Comparing several equations that predict peak VO2 using the 20-m multistage-shuttle run-test in 8-10-year-old children

This study compared the validity of reported equations as predictors of peak VO₂ in 8–10-year-old children. Participants (90 boys and girls aged 8–10 years) performed the multistage-shuttle-run-test (MSRT) and peak VO₂ was measured in field using a portable gas analyser. The equations that estimated peak VO₂ from the MSRT performance were chosen according to the age range of this study. As follows, the FITNESSGRAM reports and the equations of Leger et al. (Can J Appl Sport Sci 5: 77–84, 1988), Barnett et al. (Pediatr Exerc Sci 5:42–50, 1993), Matsuzaka et al. (Pediatr Exerc Sci 16:113–125, 2004) and Fernhall et al. (Am J Ment Retard 102:602–612, 1998) were used to estimate the peak VO₂ and compared with the directly measured value. The equation of Leger et al. (Can J Appl Sport Sci 5: 77–84, 1988) provided a mean difference (d) of 4.7 ml kg⁻¹ min⁻¹ and a 1.0 slope. The equation of Matsuzaka et al. (Pediatr Exerc Sci 16:113–125, 2004)(a) using maximal speed (MS) showed a higher d (5.4) than the remaining using total laps d (4.2). The equation of Barnett et al. (Pediatr Exerc Sci 5:42–50, 1993)(a) that includes triceps skinfold and MS showed the highest d (6.1) but the smallest range (24.1) and slope (0.6). Data from the FITNESSGRAM had the smallest d (1.8 ml kg⁻¹ min⁻¹), but also had the highest range between limits of agreement (28.6 ml kg⁻¹ min⁻¹) and a 1.2 slope. The lowest slope (0.4) and range (22.2 ml kg⁻¹ min⁻¹) were observed using the equation of Fernhall et al. (Am J Ment Retard 102:602–612, 1998). Log transformation of the data revealed that the equations of Matsuzaka et al. (Pediatr Exerc Sci 16:113–125, 2004)(a) (1.1*/÷1.25) and Fernhall et al. (Am J Ment Retard 102:602–612, 1998) (1.17*/÷1.25) showed the closest agreement among all, but they still yield unsatisfactory accuracy.     

Effects of visual stimuli on temporal order judgments of unimanual finger stimuli

Successive tactile stimuli, delivered one to each hand, are referred to spatial representation before they are ordered in time (Yamamoto and Kitazawa in Nat Neurosci 4:759–765 2001a). In the present study, we examined if this applies even when they are delivered unilaterally to fingers of a single hand. Tactile stimuli were delivered left-to-rightward relative to the body (2nd–3rd–4th) or in reverse with stimulus onset asynchrony of 100 ms. Simultaneously with the delivery of tactile stimuli, three of nine small squares arranged in a matrix of 3 × 3 were turned on as if they appeared near the tips of the fingers. Although subjects were instructed to ignore the visual stimuli and make a forced choice between the two orders of tactile stimuli, the correct-judgment probability depended on the direction of visual stimuli. It was greater than 95% when the direction of visual stimuli matched that of the tactile stimuli, but less than 50% when they were opposite to each other. When the right hand was rotated counterclockwise on the horizontal plane (90°) so that the fingers were pointing to the left, the preferred direction of visual stimuli that yielded the peak correct judgment was also rotated, although not to the full extent. These results show that subjects cannot be basing their tactile temporal order judgment solely on a somatotopic map, but rather on a spatial map on which both visual and tactile signals converge. An erratum to this article can be found at     

Tactile acuity in experienced Tai Chi practitioners: evidence for use dependent plasticity as an effect of sensory-attentional training

The scientific discovery of novel training paradigms has yielded better understanding of basic mechanisms underlying cortical plasticity, learning and development. This study is a first step in evaluating Tai Chi (TC), the Chinese slow-motion meditative exercise, as a training paradigm that, while not engaging in direct tactile stimulus training, elicits enhanced tactile acuity in long-term practitioners. The rationale for this study comes from the fact that, unlike previously studied direct-touch tactile training paradigms, TC practitioners focus specific mental attention on the body’s extremities including the fingertips and hands as they perform their slow routine. To determine whether TC is associated with enhanced tactile acuity, experienced adult TC practitioners were recruited and compared to age–gender matched controls. A blinded assessor used a validated method (Van Boven et al. in Neurology 54(12): 2230–2236, 2000) to compare TC practitioners’ and controls’ ability to discriminate between two different orientations (parallel and horizontal) across different grating widths at the fingertip. Study results showed that TC practitioners’ tactile spatial acuity was superior to that of the matched controls (P < 0.04). There was a trend showing TC may have an enhanced effect on older practitioners (P < 0.066), suggesting that TC may slow age related decline in this measure. To the best of our knowledge, this is the first study to evaluate a long-term attentional practice’s effects on a perceptual measure. Longitudinal studies are needed to examine whether TC initiates or is merely correlated with perceptual changes and whether it elicits long-term plasticity in primary sensory cortical maps. Further studies should also assess whether related somatosensory attentional practices (such as Yoga, mindfulness meditation and Qigong) achieve similar effects.     

Human discrimination of rotational velocities

Vestibular reflexes are critically important for stabilizing gaze and maintaining posture, but comparatively little is known about conscious perceptions of vestibular stimuli and how they may relate to balance function. We used psychophysical methods to determine the ability of normal subjects and a vestibular-deficient subject to discriminate among velocities of earth-vertical sinusoidal rotations. Discrimination thresholds in normal subjects rose from 2.26 deg/s at a peak velocity of 20 deg/s up to 5.16 deg/s at 150 deg/s. The relationship between threshold and peak angular velocity was well described by the power law function ΔI = 0.88I ^0.37, where I is the magnitude of the stimulus and ΔI is the discrimination threshold. The subject with bilateral vestibular hypofunction had thresholds more than an order of magnitude worse than normals. The performance of normal subjects is much better than that predicted by Weber’s Law, which states that discrimination thresholds increase proportionally with stimulus magnitude (i.e., ΔI/I = C, where C is the “Weber fraction”). This represents a remarkable exception to other sensory systems and may reflect the vestibular system’s ability to stabilize gaze and maintain posture even at high stimulus intensities. Quantifying this relationship may help elucidate the role of higher-level processes in maintaining balance and provide information to diagnose and guide therapy of patients with central causes for imbalance.     

Short and medium latency muscle responses evoked by electrical vestibular stimulation are a composite of all stimulus frequencies

Electrical vestibular stimulation produces biphasic responses in muscles maintaining balance. The two components of these muscle responses (termed the short latency and medium latency components) are believed to be independent and elicited by vestibular stimuli of different frequencies. We tested these hypotheses by determining (a) if frequency-specific stimulation protocols could evoke independently the short and medium latency responses and (b) whether these two components are triggered by distinct brain regions with a fixed time delay, interacting around 10 Hz. First, subjects were provided 10–25 Hz, 0–10 Hz, and 0–25 Hz vestibular stimuli to selectively modulate the short latency, medium latency, or both components of the response; and second, they were provided twenty sinusoidal stimuli from 1 to 20 Hz with a 0–20 Hz control trial, designed to determine whether an interaction between the short and medium latency responses occurs at a specific stimulation frequency. Both the 0–10 Hz and 10–25 Hz vestibular stimuli elicited multiphasic waveforms, suggesting the short and medium latency components were not modulated independently by the frequency-specific stimuli. Sinusoidal vestibular stimuli evoked responses at the stimulated frequency but no evidence of a reflex component interaction was observed. Instead, summation of the responses evoked by each of the sinusoidal stimuli resembled the biphasic response to broad bandwidth stimuli. Due to the lack of interaction and linear contribution of all stimulus frequencies to both the short and medium latency responses, the present results support the use of broad bandwidth electrical vestibular signal for physiological or clinical testing.     

Relevance of individual characteristics for thermoregulation during exercise in a hot-dry environment

The aim of this study was to investigate the relevance of individual characteristics for thermoregulation during prolonged cycling in the heat. For this purpose, 28 subjects cycled for 60 min at 60% VO_2peak in a hot-dry environment (36 ± 1°C; 25 ± 2% relative humidity, airflow 2.5 m/s). Subjects had a wide range of body mass (99–43 kg), body surface area (2.2–1.4 m²), body fatness (28–5%) and aerobic fitness level (VO_2peak = 5.0–2.1 L/min). At rest and during exercise, rectal and mean skin temperatures were measured to calculate the increase in body temperature (ΔT _body) during the trial. Net metabolic heat production (M _NET) and potential heat loss (by means of evaporation, radiation and convection) were calculated. Although subjects exercised at the same relative intensity, ΔT _body presented high between-subjects variability (range from 0.44 to 1.65°C). ΔT _body correlated negatively with body mass (r = −0.49; P < 0.01), body surface area (r = −0.47; P < 0.01) and T_body at rest (r = −0.37; P < 0.05), but it did not significantly correlate with body fatness (r = 0.12; P > 0.05). ΔT _body positively correlated with the body surface area/mass ratio (r = 0.46; P < 0.01) and the difference between M _NET and potential heat loss (r = 0.56; P < 0.01). In conclusion, a large body size (mass and body surface area) is beneficial to reduce ΔT _body during cycling exercise in the heat. However, subjects with higher absolute heat production (more aerobically fit) accumulate more heat because heat production may exceed potential heat loss (uncompensability).     

Target switching in curved human arm movements is predicted by changing a single control parameter

Straight-line movements have been studied extensively in the human motor-control literature, but little is known about how to generate curved movements and how to adjust them in a dynamic environment. The present work studied, for the first time to my knowledge, how humans adjust curved hand movements to a target that switches location. Subjects (n = 8) sat in front of a drawing tablet and looked at a screen. They moved a cursor on a curved trajectory (spiral or oval shaped) toward a goal point. In half of the trials, this goal switched 200 ms after movement onset to either one of two alternative positions, and subjects smoothly adjusted their movements to the new goal. To explain this adjustment, we compared three computational models: a superposition of curved and minimum-jerk movements (Flash and Henis in J Cogn Neurosci 3(3):220–230, 1991), Vector Planning (Gordon et al. in Exp Brain Res 99(1):97–111, 1994) adapted to curved movements (Rescale), and a nonlinear dynamical system, which could generate arbitrarily curved smooth movements and had a point attractor at the goal. For each model, we predicted the trajectory adjustment to the target switch by changing only the goal position in the model. As result, the dynamical model could explain the observed switch behavior significantly better than the two alternative models (spiral: P = 0.0002 vs. Flash, P = 0.002 vs. Rescale; oval: P = 0.04 vs. Flash; P values obtained from Wilcoxon test on R ² values). We conclude that generalizing arbitrary hand trajectories to new targets may be explained by switching a single control command, without the need to re-plan or re-optimize the whole movement or superimpose movements.     

A spin-drying technique for lyopreservation of mammalian cells

Stabilization of cellular material in the presence of glass-forming sugars at ambient temperatures is a viable approach that has many potential advantages over current cryogenic strategies. Experimental evidence indicates the possibility to preserve biomolecules in glassy matrices of low-molecular mobility using “glass-forming” sugars like trehalose at ambient temperatures. However, when cells are desiccated in trehalose solution using passive drying techniques, a glassy skin is formed at the liquid/vapor interface of the sample. This glassy skin prevents desiccation of the sample beyond a certain level of dryness and induces non-uniformities in the final water content. Cells trapped underneath this glassy skin may degrade due to a relatively high molecular mobility in the sample. This undesirable result underscores the need for development of a uniform, fast drying technique. In the present study, we report a new technique based on the principles of “spin drying” that can effectively address these problems. Forced convective evaporation of water along with the loss of solution due to centrifugal force leads to rapid vitrification of a thin layer of trehalose containing medium that remains on top of cells attached to the spinning glass substrate. The glassy layer produced has a consistent thickness and a small “surface-area-to-volume” ratio that minimizes any non-homogeneity. Thus, the chance of entrapping cells in a high-mobility environment decreases substantially. We compared numerical predictions to experimental observations of the drying time of 0.2–0.6 M trehalose solutions at a variety of spinning speeds ranging from 1000 to 4000 rpm. The model developed here predicts the formation of sugar films with thicknesses of 200–1000 nm, which was in good agreement with experimental results. Preliminary data suggest that after spin drying cells to about 0.159 ± 0.09 gH₂O/gdw (n = 11, ±SE), more than 95% of cells were able to preserve their membrane integrity. Membrane integrity after spin drying is therefore considerably higher than what is achieved by conventional drying methods; where about 90% of cells lose membrane integrity at 0.4 gH₂O/gdw (Acker et al. Cell Preserv. Technol. 1(2):129–140, 2002; Elliott et al. Biopreserv. Biobank. 6(4):253–260, 2009).     

Differential Genetic Etiology of Reading Difficulties as a Function of IQ: An Update

In order to test the hypothesis that the genetic etiology of reading disability differs as a function of IQ, composite reading performance data from 308 pairs of identical (monozygotic, MZ) twins and 440 pairs of fraternal (dizygotic, DZ) twins (254 same-sex and 186 opposite-sex) in which at least one member of each pair was classified as reading-disabled were subjected to multiple regression analysis (DeFries and Fulker, Behav Genet 15:467–473, 1985; Acta Genet Med Gemellol 37:205–216, 1988). In the total sample, heritability of the group deficit in reading performance (h_g²) was .61 (±.06). However, results of fitting an extended regression model to reading performance and IQ data suggested that the genetic etiology of reading disability differs as a linear function of IQ (p ≤ .04). When the basic regression model was fitted separately to data from twin pairs with Wechsler (Examiner's manual: Wechsler intelligence scale for children—revised, 1974; Examiner's manual: Wechsler adult intelligence scale—revised, 1981) Full Scale IQ scores in the upper and lower 25% of the sample, resulting estimates of h_g² were .75 (±.12) and .50 (±.10), respectively (p ≤ .045). These results suggest that reading difficulties in children with a higher IQ are due substantially to genetic influences and may require intensive remediation efforts.     

Peripheral photoplethysmography variability analysis of sepsis patients

Sepsis is associated with impairment in autonomic regulatory function. This work investigates the application of heart rate and photoplethysmogram (PPG) waveform variability analysis in differentiating two categories of sepsis, namely systemic inflammatory response syndrome (SIRS) and severe sepsis. Electrocardiogram-derived heart period (RRi) and PPG waveforms, measured from fingertips (Fin-PPG) and earlobes (Ear-PPG), of Emergency Department sepsis patients (n = 28) with different disease severity, were analysed by spectral technique, and were compared to control subjects (n = 10) in supine and 80° head-up tilted positions. Analysis of covariance (ANCOVA) was applied to adjust for the confounding factor of age. Low-frequency (LF, 0.04–0.15 Hz), mid-frequency (MF, 0.09–0.15 Hz) and high-frequency (HF, 0.15–0.60 Hz) powers were computed. The normalised MF power in Ear-PPG (MFnu_Ear) was significantly reduced in severe sepsis patients with hyperlactataemia (lactate > 2 mmol/l), compared to SIRS patients (P < 0.05). Moreover, in a group of normal controls, MFnu_Ear was not altered by head-up tilting (P > 0.05), suggesting that there may be a link between 0.1 Hz ear blood flow oscillation and tissue metabolic changes in sepsis, in addition to autonomic factors. The study highlighted the value of PPG spectral analysis in the non-invasive assessment of peripheral vascular regulation in sepsis patients, with potential implications in monitoring the progression of sepsis.     

Validity of accelerometry in ambulatory children and adolescents with cerebral palsy

To evaluate the validity of the ActiGraph accelerometer for the measurement of physical activity intensity in children and adolescents with cerebral palsy (CP) using oxygen uptake (VO₂) as the criterion measure. Thirty children and adolescents with CP (mean age 12.6 ± 2.0 years) wore an ActiGraph 7164 and a Cosmed K4b² portable indirect calorimeter during four activities; quiet sitting, comfortable paced walking, brisk paced walking and fast paced walking. VO₂ was converted to METs and activity energy expenditure and classified as sedentary, light or moderate-to-vigorous intensity according to the conventions for children. Mean ActiGraph counts min⁻¹ were classified as sedentary, light or moderate-to-vigorous (MVPA) intensity using four different sets of cut-points. VO₂ and counts min⁻¹ increased significantly with increases in walking speed (P < 0.001). Receiver operating characteristic (ROC) curve analysis indicated that, of the four sets of cut-points evaluated, the Evenson et al. (J Sports Sci 26(14):1557–1565, 2008) cut-points had the highest classification accuracy for sedentary (92%) and MVPA (91%), as well as the second highest classification accuracy for light intensity physical activity (67%). A ROC curve analysis of data from our participants yielded a CP-specific cut-point for MVPA that was lower than the Evenson cut-point (2,012 vs. 2,296 counts min⁻¹), however, the difference in classification accuracy was not statistically significant 94% (95% CI = 88.2–97.7%) vs. 91% (95% CI = 83.5–96.5%). In conclusion, among children and adolescents with CP, the ActiGraph is able to differentiate between different intensities of walking. The use of the Evenson cut-points will permit the estimation of time spent in MVPA and allows comparisons to be made between activity measured in typically developing adolescents and adolescents with CP.     

Respiratory compensation and blood pH regulation during variable intensity exercise in trained versus untrained subjects

To determine whether endurance-trained cyclists (T; n = 10) have a superior blood-respiratory buffering for metabolic acidosis relative to untrained subjects (UT; n = 10) during variable intensity exercise (VAR). On three occasions, T and UT pedaled for 24 min alternating high- and low-intensities as percentage of their second ventilatory threshold (VT₂): VAR_LOW 87.5–37.5% VT₂, VAR_MODERATE 125–25% VT₂, and VAR_HIGH 162.5–12.5% VT₂ to complete the same amount of work. Before and just after each VAR trial, maximal cycling power (P_MAX) was assessed. For each trial, the respiratory compensation for exercise acidosis (ventilatory equivalent for CO₂) and the final blood pH, lactate and bicarbonate concentrations were similar for T and UT subjects. However, after VAR_HIGH, UT reduced P_MAX (−14 ± 1%; P < 0.05) while T did not. Our data suggest that endurance training confers adaptations to withstand the low pH provoked by VAR without losing cycling power, although this response is not due to differences in blood-respiratory buffering.     

Aerobic fitness testing in 6- to 9-year-old children: reliability and validity of a modified Yo–Yo IR1 test and the Andersen test

This study analysed the reliability and validity of two intermittent running tests (the Yo–Yo IR1 test and the Andersen test) as tools for estimating VO_2max in children under the age of 10. Two groups, aged 6–7 years (grade 0, n = 18) and 8–9 years (grade 2, n = 16), carried out two repetitions of a modified Yo–Yo IR1 test (2 × 16 m) and the Andersen test, as well as an incremental treadmill test, to directly determine the VO_2max. No significant differences were observed in test–retest performance of the Yo–Yo IR1 test [693 ± 418 (±SD) and 670 ± 328 m, r ² = 0.79, CV = 19%, p > 0.05, n = 32) and the Andersen test (988 ± 77 and 989 ± 87 m, r ² = 0.86, CV = 3%, p > 0.05, n = 31). The Yo–Yo IR1 (r ² = 0.47, n = 31, p < 0.002) and Andersen test performance (r ² = 0.53, n = 32, p < 0.001) correlated with the VO_2max. Yo–Yo IR1 performance correlated with Andersen test performance (r ² = 0.74, n = 32, p < 0.0001). In conclusion, the Yo–Yo IR1 and the Andersen tests are reproducible and can be used as an indicator of aerobic fitness for 6- to 9-year-old children.     

Physical fitness factors to predict male Olympic wrestling performance

To determine differences in maximal strength and muscle power output of the arm and leg extensor muscles, peak and mean power during a modified standing crank-arm Wingate test, running speed, muscle extensibility, and anthropometric markers between elite and amateurs wrestlers according to the weight classes system; 92 male wrestlers were assigned into 6 groups according to their body mass (light, middle and heavy weight) and their competitive level (elite and amateur): Light Weight (body mass ranged between 55 and 68 kg) in elite (LW_E, n = 18) and amateur (LW_A, n = 15) level; Middle Weight (body mass ranged between 68 and 84 kg) in elite (MW_E, n = 18) and amateur (MW_A, n = 19) level; and Heavy Weight (body mass ranged between 84 and 100 kg) in elite (HW_E, n = 10) and amateur (HW_A, n = 12) level. Elite wrestlers were older (8–12%), had more training experience (25–37%), fat-free mass (3–5%), maximal strength in absolute and relative terms (8–25%), muscle power (14–30%), mean and peak power during crank-arm Wingate testing in absolute and relative terms (13–22%), jumping height (8–17%) as well as grip (6–19%) and back strength (7–20%) compared to amateur wrestlers. However, no differences were observed between elite and amateur groups in height, body mass index, percentage of body fat, hamstring extensibility and running speed. The present results suggest that the higher absolute and relative values of maximal strength, muscle power, and anaerobic metabolism, explained in part by the differences in lean mass and neural activation patterns, will give elite wrestlers a clear advantage during the most frequently used techniques in Olympic wrestling.     

Neural noise distorts perceived motion: the special case of the freezing illusion and the Pavard and Berthoz effect

When a slowly moving pattern is presented on a monitor which itself is moved, the pattern appears to freeze on the screen (Mesland and Wertheim in Vis Res 36(20):3325–3328, 1996) even if we move our head with the monitor, as with a head mounted display (Pavard and Berthoz in Perception 6:529–540, 1977). We present a simple model of these phenomena, which states that the perceived relative velocity between two stimuli (the pattern and the moving monitor) is proportional to the difference between the perceived velocities of these stimuli in space, minus a noise factor. The latter reflects the intrinsic noise in the neural signals that encode retinal image velocities. With noise levels derived from the literature the model fits empirical data well and also predicts strong distortions of visually perceived motion during vestibular stimulation, thus explaining both illusions as resulting from the same mechanism.     

Responses to Light of Sensorimotor and Visual Cortex Neurons in Rabbits with a Cryptic Focus of Excitation (a defensive dominant) in the CNS

In the sensorimotor cortex of rabbits with a formed cryptic (subthreshold) focus of excitation in the CNS, the spike frequencies of neurons responding to light stimulation were significantly lower (p = 0.01) than the spike frequencies of neurons not responding to light. Similar findings were obtained in the visual cortex of intact rabbits. In this case too, the spike frequencies of neurons responding to stimulation were significantly lower (p = 0.01) than the spike frequencies of neurons not responding to light stimulation. In both intact rabbits and rabbits with a cryptic focus of excitation formed in the CNS, 36 % of neurons in the sensorimotor cortex responded to light stimuli not specific to this area. In the sensorimotor cortex of rabbits with a cryptic focus of excitation formed in the CNS, as compared with intact rabbits, there were significantly more (p = 0.01) cells responding to light stimuli with latent periods of less than 100 msec and significantly fewer (p = 0.02) responding to light stimuli with latencies of 200–300 msec. In the visual cortex of rabbits with a formed cryptic focus of excitation in the CNS, as compared with intact rabbits, significantly fewer (p = 0.01) neurons responded to light stimuli with latent periods of 50–100 msec.     

Cardiac output and oxygen uptake relationship during physical effort in men and women over 60 years old

This study investigated the relationship between oxygen uptake (VO₂), cardiac output (Q), stroke volume (SV), and heart rate (HR) in 54 men and 77 women (age = 69 ± 5 years) during incremental effort. Subjects performed a maximal cycle-ergometer test and VO₂ was directly measured. HR and SV were assessed by ECG and cardiograph impedance. Regression equations were calculated for Q–VO₂, HR–VO₂, and Q–HR relationships. The equations obtained for women were (a) Q (l min⁻¹) = 2.61 + 4.67 VO₂ (l min⁻¹)(r ² = 0.84); (b) HR (bpm) = 62.03 + 46.55 VO₂ (l min⁻¹) (r ² = 0.72); (c) \textSV \text(ml)=100.6[1- \texte^{-2.6  \textVO₂  (1 \textmin-1)}]{\text{SV}\,{\text{(ml)}}}=100.6[1- {\text{e}}^{-2.6\; {\text{VO}_2}\;{(1\,{\text{min}}^{-1})}}] (r ² = 0.41); (d) HR (bpm) = 41.48 + 9.24 Q (l min⁻¹) (r ² = 0.73). Equations for men were (a) Q (l min⁻¹) = 2.52 + 5.70 VO₂ (l min⁻¹) (r ² = 0.89); (b) HR (bpm) = 66.31 + 32.35 VO₂ (l min⁻¹) (r ² = 0.72); (c) \textSV \text(ml)=143.7[1- \texte^{-1.7  \textVO₂  (1 \textmin-1)}]{\text{SV}\,{\text{(ml)}}}=143.7[1- {\text{e}}^{-1.7\; {\text{VO}_2}\;{(1\,{\text{min}}^{-1})}}] (r ² = 0.47); (d) HR (bpm) = 56.33 + 5.25 Q (l min⁻¹) (r ² = 0.69). The intercepts for Q–VO₂ and HR–VO₂ equations were similar for both genders, but the slopes were different (P < 0.05). The SV increased from baseline to 50–60% of VO₂ peak in both groups. No gender effect was found in SV increasing pattern, but the absolute values were in general higher for men (P > 0.05). A significant difference between men and women was observed for both slopes and intercepts in the Q–HR relationship (P < 0.05). In conclusion, (a) Q–VO₂ relation was linear during progressive effort; (b) regression intercepts were similar, but the slopes were higher for men compared to women; (c) SV–VO₂ relationship was nonlinear and maximum SV was reached at very submaximal workload; (d) older men exhibited higher Q upward potential as well higher SV but lower HR for a given submaximal workload than women of similar age.     

The effects of voluntary contraction intensity and gender on perceived exertion during isokinetic quadriceps exercise

The objectives of the present study were to: (1) examine perceived exertion across different target voluntary contraction intensities, (2) compare perceived exertion ratings with actual target intensities, and (3) compare perceived exertion ratings between males and females. The subjects for this study included 30 healthy, college-aged male (n=15) and female (n=15) volunteers. All subjects were free of orthopedic, cardiopulmonary, systemic and neurological disease. Each subject completed five maximal isokinetic, concentric quadriceps contractions in a seated position at 60° · s⁻¹ to determine their single, highest peak torque. All subjects then completed, in a random order, 3–5 submaximal isokinetic contractions at 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% of their single, highest peak torque. Each relative contraction level (i.e., percentage) was achieved by having the subjects attempt to match the peak of their torque curve to a horizontal line on a computer monitor. Perceived exertion was measured by asking the subjects to provide a number that corresponded to the feelings in their quadriceps during exercise by viewing a modified category-ratio (CR-10) scale. The results of a two-factor (gender × intensity) analysis of variance revealed a significant, intensity main effect (F _8,232=92.19, P < 0.001, η²=0.77, 1–β=0.99) and no significant gender main effect (F _8,232=2.66, P = 0.11, η²=0.09, 1–β=0.35) or interactions (F _8,232 = 1.01, P=0.43, η²=0.04, 1–β=0.46). The findings of this study demonstrate that perceived exertion is significantly (P < 0.05) different from the specific target values on the CR-10 scale at 10%, and 50–90% maximum voluntary contraction. The results revealed that the increase in perceived exertion across the contraction intensities could be fit to both linear (F _1,29=205.41, P < 0.001, η²=0.88, 1–β=0.99) and quadratic (F _1,29=10.05, P=0.004, η²=0.26, 1–β=0.87) trends. These findings suggest that perceived exertion is underestimated during submaximal isokinetic exercise, and is not different between males and females. Accepted: 18 October 2000     

Audio-visual facilitation of the mu rhythm

Previous studies demonstrate that perception of action presented audio-visually facilitates greater mirror neuron system (MNS) activity in humans (Kaplan and Iacoboni in Cogn Process 8(2):103–113, 2007) and non-human primates (Keysers et al. in Exp Brain Res 153(4):628–636, 2003) than perception of action presented unimodally. In the current study, we examined whether audio-visual facilitation of the MNS can be indexed using electroencephalography (EEG) measurement of the mu rhythm. The mu rhythm is an EEG oscillation with peaks at 10 and 20 Hz that is suppressed during the execution and perception of action and is speculated to reflect activity in the premotor and inferior parietal cortices as a result of MNS activation (Pineda in Behav Brain Funct 4(1):47, 2008). Participants observed experimental stimuli unimodally (visual-alone or audio-alone) or bimodally during randomized presentations of two hands ripping a sheet of paper, and a control video depicting a box moving up and down. Audio-visual perception of action stimuli led to greater event-related desynchrony (ERD) of the 8–13 Hz mu rhythm compared to unimodal perception of the same stimuli over the C3 electrode, as well as in a left central cluster when data were examined in source space. These results are consistent with Kaplan and Iacoboni’s (in Cogn Process 8(2):103–113, 2007), findings that indicate audio-visual facilitation of the MNS; our left central cluster was localized approximately 13.89 mm away from the ventral premotor cluster identified in their fMRI study, suggesting that these clusters originate from similar sources. Consistency of results in electrode space and component space support the use of ICA as a valid source localization tool.