Familiarization Trial Research Articles

Immediate pre-meal water ingestion decreases voluntary food intake in lean young males.

Consuming 375-500 ml of water 30 min before a meal has been shown to reduce energy intake in older, but not younger adults. This study investigated the effects of ingesting a water preload immediately pre-meal (<1 min before eating) on within-meal ad libitum energy intake in non-obese young males. Fourteen healthy males [mean (SD) age 27 (3) years, height 1.83 (0.05) m, body weight 80.47 (9.89) kg, body fat 17.5 (4.0) %, body mass index 24.0 (2.5) kg/m(2)] completed a familiarisation trial and two experimental trials in randomised counterbalanced order. Subjects arrived at the laboratory overnight fasted and consumed an ad libitum porridge breakfast. Immediately prior to the meal, subjects consumed either a 568 ml (1 pint) water preload (preload trial) or no preload (control trial). Visual analogue scale questionnaires to assess hunger, fullness and satisfaction were completed before and after the meal in both trials, as well as after the water preload. Ad libitum energy intake was greater (P < 0.001) during control [2551 (562) kJ] than preload [1967 (454) kJ]. Ad libitum water intake was also greater (P < 0.001) during control [318 (226-975) ml] than preload [116 (0-581) ml]. The water preload increased fullness and satisfaction and decreased hunger compared to pre-trial (P < 0.001) and the control trial (P < 0.001). This study demonstrates that consumption of a 568 ml water preload immediately before a meal reduces energy intake in non-obese young males. This might therefore be an effective strategy to suppress energy intake in this population and possibly assist with weight management.

Mild hypohydration increases the frequency of driver errors during a prolonged, monotonous driving task.

Purpose: Driver error is the largest cause of road traffic accidents, accounting for around 68 % of all vehicle crashes in the UK. During long and monotonous driving, most individuals display progressive signs of visual fatigue and a loss of vigilance. Since deficits in total body water (TBW) are associated with altered mood and decrements in aspects of cognitive function, it is possible that dehydrated drivers may be more susceptible to errors in judgement and car handling. With this in mind, the aim of the present study was to examine the effects of fluid restriction, on performance during a prolonged, monotonous driving task. Methods: Eleven healthy males (age 22 ± 4 y) completed a familiarisation trial, before two experimental trials were undertaken in a randomised manner. Each experimental trial took place over two days. On day 1 volunteers were instructed to consume a volume of fluid in line with published guidelines (HYD trial) or 25 % of this intake (FR trial). Participants came to the laboratory the following morning after an overnight fast (day 2). One hour following a standard breakfast, a 120 min driving simulation task began. During the HYD trial volunteers were provided with 200 mL of fluid every hour, and on the FR trial only 25 mL was made available each hour. Body mass, serum and urine osmolality, and subjective feelings were recorded during trials. Driver errors, including instances of lane drifting or late breaking, brain activity (EEG) and heart rate were recorded throughout the driving task. Results: Pre-trial body mass (P=0.692), urine osmolality (P=0.838) and serum osmolality (P=0.574) were the same on both trials. FR resulted in a 1.1±0.7 % reduction in body mass, compared to -0.1±0.6 % in the HYD trial (P = 0.002). Urine and serum osmolality were both increased following FR (P Conclusions: The results of the present study suggest that mild hypohydration, resulted in an increase in errors during a prolonged, monotonous drive, compared to that observed while performing the same task in a hydrated condition. The magnitude of decrement reported was similar to that observed following the ingestion of alcohol resulting in a blood alcohol content of approximately 0.08 % (the current UK legal driving limit), or while sleep deprived. There is no question that both drink-driving and driving while tired increases the risk of road traffic accidents, and many countries have instigated national campaigns to educate drivers of the associated risks. Given the present fin- dings, perhaps some attention should also be directed to encouraging appropriate hydration practices among drivers. Key words: Dehydration, Cognitive function, Road traffic accident Language: en

Sex differences on the acute effects of caffeine on maximal strength and muscular endurance

The aim of this study was to look at the effects of caffeine on strength performance and to examine any differences between sexes. Sixteen moderately active, resistance-trained individuals (10 males and 8 females) performed 2 trials (excluding a familiarisation trial). The effect of 5 mg/kg body mass (BM) caffeine or a placebo on bench press (BP) one repetition maximum (1RM), squat 1RM, the number of BP reps to failure at 40% 1RM (total weight lifted; TWL), pain rating (0-10) were recorded after each final successful lift. BP 1RM was significantly greater (P=0.016), with an increase of 5.91% for males and an increase of 10.69% for females. However, there was no sex difference in squat 1RM with males producing 130.3±27.8 and 134.0±28.9 kg and females producing 66.9±6.2 and 65.3±7.0 kg for placebo and caffeine, respectively. TWL tended to increase with caffeine for males from 1,246.8±704.9 to 1,545.5±920.3 kg; with females having no effect of caffeine (397.8±245.1 to 398.8±182.7kg; P=0.06). Caffeine had no effect on pain perception. This study found that 5 mg/kg BM caffeine improved BP 1RM in resistance-trained males and females. However, for TWL there was a tendency towards improvement in males only, suggesting a sex difference to caffeine ingestion for TWL.

Acute hypoxic gas breathing severely impairs cognition and task learning in humans

Impairments in neural function are common when oxygen supply to the brain is reduced. This study examined neurocognitive processes that are vulnerable to oxygen deprivation. We induced moderate-to-severe hypoxia in healthy adults, thereby inducing impairments caused by low brain oxygen availability. 22 healthy adults participated in this matched-pairs study with a single-blind, randomised design. Baseline neurocognitive function was examined during a familiarisation trial and participants were assigned to hypoxia (10% O2) or sham (21% O2) groups. Neurocognitive performance was assessed via computerised test battery after 50min of breathing a gas mixture that reduced arterial oxygen saturation by 20% (p<0.01). Hypoxia severely reduced performance across all neurocognitive domain scores; with significant drops in neurocognitive index (−20%), composite memory (−30%), verbal memory (−34%), visual memory (−23%), processing speed (−36%), executive function (−20%), psychomotor speed (−24%), reaction time (−10%), complex attention (−19%) and cognitive flexibility (−18%; all p<0.05). Practice effects were blocked by hypoxia but occurred in sham for information processing speed (+30%), executive function (+14%), psychomotor speed (+18%), reaction time (+5%), cognitive flexibility (+14%), and overall cognitive functioning (+9%; all p<0.05). Neuropsychological performance decrements caused by acute experimental hypoxia are comparable to cognitive domains impaired with high altitude exposure and mild traumatic brain injury.

Effect of a Single Jump Practice on Vertical Jump Performance

Effect of a Single Jump Practice on Vertical Jump Performance Objective: This study aimed to elucidate the effect of a single jump practice session on vertical jump height. Thirty-two physical educational students aged from 19 to 27 years participated in this study. Methods: This study consisted of a randomized, controlled, and longitudinal design. The participants were divided into two groups; the intervention group (EX, n=16) and the control group (CG, n=16). The EX group performed five vertical jumps from a platform located at their knee height. The CG group was instructed to jump five times as high as possible without a platform. Before and after the jump practice, we determined vertical jump height, vertical ground reaction ground force, and the joint angles of trunk and lower extremity. Results: After the practice sessions, vertical jump height was significantly increased in EX, but was significantly decreased in CG. In EX, the change in vertical jump height was related to changes in the hip joint and trunk inclination angles. In CG, no change was found in the kinematic data. Conclusions: A single jump practice using a platform at one’s knee high transiently improves vertical jump height, and the change is associated with changes in the kinematics of the hip joint and trunk inclination. This implies that the coach or practitioner needs to pay attention to a protocol for familiarization trials and warm up when the vertical jump test is used to assess muscular power.

Sleep depth and continuity before and after chronic exercise in older men: Electrophysiological evidence

During later life sleep depth (slow-wave sleep, SWS) and maintenance exhibit deleterious changes, with possible negative effects on daytime function. This study assessed the effect of chronic, supervised exercise on sleep using laboratory-based polysomnography (PSG) and repeated measures in older adults. Thirteen men aged 64±3served as their own controls and had their sleep measured for a total of 6 nights: 3 before and 3 after the 16-week training intervention. Each sequence involved 1 familiarization trial followed by 2 experimental nights (exercise night; nonexercise night) measured using 13-channel PSG (combined electroencephalography, electromyography, and electro-oculography). The exercise challenges consisted of inclined treadmill brisk walking (60min, 68–69% V˙O2peak). The intervention successfully improved some parameters of aerobic fitness, i.e. ventilatory thresholds 1 and 2 (P<0.05). Acute exercise triggered increases in circulating free fatty acids and lactate levels both at baseline and after the intervention (P<0.05). Noteworthy, acute exercise following training resulted in a 71% increase in SWS during subsequent sleep in comparison with the nonexercise condition before training, respectively 2.4% and 1.4% (P<0.05). Following training, acute exercise reduced total wake time by 30% and REM onset latency by 14% (P<0.05). Acute exercise improved sleep continuity by decreasing total wake time. These results show that aerobic training could increase sleep depth and continuity, during active days, in elderly men. In habitual exercisers, these effects of aerobic exercise on sleep, although modest, might counteract those resulting from aging.

Overestimation of required recovery time during repeated sprint exercise with self-regulated recovery.

This study investigated the reliability and accuracy of self-regulated recovery time and performance during repeated sprinting. On 4 occasions, 14 men (24.5 ± 5.0 years) completed 10 × 6 seconds cycle sprints against 7.5% body mass, self-regulating (SR) recovery time to maintain performance. Subjects then repeated the test, but with a reduced recovery (RR) of 10% less recovery time. Across the first 4 trials, there were no between-trial differences in peak power output (PPO) or mean power output (MPO), recovery time, or fatigue index (p > 0.05). Random variation in recovery time was reduced across trials 3-4 (coefficient of variation [CV] = 7.5%, 95% confidence limits [CL] = 5.4-12.4%) compared with trials 1-2 (CV = 16.0, 95% CL = 11.4-27.0%) and 2-3 (CV = 10.1%, 95% CL = 7.2-16.7%) but was consistent across trials for PPO and MPO (between-trials CV, ≤3.3%). There were no trial effects for any performance, physiological, or perceptual measures when comparing SR with RR (p > 0.05), although heart rate and perceptual measures increased with subsequent sprint efforts (p ≤ 0.05). After 2 familiarization trials, subjects can reliably self-regulate recovery time to maintain performance during repeated sprints. However, subjects overestimate the amount of recovery time required, as reducing this time by 10% had no effect on performance, perceptual, or physiological parameters. Self-regulated sprinting is potentially a reliable training tool, particularly for sprint training where maintenance of work is desired. However, overestimation of required recovery time means that performance improvements may not be achieved if the goal of training is improvement of repeated sprint performance with incomplete recovery.

Impact of cafeteria feeding during lactation in the rat on novel object discrimination in the offspring.

There is increasing evidence that hyperenergetic diets have an impact on memory in rodents. However, it is largely unknown how diets, such as a cafeteria diet (CD), that mimic a Western-type diet act on learning and memory, in particular when fed during early stages of development. Here, we fed lactating dams a CD and exposed both male and female offspring to a novel object discrimination (NOD) task, a two-trial test of recognition memory in which rats exposed to two identical objects during a training/familiarisation trial can discriminate a novel from a familiar object during the subsequent choice trial. The choice trial was performed following inter-trial interval (ITI) delays of up to 4h. Maternal diet did not have an impact on exploration of the objects by either sex during the familiarisation trial. Control males discriminated the novel from the familiar object, indicating intact memory with an ITI of 1h, but not 2 or 4h. The CD delayed this natural forgetting in male rats such that discrimination was also evident after a 2h ITI. In contrast, control females exhibited discrimination following both 1 and 2h ITI, but the CD impaired performance. In summary, the present study shows that maternal exposure to the CD programmes NOD in the adult. In better-performing females, dietary programming interferes with NOD, whereas NOD was improved in males after lactational CD feeding.

Prior low- or high-intensity exercise alters pacing strategy, energy system contribution and performance during a 4-km cycling time trial.

We analyzed the influence of prior exercise designed to reduce predominantly muscle glycogen in either type I or II fibers on pacing and performance during a 4-km cycling time trial (TT). After preliminary and familiarization trials, in a randomized, repeated-measures crossover design, ten amateur cyclists performed: 1) an exercise designed to reduce glycogen of type I muscle fibers, followed by a 4-km TT (EX-FIB I); 2) an exercise designed to reduce glycogen of type II muscle fibers, followed by a 4-km TT (EX-FIB II) and; 3) a 4-km TT, without the prior exercise (CONT). The muscle-glycogen-reducing exercise in both EX-FIB I and EX-FIB II was performed in the evening, ∼12 h before the 4-km TT. Performance time was increased and power output (PO) was reduced in EX-FIB I (432.8±8.3 s and 204.9±10.9 W) and EX-FIB II (428.7±6.7 s and 207.5±9.1 W) compared to CONT (420.8±6.4 s and 218.4±9.3 W; P<0.01), without a difference between EX-FIB I and EX-FIB II (P>0.05). The PO was lower in EX-FIB I than in CONT at the beginning and middle of the trial (P<0.05). The mean aerobic contribution during EX-FIB I was also significantly lower than in CONT (P<0.05), but there was no difference between CONT and EX-FIB II or between EX-FIB I and EX-FIB II (P>0.05). The integrated electromyography was unchanged between conditions (P>0.05). Performance may have been impaired in EX-FIB I due a more conservative pacing at the beginning and middle, which was associated with a reduced aerobic contribution. In turn, the PO profile adopted in EX-FIB II was also reduced throughout the trial, but the impairment in performance may be attributed to a reduced glycolytic contribution (i.e. reduced lactate accumulation).

Effect of time of day on performance, hormonal and metabolic response during a 1000-M cycling time trial.

The aim of this study was to determine the effect of time of day on performance, pacing, and hormonal and metabolic responses during a 1000-m cycling time-trial. Nine male, recreational cyclists visited the laboratory four times. During the 1st visit the participants performed an incremental test and during the 2nd visit they performed a 1000-m cycling familiarization trial. On the 3rd and 4th visits, the participants performed a 1000-m TT at either 8 am or 6 pm, in randomized, repeated-measures, crossover design. The time to complete the time trial was lower in the evening than in the morning (88.2±8.7 versus 94.7±10.9 s, respectively, p<0.05), but there was no significant different in pacing. However, oxygen uptake and aerobic mechanical power output at 600 and 1000 m tended to be higher in the evening (p<0.07 and 0.09, respectively). There was also a main effect of time of day for insulin, cortisol, and total and free testosterone concentration, which were all higher in the morning (+60%, +26%, +31% and +22%, respectively, p<0.05). The growth hormone, was twofold higher in the evening (p<0.05). The plasma glucose was ∼11% lower in the morning (p<0.05). Glucagon, norepinephrine, epinephrine and lactate were similar for the morning and evening trials (p>0.05), but the norepinephrine response to the exercise was increased in the morning (+46%, p<0.05), and it was accompanied by a 5-fold increase in the response of glucose. Muscle recruitment, as measured by electromyography, was similar between morning and evening trials (p>0.05). Our findings suggest that performance was improved in the evening, and it was accompanied by an improved hormonal and metabolic milieu.

Assessment of Gait Variability: Towards an Optimal Testing Protocol

Gait variability is frequently used to identify rehabilitation progresses in orthopedic and neurologic diseases by means of repeated testing. However, learning effects are a significant issue. This study examined if the inter-day reliability of gait variability parameters improves with an additional familiarization trial.

Memantine prevents memory consolidation failure induced by soluble beta amyloid in rats.

It has been well documented that β-amyloid (Aβ) peptide accumulation and aggregation in the brain plays a crucial role in the pathophysiology of Alzheimer’s disease (AD). However, a new orientation of the amyloid cascade hypothesis has evidenced that soluble forms of the peptide (sAβ) are involved in Aβ-induced cognitive impairment and cause rapid disruption of the synaptic mechanisms underlying memory. The primary aim of this study was to elucidate the effects of sAβ, acutely injected intracerebrally (i.c.v., 4 μM), on the short term and long term memory of young adult male rats, by using the novel object recognition task. Glutamatergic receptors have been proposed as mediating the effect of Aβ on synaptic plasticity and memory. Thus, we also investigated the effects of sAβ on prefrontal cortex (PFC) glutamate release and the specific contribution of N-methyl-D-aspartate (NMDA) receptor modulation to the effects of sAβ administration on the cognitive parameters evaluated. We found that a single i.c.v. injection of sAβ 2 h before testing did not alter the ability of rats to differentiate between a familiar and a novel object, in a short term memory test, while it was able to negatively affect consolidation/retrieval of long term memory. Moreover, a significant increase of glutamate levels was found in PFC of rats treated with the peptide 2 h earlier. Interestingly, memory deficit induced by sAβ was reversed by a NMDA-receptor antagonist, memantine (5 mg/kg i.p), administered immediately after the familiarization trial (T1). On the contrary, memantine administered 30 min before T1 trial, was not able to rescue long term memory impairment. Taken together, our results suggest that an acute i.c.v. injection of sAβ peptide interferes with the consolidation/retrieval of long term memory. Moreover, such sAβ-induced effect indicates the involvement of glutamatergic system, proposing that NMDA receptor inhibition might prevent or lead to the recovery of early cognitive impairment.

Importance of airflow for physiologic and ergogenic effects of precooling.

Cooling the body before exercise (precooling) has been studied as an ergogenic aid for many thermal conditions; however, airflow accompanying exercise is seldom reported. To determine whether the physiologic and ergogenic benefits of precooling before endurance exercise may be negated with semirealistic airflow in hot conditions. Crossover study. Climate-controlled chamber in a research laboratory. Ten fit, healthy cyclists. After a familiarization trial, participants completed 4 randomized, counterbalanced sessions consisting of no precooling versus precooling and no fan airflow versus airflow (~4.8 m/s) during exercise. Precooling was via chest-deep immersion (~24 °C) for 1 hour or until core temperature dropped 0.5 °C. Participants then cycled at 95% ventilatory threshold in a hot environment (temperature = 30 °C, relative humidity = 50%) until volitional exhaustion, core temperature reached >39.5 °C, or heart rate reached >95% of maximum. Thermal strain was assessed via core temperature (esophageal and rectal thermistors) and mean skin temperature (thermistors at 10 sites) and cardiovascular strain via heart rate and ratings of perceived exertion. Endurance time (28 ± 12 minutes without precooling or airflow) increased by 30 ± 23 minutes with airflow (~109%; 95% confidence interval = 12, 45 minutes; P < .001) and by 16 ± 15 minutes with precooling (~61%; 95% confidence interval = 4, 25 minutes; P = .013), but it was not further extended when the strategies were combined (29 ± 21 minutes longer than control). During cycling without precooling or airflow, mean core and skin temperatures were higher than in all other trials. Precooling reduced heart rate by 7-11 beats/min during the first 5 minutes of exercise, but this attenuation ended by 15 minutes. Most laboratory-based precooling studies have (inadvertently) overestimated the extent of the physiologic and ergogenic benefits for typical athlete-endurance situations. Precooling increases work capacity effectively when airflow is restricted but may have little or no benefit when airflow is present.

Intraday Reliability and Sensitivity of Four Functional Ability Tests in Older Women

Functional tests are commonly used to evaluate the functional ability of older individuals; however, intraday reliability and sensitivity are required to enable informed decisions on whether repeated trials are necessary and to ensure that the values obtained from a single session are a patient's true score. This study aimed to investigate the intraday reliability and sensitivity of four commonly used functional tests in older individuals. Seventy-one healthy older women (mean [SD]: age, 71.7 [7.3] yrs; body mass, 64.8 [10.2] kg; stature, 1.58 [0.07] m) performed the 6-m maximum walking speed, timed 8-foot up-and-go, chair sit-and-reach, and back scratch tests three times in one single session, with 1 min between trials. Reliability between all trials was examined using intraclass correlation coefficient, and sensitivity was examined using typical error. All tests were highly reliable (intraclass correlation coefficient range, 0.89-0.99), indicating no need for a familiarization trial. Typical error between trials 2 and 1 were 0.06 m·s-1, 0.42 s, 1.13 cm, 0.92 cm for the 6-m maximum walking speed, timed 8-foot up-and-go, chair sit-and-reach, and back scratch tests, respectively. Practitioners should perform two trials to examine whether the difference between them is less than the typical error reported here. These results should help practitioners ensure that scores obtained from an individual from these functional tests are a true reflection of their functional ability rather than measurement error.

Speed, force, and power values produced from nonmotorized treadmill test are related to sprinting performance.

The relationships between 30-m sprint time and performance on a nonmotorized treadmill (TM) test and a vertical jump test were determined in this investigation. Seventy-eight physically active men and women (22.9 ± 2.7 years; 73.0 ± 14.7 kg; 170.7 ± 10.4 cm) performed a 30-second maximal sprint on the curve nonmotorized TM after 1 familiarization trial. Pearson product-moment correlation coefficients produced significant (p ≤ 0.05) moderate to very strong relationships between 30-m sprint time and body mass (r = -0.37), %fat (r = 0.79), peak power (PP) (r = -0.59), relative PP (r = -0.42), time to peak velocity (r = -0.23) and TM sprint times at 10 m (r = 0.48), 20 m (r = 0.59), 30 m (r = 0.67), 40 m (r = 0.71), and 50 m (r = 0.75). Strong relationships between 30-m sprint time and peak (r = -0.479) and mean vertical jump power (r = -0.559) were also observed. Subsequently, stepwise regression was used to produce two 30-m sprint time prediction models from TM performance (TM1: body mass + TM data and TM2: body composition + TM data) in a validation group (n = 39), and then crossvalidated against another group (n = 39). As no significant differences were observed between these groups, data were combined (n = 72) and used to create the final prediction models (TM1: r = 0.75, standard error of the estimate (SEE) = 0.27 seconds; TM2: r = 0.84, SEE = 0.22 seconds). These final movement-specific models seem to be more accurate in predicting 30-m sprint time than derived peak (r = 0.23, SEE = 0.48 seconds) and mean vertical jump power (r = 0.31, SEE = 0.45 seconds) equations. Consequently, sprinting performance on the TM can significantly predict short-distance sprint time. It, therefore, may be used to obtain movement-specific measures of sprinting force, velocity, and power in a controlled environment from a single 30-second maximal sprinting test.

Characterization of the effects of the vasopressin V2 receptor on sweating, fluid balance, and performance during exercise.

A regulatory effect of arginine vasopressin (AVP) on sweat water conservation has been hypothesized but not definitively evaluated. AVP-mediated insertion of sweat and salivary gland aquaporin-5 (AQP5) water channels through activation of the vasopressin type 2 receptor (V2R) remains an attractive, yet unexplored, mechanism that could result in a more concentrated sweat with resultant decreased water loss. Ten runners participated in a double-blind randomized control treadmill trial under three separate pharmacological conditions: a placebo, V2R agonist (0.2 mg desmopressin), or V2R antagonist (30 mg tolvaptan). After a familiarization trial, runners ran for 60 min at 60% of peak speed followed by a performance trial to volitional exhaustion. Outcome variables were collected at three exercise time points: baseline, after the steady-state run, and after the performance run. Body weight losses were <2% across all three trials. Significant pharmacological condition effects were noted for urine osmolality [F = 84.98; P < 0.0001] and urine sodium concentration ([Na(+)]) [F = 38.9; P < 0.0001], which verified both pharmacological activation and inhibition of the V2R at the kidney collecting duct. Plasma osmolality and [Na(+)] demonstrated significant exercise (F = 26.0 and F = 11.1; P < 0.0001) and condition (F = 5.1 and F = 3.8; P < 0.05) effects (osmolality and [Na(+)], respectively). No significant exercise or condition effects were noted for either sweat or salivary [Na(+)]. Significant exercise effects were noted for plasma [AVP] (F = 22.3; P < 0.0001), peak core temperature (F = 103.3; P < 0.0001), percent body weight change (F = 6.3; P = 0.02), plasma volume change (F = 21.8; P < 0.0001), and thirst rating (F = 78.2; P < 0.0001). Performance time was not altered between conditions (P = 0.80). In summary, AVP acting at V2R does not appear to regulate water losses from body fluids other than renal excretion during exercise.

A-41 Free Communication/Poster - Immunology-Supplements

Recent research suggests that neuromuscular fatigue leads to increased electromechanical delay (EMD), and that differential recovery patterns are exhibited between the leg extensor and flexor muscles. However, it is unknown whether these fatigue-induced EMD responses vary by gender. PURPOSE: The purpose of this study was to investigate the effects of a fatigue-inducing bout of submaximal intermittent isometric contractions on the EMD of the leg extensors and flexors in college-aged females and males. METHODS: Twenty (mean±SD age=21.3±1.5 yrs) females and twenty-one college-aged (age=22.0±3.5) males participated in a familiarization trial followed by 2 randomly ordered experimental fatigue sessions, separated by 7(±1) days. Experimental trials involved testing of either the leg extensor or flexor muscles only, on each respective test day. All sessions began with participants performing maximal voluntary contractions (MVCs) followed by a fatigue-inducing protocol consisting of intermittent isometric contractions of the leg extensors or flexors using a 0.6 duty cycle (6s contraction, 4s relaxation) at 50% of MVC until volitional fatigue. MVCs were again performed at 0,7,15, and 30min post fatigue. EMD was calculated as the time (ms) difference between EMG and torque onset. A three-way repeated measures ANOVA was used to analyze the EMD data. RESULTS: There was no significant three-way interaction (P=0.526), nor two way interaction for time × gender (P=0.948) or muscle × gender (P=0.636), however there was a two-way interaction for muscle × time (P=0.001). For muscle × time, the EMD was greater for the leg flexors at all post fatigue time phases compared to Pre (P=0.001-0.016), but was only greater at immediately Post (i.e., 0) for the leg extensors (P=0.001). CONCLUSIONS: These findings showed that fatigue-induced increases in EMD exhibited differential recovery patterns between muscles such that the flexor EMD values had no recovery within 30min compared to more rapid recovery for the extensors. However, no gender-related differences were observed for the fatigue-induced EMD responses. These findings may have implications for performance and injury risks following fatiguing tasks, with the duration of the effects being muscle but not gender specific.

Oxygen cost of exercise hyperpnea is greater in women compared to men (882.3)

We tested the hypothesis that the O2 cost of exercise hyperpnea is greater in women compared to men. Healthy subjects (8M, 7F) first performed a maximal step cycle exercise test with esophageal and gastric balloon instrumentation followed by a hyperpnea familiarization trial on a separate day. Cardiorespiratory parameters were measured and flow‐ and pressure‐volume loops were constructed from the same breaths (~n=10) for each exercise stage. Days 3 and 4 involved exercise hyperpnea mimicking over 5 ventilatory levels while in the cycling position. Mimicking trials were repeated (n=4) for each ventilatory level. End‐tidal CO2 was controlled to a level corresponding to each exercise stage. Respiratory muscle O2 uptake (VO2rm) was linearly related to work of breathing (WOB) in men (r=0.94, P&lt;0.001) and women (r=0.88, P&lt;0.001). The VO2rm to VE relationship was assessed by fitting a regression accounting for viscous and resistive work. There was no difference in viscous work (P=0.45); however, the resistive component was ~13x greater in women (P&lt;0.05). At maximal ventilation the absolute VO2rm was similar between sexes (0.39 vs. 0.42 l min‐1, P=0.52) despite men having a greater VE (108 vs. 169 l min‐1); but the VO2rm represented a greater fraction of whole‐body VO2 in women (14.6 vs. 9.8%, P&lt;0.05). In conclusion, the O2 cost of exercise hyperpnea is greater in women owing to a greater resistive WOB.Grant Funding Source: Natural Sciences and Engineering Research Council of Canada

A new model to study visual attention in zebrafish

The major part of cognitive tasks applied to zebrafish has not fully assessed their attentional ability, a process by which the nervous system learns, organizes sensory input and generates coordinated behaviour. In an attempt to maximize the value of zebrafish as an animal model of cognition, we tested the possibility to apply a modified version of novel object recognition test named virtual object recognition test (VORT) using 2D geometrical shapes (square, triangle, circle, cross, etc.) on two iPod 3.5-inch widescreen displays, located on two opposite walls of the water tank. Each fish was subjected to a familiarization trial (T1), and after different time delays (from 5 min to 96 h) to a novel shape recognition trial (T2). A progressive decrease, across time, of memory performance, in terms of mean discrimination index and mean exploration time, was shown. The predictive validity was tested using cholinergic drugs. Nicotine (0.02 mg/kg intraperitoneally, IP) significantly increased, while scopolamine (0.025 mg/kg IP) and mecamylamine decreased, mean discrimination index. Zebrafish discriminated different movements (vertical, horizontal, oblique) and the discrimination index increased significantly when moving poorly discriminated shapes were presented, thus increasing visual attention. Taken together these findings demonstrate that VORT is a viable, fast and useful model to evaluate sustained attention in zebrafish and for predicting the efficacy of pharmacotherapies for cognitive disorders.

How fresh a look? A reply to Heyes

How Fresh a Look? A reply to Heyes Rose M. Scott, University of California Merced Renee Baillargeon, University of Illinois Heyes (in press) argues that all of the findings of infant false-belief understanding that have been published to date can be explained in terms of perceptual novelty and other low-level domain-general processes. We object to Heyes’s account on three grounds, as explained below. False-belief understanding before age 4 Until recently, it was generally assumed that children younger than about age 4 do not understand that agents can hold false beliefs. This assumption was based mainly on results from elicited-response tasks, which require answering a direct question about the likely behavior of an agent who holds a false belief. Onishi and Baillargeon (2005) cast doubt on this assumption when they published results from a novel non-elicited-response task showing that 15-month-olds can attribute false beliefs to others. To date, over 25 reports (see Table 1) have provided converging results with children ages 7 months to 4 years, using a wide range of verbal and non- verbal non-elicited-response tasks (including violation-of-expectation, anticipatory-looking, preferential-looking, anticipatory-pointing, and prompted-action tasks). Moreover, researchers have begun to develop and test processing models explaining why elicited-response tasks pose such difficulties for young children. We submit that it is this large and highly consistent body of work, and not just the “data from these infant false belief studies”, as Heyes (in press) believes, that is “establishing a new consensus in developmental science” (p. 3). Psychological reasoning in infancy Heyes (in press) argues that the existing experiments on infant false-belief understanding “fall short of demonstrating that infants have even an implicit theory of mind” (p. 2), and that infants may represent the events in these experiments “as colours, shapes, and movements, rather than as actions on objects by agents” (p. 6). These arguments ignore the fact that the experiments on infant false-belief understanding did not take place in a vacuum: The research on early psychological reasoning over the past 20 years makes clear that infants represent simple psychological events as “actions on objects by agents”, rather than as “colours, shapes, and movements” (for a comprehensive review, see Baillargeon et al., in press). It is true that researchers disagree about the specific nature and origins of infants’ psychological-reasoning abilities; but they generally agree that infants’ responses to agents’ actions are not merely driven by perceptual novelty, because there is overwhelming evidence to the contrary. As an example, consider Woodward’s (1998) seminal preference task and the myriad of findings that it has generated. In a typical task, infants first receive familiarization trials in which agent-1 repeatedly reaches for object-A as opposed to object-B. Next, infants receive a display trial in which agent-1 is absent and infants can observe that the locations of object-A and object- B have been switched. Finally, in the test trials, the agent returns and reaches for either object-A or object-B. Based on the consistent choice information provided in the familiarization trials, infants typically attribute to agent-1 a preference for object-A, they expect agent-1 to continue acting on this preference in the test trials, and they therefore detect a violation when agent-1 reaches for object-B instead. However, infants do not show this expectation: (1) if they are uncertain whether agent-1 is really an agent (e.g., Luo & Baillargeon, 2005; Shimizu & Johnson, 2004; Woodward, 1998); (2) if object-B is absent during the familiarization trials or is present but hidden from agent-1, so that agent-1’s repeated actions on object-A no longer provide choice information (e.g., Biro, Verschoor, & Coenen, 2011; Luo & Baillargeon, 2005, 2007; Luo &