Effect of ThermaCare HeatWraps and Icy Hot Cream/Patches on Skin and Quadriceps Muscle Temperature and Blood Flow.

OBJECTIVES: The purpose of this study was to compare the effects of over-the-counter treatments-ThermaCare HeatWraps (chemical reaction to produce heat above the skin), Icy Hot Patch, and Icy Hot Cream (topically applied menthol)-on skin and deep tissue temperature. METHODS: This was a longitudinal crossover study. On each of 3 days, a ThermaCare HeatWrap, Icy Hot Cream, or Icy Hot Patch was applied randomly over the quadriceps muscle in 15 healthy volunteers with normal body mass. Skin and muscle temperature and blood flow were measured by laser flowmetry every 15 minutes for 2 hours. RESULTS: After 2 hours, mean temperature decreased by 2.1°C (7.0%; P = .02) in skin and 1.0°C (2.9%; P = .01) in muscle with Icy Hot Cream. Icy Hot Patch decreased skin and muscle temperature by 1.7°C (5.4%; P = .03) and 1.3°C (3.8%; P = .01), respectively. In contrast, ThermaCare raised skin and muscle temperature by 7.8°C (25.8%; P = .001) and 2.7°C (7.7%; P = .002), respectively; both were significantly warmer with ThermaCare vs either Icy Hot product (all P < .007). Icy Hot products produced a net decrease in skin blood flow (Cream: 56.7 flux [39.3%; P = .003]; Patch: 19.1 flux [16.7%; P = .045]). Muscle blood flow decreased with the Patch (6.7 flux [7.0%; P = .02]). After a period of fluctuations, Icy Hot Cream produced a net increase vs baseline of 7.0 flux (16.9%; P = .02). ThermaCare more than doubled blood flow in skin (83.3 flux [109.7%; P = .0003]) and muscle (25.1 flux [148.5%; P = .004]). CONCLUSIONS: In this group of 15 healthy volunteers, ThermaCare HeatWraps provided the greatest degree of tissue warming and increase in tissue blood flow.

Postural sway and motor control in trans-tibial amputees as assessed by electroencephalography during eight balance training tasks.

BACKGROUND: The purpose of this study was to investigate the changes in the Power Spectral Density (PSD) of the electroencephalogram (EEG) during 8 common sensorimotor balance training tasks of varying difficulty in single-limb trans-tibial amputees. MATERIAL AND METHODS: Eight sensorimotor balance exercises, including alteration in vision, base of support, and surface compliance, were used to test postural control and how it related to the electroencephalogram (EEG). A control group was compared to a group of people with trans-tibial amputation of 1 leg to see how the brain responds to loss of a single limb during progressively harder balance testing. Postural sway and EEG changes of the alpha, beta, and sigma wave bands were measured in 20 participants (10 controls, 10 amputees) during 8 balance tasks of varying difficulty with eyes open and closed, feet in tandem or apart, and on a foam or a firm surface. RESULTS: The power of alpha, beta, and sigma bands increased significantly in most tests when comparing the amputees to the control subjects. Balance was significantly worse in the amputees even when standing on both legs. In amputees, balance required more cortical activity than in the controls. CONCLUSIONS: This study demonstrated that amputees have considerably more difficulty in motor control for the brain during balance tasks. Balance was impaired even when standing feet apart on 2 legs and EEG showed more spectral power in all areas of the brain in the amputees.

Effect of heat and cold on tendon flexibility and force to flex the human knee.

BACKGROUND: It is commonly believed in medicine that using heat will increase the distensability and flexibility of soft tissue. If true, increased flexibility would be a positive factor to reduce injuries in sports. However, cold should have the opposite effect and is often used to treat sports injuries. This study was accomplished to quantify the effect of heat and cold on the force needed to flex the knee and laxness of the anterior and posterior cruciate ligaments. MATERIAL AND METHODS: The present study examined 20 male and female subjects to determine if heat would increase extensibility of the anterior and posterior cruciate ligaments of the knee and reduce the force needed to flex the knee. Cold exposure was examined to see if it would have the opposite effect. There were 4 experiments in the series: The first was a room temperature series; the second was a series where cold was applied with an ice pack for 20 minutes; in the third, hydrocollator heat packs were applied for 20 minutes; and in the fourth, ThermaCare heat wraps were applied for 4 hours on the quadriceps and knee. Tendon extensibility was measured with a KT2000. The force for flexing the knee was measured by passive movement being applied (CPM) to the knee through 30° and the force required to move the leg was measured. RESULTS: The results show that the anterior and posterior cruciate ligament flexibility increased and the force needed to move the knee decreased with heat by about 25% compared to cold application. CONCLUSIONS: Heat is beneficial in increasing muscle and ligament flexibility and may help reduce athletic injuries, but cold treatment may have the opposite effect.

CoQ10 and endothelial function in Asians from Korea compared to Asians born in the United States and US born Caucasians.

BACKGROUND: The vascular endothelium is the interface between the blood and vascular smooth muscle in arteries. It is easily damaged by oxidative stress. Recent studies show that Asians are more susceptible than Caucasians to impairment of endothelial function. This study examined endothelial function in US-born Caucasians, Asians from Korea, and US-born Asians (almost all Korean decent) and examined the effect of coenzyme Q10 (CoQ10) on endothelial function. MATERIAL AND METHODS: Twenty Caucasians and 30 Asians participated (<35 years old, males and females). Endothelial function was assessed by the skin blood flow response to local heat using a thermode for 6 minutes at 44°C and by vascular occlusion for 4 minutes followed by release and measurement of skin blood flow for 2 minutes. In the US-born subjects, the experiments were repeated after 2-week administration of CoQ10 or a placebo. RESULTS: When applying 6 minutes of local heat at 44°C, the skin blood flows were significantly higher in Caucasians than both Asian groups Asians. Likewise after vascular occlusion, the blood flow response was greater in Caucasians compared to Asians. Asians born in Asia had the lowest response of the 3 groups of subjects. Administering CoQ10 for 2 weeks eliminated much of the difference between the groups, whereas there was no difference with a placebo. CONCLUSIONS: These findings suggest that Asians either born in Asia or the US may have lower endothelial function than Caucasians. This may be explained, in part, by genetic variations causing increased oxidative stress from westernized diets in Asians. Co enzyme Q10 administration narrows the difference between the groups.

What is more damaging to vascular endothelial function: Diabetes, age, high BMI, or all of the above?

BACKGROUND: It is well established that there is a reduction in the skin blood flow (SBF) in response to heat with age and diabetes. While it is known that high BMI creates a stress on the cardiovascular system and increases the risk of all cause of morbidity and mortality, little is known of the effect of high BMI on SBF response to heat. Since diabetes is associated with age and a higher BMI, the interrelationship between age, BMI and SBF needs to be investigated to better understand the contribution diabetes alone has to endothelial impairment. MATERIAL AND METHODS: This study examined the SBF to heat in young and old people with low and high BMI and people with diabetes with high BMI to determine the contribution these variables have on SBF. Subjects were ten young and older people with BMI <20 and ten young and older people with BMI >20 and ten subjects with diabetes with BMI >20. The SBF response, above the quadriceps, was determined during a 6 minutes exposure to heat at 44°C. RESULTS: Even in young people, SBF after the stress of heat exposure was reduced in subjects with a high BMI. The effect of BMI was greatest in young people and lowest in older people and people with diabetes; in people with diabetes, BMI was a more significant variable than diabetes in causing impairment of blood flow to heat. BMI, for example, was responsible for 49% of the reduction in blood flow after stress heat exposure (R=-0.7) while ageing only accounted for 16% of the blood flow reduction (R=-0.397). CONCLUSIONS: These results would suggest the importance of keeping BMI low not only in people with diabetes to minimize further circulatory vascular damage, but also in young people to diminish long term circulatory vascular compromise.

Resting blood flow in the skin: does it exist, and what is the influence of temperature, aging, and diabetes?

Measurement of resting blood flow to the skin and other organs is an important indicator of health and disease and a way to assess the reaction to various stimuli and pharmaceutical interventions. However, unlike plasma ions such as sodium or potassium, it is difficult to determine what the proper value for resting blood flow really is. Part of the problem is in the measurement of blood flow; various techniques yield very different measures of skin blood flow even in the same area. Even if there were common techniques, resting blood flow to tissue, such as the skin, is determined by the interaction of a plurality of factors, including the sympathetic nervous system, temperature, pressure, shear forces on blood vessels, tissue osmolality, and a variety of other stimuli. Compounding this variability, the blood flow response to any stressor is reduced by free radicals in the blood and diminished by aging and diabetes. Race also has an effect on resting blood flow to the skin. All these factors interact to make the exact resting blood flow difficult to determine in any one individual and at any one time. This review examines the main techniques to assess blood flow, the factors that alter blood flow in the skin, and how aging and diabetes affect blood flow. Recommendations for the measurement of resting blood flow are presented.

A comparison of the effect of a variety of thermal and vibratory modalities on skin temperature and blood flow in healthy volunteers.

BACKGROUND: Circulation plays an essential role in tissue healing. Moist heat and warm water immersion have been shown to increase skin circulation; however, these heating modalities can cause burns. Recent research has shown that passive vibration can also increase circulation but without the risk of burns. MATERIAL/METHODS: The aim of this study is to compare the effects of short-duration vibration, moist heat, and a combination of the two on skin blood flow (SBF) and skin temperature (ST). Ten (10) subjects, 5 female and 5 male, aged 20-30 years of age, received two interventions a day for 3 consecutive days: Intervention 1--Active vibration only (vibration exercise), Intervention 2--passive vibration only, Intervention 3--moist heat only, Intervention 4--passive vibration combined with moist heat, Intervention 5--a commercial massaging heating pad, and Intervention 6--no intervention, resting in supine only (control). SBF and ST were measured using a laser Doppler imager during the 10 minute intervention and then throughout the nine minute recovery period. RESULTS: The mean skin blood flow following a ten-minute intervention of the combination of passive vibration and moist heat was significantly different from the control, active vibration, and the commercial massaging heating pad. Skin temperature following the ten-minute interventions of moist heat alone and passive vibration alone were both significantly different from the commercial massaging heating pad and active vibration interventions. CONCLUSIONS: The combination of passive vibration and moist heat produced the greatest increase in skin blood flow and the second highest increase in skin blood flow nine minutes post application.

The effect of type-2-diabetes-related vascular endothelial dysfunction on skin physiology and activities of daily living.

A common factor contributing to organ damage in type 2 diabetes mellitus (T2DM) is impaired tissue blood flow caused by damage to vascular endothelial cells (VECs). Damage can occur even before the clinical diagnosis of diabetes. It can be caused by both a high average blood glucose concentration and/or large daily spikes in blood glucose. While much of the present literature focuses on the damage to VECs and organs from these large glucose excursions, this review will focus on the consequence of this damage, that is, how endothelial cell damage in diabetes affects normal daily activities (e.g., exercise, reaction to typical stimuli) and various treatment modalities (e.g.. contrast baths and electrical stimulation therapy). It is important to understand the effects of VEC damage such as poor skin blood flow, compromised thermoregulation, and altered response to skin pressure in designing diabetes technologies as simple as heating pads and as complex as continuous glucose monitors. At the simplest level, people with diabetes have poor circulation to the skin and other organs. In the skin, even the blood flow response to locally applied pressure, such as during standing, is different than for people who do not have T2DM. Simple weight bearing on the foot can occlude the skin circulation. This makes the skin more susceptible to damage. In addition, endothelial damage has far-reaching effects on the whole body during normal activities of daily living, including an impaired response to local heat, such as hot packs and contrast baths, and higher body temperatures during whole body heating due to impaired blood flow and a reduced ability to sweat. Finally, because of multiple organ damage, people with T2DM have poor balance and gait and impaired exercise performance.

Enhanced healing of diabetic foot ulcers using local heat and electrical stimulation for 30 min three times per week.

BACKGROUND: Electrical stimulation (ES) with heating is effective in healing chronic wounds. However, it this effect due to ES alone or both heating and ES? The aim of the present study was to deduce the individual roles of heat and ES in the healing of chronic wounds. METHODS: The study was performed on 20 patients (mean age 48.4 ± 14.6 years) with non-healing diabetic foot ulcers (mean duration 38.9 ± 23.7 months) who received local dry heat (37°C; n = 10) or local dry heat + ES (n = 10) three times a week for 4 weeks. Patients were given ES using biphasic sine wave stimulation (30 Hz, pulse width 250 µs, current approximately 20 mA). RESULTS: Skin blood flow in and around the wound was measured with a laser Doppler flow imager. In the ES + heat group, the average wound area and volume decreased significantly by 68.4 ± 28.6% and 69.3 ± 27.1%, respectively (both P < 0.05), over the 1-month period. During the average session, blood flow increased to 102.3 ± 25.3% with local heat and to 152.3 ± 23.4% with ES + heat. In the group receiving treatment with local heat only, wounds that had not healed for at least 2 months showed 30.1 ± 22.6% healing (i.e. a decrease in wound area) after 1 month. Although this level of healing was significant, it was less than that observed in the ES + heat group (P<0.05). CONCLUSIONS: Local dry heat and ES work well together to heal chronic diabetic foot wounds; however, local heat would appear to be a relevant part of this therapy because ES alone has produced little healing in previous studies.

A device to measure heat flow through the skin in people with diabetes.

INTRODUCTION: As people age, and especially for older people with diabetes, there is increased susceptibility to burns. However, this is not true for all older people or all people with diabetes. The factors that predict burn susceptibility in specific members of the population with diabetes have not been elucidated. To understand the heat transfer properties of the skin in different parts of the body and how it is altered by skin blood flow, age, and glycemic control, a new device was developed. METHODS: The device was a Plexiglas (Arkema, Colombes, France) capsule (thermode) that has a footprint on the skin of 20 cm(2), with the side contacting the skin made of thin brass. The thermode was machined to allow the free flow of water through the interior with the exception of a small hole for a laser Doppler flow meter to assess blood flow under the capsule. Flow directors kept the water flow even on the under surface of the capsule and minimized turbulent flow until high water flow rates are forced through the capsule. RESULTS: When tested, the device provided even heat on the brass surface and could show the movement of heat into the skin and the corresponding changes in skin blood flow and temperature. In limited testing, clear differences were seen in heat flux in people with diabetes versus controls. CONCLUSION: This device might be very useful in determining the early onset of diabetes-related skin damage. Future studies should include examining different regions of the body and variables such as hemoglobin A1c.

Autonomic stress and balance--the impact of age and diabetes.

INTRODUCTION: Balance is impaired in the elderly and people with diabetes. However, the effect of attempted balance on the autonomic nervous system has not been investigated. METHODS: Ten control subjects, 10 subjects with type 2 diabetes (age range, 21-75 years), and 10 older subjects age-matched to the subjects with diabetes were examined to determine the effect of diabetes and age on balance and the associated autonomic stress. Subjects were asked to stand on a balance platform for 1-min periods under four conditions: (1) quiet standing, (2) quiet standing with eyes closed, (3) quiet standing eyes closed with the platform allowed to move side to side over a central pivot that allows the edge of the platform to rotate 4 inches up and down, and (4) the same platform with eyes closed. Blood pressure, electrocardiogram, and sway were recorded. RESULTS: Balance was worst in the subjects with diabetes, while the cardiovascular stress, as assessed by both heart rate and blood pressure, was greatest in the older group of subjects. But subjects with diabetes, while having a greater blood pressure response to the stress induced by balance, showed a poor heart rate response, probably due to diabetes-induced autonomic damage. CONCLUSION: Autonomic damage in the subjects with diabetes masked much of the stress of the inability to optimize balance in this population.

The effect of the moisture content of a local heat source on the blood flow response of the skin.

Numerous studies have examined the effect of local and global heating of the body on skin blood flow. However, the effect of the moisture content of the heat source on the skin blood flow response has not been examined. Thirty-three subjects, without diabetes or cardiovascular disease, between the ages of 22 and 32 were examined to determine the relationship between the effects of dry vs. moist heat applied for the same length of time and with the skin clamped at the same skin temperature on the blood flow response of the skin. The skin, heated with an infrared heat lamp (skin temperature monitored with a thermocouple) to 40 degrees C for 15 min, was either kept moist with wet towels or, in a separate experiment, kept dry with Drierite (a desiccant) between the towels to remove any moisture. Before and after heat exposure of the forearm, blood pressure, heart rate, skin moisture content, skin temperature, and skin blood flow were recorded. The results of the experiment showed that there was no change in skin moisture after 15 min exposure to dry heat at 40 degrees C. However, with moist heat, skin moisture increased by 43.7%, a significant increase (P < 0.05). With dry heat, blood flow increased from the resting value by 282.3% whereas with moist heat, blood flow increased by 386% over rest, a significant increase over dry heat (P < 0.05). Thus, with a set increase in skin temperature, moist heat was a better heating modality than dry heat. The reason may be linked to moisture sensitivity in calcium channels in the vascular endothelial cell.

The effect of 30 Hz vs. 50 Hz passive vibration and duration of vibration on skin blood flow in the arm.

BACKGROUND: Recently, researchers have demonstrated that Whole Body Vibration (WBV) results in significant increases in skin blood flow (SBF). No study has determined if a specific frequency or a specific duration is better at optimizing SBF. MATERIAL/METHODS: Two studies were conducted to determine, 1) if there is a difference in SBF due to passive vibration of the forearm at 30 Hz vs. 50 Hz, 2) if one frequency is superior, and 3) if there is an optimal duration. In the first study, 18 subjects (mean age 20.3+/-2.9 years) were randomly placed into a 30 Hz or 50 Hz vibration group, and in the second, seven subjects (mean age 23.3+/-3.8 years) participated in both 30 and 50 Hz vibration. Each subject's arm was passively vibrated for 10 minutes. SBF was examined during vibration and for 15 minutes of recovery. RESULTS: Both frequencies produced significant increases in SBF (p<0.05) within the first four minutes of vibration. Peak SBFs were obtained by the fifth minute. SBF remained high for minutes 4 through 10 of vibration in the second study. In the first study, SBF remained high for minutes 4 through 9. During recovery, 30 Hz vibration produced SBFs below baseline values while 50 Hz SBFs remained above baseline. Statistically one frequency was not superior to the other. CONCLUSIONS: Five minutes of 30 Hz or 50 Hz vibration produced significant increases in SBF. Clinically, 50 Hz has additional benefits because SBF increased more rapidly and did not result in vasoconstriction during the recovery period. Future studies should be done to determine if these increases in SBF could be of benefit to populations with low circulation such as those with diabetes.

The effect of whole body vibration on lower extremity skin blood flow in normal subjects.

BACKGROUND: Circulation plays a vital role in tissue healing. Increases in muscle flexibility and strength, secretion of hormones important in the regeneration and repair process, blood flow, and strength of bone tissues has been attributed to whole body vibration (WBV) combined with exercise. The purpose of the study was to determine the effects of short-duration, high-intensity, isometric weight bearing exercise (vibration exercise [VE]) and vibration only on skin blood flow (SBF). MATERIAL/METHODS: Forty-five subjects 18-43 years of age were randomly divided into three groups: Group 1 - VE, Group 2 - exercise only, and Group 3 - vibration only. SBF was measured using a laser Doppler imager at three time intervals: 1) initial base line, 2) immediately following intervention, and 3) 10-minutes following intervention. RESULTS: There was no significant difference between the three groups' SBF prior to intervention. Immediately following the intervention a difference among groups was found. Post hoc testing revealed that Group 3 subjects' mean SBF was significantly increased at both post-intervention time intervals. CONCLUSION: The study findings suggest that short duration vibration alone significantly increases SBF; doubling mean SBF for a minimum of 10 minutes following intervention. The emerging therapeutic modality of WBV as a passive intervention appears to increase SBF in individuals with healthy microcirculation.

Correlation between gait and balance in people with and without Type 2 diabetes in normal and subdued light.

BACKGROUND: Balance and gait are both impaired in people with diabetes but no study has examined both in the same subjects in people either with or even without diabetes or related these to room lighting. MATERIAL/METHODS: Twelve subjects with type 2 diabetes (D) and 15 age-matched controls (C) were examined under conditions of full light, eyes closed (no light) and low light (5 candle power). Balance was assessed during standing by a computerized posturography device. Gait was analyzed during the initiation of movement, while walking at uniform speed and during turns of 0.66 meters diameter through accelerometers, foot contact sensors and the electomyogram recorded from the gastrocnemius and tibialus anterior muscles. RESULTS: Subjects with diabetes had poorer balance during standing in diminished light compared to full light and no light conditions. When the room light was dimmed, sway during standing increased by an average of 25% in D. Control subjects did not have different sway with diminished light compared to the other lighting conditions. Gait was slower, circumduction greater and muscle use greater in D than C. There was a significant negative correlation between balance and gait; the worse the balance, the slower and poorer the gait for both groups of subjects (p<0.05), impaired balance accounting for 70% of the deviation in gait in D whereas it only accounted for 52% in C. CONCLUSIONS: Balance and gait are related in people with and without diabetes. Diabetes causes balance and gait to both be impaired compared to C.

The influence of alterations in room temperature on skin blood flow during contrast baths in patients with diabetes.

BACKGROUND: Contrast baths (CB) have been used for over two thousand years. But it only was recently that CB were shown to improve limb circulation to a greater extent than that which can be seen after continuous exposure to a warm, constant temperature, bath. However, other studies show that this type of response to temperature can be impaired if the sympathetic nervous system applies vasoconstriction to the blood vessels. Therefore the purpose of the present investigation was to examine the relationship between sympathetic outflow on the magnitude of the change of blood flow (BF) during contrast baths in controls and with people diabetes. Sympathetic vasoconstriction activity was altered by global heating. MATERIAL/METHODS: Fourteen patients with type 2 diabetes were compared to 14 age-matched controls. BF was measured during 16 minutes of serial contrast baths of the foot following 3 minutes of warm water and 1 min of cold immersion at 2 different room temperatures, 19 and 32 deg C. RESULTS: When subjects were exposed to global heating (warm room) there is a greater response to CB than when subjects were initially in a cooler room. However, for both temperatures, subjects with diabetes had a response that was over 50% less than that seen in control subjects. CONCLUSIONS: Removing sympathetic vasoconstrictor tone by global heating benefits subjects with diabetes and control subjects in their response to CB. For subjects with diabetes, global heating may be necessary to increase blood flow to acceptable levels for effective therapy.

The impact of rosiglitazone on cardiovascular responses and endurance during isometric exercise in patients with Type 2 diabetes.

BACKGROUND: Vascular endothelial function is compromised in people with diabetes reducing tissue blood flow. The present investigation was a logical extension of a previous work, examining isometric exercise performance and recovery in people with diabetes and the impact of the insulin sensitizer rosiglitazone, a drug shown to improve endothelial function. MATERIAL/METHODS: Blood pressure, heart rate and limb blood flow were examined in 12 control subjects and 8 subjects with type 2 diabetes during a series of 2 fatiguing isometric contractions at a tension of 40% of the maximum strength of the handgrip muscles; 5 minutes of rest were allowed between the contractions. RESULTS: Endurance of the first and the second contraction was significantly less in subjects with diabetes (p<0.01). HR increased significantly (p<0.01) by over three fold during exercise in control subjects compared to subjects with diabetes. There was no statistical difference in the increase in either systolic or diastolic BP during isometric exercise comparing controls to subjects with Type 2 diabetes (p>0.05), however, resting and peak blood pressures were greater in subjects with type 2 diabetes (p<0.01). Forearm blood flow, which was significantly lower at rest (p<0.01) in subjects with diabetes, only increased by about half as much during the exercise in subjects compared to control subjects. These differences were partially reversed after 3 months administration of rosiglitazone. CONCLUSIONS: Microcirculatory damage in diabetes impairs exercise performance and recovery and can be partially reversed after rosiglitazone administration.

The impact of rosiglitazone on heat tolerance in patients with type 2 diabetes.

BACKGROUND: Diabetes is associated with reduced tolerance to heat. The insulin sensitizer rosiglitazone (RSG), administered for glycemic control, has a secondary effect in increasing vascular endothelial function. The hypothesis to be tested was if administration of rosiglitazone would increase heat tolerance in people with diabetes. MATERIAL/METHODS: Thirty subjects with diabetes and thirty control subjects were examined. A subset of 21 subjects with diabetes had RSG administered at 4 mg per day for a period of 1 year. At 2 weeks, 4 weeks, 3 months, 6 months, and 1 year post administration, measurements were taken to assess any potential impact of this drug on thermoregulation. Parameters measured were sweat rate, skin temperature, body core temperature, and skin blood flow. RESULTS: Results of these experiments showed that subjects with diabetes at baseline had 1) sensory impairment, 2) sweat gland impairment 3) high skin temperatures, 4) and low blood flow reduction during heat exposure, all leading to higher core temperature compared to controls subjects. After administration of rosiglitazone for 1 year significant improvements in thermoregulation were observed. Trends for improvement in thermoregulation were observed close to that of age matched control subjects. CONCLUSIONS: Heat tolerance can be improved in people with diabetes when taking the insulin sensitizer RSG for Glycemic control, probably due to increased endothelial cell function.

Sweat production during global heating and during isometric exercise in people with diabetes.

BACKGROUND: While sweat production in response to heat is impaired in people with diabetes, sweat production has not been examined during isometric exercise. MATERIAL/METHODS: Eight subjects with type 2 diabetes and 9 control subjects exerted a fatiguing isometric contraction of the handgrip muscles at a tension of 40% of the maximum voluntary strength (MVC) after exposure to a 32 deg C environment for 30 min. compared to 10 controls and 10 subjects with diabetes exposed to a 39 deg C environment. RESULTS: Sweat was impaired to all areas of the body during heat exposure in patients with diabetes under both environmental conditions. For example, on the chest, the average sweat rates after exposure to the 32 deg environment was 259.2 +/- 55.2 nanoliters/min in control subjects and 198.3 +/- 46.2 nanoliters/min for subjects with diabetes. Compared to the 32 deg C environment, control subjects increased sweat in all 4 areas proportionally more than subjects with diabetes. Sudomotor rhythm was present in sweat in control subjects at a rate of repetition of 11 and 50 seconds but almost absent in subjects with diabetes. During exercise, sweat rates slowly increased from the beginning to the end of the exercise. But the head of the subjects with diabetes showed hypersweating while the other areas showed diminished sweating compared to control subjects. CONCLUSIONS: Thus some of the impairment in sweating may be due to central mechanisms associated with heat sensitivity or in the hypothalamus and not to the sweat glands themselves.

Cardiovascular responses and endurance during isometric exercise in patients with Type 2 diabetes compared to control subjects.

BACKGROUND: While it is well documented that diabetes impairs the microcirculation, its effect on isometric exercise has not been determined. MATERIAL/METHODS: Isometric strength and endurance of the handgrip muscles for a series of 2 fatiguing isometric contractions at a tension of 40% of the maximum strength were assessed in 10 subjects with Type 2 diabetes compared to 10 control subjects; 5 minutes were allowed between the contractions. Blood pressure (BP), heart rate (HR), blood flow (BF) of the whole arm and of the skin on the chest and foot were measured. RESULTS: Strength and endurance for the first contraction was the same in control subjects compared to subjects with Type 2 diabetes (p>0.05), but endurance of the second contraction was significantly less in subjects with diabetes (p<0.01). HR increased significantly (p<0.01) by over three fold during exercise in control subjects compared to subjects with diabetes. Resting and peak blood pressures were greater in subjects with type 2 diabetes compared to control subjects (p<0.01). Forearm blood flow was significantly lower at rest, during exercise and post exercise in subjects with diabetes compared to control subjects (p<0.01). CONCLUSIONS: The results are probably explained by the damage to the microcirculation seen in subjects with diabetes.