Biomedical subjects

H A Daanen

Publications and source records attributed to H A Daanen.

16 recordsLinked to original sources

PubMed2006

Heat strain and gross efficiency during endurance exercise after lower, upper, or whole body precooling in the heat.

The maximal power that muscles can generate is reduced at low muscle temperatures. However, in prolonged heavy exercise in the heat, a high core temperature may be the factor limiting performance. Precooling has been shown to delay the attainment of hyperthermia. It is still unclear if the whole body should be cooled or if the active muscles should be excluded from cooling in order to maintain muscle power. An experiment was performed to compare thermal strain and gross efficiency following whole body or partial body cooling. Eight well-trained participants performed 40 min of 60% VO2max cycling exercise in a 30 degrees C, 70% relative humidity climatic chamber after four different precooling sessions in a water perfused suit: N (no precooling), CC (45 min whole body precooling), WC (45 min lower body precooling), and CW (45 min upper body precooling). The uncooled body part was warmed in such a way that the core temperature did not differ from that in session N. Gross efficiency was used to compare performance between the sessions since it indicates how much oxygen is needed for a certain external load. The gross efficiency did not differ significantly between the sessions. Differences in heat loss and heat storage were observed during the first 20 min of exercise. The evaporative heat loss in session WC (305 +/- 67 W) and CW (284 +/- 68 W) differed from session N (398 +/- 77 W) and CC (209 +/- 58 W). More heat was stored in session CC (442 +/- 125 W) than in sessions WC (316 +/- 39 W), CW (307 +/- 63 W), and N (221 +/- 65 W). It was confirmed that precooling reduces heat strain during exercise in the heat. No differences in heat strain and gross efficiency were observed between precooling of the body part with the exercising muscles and precooling of the tissues elsewhere in the body.

Adolescent↗

PubMed2000

Axon reflexes in human cold exposed fingers.

Exposure of fingers to severe cold induces cold induced vasodilatation (CIVD). The mechanism of CIVD is still debated. The original theory states that an axon reflex causes CIVD. To test this hypothesis, axon reflexes were evoked by electrical stimulation of the middle fingers of hands immersed in water at either 5 degrees C or 35 degrees C. Axon reflexes were pronounced in the middle finger of the hand in warm water, but absent from the hand in cold water, even though the stimulation was rated as "rather painful" to "painful". These results showed that axon reflexes do not occur in a cold-exposed hand and thus are unlikely to explain the CIVD phenomenon.

Adult↗

PubMed2000

Cold-induced peripheral vasodilation at high altitudes--a field study.

A significant reduction in cold-induced vasodilation (CIVD) is observed at high altitudes. No agreement is found in the literature about acclimatization effects on CIVD. Two studies were performed to investigate the effect of altitude acclimatization on CIVD. In the first study 13 male subjects immersed the distal phalanx of the left middle finger in water of 0 degrees C for 30 min to evoke CIVD. Five subjects were exposed to altitudes of 5,100 to 7,000 m for 45 days (A). Eight subjects were exposed to an altitude of 5,100 m for <3 days (NA). The groups did not differ in age, weight, and stature. No significant differences were observed between A and NA. However, the maximum finger skin temperature of group A tended to return to sea level values (6.9 +/- 3.2 degrees C at sea level vs. 6.0 +/- 0.7 degrees C at altitude), while a strong reduction was observed for the NA group (7.7 +/- 4.3 degrees C vs. 3.7 +/- 3.1 degrees C). This indicates that the CIVD response at altitude tended to be stronger for the acclimatized subjects. In a second study, nine males were followed in a longitudinal study. CIVD was measured before, during and after 7 days of exposure to 4,350 m. Maximum finger skin temperature before and after exposure did not differ (8.5 +/- 2.6 degrees C vs. 7.8 +/- 1.6 degrees C), and was reduced at altitude. There was no difference in maximum finger skin temperature between the 7 days at altitude (e.g., 5.3 +/- 2.7 degrees C at day 2 and 4.7 +/- 1.1 degrees C at Day 7). It can be concluded that no acclimatization effects of CIVD occur during the first 7 days of altitude exposure, but that differences may occur after altitude exposure of several weeks.

Acclimatization↗

PubMed1999

Finger cold-induced vasodilation during mild hypothermia, hyperthermia and at thermoneutrality.

BACKGROUND: Exposure of the fingers to severe cold leads to cold-induced vasodilation (CIVD). The influence of ambient temperature on the CIVD-response is well understood and documented, but the response of CIVD to hyperthermia and mild hypothermia has rarely been investigated. METHODS: To investigate the influence of body thermal status on the CIVD response, eight subjects immersed their right hand in 5 degrees C water for 40 min during mild hypothermia (C), thermoneutrality (N) and hyperthermia (W). The mean skin temperature of the body (Tsk), the esophageal temperature (Tes), the temperature of the volar side of the distal phalanx of each immersed finger (Tfi) and the skin perfusion of the immersed middle finger (Qsk) were continuously measured. RESULTS: During the W condition the body temperatures were higher (Tes: 38.0+/-0.1 degrees C; Tsk: 37.9+/-0.7 degrees C) than during N (Tes: 36.8+/-0.2 degrees C; Tsk: 31.8+/-0.7 degrees C) and during C (Tes: 36.1+/-0.8 degrees C; Tsk: 21.2+/-1.9 degrees C). Tfi and Qsk were higher during the W condition (Tfi: 16.5+/-2.3 degrees C; Qsk: 133+/-53 perfusion units (PU)) than during N (Tfi: 8.1+/-1.7 degrees C; Qsk: 57+/-39 PU) and during C (Tfi: 6.8+/-1.2 degrees C; Qsk: 22+/-14 PU). The onset time of CIVD was significantly prolonged in condition C (13.0+/-3.8 min) as compared with N (7.2+/-2.2 min). CONCLUSION: It was concluded that the CIVD response is significantly affected by body core and skin temperatures.

Adult↗

PubMed1997

The effect of body temperature on the hunting response of the middle finger skin temperature.

The relationship between body temperature and the hunting response (intermittent supply of warm blood to cold exposed extremities) was quantified for nine subjects by immersing one hand in 8 degree C water while their body was either warm, cool or comfortable. Core and skin temperatures were manipulated by exposing the subjects to different ambient temperatures (30, 22, or 15 degrees C), by adjusting their clothing insulation (moderate, light, or none), and by drinking beverages at different temperatures (43, 37 and 0 degrees C). The middle finger temperature (Tfi) response was recorded, together with ear canal (Tear), rectal (Tre), and mean skin temperature (Tsk). The induced mean Tear changes were -0.34 (0.08) and +0.29 (0.03) degrees C following consumption of the cold and hot beverage, respectively. Tsk ranged from 26.7 to 34.5 degrees C during the tests. In the warm environment after a hot drink, the initial finger temperature (T(fi,base)) was 35.3 (0.4) degrees C, the minimum finger temperature during immersion (T(fi,min)) was 11.3 (0.5) degrees C, and 2.6 (0.4) hunting waves occurred in the 30-min immersion period. In the neutral condition (thermoneutral room and beverage) T(fi,base) was 32.1 (1.0) degrees C, T(fi,min) was 9.6 (0.3) degrees C, and 1.6 (0.2) waves occurred. In the cold environment after a cold drink, these values were 19.3 (0.9) degrees C, 8.7 (0.2) degrees C, and 0.8 (0.2) waves, respectively. A colder body induced a decrease in the magnitude and frequency of the hunting response. The total heat transferred from the hand to the water, as estimated by the area under the middle finger temperature curve, was also dependent upon the induced increase or decrease in Tear and Tsk. We conclude that the characteristics of the hunting temperature response curve of the finger are in part determined by core temperature and Tsk. Both T(fi,min) and the maximal finger temperature during immersion were higher when the core temperature was elevated; Tsk seemed to be an important determinant of the onset time of the cold-induced vasodilation response.

Adult↗

PubMed1995

Physiological criteria for functioning of hands in the cold: a review.

Hands are important instruments in daily life. Without hands man is hardly able to function independently. Proper functioning of the hands is determined by several physiological parameters. These physiological parameters in turn are influenced by environmental factors. In this view of the literature, physiological processes in manual dexterity are described and the influence of a cold environment on separate physiological processes is studied. In general, cold means loss of dexterity. For reasons of safety and performance, it is important to restrict the loss of manual dexterity. For this purpose, in this study minimum criteria are given for all separate physiological components. Most important minimum criteria are: a local skin temperature of 15 degrees C, a nerve temperature of 20 degrees C and a muscle temperature of 28 degrees C. Only during maximum dynamic work is a muscle temperature of 38 degrees C recommended. These temperatures are average values, and of course individual differences are evident.

Journal Article↗

PubMed1995

The hand in the cold, performance and risk.

When a person is exposed to cold and his metabolic rate is insufficient to maintain a positive or neutral heat balance, the body will cool down. For the extremities this will result in a drastic reduction of blood flow, resulting in a so called "physiological amputation" with extremity cooling towards ambient temperature. The dexterity decrease observed with cold extremities is most likely caused by cooling of muscles and joints, and not by effects on receptors, nerve conduction or central effects. It is shown, that dexterity decreases can be described in terms of wind chill equivalent temperature and exposure time for a certain clothing and work configuration. Further, the risk of skin freezing and reduced dexterity due to touching cold objects can be described using the contact coefficient of the respective material and the contact time. This risk is modulated by metabolic rate and hand protection (gloves). Gloves drastically reduce cooling speed and freezing risk, but they also cause increased risks due to reduced dexterity due to glove thickness. For a general description of performance and risk of hand cold exposure in relation to climate and exposure time more data are needed.

Cold Temperature↗

PubMed1993

Functional analysis of patients who have had a modified Van Nes rotationplasty.

Electromyographic analysis of gait in eight patients who had had a modified Van Nes rotationplasty was performed to compare the activity of the flexors and extensors of the ankle on the side of the operation with that of the flexors and extensors of the knee on the normal, contralateral side. The resemblance in the activity of the extensors was more pronounced than that of the flexors. In three patients, the angle of flexion of the knee throughout the gait cycle was the same on the side of the rotationplasty as on the normal side. There was more symmetry in the swing phase than has been reported for patients who have had an above-the-knee amputation. The strength of the dorsiflexors of the ankle on the side of the rotationplasty was 68 percent and that of the flexors was 71 per cent when compared with that of the muscles of the normal ankle.

Adolescent↗

PubMed1992

Decrease in back strength in asymmetric trunk postures.

The extension force against resistance was recorded in 23 postures for 12 subjects to find explanations for the decrease in back strength in asymmetric postures. A reduction in muscle force in asymmetric postures was found up to 40%, but was strongly dependent on the plane in which asymmetry occurred, and on the posture to which it referred. A quantitative relationship between the forces exerted in different asymmetric postures is discussed, as a basis for formulating universal ergonomic guidelines for optimal working postures. The reduction in force in different asymmetric postures can be explained by length of the muscle, the activation of the muscle, and the moment angle of the muscle.

Adult↗

PubMed1992

Comparison of four noninvasive rewarming methods for mild hypothermia.

Four noninvasive rewarming techniques for mildly hypothermic subjects were compared. Seven subjects were cooled in a water bath of 15 degrees C for 2 h to an average esophageal temperature (Tes) of 36 degrees C. Thereafter, the subjects were rewarmed by immersion of the body in a water bath of 42 degrees C (Method 1), the body but not the extremities in water of 42 degrees C (Method 2), only the extremities in water of 42 degrees C (Method 3), or spontaneous rewarming in blankets (Method 4). Method 1 showed the highest rewarming rate in Tes (10.1 degrees C/h) and an afterdrop in Tes of 0.18 degrees C. Method 2 showed the same afterdrop, but a lower rewarming rate (7.5 degrees C/h). In Method 3, the heat uptake of the extremities was too low to rewarm the subjects effectively. The afterdrop and rewarming rate were 0.38 degrees C and 0.8 degrees C/h, respectively. Method 4 had the lowest rewarming rate (0.2 degrees C/h), and an afterdrop (0.14 degrees C) which was not significantly lower than that of Method 1 or 2. Therefore, Method 1 is recommended for rewarming mild hypothermic subjects because of its high rewarming rate and small afterdrop.

Adult↗

PubMed1991

Physiological responses of the human extremities to cold water immersion.

Five subjects immersed their hands and feet twice during 1 hour sessions in a calorimeter bath, filled with water at 25 degrees C. Before immersion the hand (33.0 +/- 2.2 degrees C) was warmer than the foot (30.6 +/- 2.1 degrees C) and so was the blood flow: respectively 5.8 +/- 5.2 versus 0.7 +/- 0.3 ml.min-1.100 mo tissue-1 as determined by strain gauge plethysmography and 10.8 +/- 5.1 versus 6.7 +/- 5.3 by the doppler method. At the end of the immersion period the blood flow had decreased a factor of 2.9 (doppler) and 4.3 (plethysmography). The local heat transfer, determined by heat flux transducers, was highest immediately after immersion. The maximum was higher at the ventral sides than at the dorsal sides of the hand (225 +/- 93 versus 186 +/- 61 W.m-2 and the foot (178 +/- 53 versus 160 +/- 57 W.m-2). The total heat transferred to the water by hand or foot during the 60 minutes of immersion, determined by calorimetry, was 47 +/- 21 and 36 +/- 36 kJ respectively and was not statistically different due to considerable interindividual differences. Interindividual differences were also found for heat flux, rectal and local skin temperature and blood flow. These differences will have to be taken into account if a comparison is made with data from subjects with local cold injuries.

Adolescent↗

PubMed1990

Reproducibility of the mean power frequency of the surface electromyogram.

There is evidence in the literature that the decrease of mean power frequency (MPF) during exercise is greater as a muscle become more fatigued. After strenuous exercise this phenomenon can last several days. It is usually assumed, however, that the MPF has a good reproducibility. In this study the reproducibility of the MPF of the surface electromyogram of the biceps brachii muscle was investigated for five subjects on 5 successive days. Force level, muscle length and skin temperature were kept constant. The results show that interindividual differences in MPF were large (SD 11.5 Hz). However, during these 5 days, the range in MPF for individual subjects was small. The SD of the trials within subjects and days was 2.0 Hz, while the SD trials excluded). It is hypothesized that this SD may be due to variations in the electrode replacement. It is concluded that the variability in MPF for a subject is small compared to the decrease of the MPF associated with muscle fatigue and which can therefore be determined reliably during longitudinal studies.

Adult↗

PubMed1990

Shock absorption of below-knee prostheses: a comparison between the SACH and the Multiflex foot.

Shock waves were measured during walking on a treadmill on the metal tube of a below-knee KBM prosthesis, provided either with a SACH foot or with a Multiflex foot. Accelerations were measured in the axial direction and the dorso-ventral direction, about 160 mm proximal to the sole of the shoe. The accelerations had comparable amplitudes to those measured on normal legs. Dorso-ventral amplitudes (order of magnitude 4 g) were generally higher than the axial amplitudes. For some patients, the SACH foot gave much higher axial accelerations than the Multiflex foot did. In the dorso-ventral direction, the SACH foot showed a moderate resonance phenomenon in the autospectral density function in the range of 40-50 Hz. The Multiflex foot showed a more variable behaviour. For both types of feet, components above 65 Hz were negligible.

Adult↗

PubMed1989

Elastic strain energy in the low back muscles during human walking.

A simple model of the thorax, pelvis and three columns of the intrinsic lumbar back muscles (= ILBM) was constructed. The model was used to study the length of the ILBM during the different stages of the walking cycle. The length of the right ILBM (especially the lateral column) was largest at right toe off, exactly the stage of the walking cycle in which most force was needed to prevent the torso from falling forwards and laterally.

Back↗

PubMed1988

The lever arm in glenohumeral abduction after hemiarthroplasty.

Fourteen cases of hemiarthroplasty for four-part fractures of the proximal humerus were reviewed. Pain relief was satisfactory, but function was limited, mainly due to loss of glenohumeral abduction despite electromyographic proof of actively contracting abductors in all cases. Analysis of special radiographs of nine cases showed a direct relationship between the clinical results and the "humeral offset", or distance between the geometric centre of the humeral head and the lateral aspect of the greater tuberosity. This offset affects the lever arms of the glenohumeral abductor muscles. The implications for surgical technique and for the design of shoulder prostheses are discussed.

Adult↗

PubMedDate not supplied

The relation between blood lactate and ammonia in ischemic handgrip exercise.

Subjects with myopathies associated with certain enzyme defects often show abnormal concentrations of lactate (LA) and ammonia (NH3) in blood after ischemic exercise. Myoadenylate deaminase (MAD) deficient patients produce only small amounts of NH3, whereas LA rises to normal levels. On the other hand, patients with certain enzyme deficiencies in the glyco(geno)lytic pathway show the opposite. However, the concentrations in blood are dependent on the exercise performed. Standardization of tests for screening purposes, therefore, is necessary. For ischemic contractions, experiments were performed to find the optimal combination for force and frequency, using the highest LA and NH3 concentrations in blood as criteria. Eleven healthy subjects performed ischemic isometric contractions with a handgrip dynamometer at frequencies of 30 and 50/min(-1) and force levels of 50%, 65%, and 80% of maximal voluntary contraction (MVC). A combination of 30/min(-1) and 80% MVC was found to give the best results.

Adult↗