Pathophysiology of battlefield associated traumatic brain injury

As more data is accumulated from Operation Iraqi Freedom and Operation Enduring Freedom (OEF in Afghanistan), it is becoming increasing evident that traumatic brain injury (TBI) is a serious and highly prevalent battle related injury. Although traditional TBIs such as closed head and penetrating occur in the modern battle space, the most common cause of modern battle related TBI is exposure to explosive blast. Many believe that explosive blast TBI is unique from the other forms of TBI. This is because the physical forces responsible for explosive blast TBI are different than those for closed head TBI and penetrating TBI. The unique force associated with explosive blast is the blast shock pressure wave. This shock wave occurs over a very short period, milliseconds, and has a specific profile known as the Freidlander curve. This pressure–time curve is characterized by an initial very rapid up-rise followed by a longer decay that reaches a negative inflection point before returning to baseline. This is important as the effect of this shock pressure on brain parenchyma is distinct. The diffuse interaction of the pressure wave with the brain leads to a complex cascade of events that affects neurons, axons, glia cells, and vasculature. It is only by properly studying this disease will meaningful therapies be realized.     

Measuring Head Kinematics in Football: Correlation Between the Head Impact Telemetry System and Hybrid III Headform

Over the last decade, advances in technology have enabled researchers to evaluate concussion biomechanics through measurement of head impacts sustained during play using two primary methods: (1) laboratory reconstruction of open-field head contact, and (2) instrumented helmets. The purpose of this study was to correlate measures of head kinematics recorded by the Head Impact Telemetry (HIT) System (Simbex, NH) with those obtained from a Hybrid III (HIII) anthropometric headform under conditions that mimicked impacts occurring in the NFL. Linear regression analysis was performed to correlate peak linear acceleration, peak rotational acceleration, Gadd Severity Index (GSI), and Head Injury Criterion (HIC₁₅) obtained from the instrumented helmet and HIII. The average absolute location error between instrumented helmet impact location and the direction of HIII head linear acceleration were also calculated. The HIT System overestimated Hybrid III peak linear acceleration by 0.9% and underestimated peak rotational acceleration by 6.1% for impact sites and velocities previously identified by the NFL as occurring during play. Acceleration measures for all impacts were correlated; however, linear was higher (r ² = 0.903) than rotational (r ² = 0.528) primarily due to lower HIT System rotational acceleration estimates at the frontal facemask test site. Severity measures GSI and HIC were also found to be correlated, albeit less than peak linear acceleration, with the overall difference between the two systems being less than 6.1% for either measure. Mean absolute impact location difference between systems was 31.2 ± 46.3° (approximately 0.038 ± 0.050 m), which was less than the diameter of the impactor surface in the test. In instances of severe helmet deflection (2.54–7.62 cm off the head), the instrumented helmet accurately measured impact location but overpredicted all severity metrics recorded by the HIII. Results from this study indicate that measurements from the two methods of study are correlated and provide a link that can be used to better interpret findings from future study using either technology.     

Brain Injuries from Blast

Traumatic brain injury (TBI) from blast produces a number of conundrums. This review focuses on five fundamental questions including: (1) What are the physical correlates for blast TBI in humans? (2) Why is there limited evidence of traditional pulmonary injury from blast in current military field epidemiology? (3) What are the primary blast brain injury mechanisms in humans? (4) If TBI can present with clinical symptoms similar to those of Post-Traumatic Stress Disorder (PTSD), how do we clinically differentiate blast TBI from PTSD and other psychiatric conditions? (5) How do we scale experimental animal models to human response? The preponderance of the evidence from a combination of clinical practice and experimental models suggests that blast TBI from direct blast exposure occurs on the modern battlefield. Progress has been made in establishing injury risk functions in terms of blast overpressure time histories, and there is strong experimental evidence in animal models that mild brain injuries occur at blast intensities that are similar to the pulmonary injury threshold. Enhanced thoracic protection from ballistic protective body armor likely plays a role in the occurrence of blast TBI by preventing lung injuries at blast intensities that could cause TBI. Principal areas of uncertainty include the need for a more comprehensive injury assessment for mild blast injuries in humans, an improved understanding of blast TBI pathophysiology of blast TBI in animal models and humans, the relationship between clinical manifestations of PTSD and mild TBI from blunt or blast trauma including possible synergistic effects, and scaling between animals models and human exposure to blasts in wartime and terrorist attacks. Experimental methodologies, including location of the animal model relative to the shock or blast source, should be carefully designed to provide a realistic blast experiment with conditions comparable to blasts on humans. If traditional blast scaling is appropriate between species, many reported rodent blast TBI experiments using air shock tubes have blast overpressure conditions that are similar to human long-duration nuclear blasts, not high explosive blasts.     

Skull Flexure as a Contributing Factor in the Mechanism of Injury in the Rat when Exposed to a Shock Wave

The manner in which energy from an explosion is transmitted into the brain is currently a highly debated topic within the blast injury community. This study was conducted to investigate the injury biomechanics causing blast-related neurotrauma in the rat. Biomechanical responses of the rat head under shock wave loading were measured using strain gauges on the skull surface and a fiber optic pressure sensor placed within the cortex. MicroCT imaging techniques were applied to quantify skull bone thickness. The strain gauge results indicated that the response of the rat skull is dependent on the intensity of the incident shock wave; greater intensity shock waves cause greater deflections of the skull. The intracranial pressure (ICP) sensors indicated that the peak pressure developed within the brain was greater than the peak side-on external pressure and correlated with surface strain. The bone plates between the lambda, bregma, and midline sutures are probable regions for the greatest flexure to occur. The data provides evidence that skull flexure is a likely candidate for the development of ICP gradients within the rat brain. This dependency of transmitted stress on particular skull dynamics for a given species should be considered by those investigating blast-related neurotrauma using animal models.     

Training for a new environment: Using military operational concepts in counseling veterans

Since September 11, 2001, the United States has engaged in an extended period of military conflict, resulting in 4.1 million men and women serving in support of Operation Enduring Freedom, Operation Iraqi Freedom, and Operation New Dawn. Whereas not all servicemembers experience mental health issues, many have experienced difficulties with readjusting to the civilian world, often requiring mental health services both inside and outside of the Department of Veterans Affairs. Issues related to stigma and military culture contribute to barriers not only for veterans seeking treatment but for clinicians providing services who may lack experience with military culture. This article provides a framework to use military concepts in clinical sessions to further therapeutic engagement with the military/veteran client.     

Upper body power as a determinant of classical cross-country ski performance

The purpose of this study was to evaluate the relationship between short (≤60 s) and long duration (4–12 min) measures of upper body power (UBP) and mass start classical cross-country ski performance. Several experienced skiers (eight men, five women) completed three separate tests of UBP on a double poling ergometer: two tests of highest average power output for 10 s (UBP₁₀) and 60 s (UBP₆₀), and an incremental test to exhaustion to measure peak oxygen uptake (VO_2PEAK) and peak power output (UBP_PEAK). Lastly, subjects competed in a 10-km classical cross-country ski race from which race speed (RS) was computed. RS correlated highly with UBP₁₀ (r = 0.93; P < 0.05), UBP₆₀ (r = 0.92; P < 0.05), and UBP_PEAK (r = 0.94; P < 0.05); the correlation was lower but still significant for VO_2PEAK (r = 0.88; P < 0.05). These findings suggest that both short and long duration measures of UBP are important determinants of mass start classical ski race performance.     

Validation of Concussion Risk Curves for Collegiate Football Players Derived from HITS Data

For several years, Virginia Tech and other schools have measured the frequency and severity of head impacts sustained by collegiate American football players in real time using the Head Impact Telemetry (HIT) System of helmet-mounted accelerometers. In this study, data from 37,128 head impacts collected at Virginia Tech during games from 2006 to 2010 were analyzed. Peak head acceleration exceeded 100 g in 516 impacts, and the Head Injury Criterion (HIC) exceeded 200 in 468 impacts. Four instrumented players in the dataset sustained a concussion. These data were used to develop risk curves for concussion as a function of peak head acceleration and HIC. The validity of this biomechanical approach was assessed using epidemiological data on concussion incidence from other sources. Two specific aspects of concussion incidence were addressed: the variation by player position, and the frequency of repeat concussions. The HIT System data indicated that linemen sustained the highest overall number of head impacts, while skill positions sustained a higher number of more severe head impacts (peak acceleration > 100 g or HIC > 200). When weighted using injury risk curves, the HIT System data predicted a higher incidence of concussion in skill positions compared to linemen at rates that were in strong agreement with the epidemiological literature (Pearson’s r = 0.72–0.87). The predicted rates of repeat concussions (21–39% over one season and 33–50% over five seasons) were somewhat higher than the ranges reported in the epidemiological literature. These analyses demonstrate that simple biomechanical parameters that can be measured by the HIT System possess a high level of power for predicting concussion.     

Variation of the impact duration during the in vitro insertion of acetabular cup implants

The acetabular cup (AC) is an implant impacted into a bone cavity and used for hip prosthesis surgery. Initial stability of the AC is an important factor for long term surgical success. The aim of this study is to determine the variations of the impact duration during AC implant insertion.Twenty-two bone samples taken from bovine femurs were prepared ex vivo for the insertion of an acetabular cup implant, following the surgical procedure used in the clinic. For each bone sample, ten impacts were applied using reproducible mass falls (3.5 kg) in order to insert the AC implant. Each impact duration was recorded using a wide bandwidth force sensor.For all bone samples, the impact duration was shown to first decrease as a function of the impact number, then reaching a stationary value equal in average to 4.2 ± 0.7 ms after an average number of 4.1 ± 1.7 impacts. The impact duration may be related to variations of the bone–implant interface contact rigidity because of an increase the amount of bone tissue in contact with the AC implant.Measurements of impact duration have a good potentiality for clinical application to assist the surgeon during the insertion of the AC implant, providing valuable information on the bone–implant interface contact properties.     

A psychophysiological investigation of emotion regulation in chronic severe posttraumatic stress disorder

There have been few direct examinations of the volitional control of emotional responses to provocative stimuli in PTSD. To address this gap, an emotion regulation task was administered to 27 Operation Enduring Freedom/Operation Iraqi Freedom combat veterans and 23 healthy controls. Neutral and aversive photographs were presented to participants who did or did not employ emotion regulation strategies. Objective indices included corrugator electromyogram, the late positive potential, and the electrocardiogram. On uninstructed trials, participants with PTSD exhibited blunted cardiac reactivity rather than the exaggerated cardioacceleratory responses seen in trauma cue reactivity studies. On interleaved regulation trials, no measure evidenced group differences in voluntary emotion regulation. Persons with PTSD may not differ from normals in their capacity to voluntarily regulate normative emotional responses to provocative stimuli in the laboratory, though they may nevertheless respond differentially on uninstructed trials and endorse symptoms of dyscontrol pathognomonic of the disorder outside of the laboratory.     

指端光电容积脉搏波在循环功能动态监测中的意义

目的探讨指端光电容积脉搏波在循环功能动态监测中的意义。方法择期骨伤科手术治疗患者110例,其中男性69例,女性41例;年龄29～69岁。麻醉手术期间动态记录容积脉搏波变化,提取波峰形态和血流曲线上Y1、Y2、Y33个特征参数,观察并分析其变化规律。结果波形分为两类,主波峰Y1大致归为5种形态：锐锋1、锐锋2、前钝后锐峰、钝圆峰、前锐后钝峰,其动态变化与小动脉和微动脉的紧张性和弹性直接相关。Y1、Y2、Y33个特征参数值的动态变化在一定范围内与失血量及失血速度密切相关。结论①分析指端光电容积脉搏波峰形动态变化有助于评估人体小动脉和微动脉血管紧张性和弹性,监测微循环血流灌注变化。②分析Y1、Y2、Y33个特征参数值的动态变化有助于及时发现微循环血流灌注量减少,早期预测失血性休克的发生、发展,指导临床液体复苏治疗。     

The effects of 6-week-decoupled bi-pedal cycling on submaximal and high intensity performance in competitive cyclists and triathletes

Aim of this work was to examine the effects of decoupled two-legged cycling on (1) submaximal and maximal oxygen uptake, (2) power output at 4 mmol L⁻¹ blood lactate concentration, (3) mean and peak power output during high intensity cycling (30 s sprint) and (4) isometric and dynamic force production of the knee extensor and flexor muscles. 18 highly trained male competitive male cyclists and triathletes (age 24 ± 3 years; body height 179 ± 11 cm; body mass 78 ± 8 kg; peak oxygen uptake 5,070 ± 680 mL min⁻¹) were equally randomized to exercise on a stationary cycle equipped either with decoupled or with traditional crank system. The intervention involved 1 h training sessions, 5 times per week for 6 weeks at a heart rate corresponding to 70% of VO_2peak. VO₂ at 100, 140, 180, 220 and 260 and power output at 4 mmol L⁻¹ blood lactate were determined during an incremental test. VO_2peak was recorded during a ramp protocol. Mean and peak power output were assessed during a 30 s cycle sprint. The maximal voluntary isometric strength of the quadriceps and biceps femoris muscles was obtained using a training machine equipped with a force sensor. No differences were observed between the groups for changes in any variable (P = 0.15–0.90; effect size = 0.00–0.30). Our results demonstrate that a 6 week (30 sessions) training block using decoupled crank systems does not result in changes in any physiological or performance variables in highly trained competitive cyclists.     

Home dim light melatonin onsets with measures of compliance in delayed sleep phase disorder

The dim light melatonin onset (DLMO) assists with the diagnosis and treatment of circadian rhythm sleep disorders. Home DLMOs are attractive for cost savings and convenience, but can be confounded by home lighting and sample timing errors. We developed a home saliva collection kit with objective measures of light exposure and sample timing. We report on our first test of the kit in a clinical population. Thirty‐two participants with delayed sleep phase disorder (DSPD; 17 women, aged 18–52 years) participated in two back‐to‐back home and laboratory phase assessments. Most participants (66%) received at least one 30‐s epoch of light >50 lux during the home phase assessments, but for only 1.5% of the time. Most participants (56%) collected every saliva sample within 5 min of the scheduled time. Eighty‐three per cent of home DLMOs were not affected by light or sampling errors. The home DLMOs occurred, on average, 10.2 min before the laboratory DLMOs, and were correlated highly with the laboratory DLMOs (r = 0.93, P < 0.001). These results indicate that home saliva sampling with objective measures of light exposure and sample timing, can assist in identifying accurate home DLMOs.     

The PWC170: comparison of different stage lengths in 11–16 year olds

It is unknown how the estimation of aerobic fitness in children and adolescents compares among physical working capacity (PWC) protocols with different stage lengths. The purpose of this study was twofold: (1) compare PWC tests with 2-, 3-, and 6-min stage lengths in youth, and (2) examine the relationship between PWC at a heart rate (HR) of 170 beats min⁻¹ (PWC170) and peak oxygen consumption (VO₂peak). Fifty youth (31 m, 19 f), aged 11–16 years participated. Each participant visited the laboratory twice and performed three PWC tests (2-, 3-, 6-min stages) on a cycle ergometer. Tests usually consisted of three stages of increasing loads with the goal of reaching HR ≥ 165 beats min⁻¹. Individual regression lines were created to predict workload at HR = 170 beats∙min⁻¹ for each test. Participants completed two VO_2peak tests, both running and cycling. Repeated measures ANOVA was used to compare PWC170 values. Pearson correlation was used to assess the relationships between VO_2peak and power output for different PWC170 stage lengths. The three PWC170 protocols differ significantly; therefore, it is not advisable to directly compare results from different protocols. Furthermore, PWC170 showed moderate associations with VO_2peak, with the 2-min protocol showing the best correlation.     

Enhancement of the finger cold-induced vasodilation response with exercise training

Cold-induced vasodilatation (CIVD) is a cyclical increase in finger temperature that has been suggested to provide cryoprotective function during cold exposures. Physical fitness has been suggested as a potential factor that could affect CIVD response, possibly via central (increased cardiac output, decreased sympathetic nerve activity) and/or peripheral (increased microcirculation) cardiovascular and neural adaptations to exercise training. Therefore, the purpose of this study was to investigate the effect of endurance exercise training on the CIVD response. Eighteen healthy males trained 1 h d⁻¹ on a cycle ergometer at 50% of peak power output, 5 days week⁻¹ for 4-weeks. Pre, Mid, Post, and 10 days after the cessation of training and on separate days, subjects performed an incremental exercise test to exhaustion (\mathop V ^· \textO_2\textpeak ), (\mathop V\limits^{ \cdot }\!\! {\text{O}}_{{2{\text{peak}}}} ), and a 30-min hand immersion in 8°C water to examine their CIVD response. The exercise-training regimen significantly increased \mathop V ^·\textO_2\textpeak \mathop V\limits^{ \cdot }\!\!{\text{O}}_{{2{\text{peak}}}} (Pre: 46.0 ± 5.9, Mid: 52.5 ± 5.7, Post: 52.1 ± 6.2, After: 52.6 ± 7.6 ml kg⁻¹ min⁻¹; P < 0.001). There was a significant increase in average finger skin temperature (Pre: 11.9 ± 2.4, After: 13.5 ± 2.5°C; P < 0.05), the number of waves (Pre: 1.1 ± 1.0, After: 1.7 ± 1.1; P < 0.001) and the thermal sensation (Pre: 1.7 ± 0.9, After: 2.5 ± 1.4; P < 0.001), after training. In conclusion, the aforementioned endurance exercise training significantly improved the finger CIVD response during cold-water hand immersion.     

Maximum Principal Strain and Strain Rate Associated with Concussion Diagnosis Correlates with Changes in Corpus Callosum White Matter Indices

On-field monitoring of head impacts, combined with finite element (FE) biomechanical simulation, allow for predictions of regional strain associated with a diagnosed concussion. However, attempts to correlate these predictions with in vivo measures of brain injury have not been published. This article reports an approach to and preliminary results from the correlation of subject-specific FE model-predicted regions of high strain associated with diagnosed concussion and diffusion tensor imaging to assess changes in white matter integrity in the corpus callosum (CC). Ten football and ice hockey players who wore instrumented helmets to record head impacts sustained during play completed high field magnetic resonance imaging preseason and within 10 days of a diagnosed concussion. The Dartmouth Subject-Specific FE Head model was used to generate regional predictions of strain and strain rate following each impact associated with concussion. Maps of change in fractional anisotropy (FA) and median diffusivity (MD) were generated for the CC of each athlete to correlate strain with change in FA and MD. Mean and maximum strain rate correlated with change in FA (Spearman ρ = 0.77, p = 0.01; 0.70, p = 0.031), and there was a similar trend for mean and maximum strain (0.56, p = 0.10; 0.6, p = 0.07), as well as for maximum strain with change in MD (−0.63, p = 0.07). Change in MD correlated with injury-to-imaging interval (ρ = −0.80, p = 0.006) but change in FA did not (ρ = 0.18, p = 0.62). These results provide preliminary confirmation that model-predicted strain and strain rate in the CC correlate with changes in indices of white matter integrity.     

Maternal stress and hair cortisol among pregnant women following hurricane Florence

Natural disasters represent major stressors, resulting in psychological distress and physiological responses such as increased cortisol. During pregnancy, this impacts not only maternal well-being, but also fetal development. In 2018, Hurricane Florence caused extensive damage across the eastern United States. Studies indicated that compared to married pregnant women, unmarried pregnant women had higher risk of distress. Here we assess hair cortisol among a subsample of participants, and variations based on marital status.

Methods

We analyzed multiple stress measures among 37 participants who were pregnant during Hurricane Florence. We used questionnaires modeled on previous studies to assess hardship associated with the hurricane, psychological distress, sociodemographic characteristics, social support, and food security. We analyzed cortisol concentrations in proximal and distal hair sections, representing stress around the time of the disaster (distal) and 3–4 months following the disaster (proximal). We used linear regression to test relationships between hair cortisol and self-report stress measures, and variations based on marital status.

Results

Self-report measures of distress and hardship were similar among married and unmarried participants. Mean cortisol levels in distal and proximal sections were higher among unmarried participants. Controlling for confounding variables, hardship was not associated with hair cortisol. Distress predicted cortisol in distal sections (β = .482, p = .018), with a trend for proximal sections (β = .368, p = .055). Marital status was a significant predictor of distal (β = .388, p = .027) and proximal (β = .333, p = .047) hair cortisol, explaining 8.6%–11.7% of unique variance.

Conclusions

Preexisting and intersecting risk factors likely place unmarried pregnant individuals at risk of stress during and following a disaster.     

Alpha‐wave frequency characteristics in health and insomnia during sleep

Appearances of alpha waves in the sleep electrencephalogram indicate physiological, brief states of awakening that lie in between wakefulness and sleep. These microstates may also cause the loss in sleep quality experienced by individuals suffering from insomnia. To distinguish such pathological awakenings from physiological ones, differences in alpha‐wave characteristics between transient awakening and wakefulness observed before the onset of sleep were studied. In polysomnographic datasets of sleep‐healthy participants (n = 18) and patients with insomnia (n = 10), alpha waves were extracted from the relaxed, wake state before sleep onset, wake after sleep‐onset periods and arousals of sleep. In these, alpha frequency and variability were determined as the median and standard deviation of inverse peak‐to‐peak intervals. Before sleep onset, patients with insomnia showed a decreased alpha variability compared with healthy participants (P < 0.05). After sleep onset, both groups showed patterns of decreased alpha frequency that was lower for wake after sleep‐onset periods of shorter duration. For patients with insomnia, alpha variability increased for short wake after sleep‐onset periods. Major differences between the two groups were encountered during arousal. In particular, the alpha frequency in patients with insomnia rebounded to wake levels, while the frequency in healthy participants remained at the reduced level of short wake after sleep‐onset periods. Reductions in alpha frequency during wake after sleep‐onset periods may be related to the microstate between sleep and wakefulness that was described for such brief awakenings. Reduced alpha variability before sleep may indicate a dysfunction of the alpha generation mechanism in insomnia. Alpha characteristics may also prove valuable in the study of other sleep and attention disorders.     

<Emphasis Type="Italic">In situ</Emphasis> and <Emphasis Type="Italic">ex vivo</Emphasis> evaluation of a wireless magnetoelastic biliary stent monitoring system

This paper presents the in situ and ex vivo evaluation of a system that wirelessly monitors the accumulation of intimal tissue and sludge in a biliary stent. The sensing element, located within the stent, is a magnetoelastic resonator that is queried by a wireless radio frequency signal. The in situ testing uses a commercially-available self-expanding biliary stent enhanced with a 1 mm × 25 mm magnetoelastic ribbon sensor (formed from Metglas™ 2605SA1). The stent has a conformal magnetic layer (consisting of strontium ferrite particles suspended in polydimethylsiloxane) that biases the sensor. The external interrogation module is able to acquire a signal from the sensor from a distance of at least 5 cm while the sensor is implanted in a porcine carcass and loaded with biological fluids. The ex vivo testing uses bile harvested from the porcine carcass. The response of a 1 mm × 25 mm magnetoelastic ribbon sensor is first calibrated with fluids of known density and viscosity, and the calibrated sensor is used to estimate that the viscosity of the harvested bile is 2.7–3.7 cP. The test results presented in this paper illustrate the fundamental usability of the system when the sensor is implanted, loaded by biological fluids, and interrogated in a surgical setup.     

Influence of age, sex, and aerobic capacity on forearm and skin blood flow and vascular conductance

This study investigated the influence of age, sex, and aerobic capacity on resting and peak forearm and cutaneous blood flow (FBF, CBF). We recruited 93 female and 129 male subjects (age range 16–76 years). FBF and CBF were assessed by plethysmography and laser-Doppler flowmetry, respectively. Peak FBF was obtained following 5 min forearm vascular occlusion and peak CBF in response to local skin heating of 42°C. Blood pressure was measured manually and by Finapres. Maximal oxygen uptake (VO_2max) was obtained from a treadmill exercise stress test. Age was associated with declines in resting FBF (y = −1.176 ln(x) + 6.6899, r ² = 0.45) and peak FBF (y = −17.21 ln(x) + 93.843, r ² = 0.53) (both p < 0.05). Peak CBF decreased with increasing age (y = −223.6 ln(x) + 1,102.9, r ² = 0.34) (p < 0.05), but resting CBF was unchanged (p > 0.05). Males had higher resting and peak FBF than females (p < 0.05) and these variables were related to ageing better in males (y = −1.245 ln(x) + 7.188, r ² = 0.71 and y = −18.53 ln(x) + 102.82, r ² = 0.69) than in females (y = −1.149 ln(x) + 6.4307, r ² = 0.38 and y = −16.59 ln(x) + 88.872, r ² = 0.55). There were no sex differences in resting CBF (p > 0.05). Peak CBF was much better related to ageing in males than females (y = −276.1 ln(x) + 1,365.4, r ² = 0.53 vs. y = −183.1 ln(x) + 907.86, r ² = 0.28). VO_2max decreased with advancing age and this decline was associated with the decline in peak FBF (y = −0.5933x + 10.91, r ² = 0.36, p < 0.05) but not with peak CBF (p > 0.05). These results suggest that healthy ageing is associated with a curvilinear decline in resting and peak forearm and peak cutaneous vasodilator capacity, with males more severely affected than females. The data indicate that peak FBF is influenced by VO_2max but peak CBF is not.