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Papers by Michael Buono

Research paper thumbnail of An Inquiry-Based Learning Model for an Exercise Physiology Laboratory Course

Advances in Physiology Education, 2001

We developed an inquiry-based learning model to better stimulate undergraduate students’ cognitiv... more We developed an inquiry-based learning model to better stimulate undergraduate students’ cognitive development of exercise physiology laboratory concepts. The course core is the two independent research projects that students, working in small groups, complete during the last 9 wk of the semester. Student groups develop their own research question and hypothesis, design the experiment, collect and analyze the data, and report their findings to the rest of the class using presentation software. To help with success of the research projects, students are taken through a series of guided-inquiry laboratory activities during the initial 6 wk of the semester to develop laboratory skills and an understanding of the scientific process. Observations of student behaviors reflected a high level of enthusiasm and engagement in laboratory activities. Surveys, journal entries, and interviews indicated that students felt empowered by having ownership in their projects, which may be the key reason...

Research paper thumbnail of Cold Acclimation Does Not Alter Physiological or Perceptual Responses During Subsequent Exercise in the Heat

Military Medicine, 2017

Introduction: Warfighters often train and conduct operations in cold environments. Specifically, ... more Introduction: Warfighters often train and conduct operations in cold environments. Specifically, military trainees and divers that are repeatedly exposed to cold water may experience inadvertent cold acclimatization, which results in body heat retention. These same warfighters can quickly switch between environments (cold to hot or hot to cold) given the nature of their work. This may present a risk of early onset of hyperthermia when cold-acclimatized warfighters are subsequently exposed to physiological insults that increase body temperature, such as exercise and heat stress. However, there is currently no evidence that suggests this is the case. The purpose of this work, therefore, is to determine what impact, if any, repeated immersion in cold water has on subsequent exercise in the heat. Materials and Methods: Twelve healthy subjects (values in mean ± SD: age, 25.6 ± 5.2 years; height, 174.0 ± 8.9 cm; weight, 75.6 ± 13.1 kg) voluntarily provided written informed consent in accordance with the San Diego State University Institutional Review Board. They first completed 120 minutes of moderate treadmill walking in 40°C and 40% relative humidity. During this trial, subjects' physiological and perceptual responses were recorded. Twenty-four hours later, subjects began a cold acclimation protocol, which consisted of seven, 90-minute immersions in cold water (10°C, water level to chest). Each immersion was also separated by 24 hours. Subjects then repeated a subsequent trial of exercise in the heat 24 hours after the final immersion of the cold acclimation protocol. Results: Results from cold acclimation revealed no change in core temperature, a decrease in skin temperature, and attenuated shivering and lactate responses, which supports a successful insulative-hypothermic cold acclimation response. This type of cold acclimation response primarily results in heat retention with associated energy conservation. Findings for heat trials (pre-cold acclimation and post-cold acclimation) revealed no differences between trials for all measurements, suggesting that cold acclimation did not influence physiological or perceptual responses during exercise in the heat. Conclusion: Our findings indicate that military divers or trainees that are frequently exposed to cold water, and hence have the ability to experience cold acclimatization, will likely not be at greater risk of increased thermal strain when subsequently exposed to physical activity in hot environments. In this study, no physiological or perceptual differences were observed between trials before and after cold acclimation, suggesting that cold acclimation does not present a greater hyperthermia risk during subsequent exercise in the heat.

Research paper thumbnail of Validity and Reliability of Predicting Maximum Oxygen Uptake via Field Tests in Children and Adolescents

Pediatric Exercise Science, 1991

The purpose of this study was to determine the validity and reliability of three of the most comm... more The purpose of this study was to determine the validity and reliability of three of the most commonly used field tests to predict maximum oxygen uptake in children and adolescents. VO2max was directly measured during a maximal treadmill test in 90 children (10-18 yrs). Each subject also performed, in duplicate, a timed distance run (1 mile), a step test, and a submaximal cycle ergometer test. A multiple regression equation was developed with directly measured VO2max as the dependent variable and mile-run time, gender, skinfold thickness, and body weight as independent variables. The equation had a multiple R=0.84 and a standard error of estimate of 9%, or 4.3 ml/kg/min. The results suggest that when the three most commonly used field tests to predict aerobic capacity are compared in the same group of children, the timed distance run is superior in both validity and reliability.

Research paper thumbnail of Hyperthermia during exercise – a double-edged sword

Temperature, 2016

An excessive elevation in body temperature is known to decrease exercise performance. The physiol... more An excessive elevation in body temperature is known to decrease exercise performance. The physiological mechanisms involved with hyperthermia-induced fatigue include central nervous system dysfunction and cardiovascular instability. Conversely, a moderate increase in body temperature has been shown to actually improve exercise performance. Asmussen and Boje 1 reported that sprint performance improved by approximately 5% for each 1 C increase in muscle temperature. The improvement was attributed to the wellknown Q 10 temperature effect on numerous biochemical processes. However, are there other potential benefits of hyperthermia during exercise? Recently we published findings that suggest another possible benefit of moderate hyperthermia during exercise, namely improved blood viscosity. 2 This is important as blood viscosity plays a critical role in limiting exercise capacity and is significantly correlated to maximal oxygen uptake. 3 It is inevitable that during exercise there is an increase in hematocrit, induced by several mechanisms including fluid shifts due to increases in blood pressure, dehydration, and water trapping in working skeletal muscle. The exercise-induced hemoconcentration has traditionally been viewed to have both positive and negative consequences as it simultaneously increases both oxygen carrying capacity and blood viscosity. In fact, over the last 30 y at least 10 studies have reported that various forms of exercise increase blood viscosity by between 5 to 15%. However, in an effort to isolate the effect of increases in hematocrit on blood viscosity, they measured both the pre-and post-exercise blood samples at 37 C. This discounts the fact that exercise almost always elevates core and blood temperature. Thus, past studies that reported an increase in blood viscosity following exercise did not replicate real in vivo conditions and therefore likely missed any affect that exercise-induced hyperthermia may have had on mitigating change in blood viscosity. The results of our recent study challenge the dogma that exercise increases blood viscosity. Specifically we found that exercise-induced hemoconcentration significantly increased blood viscosity by 9%. This finding agrees with all of the past studies. However, we also found that exercise-induced hyperthermia significantly decreased blood viscosity by 7%. When both factors were considered together, there was no overall change in blood viscosity. Thus, the effects of hemoconcentration and hyperthermia counterbalanced each other so that there was no change in blood viscosity, at a given shear rate, following prolonged, moderate intensity exercise in the heat. Therefore, we suggest that moderate hyperthermia during exercise may be beneficial because it attenuates the increase in blood viscosity brought about by hemoconcentration. Our results suggest that hyperthermia decreases blood viscosity by increasing red blood cell deformability. The exact mechanism is currently unknown; however increased temperature may result in more spontaneous dissociations of the spectrin network where in junctions with the phospholipid bilayer. This reduced tension within the cytoskeleton could ultimately decrease membrane stiffness and improve red blood cell deformability. Our results may also help to explain why past findings 4 have reported that a high hematocrit decreases blood flow much more in resting muscle than in exercising muscle. It could be theorized that the blood flow preserving effect of muscle contractions reported in these studies was at least partially due to a hyperthermia-induced reduction in blood viscosity in the exercising muscle.

Research paper thumbnail of The physiological responses to Bikram yoga in novice and experienced practitioners

Alternative therapies in health and medicine

Bikram yoga has gained a large following, possibly because of widespread claims boasting energy e... more Bikram yoga has gained a large following, possibly because of widespread claims boasting energy expenditure of up to 1000 calories per session. However, these claims are unfounded because no scientific study has investigated the metabolic response to a complete, standardized Bikram yoga class. This study intends to determine energy expenditure, heart rate, and sweat rate in novice and experienced practitioners from a standardized Bikram yoga class. Data were collected in the environmental chamber of the Exercise Physiology Laboratory at San Diego State University in California, USA. Male (n = 5) and female (n = 19) participants between the ages of 18 and 57 y were recruited through flyers in yoga studios throughout San Diego. Participants were classified as experienced or novice practitioners, having completed ≥20 or <20 sessions, respectively. Participants were guided through a standardized 90-min yoga class performed in a hot environment using Bikram's Standard Beginning Di...

Research paper thumbnail of Effect of air temperature on the rectal temperature gradient at rest and during exercise

International journal of physiology, pathophysiology and pharmacology, 2014

The purpose of the current study was to determine the effect of air temperature on the rectal tem... more The purpose of the current study was to determine the effect of air temperature on the rectal temperature gradient at rest and during exercise. It was hypothesized that the rectal temperature gradient would be exacerbated in cold environments and attenuated in warm environments both at rest and during exercise. Each subject completed three exercise bouts on a motor driven treadmill at approximately 55% of their previously determined maximal oxygen uptake. Three different air temperatures (10, 22, 39°C) were used for the exercise bouts. Rectal temperature was measured at rest and every 5 min during each exercise bout using 4 temperature sensors affixed at 4, 7, 10 and 13 cm past the anal sphincter. Readings obtained from the 4-cm depth were significantly (p<0.05) lower than those obtained at deeper insertion depths both at rest and during exercise for all three air temperatures. Furthermore, the results showed that the rectal temperature gradient was exacerbated in cold environmen...

Research paper thumbnail of Does anticipatory sweating occur prior to fluid consumption?

International journal of physiology, pathophysiology and pharmacology, 2012

The purpose of this study was to examine if anticipatory sweating occurs prior to fluid consumpti... more The purpose of this study was to examine if anticipatory sweating occurs prior to fluid consumption in dehydrated subjects. It was hypothesized that there would first be an anticipatory response to the sight of water, and then with drinking, a second response caused by mechanical stimulation of oropharyngeal nerves. Dehydrated subjects (n=19) sat in a heat chamber for 30 minutes. At minute 15, a resistance hygrometer capsule was attached and sweat rate was measured every 3 seconds. At minute 35:00, a researcher entered the room with previously measured water (2 ml/kg euhydrated body weight). At minute 35:30, the subject was allowed to drink. Data collection continued for 5 minutes post consumption. As expected, 16 of the 19 subjects responded to oropharyngeal stimuli with increased sweat rate. However, the new finding was that a majority (12 of 19) also showed an anticipatory sweating response prior to fluid consumption. Subjects were divided into 4 groups based on the magnitude of ...

Research paper thumbnail of Effect of aerobic training on the plasma ACTH response to exercise

PsycEXTRA Dataset

A previous study has shown that plasma adrenocorticotropin (ACTH) secretion during submaximal exe... more A previous study has shown that plasma adrenocorticotropin (ACTH) secretion during submaximal exercise is increased following training. This finding is in contrast to studies of other hormones such as glucagon, epinephrine and growth hormone, all of which show decreases following training. This study reexamines the effect of training on plasma ACTH levels during exercise. Ten adult volunteers were split into a control and an exercise group. The exercise group underwent a 12 week training program consisting of running 3.5 kilometers per day, three days per week. Before and after the training program all subjects were tested for plaesm ACTH response to a 150 Watt workload for 15 minutes. The experimental group showed an 11% increase in Hex Vo 2 following training while the control group's Max Vo 2 was unchanged. The experimental group's ACTS response to the submaximal workload was decreased 63% (p<O.O5). while the control group's response was unchanged. These data suggest that the ACTH response to exercise is blunted following training. This response is similar to that of other hormones such as glucagon. epinephrine and growth hormone. Such a finding is in agreement with previous studies that have shown that ACTH follows an intensity dependent pattern during exercise.

Research paper thumbnail of When Posture is Controlled, Acute Hypoxia does not Decrease Core Temperature

Advances in Life Sciences, 2012

It has been reported that acute hypoxia causes a reduction in core temperature in humans. It was ... more It has been reported that acute hypoxia causes a reduction in core temperature in humans. It was hypothesized that this occurs due to both a decrease in metabolic rate and an increase in skin b lood flo w. Ho wever, other studies have found that core temperature decreases with changes in posture. The methods in prev ious studies finding hypo xia to decrease core temperature did not control for postural changes. Thus, further examination is warranted to examine the effect of hypo xia on core temperature while controlling for posture change. Ten healthy adults, between the ages of 18 and 45 were recruited to participate. Subjects completed one trial consisting of breathing normo xic air (20.9%) for a 2 hour period and hypoxic air for a 1 hour period, while systematically changing posture. During this time core temperature and skin blood flow were recorded every 5 minutes. The results showed that mean core body temperature significantly (p < 0.05) decreased by 0.4℃ when the subjects transitioned from a standing to lying position. Ho wever, acute hypoxia, which reduced the mean o xygen saturation to 85%, d id not significantly affect core temperature. Such results suggest that when posture is controlled, acute hypoxia does not significantly decrease core body temperature. Thus, the results of previous studies that have reported decreases in core temperature with acute hypoxia, but failed to control for posture, need to be questioned.

Research paper thumbnail of Alterations in the Rate of Limb Movement Using a Lower Body Positive Pressure Treadmill Do Not Influence Respiratory Rate or Phase III Ventilation

BioMed research international, 2015

The purpose of this study was to determine the effect of alterations in rate of limb movement on ... more The purpose of this study was to determine the effect of alterations in rate of limb movement on Phase III ventilation during exercise, independent of metabolic rate, gait style, and treadmill incline. Subjects completed five submaximal exercise bouts on a lower body positive pressure treadmill (AlterG P 200). The percent body weight for the five exercise bouts was 100, 87, 75, 63, and 50% and each was matched for carbon dioxide production (V CO2 ). Naturally, to match the V CO2 while reducing the body weight up to 50% of normal required a significant increase in the treadmill speed from 3.0 ± 0.1 to 4.1 ± 0.2 mph, which resulted in a significant (P < 0.05) increase in the mean step frequency (steps per minute) from 118 ± 10 at 3 mph (i.e., 100% of body weight) to 133 ± 6 at 4.1 mph (i.e., 50% of body weight). The most important finding was that significant increases in step frequency did not significantly alter minute ventilation or respiratory rate. Such results do not support ...

Research paper thumbnail of The effect of an acute bout of exercise on selected pulmonary function measurements

Medicine & Science in Sports & Exercise, 1981

Research paper thumbnail of Effect of Acute Exposure to Moderate Altitude on Peripheral Sweating

Medicine & Science in Sports & Exercise, 2002

This study aimed to assess the effect of acute exposure to moderate altitude on kinematic variabl... more This study aimed to assess the effect of acute exposure to moderate altitude on kinematic variables of the ippon-seoi-nage and on the mechanical outputs of the countermovement jump (CMJ). Thirteen elite male judokas from the Spanish Judo Training Centre in Valencia (age: 21.54 ± 2.15 years) participated in the study. All of them performed an incremental CMJ test and an ippon-seoi-nage technique test before (N) and after the ascent to a moderate altitude of 2320 m above the sea level (H). A linear velocity transducer was attached to the bar to assess the mechanical outputs of each loaded CMJ at different percentages of their own body weight (25, 50, 75 and 100%). A wearable sensor was used to assess the kinematic variables (times, accelerations and angular velocities) transferred to a dummy during the technique test. The kinematic variables showed great individual reliability (CV = 8.46% in N; CV = 8.37% in H), which contrasted with low reliability observed when the whole group was considered. The smallest important CV ratio (>1.15) showed that H caused changes in the reliability of the kinematic variables, with some variables becoming more reliable and others losing the reliability they had in N. H also caused small increments in peak velocity across all loads tested in the CMJ (+3.67%; P<0.05). In contrast, no changes in the kinematic variables were verified. In addition, there was no association between leg extension capability and the acceleration (r =-0.16 ± 0.19 in N; r =-0.24 ± 0.19 in H) or angular velocity (r =-0.19 ± 0.24 in N; r =-0.30 ± 0.26 in H) of the ippon-seoi-nage, nor was acute exposure to H found to affect this association (P>0.05). Differences between individual and within-groups CV confirm the individual adaptations that each judoka makes during this technique. Additionally, the CV ratio shows a change in the space-time pattern of the technique in H. Therefore, it would be necessary to include an adaptation period to adapt the technique after the ascent in altitude. Further studies are needed to confirm the relationship and transference from the velocity gains in CMJ during altitude training.

Research paper thumbnail of Physiological End-Points During Exercise in the Heat

Medicine & Science in Sports & Exercise, 1992

During exercise testing, research subjects are frequently encouraged to continue their effort unt... more During exercise testing, research subjects are frequently encouraged to continue their effort until volitional fatigue has been reached. Typically a core temperature k 39.0°C and/or a heart rate k 180 bpm are used as end-of-test criteria. This study investigated the similarity of these physiological end-points with stroke volume as markers of volitional fatigue during exercise in the heat. Eight, heat acclimated males walked approximately 20-min at tImph and 3% grade every hour (with , 40-min seated rest) In 43.3, 50.6 and 57.2°C ambient air temperatures, for 6 hours or until their volitional fatigue. To provide a comparison environment the above workload and heat exposures were repeated with and without wearing a passive Ice vest. Rectal temperature (Tre), heart rate (HR), cardiac output (CO) and stroke volume (SV) were determined each hour during each of the walks. Volitional fatigue was not reached at the 43.3°C vest condition, therefore, it was not included In this analysis. End exercise Tre; HR, and SV results were as follows:

Research paper thumbnail of The Effects of Exercise, Heat and Microclimate Cooling on Cardiovascular Drift

Medicine & Science in Sports & Exercise, 1992

Research paper thumbnail of Peripheral sweat gland function, but not whole-body sweat rate, increases in women following humid heat acclimation

Journal of Thermal Biology, 2010

The purpose of this study was to compare both the whole-body and pharmacological-induced sweat ra... more The purpose of this study was to compare both the whole-body and pharmacological-induced sweat rates of men and women following humid heat acclimation.

Research paper thumbnail of Peripheral sweat gland function is improved with humid heat acclimation

Journal of Thermal Biology, 2009

The purpose of this study was to determine if humid heat acclimation improves thermoregulatory fu... more The purpose of this study was to determine if humid heat acclimation improves thermoregulatory function at the level of the eccrine sweat gland. Keywords: Core temperature Pilocarpine-induced sweat rate Whole-body sweat rate 2. Mean rectal temperature and heart rate were significantly (p<O.OS) reduced by O.5'C and 17bpm. respectively. during an 8-day heat acclimation protocol in 13 male subjects. 3. Whole-body sweat rate was also significantly increased 20% during the same time period. The most important new finding was that humid heat acclimation produced a significant 63% increase in pilocarpine-induced sweat rate. These results strongly suggest that heat acclimation improves sweat gland function via a peripheral mechanism.

Research paper thumbnail of Effect of Skin Temperature on the Cholinergic Sensitivity of the Human Eccrine Sweat Gland

The Japanese Journal of Physiology, 2003

Although sweat gland activity is directly controlled by the central nervous system (CNS), which d... more Although sweat gland activity is directly controlled by the central nervous system (CNS), which detects changes in core body temperature, sweat glands can also be influenced by local conditions. For example, an increase in local skin temperature (T skin) results in increased sweating. However, the mechanism by which this occurs remains unclear. Little research has been performed to answer this question, but two main possibilities have been suggested. First, an increase in local T skin results in a greater release of sudomotor neurotransmitter, causing a greater sweat response [1, 2]. Second, sweat glands may exhibit an enhanced sensitivity to a given neurotransmitter following a rise in local T skin [3, 4]. Qualitative observations on two subjects tested by Ogawa [3] suggested that increasing T skin from approximately 23 to 36°C resulted in a decreased amount of pilocarpine or acetylcholine needed to induce a noticeable sweating response. Similar results were found in the same study when T skin was increased from 26 to 29.5 and then to 32°C on one subject. Follow-up work on four subjects by Ogawa and Asayama [4] indicated that an increase in T skin from approximately 37 to 42°C increased the rate of pilocarpine-induced sweat production. Although the small sample sizes prevented statistical analysis, these collective results suggested that local heating fa

Research paper thumbnail of Skin Blood Flow Affects In Vivo Near-Infrared Spectroscopy Measurements in Human Skeletal Muscle

The Japanese Journal of Physiology, 2005

Leg skin blood flow (SkBF) was increased and decreased following local heating and intradermal ep... more Leg skin blood flow (SkBF) was increased and decreased following local heating and intradermal epinephrine injection. Epinephrine decreased muscle saturation (StO 2), and heating the leg increased StO 2. The results

Research paper thumbnail of Thermoregulatory Effects of Exercise in a Hyperconvective Environment

Research paper thumbnail of Thermoregulation in Burn Patients During Exercise

The Journal of Burn Care & Rehabilitation, 2003

The purpose of this study was to assess the ability of patients with burns on 30 to 40% and 60% o... more The purpose of this study was to assess the ability of patients with burns on 30 to 40% and 60% or greater of their BSA to thermoregulate their core temperature during exercise in the heat. Two groups (n = 3 in each) of subjects with healed third-degree burns (34.0 ± 1.4% and 77.7 ± 12.4%, respectively) and a group of unburned subjects (n = 2) exercised for 1 hour on a cycle ergometer at 75 Watts in an environmental chamber set at 35°C and 60% relative humidity. Subjects were monitored for rectal and skin temperatures, heart rate, whole body sweat rate, skin blood flow, and active sweat gland density (number per cm2) in unburned, burned, and harvested skin. The results demonstrated that patients with burns on 60% or greater BSA did not show an intolerance to moderate exercise in the heat, as evidenced by only a moderate rise in rectal temperature and heart rate. Furthermore, the responses were similar to those of the unburned subjects.

Research paper thumbnail of An Inquiry-Based Learning Model for an Exercise Physiology Laboratory Course

Advances in Physiology Education, 2001

We developed an inquiry-based learning model to better stimulate undergraduate students’ cognitiv... more We developed an inquiry-based learning model to better stimulate undergraduate students’ cognitive development of exercise physiology laboratory concepts. The course core is the two independent research projects that students, working in small groups, complete during the last 9 wk of the semester. Student groups develop their own research question and hypothesis, design the experiment, collect and analyze the data, and report their findings to the rest of the class using presentation software. To help with success of the research projects, students are taken through a series of guided-inquiry laboratory activities during the initial 6 wk of the semester to develop laboratory skills and an understanding of the scientific process. Observations of student behaviors reflected a high level of enthusiasm and engagement in laboratory activities. Surveys, journal entries, and interviews indicated that students felt empowered by having ownership in their projects, which may be the key reason...

Research paper thumbnail of Cold Acclimation Does Not Alter Physiological or Perceptual Responses During Subsequent Exercise in the Heat

Military Medicine, 2017

Introduction: Warfighters often train and conduct operations in cold environments. Specifically, ... more Introduction: Warfighters often train and conduct operations in cold environments. Specifically, military trainees and divers that are repeatedly exposed to cold water may experience inadvertent cold acclimatization, which results in body heat retention. These same warfighters can quickly switch between environments (cold to hot or hot to cold) given the nature of their work. This may present a risk of early onset of hyperthermia when cold-acclimatized warfighters are subsequently exposed to physiological insults that increase body temperature, such as exercise and heat stress. However, there is currently no evidence that suggests this is the case. The purpose of this work, therefore, is to determine what impact, if any, repeated immersion in cold water has on subsequent exercise in the heat. Materials and Methods: Twelve healthy subjects (values in mean ± SD: age, 25.6 ± 5.2 years; height, 174.0 ± 8.9 cm; weight, 75.6 ± 13.1 kg) voluntarily provided written informed consent in accordance with the San Diego State University Institutional Review Board. They first completed 120 minutes of moderate treadmill walking in 40°C and 40% relative humidity. During this trial, subjects' physiological and perceptual responses were recorded. Twenty-four hours later, subjects began a cold acclimation protocol, which consisted of seven, 90-minute immersions in cold water (10°C, water level to chest). Each immersion was also separated by 24 hours. Subjects then repeated a subsequent trial of exercise in the heat 24 hours after the final immersion of the cold acclimation protocol. Results: Results from cold acclimation revealed no change in core temperature, a decrease in skin temperature, and attenuated shivering and lactate responses, which supports a successful insulative-hypothermic cold acclimation response. This type of cold acclimation response primarily results in heat retention with associated energy conservation. Findings for heat trials (pre-cold acclimation and post-cold acclimation) revealed no differences between trials for all measurements, suggesting that cold acclimation did not influence physiological or perceptual responses during exercise in the heat. Conclusion: Our findings indicate that military divers or trainees that are frequently exposed to cold water, and hence have the ability to experience cold acclimatization, will likely not be at greater risk of increased thermal strain when subsequently exposed to physical activity in hot environments. In this study, no physiological or perceptual differences were observed between trials before and after cold acclimation, suggesting that cold acclimation does not present a greater hyperthermia risk during subsequent exercise in the heat.

Research paper thumbnail of Validity and Reliability of Predicting Maximum Oxygen Uptake via Field Tests in Children and Adolescents

Pediatric Exercise Science, 1991

The purpose of this study was to determine the validity and reliability of three of the most comm... more The purpose of this study was to determine the validity and reliability of three of the most commonly used field tests to predict maximum oxygen uptake in children and adolescents. VO2max was directly measured during a maximal treadmill test in 90 children (10-18 yrs). Each subject also performed, in duplicate, a timed distance run (1 mile), a step test, and a submaximal cycle ergometer test. A multiple regression equation was developed with directly measured VO2max as the dependent variable and mile-run time, gender, skinfold thickness, and body weight as independent variables. The equation had a multiple R=0.84 and a standard error of estimate of 9%, or 4.3 ml/kg/min. The results suggest that when the three most commonly used field tests to predict aerobic capacity are compared in the same group of children, the timed distance run is superior in both validity and reliability.

Research paper thumbnail of Hyperthermia during exercise – a double-edged sword

Temperature, 2016

An excessive elevation in body temperature is known to decrease exercise performance. The physiol... more An excessive elevation in body temperature is known to decrease exercise performance. The physiological mechanisms involved with hyperthermia-induced fatigue include central nervous system dysfunction and cardiovascular instability. Conversely, a moderate increase in body temperature has been shown to actually improve exercise performance. Asmussen and Boje 1 reported that sprint performance improved by approximately 5% for each 1 C increase in muscle temperature. The improvement was attributed to the wellknown Q 10 temperature effect on numerous biochemical processes. However, are there other potential benefits of hyperthermia during exercise? Recently we published findings that suggest another possible benefit of moderate hyperthermia during exercise, namely improved blood viscosity. 2 This is important as blood viscosity plays a critical role in limiting exercise capacity and is significantly correlated to maximal oxygen uptake. 3 It is inevitable that during exercise there is an increase in hematocrit, induced by several mechanisms including fluid shifts due to increases in blood pressure, dehydration, and water trapping in working skeletal muscle. The exercise-induced hemoconcentration has traditionally been viewed to have both positive and negative consequences as it simultaneously increases both oxygen carrying capacity and blood viscosity. In fact, over the last 30 y at least 10 studies have reported that various forms of exercise increase blood viscosity by between 5 to 15%. However, in an effort to isolate the effect of increases in hematocrit on blood viscosity, they measured both the pre-and post-exercise blood samples at 37 C. This discounts the fact that exercise almost always elevates core and blood temperature. Thus, past studies that reported an increase in blood viscosity following exercise did not replicate real in vivo conditions and therefore likely missed any affect that exercise-induced hyperthermia may have had on mitigating change in blood viscosity. The results of our recent study challenge the dogma that exercise increases blood viscosity. Specifically we found that exercise-induced hemoconcentration significantly increased blood viscosity by 9%. This finding agrees with all of the past studies. However, we also found that exercise-induced hyperthermia significantly decreased blood viscosity by 7%. When both factors were considered together, there was no overall change in blood viscosity. Thus, the effects of hemoconcentration and hyperthermia counterbalanced each other so that there was no change in blood viscosity, at a given shear rate, following prolonged, moderate intensity exercise in the heat. Therefore, we suggest that moderate hyperthermia during exercise may be beneficial because it attenuates the increase in blood viscosity brought about by hemoconcentration. Our results suggest that hyperthermia decreases blood viscosity by increasing red blood cell deformability. The exact mechanism is currently unknown; however increased temperature may result in more spontaneous dissociations of the spectrin network where in junctions with the phospholipid bilayer. This reduced tension within the cytoskeleton could ultimately decrease membrane stiffness and improve red blood cell deformability. Our results may also help to explain why past findings 4 have reported that a high hematocrit decreases blood flow much more in resting muscle than in exercising muscle. It could be theorized that the blood flow preserving effect of muscle contractions reported in these studies was at least partially due to a hyperthermia-induced reduction in blood viscosity in the exercising muscle.

Research paper thumbnail of The physiological responses to Bikram yoga in novice and experienced practitioners

Alternative therapies in health and medicine

Bikram yoga has gained a large following, possibly because of widespread claims boasting energy e... more Bikram yoga has gained a large following, possibly because of widespread claims boasting energy expenditure of up to 1000 calories per session. However, these claims are unfounded because no scientific study has investigated the metabolic response to a complete, standardized Bikram yoga class. This study intends to determine energy expenditure, heart rate, and sweat rate in novice and experienced practitioners from a standardized Bikram yoga class. Data were collected in the environmental chamber of the Exercise Physiology Laboratory at San Diego State University in California, USA. Male (n = 5) and female (n = 19) participants between the ages of 18 and 57 y were recruited through flyers in yoga studios throughout San Diego. Participants were classified as experienced or novice practitioners, having completed ≥20 or <20 sessions, respectively. Participants were guided through a standardized 90-min yoga class performed in a hot environment using Bikram's Standard Beginning Di...

Research paper thumbnail of Effect of air temperature on the rectal temperature gradient at rest and during exercise

International journal of physiology, pathophysiology and pharmacology, 2014

The purpose of the current study was to determine the effect of air temperature on the rectal tem... more The purpose of the current study was to determine the effect of air temperature on the rectal temperature gradient at rest and during exercise. It was hypothesized that the rectal temperature gradient would be exacerbated in cold environments and attenuated in warm environments both at rest and during exercise. Each subject completed three exercise bouts on a motor driven treadmill at approximately 55% of their previously determined maximal oxygen uptake. Three different air temperatures (10, 22, 39°C) were used for the exercise bouts. Rectal temperature was measured at rest and every 5 min during each exercise bout using 4 temperature sensors affixed at 4, 7, 10 and 13 cm past the anal sphincter. Readings obtained from the 4-cm depth were significantly (p<0.05) lower than those obtained at deeper insertion depths both at rest and during exercise for all three air temperatures. Furthermore, the results showed that the rectal temperature gradient was exacerbated in cold environmen...

Research paper thumbnail of Does anticipatory sweating occur prior to fluid consumption?

International journal of physiology, pathophysiology and pharmacology, 2012

The purpose of this study was to examine if anticipatory sweating occurs prior to fluid consumpti... more The purpose of this study was to examine if anticipatory sweating occurs prior to fluid consumption in dehydrated subjects. It was hypothesized that there would first be an anticipatory response to the sight of water, and then with drinking, a second response caused by mechanical stimulation of oropharyngeal nerves. Dehydrated subjects (n=19) sat in a heat chamber for 30 minutes. At minute 15, a resistance hygrometer capsule was attached and sweat rate was measured every 3 seconds. At minute 35:00, a researcher entered the room with previously measured water (2 ml/kg euhydrated body weight). At minute 35:30, the subject was allowed to drink. Data collection continued for 5 minutes post consumption. As expected, 16 of the 19 subjects responded to oropharyngeal stimuli with increased sweat rate. However, the new finding was that a majority (12 of 19) also showed an anticipatory sweating response prior to fluid consumption. Subjects were divided into 4 groups based on the magnitude of ...

Research paper thumbnail of Effect of aerobic training on the plasma ACTH response to exercise

PsycEXTRA Dataset

A previous study has shown that plasma adrenocorticotropin (ACTH) secretion during submaximal exe... more A previous study has shown that plasma adrenocorticotropin (ACTH) secretion during submaximal exercise is increased following training. This finding is in contrast to studies of other hormones such as glucagon, epinephrine and growth hormone, all of which show decreases following training. This study reexamines the effect of training on plasma ACTH levels during exercise. Ten adult volunteers were split into a control and an exercise group. The exercise group underwent a 12 week training program consisting of running 3.5 kilometers per day, three days per week. Before and after the training program all subjects were tested for plaesm ACTH response to a 150 Watt workload for 15 minutes. The experimental group showed an 11% increase in Hex Vo 2 following training while the control group's Max Vo 2 was unchanged. The experimental group's ACTS response to the submaximal workload was decreased 63% (p<O.O5). while the control group's response was unchanged. These data suggest that the ACTH response to exercise is blunted following training. This response is similar to that of other hormones such as glucagon. epinephrine and growth hormone. Such a finding is in agreement with previous studies that have shown that ACTH follows an intensity dependent pattern during exercise.

Research paper thumbnail of When Posture is Controlled, Acute Hypoxia does not Decrease Core Temperature

Advances in Life Sciences, 2012

It has been reported that acute hypoxia causes a reduction in core temperature in humans. It was ... more It has been reported that acute hypoxia causes a reduction in core temperature in humans. It was hypothesized that this occurs due to both a decrease in metabolic rate and an increase in skin b lood flo w. Ho wever, other studies have found that core temperature decreases with changes in posture. The methods in prev ious studies finding hypo xia to decrease core temperature did not control for postural changes. Thus, further examination is warranted to examine the effect of hypo xia on core temperature while controlling for posture change. Ten healthy adults, between the ages of 18 and 45 were recruited to participate. Subjects completed one trial consisting of breathing normo xic air (20.9%) for a 2 hour period and hypoxic air for a 1 hour period, while systematically changing posture. During this time core temperature and skin blood flow were recorded every 5 minutes. The results showed that mean core body temperature significantly (p < 0.05) decreased by 0.4℃ when the subjects transitioned from a standing to lying position. Ho wever, acute hypoxia, which reduced the mean o xygen saturation to 85%, d id not significantly affect core temperature. Such results suggest that when posture is controlled, acute hypoxia does not significantly decrease core body temperature. Thus, the results of previous studies that have reported decreases in core temperature with acute hypoxia, but failed to control for posture, need to be questioned.

Research paper thumbnail of Alterations in the Rate of Limb Movement Using a Lower Body Positive Pressure Treadmill Do Not Influence Respiratory Rate or Phase III Ventilation

BioMed research international, 2015

The purpose of this study was to determine the effect of alterations in rate of limb movement on ... more The purpose of this study was to determine the effect of alterations in rate of limb movement on Phase III ventilation during exercise, independent of metabolic rate, gait style, and treadmill incline. Subjects completed five submaximal exercise bouts on a lower body positive pressure treadmill (AlterG P 200). The percent body weight for the five exercise bouts was 100, 87, 75, 63, and 50% and each was matched for carbon dioxide production (V CO2 ). Naturally, to match the V CO2 while reducing the body weight up to 50% of normal required a significant increase in the treadmill speed from 3.0 ± 0.1 to 4.1 ± 0.2 mph, which resulted in a significant (P < 0.05) increase in the mean step frequency (steps per minute) from 118 ± 10 at 3 mph (i.e., 100% of body weight) to 133 ± 6 at 4.1 mph (i.e., 50% of body weight). The most important finding was that significant increases in step frequency did not significantly alter minute ventilation or respiratory rate. Such results do not support ...

Research paper thumbnail of The effect of an acute bout of exercise on selected pulmonary function measurements

Medicine & Science in Sports & Exercise, 1981

Research paper thumbnail of Effect of Acute Exposure to Moderate Altitude on Peripheral Sweating

Medicine & Science in Sports & Exercise, 2002

This study aimed to assess the effect of acute exposure to moderate altitude on kinematic variabl... more This study aimed to assess the effect of acute exposure to moderate altitude on kinematic variables of the ippon-seoi-nage and on the mechanical outputs of the countermovement jump (CMJ). Thirteen elite male judokas from the Spanish Judo Training Centre in Valencia (age: 21.54 ± 2.15 years) participated in the study. All of them performed an incremental CMJ test and an ippon-seoi-nage technique test before (N) and after the ascent to a moderate altitude of 2320 m above the sea level (H). A linear velocity transducer was attached to the bar to assess the mechanical outputs of each loaded CMJ at different percentages of their own body weight (25, 50, 75 and 100%). A wearable sensor was used to assess the kinematic variables (times, accelerations and angular velocities) transferred to a dummy during the technique test. The kinematic variables showed great individual reliability (CV = 8.46% in N; CV = 8.37% in H), which contrasted with low reliability observed when the whole group was considered. The smallest important CV ratio (>1.15) showed that H caused changes in the reliability of the kinematic variables, with some variables becoming more reliable and others losing the reliability they had in N. H also caused small increments in peak velocity across all loads tested in the CMJ (+3.67%; P<0.05). In contrast, no changes in the kinematic variables were verified. In addition, there was no association between leg extension capability and the acceleration (r =-0.16 ± 0.19 in N; r =-0.24 ± 0.19 in H) or angular velocity (r =-0.19 ± 0.24 in N; r =-0.30 ± 0.26 in H) of the ippon-seoi-nage, nor was acute exposure to H found to affect this association (P>0.05). Differences between individual and within-groups CV confirm the individual adaptations that each judoka makes during this technique. Additionally, the CV ratio shows a change in the space-time pattern of the technique in H. Therefore, it would be necessary to include an adaptation period to adapt the technique after the ascent in altitude. Further studies are needed to confirm the relationship and transference from the velocity gains in CMJ during altitude training.

Research paper thumbnail of Physiological End-Points During Exercise in the Heat

Medicine & Science in Sports & Exercise, 1992

During exercise testing, research subjects are frequently encouraged to continue their effort unt... more During exercise testing, research subjects are frequently encouraged to continue their effort until volitional fatigue has been reached. Typically a core temperature k 39.0°C and/or a heart rate k 180 bpm are used as end-of-test criteria. This study investigated the similarity of these physiological end-points with stroke volume as markers of volitional fatigue during exercise in the heat. Eight, heat acclimated males walked approximately 20-min at tImph and 3% grade every hour (with , 40-min seated rest) In 43.3, 50.6 and 57.2°C ambient air temperatures, for 6 hours or until their volitional fatigue. To provide a comparison environment the above workload and heat exposures were repeated with and without wearing a passive Ice vest. Rectal temperature (Tre), heart rate (HR), cardiac output (CO) and stroke volume (SV) were determined each hour during each of the walks. Volitional fatigue was not reached at the 43.3°C vest condition, therefore, it was not included In this analysis. End exercise Tre; HR, and SV results were as follows:

Research paper thumbnail of The Effects of Exercise, Heat and Microclimate Cooling on Cardiovascular Drift

Medicine & Science in Sports & Exercise, 1992

Research paper thumbnail of Peripheral sweat gland function, but not whole-body sweat rate, increases in women following humid heat acclimation

Journal of Thermal Biology, 2010

The purpose of this study was to compare both the whole-body and pharmacological-induced sweat ra... more The purpose of this study was to compare both the whole-body and pharmacological-induced sweat rates of men and women following humid heat acclimation.

Research paper thumbnail of Peripheral sweat gland function is improved with humid heat acclimation

Journal of Thermal Biology, 2009

The purpose of this study was to determine if humid heat acclimation improves thermoregulatory fu... more The purpose of this study was to determine if humid heat acclimation improves thermoregulatory function at the level of the eccrine sweat gland. Keywords: Core temperature Pilocarpine-induced sweat rate Whole-body sweat rate 2. Mean rectal temperature and heart rate were significantly (p<O.OS) reduced by O.5'C and 17bpm. respectively. during an 8-day heat acclimation protocol in 13 male subjects. 3. Whole-body sweat rate was also significantly increased 20% during the same time period. The most important new finding was that humid heat acclimation produced a significant 63% increase in pilocarpine-induced sweat rate. These results strongly suggest that heat acclimation improves sweat gland function via a peripheral mechanism.

Research paper thumbnail of Effect of Skin Temperature on the Cholinergic Sensitivity of the Human Eccrine Sweat Gland

The Japanese Journal of Physiology, 2003

Although sweat gland activity is directly controlled by the central nervous system (CNS), which d... more Although sweat gland activity is directly controlled by the central nervous system (CNS), which detects changes in core body temperature, sweat glands can also be influenced by local conditions. For example, an increase in local skin temperature (T skin) results in increased sweating. However, the mechanism by which this occurs remains unclear. Little research has been performed to answer this question, but two main possibilities have been suggested. First, an increase in local T skin results in a greater release of sudomotor neurotransmitter, causing a greater sweat response [1, 2]. Second, sweat glands may exhibit an enhanced sensitivity to a given neurotransmitter following a rise in local T skin [3, 4]. Qualitative observations on two subjects tested by Ogawa [3] suggested that increasing T skin from approximately 23 to 36°C resulted in a decreased amount of pilocarpine or acetylcholine needed to induce a noticeable sweating response. Similar results were found in the same study when T skin was increased from 26 to 29.5 and then to 32°C on one subject. Follow-up work on four subjects by Ogawa and Asayama [4] indicated that an increase in T skin from approximately 37 to 42°C increased the rate of pilocarpine-induced sweat production. Although the small sample sizes prevented statistical analysis, these collective results suggested that local heating fa

Research paper thumbnail of Skin Blood Flow Affects In Vivo Near-Infrared Spectroscopy Measurements in Human Skeletal Muscle

The Japanese Journal of Physiology, 2005

Leg skin blood flow (SkBF) was increased and decreased following local heating and intradermal ep... more Leg skin blood flow (SkBF) was increased and decreased following local heating and intradermal epinephrine injection. Epinephrine decreased muscle saturation (StO 2), and heating the leg increased StO 2. The results

Research paper thumbnail of Thermoregulatory Effects of Exercise in a Hyperconvective Environment

Research paper thumbnail of Thermoregulation in Burn Patients During Exercise

The Journal of Burn Care & Rehabilitation, 2003

The purpose of this study was to assess the ability of patients with burns on 30 to 40% and 60% o... more The purpose of this study was to assess the ability of patients with burns on 30 to 40% and 60% or greater of their BSA to thermoregulate their core temperature during exercise in the heat. Two groups (n = 3 in each) of subjects with healed third-degree burns (34.0 ± 1.4% and 77.7 ± 12.4%, respectively) and a group of unburned subjects (n = 2) exercised for 1 hour on a cycle ergometer at 75 Watts in an environmental chamber set at 35°C and 60% relative humidity. Subjects were monitored for rectal and skin temperatures, heart rate, whole body sweat rate, skin blood flow, and active sweat gland density (number per cm2) in unburned, burned, and harvested skin. The results demonstrated that patients with burns on 60% or greater BSA did not show an intolerance to moderate exercise in the heat, as evidenced by only a moderate rise in rectal temperature and heart rate. Furthermore, the responses were similar to those of the unburned subjects.