likely not be at greater risk of increased thermal strain when subsequently exposed to physical activity in hot environments. In this study, no physiological or perceptual differences were observed between trials before and after cold acclimation, suggesting that cold acclimation does not present a greater hyperthermia risk during subsequent exercise in the heat.

Effects of an over-the-counter vented mouthguard on cardiorespiratory responses to exercise and physical agility.

Many athletes avoid using mouthguards because they believe that they impair their ability to breath and negatively affect performance. Recently, some manufacturers have developed "vented" mouthguards (VentMGs) to address this concern. The purposes of this investigation were to describe the impact of a commercially available "vented" boil-and-bite mouthguard on the physiological responses to graded exercise and to determine whether the use of the same mouthguard influences performance during traditional physical agility tests. Recreationally trained males (n = 15) (age = 24 ± 1 year; (Equation is included in full-text article.)= 43.5 ± 1.9 ml·kg·min; body mass index = 25.2 ± 0.9) completed 3 randomly assigned trials where they wore no mouthguard (control), a traditional mouthguard (TradMG), or a VentMG. During each trial, subjects completed a modified maximal exercise test on a cycle ergometer and a series of physical agility tests (40-m dash, vertical leap, broad jump, 3-cone drill, and shuttle run). No differences were seen between control and the TradMG in any cardiorespiratory measures at any time during the maximal exercise test. Ventilation and blood lactate were lower (p ≤ 0.05) during VentMG at 200 W and at MAX; however, no differences in (Equation is included in full-text article.)were observed. Although TradMG had no impact on physical agility, VentMG produced a higher (1.9 cm; p = 0.03) vertical leap than control. Both mouthguard conditions negatively affected perceptions of breathability, comfort, and ability to communicate, but no differences existed between the 2 conditions. These findings confirm that TradMG has no negative impact on physiological function during exercise and physical agility; however, VentMG may have a positive impact at higher workload and on vertical leap.

Effect of methadone maintenance treatment on heroin craving, a literature review.

Despite agreement that methadone maintenance treatment (MMT) is an effective and safe option for treatment of heroin dependence, there have been controversies about its effect on heroin craving. A systematic literature review of the PubMed database was used to find studies eligible for inclusion in the study. The authors present the results of 16 articles that met all inclusion criteria. Overall, 7 studies reported that methadone could reduce heroin craving, 4 studies reported that patients in MMT are still at risk of having heroin craving, 1 study reported that methadone could increase heroin craving, and 4 studies reported that methadone has a neutral effect on heroin craving. One may speculate from these data that methadone may help with heroin craving, but patients in MMT may still be at risk of cue-induced heroin cravings. Methadone provides a helpful tool for reducing some components of craving and risk of relapse for patient receiving MMT.

Impact of prolonged exercise in the heat and carbohydrate supplementation on performance of a virtual environment task.

PURPOSE: The purpose of this investigation was to determine whether performance of a virtual environment (VE) task is influenced by exercise in the heat and carbohydrate supplementation. METHODS: Ten males completed four exercise trials to fatigue. During each trial, subjects cycled at a submaximal workload. Subjects exercised in a normal environment (NORM) and in a hot environment on different occasions. During exercise, subjects drank 10 mL x kg(-1) x hour(-1) of body weight of a 6% carbohydrate beverage (CHO) or a placebo. Subjects completed a VE task before, during exercise, and after fatigue. RESULTS: More failures occurred during placebo than CHO during exercise. The NORM CHO trial had the fewest failures at fatigue. More kills occurred during exercise in the NORM CHO. CONCLUSIONS: Performance of a VE task was negatively influenced by prolonged exercise and heat stress. CHO supplementation may have a positive impact on performance of the VE task following prolonged exercise.

Changes in EEG during graded exercise on a recumbent cycle ergometer.

Previous studies have shown changes in brain activity as a result of exercise; however, few studies have examined changes during exercise. The purpose of this study was to examine brain activity during a graded exercise test. Twenty male participants performed a graded exercise test on a recumbent cycle ergometer. Exercise intensity was set initially at 50W and was increased by 50W every 2 minutes until volitional fatigue was reached. Electroencephalography (EEG) was measured prior to the onset of exercise, during the last minute of each stage of exercise, immediately post-exercise, and 10 minutes into recovery. EEG was recorded from 8 scalp sites leading to analysis of alpha 1, alpha 2, beta 1, beta 2, and theta activities. Expired air was collected and analyzed for ventilation rate (VE), VO2, % of peak VO2, and Respiratory Exchange Ratio (RER). No differences were seen in EEG between the hemispheres of the brain. There was, however, a significant increase in brain activity across the spectrum occurring at 200 W through immediately post-exercise. Brain activity returned to pre- exercise levels by 10 minutes post. VO2, % of peak VO2 and RER increased linearly with exercise intensity. VE increased linearly through 200 W; however, a disproportionate increase was seen in VE from 200 W to peak exercise. The results of this investigation demonstrate that brain activity may be related to exercise intensity. Future research will want to examine how these changes in brain activity influence affective, perceptual and cognitive changes often associated with exercise. Efforts will also need to be made to determine if changes in brain activity during exercise are mediated by central (within the brain) or peripheral mechanisms. Key pointsEEG can be recorded during exercise.Brain EEG activity increases during exercise and may be related to exercise intensity.Brain EEG activity returns to resting levels quickly after the cessation of exercise.

Lack of relationship between functional and perceived quality of life outcomes following pulmonary rehabilitation.

UNLABELLED: Individuals with chronic obstructive pulmonary disease (COPD) have been shown to benefit from participation in pulmonary rehabilitation (PR) programs that include exercise training and education. PURPOSE: To examine the relationship between improvements in 6 minute walk distance and perceived quality of life in individuals with COPD following completion of a PR program. METHODS: The records of 139 individuals completing a PR program (3 times a week for 8 weeks) were retrospectively examined. Prior to entry and upon completion of the program each individual completed a 6 minute walk test (6MWT), the SF-36 Health survey, and the UCSD Shortness of Breath Questionnaire (SOB). SF-36 results were analyzed according to 8 subscales [Physical Functioning (PF), Role Physical (RF), Bodily Pain (BP), General Health (GH), Vitality (V), Social Functioning (SF), Role Emotional (RE), and Mental Health (MH)]. RESULTS: PR resulted in significant improvements in 6MWTdistance (Pre = 845 +/- 37 ft, Post = 1127 +/- 32 ft, p < 0.001), PF (p < 0.001), RF (p = 0.001), Vitality (p = 0.002), SF (p < 0.001), RE (p = 0.037), MH (p < 0.001) and SOB (Pre = 53 +/- 2, Post = 47 +/- 2, p < 0.001). The change in 6MWT distance was not related to changes in PF (r = 0.17), RF (r = 0.03), GH (r = 0.03), Vitality (r = -0.001), SF (r = 0.01), RE (r = 0.06), MH (r = -0.04) or SOB (r = 0.12). The magnitude of improvement in 6MWT distance (68%) was much greater than that observed in PF (15%), RF (16%), GH (6%), VT (18%), SF (20%), RE (14%), MH (14%), or SOB (8%). CONCLUSIONS: PR has a positive impact on 6 minute walk distance and perceived quality of life in individuals with COPD; however, changes in 6 minute walk distance appear to have no relationship to changes in perceived quality of life.

The effects of protease supplementation on skeletal muscle function and DOMS following downhill running.

Protease supplementation has been shown to attenuate soft tissue injury resulting from intense exercise. The aim of this study was to evaluate the effects of protease supplementation on muscle soreness and contractile performance after downhill running. Ten matched pairs of male participants ran at a -10% grade for 30 min at 80% of their predicted maximal heart rate. The participants consumed two protease tablets (325 mg pancreatic enzymes, 75 mg trypsin, 50 mg papain, 50 mg bromelain, 10 mg amylase, 10 mg lipase, 10 mg lysozyme, 2 mg chymotrypisn) or a placebo four times a day beginning 1 day before exercise and lasting a total of 4 days. The participants were evaluated for perceived muscle soreness of the front and back of the dominant leg, pressure pain threshold by dolorimetry of the anterior medial, anterior lateral, posterior medial and posterior lateral quadrants of the thigh, and knee extension/flexion torque and power. The experimental group demonstrated superior recovery of contractile function and diminished effects of delayed-onset muscle soreness after downhill running when compared with the placebo group. Our results indicate that protease supplementation may attenuate muscle soreness after downhill running. Protease supplementation may also facilitate muscle healing and allow for faster restoration of contractile function after intense exercise.

Characteristics of individuals who fell while receiving home health services.

BACKGROUND AND PURPOSE: Many patients receiving home health services are at risk for falling, but fall risk factors have not been previously investigated in this population. A retrospective record review was used to describe individuals who fell while being served by a home health agency. SUBJECTS: The 98 individuals who fell while receiving home health services were compared with a random sample of 98 subjects served by the home health agency during the same period who did not report falling. METHODS: Subjects were compared by age, sex, days of receiving home health services, number of falls prior to admission to the home health agency, diagnosis, medication category, home health services received, and type of health care coverage. In the group with falls, causes of falls and interventions were described. RESULTS: The group with falls had comorbidities of neurological and cardiovascular impairment, took more medications associated with increased risk of falling, and had almost 3 times the number of falls prior to admission than the group without falls. DISCUSSION AND CONCLUSION: Home care providers should consider medical history, medication usage, and fall history as risk factors for falls in the home environment.