Age-related differences in cutaneous warm sensation thresholds of human males in thermoneutral and cool environments

The purpose of this study was to investigate age-related differences in cutaneous temperature thresholds for warm thermal sensitivity in a thermoneutral (28 °C) and in a cool environment (22 °C). Peripheral warm thresholds were measured on nine body regions (cheek, chest, abdomen, upper arm, forearm, hand, thigh, shin, and foot) using a thermal stimulator in 12 young (22±1 years) and 13 elderly male subjects (67±3 years). The results showed that: (1) mean skin temperature did not differ by age in both environments; (2) the cutaneous warm thresholds for the hand, shin, and foot were significantly higher for the elderly than for the young in both environments (p<0.01), whereas the remaining body parts showed no age difference; (3) the most insensitive region for elderly males was the shin for both environments (p<0.01), while for young there was no statistical significant difference with T_a 28 °C; (4) the shin of the elderly was seven and nine times less sensitive to warmth when compared to those of the cheek at T_a 28 and 22 °C, respectively; and (5) warm thresholds were 3-4 °C greater at T_a 22 °C than at 28 °C, only for the elderly males' shin and foot (p<0.05), while for young the difference between T_a 22 and 28 °C was not statistically significant. The results indicate that age-related differences in cutaneous warm perception appear to be non-uniform over the body and significant on extremities; there is a greater bluntness of warm sensitivity in the cool environment for elderly males.     

Comparing sensibility for touch,cold, and warmth in different skin areas

The primary objective of this pilot study was to assess if the magnitude estimation of suprathreshold brushing, warmth (40?°C), and cold (25?°C) stimuli of the skin over the dorsum of the hand and the dorsum of the foot are comparable to the perceived intensity for the same stimuli applied to the skin over any of the following areas: forehead, m. trapezius, m. deltoideus, thoracic back, and lumbar back, respectively. Thirty-two subjects aged 18–64 years were included. Participants were examined by two physicians on two different occasions, 1–58 days apart. Participants rated the magnitude of the perceived sensation of each stimulus on an 11-point numerical rating scale (NRS) 0–10, where 0 was anchored to “no sensation at all for touch/cold/warmth” and 10 anchored to “the most intense imaginable non-painful sensation of touch/cold/warmth”. The criterion for sensory equivalence for one modality was arbitrarily considered satisfactory if two regions had the same numerical rating ±1 point in at least 85% of the individuals. Based on the pre-study criteria for sensory equivalence applied in this study only one area was found to be equivalent to the foot skin for the percept of brushing, that is, the skin over the deltoid muscle and one area for the hand, that is, the skin over the forehead. We failed to find any area with equivalent sensitivity to the hand or the foot for the cold or warm stimuli.     

Site-dependent and subject-related variations in perioral thermal sensitivity

The Marstock method of limits was used to obtain thresholds for detection of cooling, warming, cold pain and heat pain for 34 young adults, upon eight spatially matched sites on the left and right sides of the face, the right ventral forearm and the scalp. Male and female subjects were tested by both a male and a female experimenter. Neither the experimenter nor the gender of the subject individually influenced the thresholds. The thermal thresholds varied greatly across facial sites: sixfold and tenfold for cool and warmth, respectively, from the most sensitive sites on the vermilion to the least sensitive facial site, the preauricular skin. Warm thresholds were 68% higher than cool thresholds, on average, and 12% higher on the left compared to the right side of the face. The mean cold pain threshold increased from 21.0°C on the hairy upper lip to 17.8°C on the preauricular skin. Sites on the upper lip were also most sensitive to noxious heat with pain thresholds of 42–43°C. The scalp was notably insensitive to innocuous and noxious changes in temperature. For the sensations of nonpainful cool and warmth, the more sensitive a site, the less the estimates of the thresholds differed between subjects. In contrast, for heat pain, the more sensitive a site, the more the estimates differed between subjects. Subjects who were relatively more sensitive to cool tended to be relatively more sensitive to warmth. Subjects’ sensitivities to nonpainful cool and warmth were less predictive of their sensitivities to painful cold and heat, respectively. Short-term within-subject variability increased with the magnitude of the thresholds. The lower the threshold, the more similar were repeated measurements of it, within a 5–25?s period.     

Site-dependent and subject-related variations in perioral thermal sensitivity

The Marstock method of limits was used to obtain thresholds for detection of cooling, warming, cold pain and heat pain for 34 young adults, upon eight spatially matched sites on the left and right sides of the face, the right ventral forearm and the scalp. Male and female subjects were tested by both a male and a female experimenter. Neither the experimenter nor the gender of the subject individually influenced the thresholds. The thermal thresholds varied greatly across facial sites: sixfold and tenfold for cool and warmth, respectively, from the most sensitive sites on the vermilion to the least sensitive facial site, the preauricular skin. Warm thresholds were 68% higher than cool thresholds, on average, and 12% higher on the left compared to the right side of the face. The mean cold pain threshold increased from 21.0 degrees C on the hairy upper lip to 17.8 degrees C on the preauricular skin. Sites on the upper lip were also most sensitive to noxious heat with pain thresholds of 42-43 degrees C. The scalp was notably insensitive to innocuous and noxious changes in temperature. For the sensations of nonpainful cool and warmth, the more sensitive a site, the less the estimates of the thresholds differed between subjects. In contrast, for heat pain, the more sensitive a site, the more the estimates differed between subjects. Subjects who were relatively more sensitive to cool tended to be relatively more sensitive to warmth. Subjects' sensitivities to nonpainful cool and warmth were less predictive of their sensitivities to painful cold and heat, respectively. Short-term within-subject variability increased with the magnitude of the thresholds. The lower the threshold, the more similar were repeated measurements of it, within a 5-25 s period.     

Thermal sensitivity mapping - warmth and cold detection thresholds of the human torso

Skin as the largest organ of the human body accomplishes many important functions, including thermoregulation. In this context, investigating cold (CDT) and warmth detection thresholds (WDT) constitutes an important research branch, and investigating thermal thresholds has a significant impact on the clothing and fabric textile industry. In this regard, not only the extremities, but also torso regions are of high relevance. However, only few examinations have conducted detailed mapping studies of the human torso. Additionally, some of these studies show certain methodological limitations. Furthermore, the issue of whether cutaneous thermal sensitivity is gender-dependent is still controversial. Therefore, the present study investigated the cutaneous thermal sensitivity (CDT, WDT) of 42 male and female young and healthy subjects. Measurements were taken at 11 anatomical regions. We found that gender plays an important role when investigating thermal thresholds: Females tended to be more sensitive than males. We also found considerable differences between the tested regions, even within the anterior torso, for example. We identified locations which were constantly sensitive (lower back), while others were consistently insensitive (e.g. scapula). We also detected greater data variability for males compared to females, and for WDT compared to CDT. Furthermore, mainly for WDT, we found a proximal-to-distal increase of thermal torso and upper arm sensitivity. In line with previous investigations, our subjects were more sensitive to cold than to warmth. The findings of this study have important implications. First, our data may complement basic research, e.g. in terms of reference data of body regional maps. Second, our data provides important insights that could be leveraged in the textile industry, and also used to optimize current broadly applicable test methods and tools, like thermal manikins and thermophysiological models.     

Gender differences in chemosensory perception and event-related potentials

The present study investigated chemosensory gender differences by means of ratings of total nasal chemosensory intensity, unpleasantness and sensory irritation and simultaneous recordings of chemosensory event-related potentials (CSERPs) for three concentrations of the olfactory/trigeminal stimulus pyridine in 19 women and 17 men, all young adults. Results show that, compared to men, women gave higher intensity and unpleasantness ratings, in particular for the highest stimulus concentration. The gender differences in perceived intensity are reflected in the signal-to-noise ratio of the individual CSERP averages, revealing more identifiable early components (P1, N1) in women than in men. The late positive component, labeled P2/P3, displayed larger amplitudes at all electrode sites and shorter latencies at Cz, in women compared to men. The effects of increased pyridine concentration on perception (larger in women) and CSERPs (similar across gender) imply that the two measures involve partially different neural processing. CSERP component identifiability is proposed here as a general means of assessing signal-to-noise ratio of the CSERPs.     

Subjects with Knee Osteoarthritis Exhibit Widespread Hyperalgesia to Pressure and Cold

Hyperalgesia to mechanical and thermal stimuli are characteristics of a range of disorders such as tennis elbow, whiplash and fibromyalgia. This study evaluated the presence of local and widespread mechanical and thermal hyperalgesia in individuals with knee osteoarthritis, compared to healthy control subjects. Twenty-three subjects with knee osteoarthritis and 23 healthy controls, matched for age, gender and body mass index, were recruited for the study. Volunteers with any additional chronic pain conditions were excluded. Pain thresholds to pressure, cold and heat were tested at the knee, ipsilateral heel and ipsilateral elbow, in randomized order, using standardised methodology. Significant between-groups differences for pressure pain and cold pain thresholds were found with osteoarthritic subjects demonstrating significantly increased sensitivity to both pressure (p = .018) and cold (p = .003) stimuli, compared with controls. A similar pattern of results extended to the pain-free ipsilateral ankle and elbow indicating widespread pressure and cold hyperalgesia. No significant differences were found between groups for heat pain threshold, although correlations showed that subjects with greater sensitivity to pressure pain were also likely to be more sensitive to both cold pain and heat pain. This study found widespread elevated pain thresholds in subjects with painful knee osteoarthritis, suggesting that altered nociceptive system processing may play a role in ongoing arthritic pain for some patients.     

Gender differences in polysomnographic sleep in young healthy sleepers

Middle-aged and elderly populations exhibit gender differences in polysomnographic (PSG) sleep; however, whether young men and women also show such differences remains unclear. Thirty-one young healthy sleepers (16 men and 15 women, aged 18 to 30 yr, mean+/-SD, 20.5+/-2.4 yr) completed 3 consecutive overnight sessions in a sleep laboratory, after maintaining a stable sleep-wake cycle for 1 wk before study entry. Standard PSG sleep and self-rated sleepiness data were collected each night. Across nights, women showed better sleep quality than men: they fell asleep faster (shorter sleep onset latency) and had better sleep efficiency, with more time asleep and less time awake (all differences showed large effect sizes, d=0.98 to 1.12). By contrast, men were sleepier than women across nights. Both men and women demonstrated poorer overall sleep quality on the first night compared with the subsequent 2 nights of study. We conclude young adult healthy sleepers show robust gender differences in PSG sleep, like older populations, with better sleep quality in women than in men. These results highlight the importance of gender in sleep and circadian rhythm research studies employing young subjects and have broader implications for women's health issues relating to these topics.     

Gender differences in cardiovascular and metabolic responses to cold and exercise

This study was conducted because of the paucity of information concerning gender differences in the cardiovascular and metabolic responses to cold stress. Lightly clad men (n = 8) and women (n = 8) were tested in 21 and 5 degrees C environments during a 20-min rest, followed by 20 min each of 50, 100, and 150 W of exercise. At 21 degrees C there was no gender differences in VO2 or cardiac output. Cold lowered skin temperature more in women than in men, but women demonstrated no differences in heart rate, stroke volume, or VO2 at 5 and 21 degrees C. The women's noradrenaline levels in the cold were higher than comparable 21 degrees C data at rest and 50 W and increased with work intensity in both tests. In contrast, men had a lower heart rate, higher stroke volume, and higher VO2 throughout the 5 degrees C treatment compared with 21 degrees C. The men's noradrenaline response to 5 degrees C was similar to that of women at rest and 50 W, but the level subsequently declined at 100 and 150 W. Thus, the women do not show a heart rate-stroke volume shift in either resting or exercising states in cold environments. Furthermore, the data fail to support that either skin cooling or changes in noradrenaline cause the bradycardia and enhanced stroke volume seen in men.     

Three protocols for measuring subcutaneous fat thickness on the upper extremities

Three protocols for measuring subcutaneous fat thickness were compared and their level of association determined in young adults. Subjects included 21 men and 21 women, 18-24 years of age. Skinfold calipers, A- and B-mode ultrasound were used to measure the thickness of the subcutaneous fat layer overlying the anterior and posterior aspects of the upper arm. Each protocol was independently administered within a 30-min block of time in a randomly rotated sequence. Significant differences (p less than 0.05) between protocols were observed depending upon site of measurement and gender of the subject. At both the anterior and posterior sites for men, B-mode and halved skinfold were similar but significantly less than A-mode measurements. At the anterior site for women, A-mode and skinfold were similar but significantly greater than B-mode measurements. At the posterior site for women, all three measurements were similar. Correlations between the protocols were positive with men's levels ranging from 0.59 to 0.74, while women's levels were from 0.39 to 0.89. It was concluded that although skinfold calipers, A-mode ultrasound, and B-mode ultrasound may be used to obtain moderately associated measurements of upper-arm subcutaneous fat thickness in young adults, the three protocols yield inconsistently similar data.     

Gender bias in the effects of arms and countermovement on jumping performance

The ability to jump high is considered important in a number of sports. It is commonly accepted that the use of the arms and a counter movement increase jump height. In some sport situations (e.g., volley ball block, basketball rebound), athletes may not be able to utilize a counter movement or arm swing. The purpose of this study is to examine gender differences in the contribution of the arm swing and counter movement to vertical jump height. Fifty college students, 25 men (age = 21.4 +/- 1.7 years, height = 182.2 +/- 8 cm, weight = 83.7 +/- 12.4 kg) and 25 women (age = 20.7 +/- 1.6 years, height = 166.7 +/- 6.3 cm, weight = 61.5 +/- 7.0 kg), performed 4 jumping movements: squat jumps with hands on hips (SNA), counter movement jump with hands on hips (CMNA), squat jump with arm swing (SA), and counter movement with arm swing (CMA). Significant differences were found between men's and women's performance, as well as between each type of jump within each gender. A mixed-model analysis of variance detected gender differences with respect to changes in the jumping movement. For both sexes the jumps in order from worst to best were SNA, CMNA, SA, and CMA. Peak power values for men were 4,057, 4,020, 4,644, and 4,747 W, respectively, for the 4 jumps. The female power values were 2,543, 2,445, 2,842, and 2,788 W, respectively, for the 4 jumps. Arms increased jump height more than a counter movement for both genders, with jump heights for men at 29.6, 31, 36, and 38 cm, respectively, and those of women 21, 22, 26, and 27 cm, respectively. Use of the arms was found to increase the jump height of the men significantly more than that of women. Changes in jumping movements affect men and women differently. The greater increase in jump height for the men when using the arm swing could be because of greater upper body strength of men compared with women. This could have applications to training and upper body strength and also to modeling of jumping movements.     

Taste perception with age: generic or specific losses in threshold sensitivity to the five basic tastes?

Detection thresholds for NaCl, KCl, sucrose, aspartame, acetic acid, citric acid, caffeine, quinine HCl, monosodium glutamate (MSG) and inosine 5'-monophosphate (IMP) were assessed in 21 young (19-33 years) and 21 elderly (60-75 years) persons by taking the average of six ascending two-alternative forced choice tests. A significant overall effect was found for age, but not for gender. However, an interaction effect of age and gender was found. The older men were less sensitive than the young men and women for acetic acid, sucrose, citric acid, sodium and potassium chloride and IMP. To detect the compound dissolved in water they needed a 1.32 (aspartame) to 5.70 times (IMP) higher concentration than the younger subjects. A significant decline in thresholds with replication was shown. The age effect found could be attributed predominantly to a generic taste loss.     

Influence of gender on post-tetanic potentiation in human dorsiflexors

Twitch contractions of the ankle dorsiflexors were evoked before and after 7 s of tetanic stimulation at 100 Hz in young women and men. Torque decreased more in men (18%) than in women (12%) during the tetanus. There was no gender difference in twitch peak torque potentiation over the 5-min post-tetanus. Potentiation was 42% (women) and 45% (men) at 5 s post-tetanus, and still present at 5 min (women 24%, men 25%). The immediate (5 s) shortening of twitch rise time was similar in women (14%) and men (13%), but during the 5-min men's rise time came to exceed whereas women's only approached pretetanus values (e.g., +9% vs. -1% at 5 min). The immediate decrease in half-relaxation time was also similar in women (24%) and men (22%); however, women's but not men's values remained less than pretetanus values for most of the 5-min period. Twitch rate of torque development increased similarly (75%) in women and men at 5 s, with no gender difference over 5 min. In contrast, rate of torque relaxation increased significantly only in men. Rate of torque development normalized to peak torque was similar in women and men pretetanus and increased similarly 5 s post-tetanus, but women had greater values through most of the 5-min post-tetanus. Normalized rate of torque relaxation was similar in women and men and not affected by tetanus. In the dorsiflexor muscles, young women and men show a similar amount and pattern of twitch force potentiation, but there are gender differences in time-related twitch contractile properties in the first 5 min after tetanus.     

Differences in the sensations of warmth on the anterior torso of normal and spinal-cord transected individuals

The threshold to warming was measured at 10 sites on the anterior torso between the umbilicus and the clavicle of normal and spinal-cord transected individuals. In normal individuals, thresholds were higher on the thorax than on the abdomen. Men had higher and more variable thresholds than women. Magnitude estimations of supra-threshold stimuli showed that men offer verbal estimates of warmth that are about half of the size of the estimates given by women to the same stimuli. The psychometric function shows that in women, the sensation of warmth grows more rapidly than in men after starting from a higher initial value. After spinal-cord injury, thresholds for detection of warming were elevated. This effect was most noticeable within 8 cm of the anesthetic zone, but farther away, thresholds were still elevated but uniform as a function of distance, being about 30% higher than in normal individuals. After spinal-cord injury, the psychometric functions show that small stimuli elicit relatively large sensations and that these sensations grow more slowly with increasing skin temperatures than for normal individuals. Thus, for small warm stimuli spinal-cord-injured patients (both men and women) have a response similar to normal women but the slope of the psychometric function is flat, being similar to the slope observed for normal men.     

Spatial variation in sensitivity as a factor in measurements of spatial summation of warmth and cold

Perception of cutaneous heating and cooling depends strongly on stimulus size. Although this dependence has been attributed solely to spatial summation, topographical variations in temperature sensitivity may also play a role. These variations, which differentially affect perception of small stimuli, may have led to overestimation of spatial summation. This possibility was investigated by measuring detection thresholds and perceived intensity for heating and cooling on the volar surface of the forearm using a multiple-thermode stimulus array. By keeping the array in place throughout each testing session we were able to measure threshold sensitivity and suprathreshold responsiveness at eight individual sites and for combinations of these sites having total stimulus areas of 0.64-5.12 cm2. When spatial summation was calculated in the traditional way by averaging the data for all stimuli of each size, the results agreed closely with previous estimates of summation for warmth and cold. When calculations were based instead on the most sensitive test site for each stimulus size, estimates of summation were reduced by about two-thirds. This outcome indicates that the spatial heterogeneity of thermal sensitivity likely contributed to estimates of spatial summation reported in earlier psychophysical studies. A schematic model of cutaneous thermoreception is presented that shows how neural summation and the density of innervation may combine to produce the psychophysical effects of increasing stimulus size (spatial enhancement).     

Differences in the sensations of warmth on the anterior torso of normal and spinal-cord transected individuals

The threshold to warming was measured at 10 sites on the anterior torso between the umbilicus and the clavicle of normal and spinal-cord transected individuals. In normal individuals, thresholds were higher on the thorax than on the abdomen. Men had higher and more variable thresholds than women. Magnitude estimations of supra-threshold stimuli showed that men offer verbal estimates of warmth that are about half of the size of the estimates given by women to the same stimuli. The psychometric function shows that in women, the sensation of warmth grows more rapidly than in men after starting from a higher initial value. After spinal-cord injury, thresholds for detection of warming were elevated. This effect was most noticeable within 8 cm of the anesthetic zone, but farther away, thresholds were still elevated but uniform as a function of distance, being about 30% higher than in normal individuals. After spinal-cord injury, the psychometric functions show that small stimuli elicit relatively large sensations and that these sensations grow more slowly with increasing skin temperatures than for normal individuals. Thus, for small warm stimuli spinal-cord-injured patients (both men and women) have a response similar to normal women but the slope of the psychometric function is flat, being similar to the slope observed for normal men.     

Single-Point but Not Tonic Cuff Pressure Pain Sensitivity Is Associated with Level of Physical Fitness – A Study of Non-Athletic Healthy Subjects

Exercise is often used for pain rehabilitation but the link between physical activity level and pain sensitivity is still not fully understood. Pressure pain sensitivity to cuff algometry and conditioned pain modulation (CPM) were evaluated in highly active men (n=22), normally active men (n=26), highly active women (n=27) and normally active women (n=23) based on the Godin Leisure-Time Exercise Questionnaire. Cuff pressure pain sensitivity was assessed at the arm and lower leg. The subjects scored the pain intensity on an electronic Visual Analogue Scale (VAS) during ten minutes with 25 kPa constant cuff pressure and two minutes with zero pressure. The maximal VAS score and area under the VAS-curve were extracted. Pressure pain thresholds (PPT) were recorded by manual pressure algometry on the ipsilateral tibialis anterior muscle before, during and after the tonic arm stimulation. Tonic cuff stimulation of the arm and leg resulted in higher VAS peak scores in women compared with men (p<0.04). In all groups the PPTs were reduced during and after the cuff stimulation compared with baseline (p=0.001). PPT were higher in men compared with women (p=0.03) and higher in highly physical active compared with normal active (p=0.048). Besides the well-known gender difference in pressure pain sensitivity this study demonstrates that a high physical fitness degree in non-athletic subjects is associated with increased pressure pain thresholds but does not affect cuff pressure pain sensitivity in healthy people.     

Effects of age and regular exercise on muscle strength and endurance

Twenty male and 20 female non-professional tennis players were classified into two different age groups (n = 10 per group): young active men (30.4 +/- 3.3 years), young active women (27.5 +/- 4.3 years), elderly active men (64.4 +/- 3.7 years), and elderly active women (65.3 +/- 4.5 years). These individuals were matched (n = 10 per group) according to sex, age, height and mass to sedentary individuals of the same socio-economical background: young sedentary men (29.2 +/- 3.4 years), young sedentary women (25.6 +/- 4.4 years), elderly sedentary men (65.2 +/- 3.2 years) and elderly sedentary women (65.6 +/- 4.4 years). An isokinetic dynamometer was used to measure the strength of the knee extensors and flexors (two separate occasions) and the endurance of the extensors. Vastus lateralis electromyogram (EMG) was measured concomitantly. Significant sex, age and exercise effects (P less than 0.001) were observed for peak torque of both muscle groups. The effect of age on extensor strength was more pronounced at high speeds where men were also able to generate larger relative torques than women. No age or sex effects were noted for muscle endurance. However, muscles of active individuals demonstrated a greater resistance to fatigue than those of sedentary individuals. In conclusion, men were found to be stronger than women, age was associated with a decrease in muscle strength, but not of muscle endurance, and tennis players were stronger and had muscles that were more resistant to fatigue than their sedentary pairs in both age groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Individual differences in temperature perception: evidence of common processing of sensation intensity of warmth and cold

The longstanding question of whether temperature is sensed via separate sensory systems for warmth and cold was investigated by measuring individual differences in perception of nonpainful heating and cooling. Sixty-two subjects gave separate ratings of the intensity of thermal sensations (warmth, cold) and nociceptive sensations (burning/stinging/pricking) produced by cooling (29 degrees C) or heating (37 degrees C) local regions of the forearm. Stimuli were delivered via a 4 x 4 array of 8 mm x 8 mm Peltier thermoelectric modules that enabled test temperatures to be presented sequentially to individual modules or simultaneously to the full array. Stimulation of the full array showed that perception of warmth and cold were highly correlated (Pearson r = 0.83, p < 0.05). Ratings of nonpainful nociceptive sensations produced by the two temperatures were also correlated, but to a lesser degree (r = 0.44), and the associations between nociceptive and thermal sensations (r = 0.35 and 0.22 for 37 and 29 degrees C, respectively) were not significant after correction for multiple statistical tests. Intensity ratings for individual modules indicated that the number of responsive sites out of 16 was a poor predictor of temperature sensations but a significant predictor of nociceptive sensations. The very high correlation between ratings of thermal sensations conflicts with the classical view that warmth and cold are mediated by separate thermal modalities and implies that warm-sensitive and cold-sensitive spinothalamic pathways converge and undergo joint modulation in the central nervous system. Integration of thermal stimulation from the skin and body core within the thermoregulatory system is suggested as the possible source of this convergence.