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Biomedical subjects

Hannu Rintamäki

Publications and source records attributed to Hannu Rintamäki.

18 recordsLinked to original sources
PubMed2006

Factors affecting outdoor exposure in winter: population-based study.

The extent of outdoor exposure during winter and factors affecting it were examined in a cross-sectional population study in Finland. Men and women aged 25-74 years from the National FINRISK 2002 sub-study (n=6,591) were queried about their average weekly occupational, leisure-time and total cold exposure during the past winter. The effects of gender, age, area of residence, occupation, ambient temperature, self-rated health, physical activity and education on cold exposure were analysed. The self-reported median total cold exposure time was 7 h/week (8 h men, 6 h women),<1 h/week (2 h men, 0 h women) at work, 4 h/week (5 h men, 4 h women) during leisure time and 1 h/week (1 h men, 1.5 h women) while commuting to work. Factors associated with increased occupational cold exposure among men were: being employed in agriculture, forestry and industry/mining/construction or related occupations, being less educated and being aged 55-64 years. Factors associated with increased leisure-time cold exposure among men were: employment in industry/mining/construction or related occupations, being a pensioner or unemployed, reporting at least average health, being physically active and having college or vocational education. Among women, being a housewife, pensioner or unemployed and engaged in physical activity increased leisure-time cold exposure, and young women were more exposed than older ones. Self-rated health was positively associated with leisure time cold exposure in men and only to a minor extent in women. In conclusion, the subjects reported spending 4% of their total time under cold exposure, most of it (71%) during leisure time. Both occupational and leisure-time cold exposure is greater among men than women.

Adult↗
PubMed2006

Urinary melatonin: a noninvasive method to follow human pineal function as studied in three experimental conditions.

The aim of this study was to examine whether urinary melatonin, rather than urinary 6-sulfatoxymelatonin (aMT6s), can be used as an indicator of diurnally and seasonally changing melatonin secretion. The subjects (n=15) spent three separate 24-hr periods in a climatic chamber during winter (n=7) and summer (n=8). Blood and urine samples were obtained during each period at 2- to 5-hr intervals. Serum melatonin and urinary melatonin and aMT6s were assayed by radioimmunoassay. The serum melatonin levels increased nearly 10-fold from low daytime to high nocturnal values. The mean nocturnal increase of urinary melatonin was 1.7-fold and that of urinary aMT6s was 4.6-fold. Both urinary melatonin and aMT6s correlated significantly with area under the curve melatonin in serum during the night, during the day and throughout the entire 24-hr observation period in all cases. The ratio between urinary melatonin and aMT6s excretion showed significant diurnal variation, being ninefold higher at 16:00 hr than at 07:00 or at 09:00 hr. The ninefold decrease in the urinary melatonin/aMT6s excretion ratio between the evening and the morning may reflect increased liver metabolism of melatonin during the night. Both urinary melatonin and aMT6s are good indicators of melatonin secretion, but the variation is significantly smaller for the former molecule.

Adult↗
PubMed2006

Heat strain in cold.

In spite of increased environmental cold stress, heat strain is possible also in a cold environment. The body heat balance depends on three factors: environmental thermal conditions, metabolic heat production and thermal insulation of clothing and other protective garments. As physical exercise may increase metabolic heat production from rest values by ten times or even more, the required thermal insulation of clothing may vary accordingly. However, in most outdoor work, and often in indoor cold work, too, the thermal insulation of clothing is impractical, difficult or impossible to adjust according to the changes in physical activity. This is especially true with whole body covering garments like chemical protective clothing. As a result of this imbalance, heat strain may develop. In cold all the signs of heat strain (core temperature above 38 degrees C, warm or hot thermal sensations, increased cutaneous circulation and sweating) may not be present at the same time. Heat strain in cold may be whole body heat strain or related only to torso or core temperature. Together with heat strain in torso or body core, there can be at the same time even cold strain in peripheral parts and/or superficial layers of the body. In cold environment both the preservation of insulation and facilitation of heat loss are important. Development of clothing design is still needed to allow easy adjustments of thermal insulation.

Cold Temperature↗
PubMed2006

Changes in neuromuscular function due to intermittently increased workload during repetitive work in cold conditions.

OBJECTIVES: This study attempted to determine whether repetitive work in the cold affects the number of electromyographic (EMG) gaps and whether cold-induced deterioration in neuromuscular function can be restored by altering work intensity. METHODS: During 2 hours of simulated sausage packing, the occurrence of EMG gaps was studied in eight upper-extremity muscles at 19 degrees C and 4 degrees C. The additional effect of continuous, light repetitive work [wrist flexion-extension 10% of the maximal voluntary contraction (MVC), Cwork] and intermittently increased workload (10% or 30% MVC) (Iwork) on forearm muscle EMG gaps, the median frequency of the EMG spectrum, EMG activity, and muscle fatigue (as indicated by changes in the MVC of wrist flexion) at 4 degrees C was studied. RESULTS: During work simulation, the mean skin temperature decreased from 33.3 (SD 0.1) degrees C to 30.6 (SD 0.2) degrees C (P<0.05), and the number of EMG gaps diminished in seven muscles by 1.4-68.2% (P<0.05). During Iwork there were 44% and 37% more EMG gaps in the forearm flexors and extensors, respectively, and the median frequency shifted to higher frequencies (P<0.05) as compared with the situation in Cwork. The average EMG activity of the forearm flexors was 13% lower (P<0.05) during Iwork than during Cwork. Wrist flexion MVC decreased 18% and 15% in Cwork and Iwork, respectively. CONCLUSIONS: The cold-induced decrease in the number of EMG gaps and increased muscle strain and fatigue can be, at least partially, restored by intermittently increasing the workload (ie, breaking the monotonous work cycle).

Adult↗
PubMed2006

The effect of training of military skills on performance in cold environment.

This study was conducted to evaluate how training for disassembling and assembling a weapon and patrol data message terminal and loading a magazine in different temperatures affected the ability to perform those skills in a cold environment. One group trained six times on separate days in a warm environment (19 degrees C), the second group trained three times in a warm environment and then three times in a cold environment (-15 degrees C), and the third group trained six times in the cold environment. Training first in warm and then in cold shortened performance time by 6% to 28%, in comparison to training only in a warm environment. Also, training in cold made the subjects faster than training in warm. In conclusion, before performing military operations in a cold environment, it is most beneficial to train first in warm and then in cold. Training only in warm produces the lowest level of performance in a cold environment.

Adaptation, Physiological↗
PubMed2005

Effect of repeated exposures to cold on cognitive performance in humans.

The effects of repeated exposure to cold temperature on cognitive performance were examined in 10 male subjects who were exposed to control (25 degrees C) and cold (10 degrees C) conditions on 10 successive days. A cognitive test battery (ANAM-ICE) was administered each day to assess complex and simple cognitive functioning accuracy, efficiency and response time. Rectal (T(rect)) and skin temperatures, thermal sensations, metabolic rate (M) and cardiovascular reactivity were also recorded. With the used cold exposure, inducing cold sensations and discomfort, superficial skin cooling (6-7 degrees C) and a slightly lowered T(rect) (0.4 degrees C) we observed three distinct patterns of cognitive performance: 1) negative, reflected in increased response times and decreased accuracy and efficiency; 2) positive, reflected in decreased response time and increased efficiency; and 3) mixed, reflected in a pattern of increases in both accuracy and response time and decreases in efficiency, and a pattern of decreases in both accuracy and response time. T(rect), thermal sensations, diastolic blood pressure (DBP) and heart rate (HR) were independent predictors of decreased accuracy, but also decreased response time. Cognitive performance efficiency was significantly improved and response times shorter over the 10-d period both under control and cold exposures suggesting a learning effect. However, the changes in cognitive performance over the 10-d period did not differ markedly between control and cold, indicating that the changes in the thermal responses did not improve performance. The results suggest that cold affects cognitive performance negatively through the mechanisms of distraction and both positively and negatively through the mechanism of arousal.

Acclimatization↗
PubMed2005

Influence of seasonally adjusted exposure to cold and darkness on cognitive performance in circumpolar residents.

The effects of seasonally adjusted 24-h exposure to cold and darkness on cognitive performance in urban circumpolar residents was assessed in 15 male subjects who spent three 24-h periods in a climatic chamber at 65 degrees latitude during the winter (January-March) and/or summer (August-September). Each subject was exposed to three different environmental conditions in random order: (1) 22 degrees C temperature and 500 lx lighting; (2) 10 degrees C temperature and 500 lx lighting; and (3) 10 degrees C temperature and 0.5-l lx lighting. Accuracy on an addition-subtraction task was significantly greater in the summer than in the winter (p= 0.038), while accuracy on a repeated acquisition task was significantly greater in the winter than in the summer (p < 0.001). Independent of season, exposure to cold and darkness was significantly associated with a decline in response time on five cognitive tests, an improvement in accuracy on three tests measuring complex cognitive tasks, and a decline in accuracy on two tests measuring simple tasks. Increased performance on complex tasks may result from increased arousal in response to the combination of cold temperatures and dim light characteristic of the winter in urban circumpolar settings.

Adult↗
PubMed2005

Impacts of cold climate on human heat balance, performance and health in circumpolar areas.

In circumpolar areas the climate remains cool or thermoneutral during the majority of the days of the year spite of global warming. Therefore, health consequences related to cold exposure represent also in the future the majority of climate-related adverse health effects. Hot summers may be an exception. At ambient temperatures below +10 - +12 degrees C, humans experience cold stress of varying degree. Man can compensate a 10 degrees C change in ambient temperature by changing metabolic heat production by 30-40 W m(-2) or by wearing an additional/taking off ca. 0.4 clo units (corresponding to one thick clothing layer). Cold ambient temperature may be a risk for human health and cause varying levels of performance limitations. The impacts of cold exposure on health and wellbeing cause a burden to many societies in terms of lowered productivity and higher costs related to health care systems as well as public health planning and management. In order to provide preventive and protective public health actions for cold-induced adverse health effects, it is important to recognize cold related injuries, illnesses and symptoms and their turn-up temperatures, and to identify the most at-risk population subgroups and factors that increase or decrease the health risks posed by cold ambient temperatures. The majority of cold-related harmful health impacts can be prevented or managed by correct preventive and protective actions. Rapid unpredictable changes are more difficult to compensate because of lack of experience (affecting attitude and skills), preparedness (vehicles, garments, supplies, logistics etc.) and/or acclimatization.

Acclimatization↗
PubMed2005

Postural sway during single and repeated cold exposures.

INTRODUCTION: Tissue cooling changes sensory and neuromuscular functions that are also involved in postural control. The purpose of the study was to determine how acute and repeated exposures to cold affect whole body postural control. METHODS: Postural sway was measured from 10 subjects during standing with eyes open (EO) and closed (EC) using an inclinometer-based method. Sway was assessed at at 10 degrees C on 10 consecutive days and at 25 degrees C on days 1, 5, and 10. Sway path length, area, velocity, side-to-side and forward-backward movement were assessed. At the same time, rectal and skin temperatures, muscle tonus/ shivering, thermal sensations, and comfort were recorded. RESULTS: Acute exposure to 10 degrees C caused thermal discomfort, significantly lowered (26.1-26.5 degrees C) mean skin temperatures, slightly lowered rectal temperature (36.7 degrees C) and increased (140-260%) muscle tone, increased sway path length (67-87%, p < 0.05), velocity (63-71%, p < 0.05), total sway area (42-67%, p < 0.05), and forward-backward movement (35-57%, p < 0.05) compared with 25 degrees C. Side-to-side movements were not altered in the cold. Postural sway increased with EC, and further when exposed to cold, but the effect of cold was smaller compared with EO. Repeated exposures over the 10-d period decreased sway 10-40% both at 25 degrees C and at 10 degrees C (p < 0.05-0.01), suggesting motor learning. The difference in sway between 25 degrees C and 10 micro C remained the same throughout the 10-d period, suggesting that the observed cold habituation responses do not affect sway. CONCLUSIONS: The results demonstrate that postural control is impaired in cold, which may affect physical performance in cold environmental conditions.

Adult↗
PubMed2004

Seasonal changes in thermal responses of urban residents to cold exposure.

To determine whether urban circumpolar residents show seasonal acclimatisation to cold, thermoregulatory responses and thermal perception during cold exposure were examined in young men during January-March (n=7) and August-September (n=8). Subjects were exposed for 24 h to 22 and to 10 degrees C. Rectal (T(rect)) and skin temperatures were measured throughout the exposure. Oxygen consumption (VO(2)), finger skin blood flow (Q(f)), shivering and cold (CDT) and warm detection thresholds (WDT) were assessed four times during the exposure. Ratings of thermal sensations, comfort and tolerance were recorded using subjective judgement scales at 1-h intervals. During winter, subjects had a significantly higher mean skin temperature at both 22 and 10 degrees C compared with summer. However, skin temperatures decreased more at 10 degrees C in winter and remained higher only in the trunk. Finger skin temperature was higher at 22 degrees C, but lower at 10 degrees C in the winter suggesting an enhanced cold-induced vasoconstriction. Similarly, Q(f) decreased more in winter. The cold detection threshold of the hand was shifted to a lower level in the cold, and more substantially in the winter, which was related to lower skin temperatures in winter. Thermal sensations showed only slight seasonal variation. The observed seasonal differences in thermal responses suggest increased preservation of heat especially in the peripheral areas in winter. Blunted vasomotor and skin temperature responses, which are typical for habituation to cold, were not observed in winter. Instead, the responses in winter resemble aggravated reactions of non-cold acclimatised subjects.

Adult↗
PubMed2004

The occurrence of frostbite and its risk factors in young men.

OBJECTIVES: Previous studies have paid little attention to the occurrence of frostbites and related risk factors. The purpose of this study is to analyse the life-time occurrence of frostbite in young men and its association with the cold-provoked white finger syndrome (CPWF), smoking and hand vibration. METHODS: The study population consisted of 5839 Finnish men aged 17-30 years entering military service. Data was collected for cases of first-degree, or more severe, frostbite affecting the head and extremities. Logistic analysis was used to assess the risk of frostbite with respect to CPWF, smoking and hand vibration. RESULTS: The life-time and annual occurrences of frostbite were 44% and 2.2%, respectively (n = 2555). 2333 subjects (41%) had suffered first-degree freezing injury and 671 (12%) suffered severe injury at some time in their lives. The sites most prone to frostbite were the head, 1668 cases (31%), followed by the hands, 1154 (20%), and the feet, 810 (15%). The risk for frostbite in different body parts was increased among the subjects with CPWF (95% CI: 1.66 to 3.87), regular smokers (95% CI: 1.02 to 3.15) and those exposed to vibration (95% CI: 1.07 to 4.03). CONCLUSIONS: A synergistic increase of frostbite was reported between CPWF and regular smokers, and between CPWF and hand/arm vibration in both exposure classes analysed. The life-time occurrence of frostbite among young healthy men was high. Frostbite, and its association with CPWF, smoking and hand/arm vibration should be noted by the health care personnel in circumpolar countries.

Adolescent↗
PubMed2003

Face cooling by cold wind in walking subjects.

The effects of low to moderate wind speeds on face temperature, thermal and pain sensations while subjects walked on a treadmill during cold exposure were studied in eight healthy men. The purpose of the study was to evaluate further the risk of frostbite at different activity levels. The walking speed was 2.8 km h(-1) and two inclination levels were used, 0 degrees and 6 degrees. The subjects were exposed to -10 degrees C and 0, 1 or 5 m s(-1) wind for 60 min dressed in cold-protective clothing with only the face unprotected. Results from previous experiments with the same subjects standing for 30 min were included in the analysis of the data. Each individual was exposed to all combinations of air velocity and activity level. The exposure to -10 degrees C and the highest wind speed used would carry no risk of frostbite according to the wind chill index. Cold lowered the skin temperature of the face significantly and wind further increased skin cooling. The activity level did not affect forehead and cheek temperatures, but the average nose skin temperature was higher and pain sensations were reduced at a higher work rate. The predicted risk of frostbite in the nose, based on average responses, would thus be less at a higher work rate. However, the results indicate that exercise does not necessarily protect all individuals from frostbite at moderate air speeds, since the nose skin temperature of 25% of the subjects dropped to 0 degrees C at 5 m s(-1) during both standing and walking. Thus the potential individual risk of frostbite in the nose is similar during light exercise and standing. Moreover, the risk of frostbite seems to be underestimated by the wind chill index under the conditions tested in this study.

Adult↗
PubMed2003

Physical activity and social status in adolescence as predictors of physical inactivity in adulthood.

BACKGROUND: Physical inactivity is related to an increased risk of certain chronic diseases. The aim here was to evaluate how physical activity and social status in adolescence are associated with physical inactivity in adulthood. METHODS: The sample comprised 3664 males and 4130 females who answered questions on physical activity and social status at 14 and 31 years of age in follow-up surveys of the Northern Finland birth cohort of 1966. Associations between explanatory factors and physical inactivity in adulthood were analyzed using multivariable logistic regression. RESULTS: Infrequent participation in sports after school hours at 14 years of age and, in males, additionally a low grade in school sports, was associated with physical inactivity at the age of 31 years, independent of social circumstances in adulthood. Low social class of the childhood family was associated with physical inactivity in adolescence but not with inactivity at 31 years of age. Poor school achievement in adolescence was associated with adult inactivity independent of adolescent physical activity. CONCLUSION: Infrequent participation in sports, a low grade in school sports, and poor school achievements in adolescence were associated with physical inactivity in adulthood. Participation in sports is to be strongly supported among all adolescents because of its long-term beneficial effects on adult health through its tendency to reduce the probability of adult inactivity.

Adolescent↗
PubMed2003

Force control of isometric elbow flexion with visual feedback in cold with and without shivering.

BACKGROUND: Exposure to cold impairs manual performance through effects on muscle tissue and control mechanisms. The purpose of this study was to assess the influence of increased muscle tone and shivering on ability to maintain required force during isometric flexion over a wide range of effort levels. METHODS: Lightly clad male subjects (n = 6) were exposed to thermoneutral air (TN, 27 degrees C) for 30 min, or to cold air (CA, 10 degrees C) for 30 min followed by a cold drink (1 L, 8 degrees C) to cause vigorous shivering (SH). At the end of each condition, subjects performed isometric elbow flexion at 10, 20, 40, and 80% of individual maximal voluntary contraction (MVC) for 10 s each, using digital visual feedback to control the force. We analyzed mean force output (F), the coefficient of force variation (FCv), information transmission (F/SD), and the coefficient of force auto-correlation (Ra), and the averaged electromyogram (aEMG) from elbow flexors, elbow extensor, and pectoral girdle muscles. RESULTS: Compared with TN, CA with increased muscle tone raised the aEMG by 5-30% but did not impair any of the force characteristics. In SH, F was not affected, while FCv and Ra were significantly increased at 10% MVC, while aEMG increased by 30-400% depending on the specific muscle and MVC level. CONCLUSION: Neither thermoregulatory muscle tone nor shivering influenced the control of force output during isometric elbow flexion, except that at the lowest MVC (10%) the force output was more variable during shivering.

Adult↗
PubMed2002

Occupational physical activity is related to physical fitness in young workers.

PURPOSE: We evaluated the association between occupational physical activity and fitness in young workers, taking into account leisure-time physical activity, body size, and smoking. METHODS: The study population comprised 2188 men and 1987 women, members of the Northern Finland birth cohort 1966, who participated in the 1997-1998 follow-up survey and were employed at the time of the survey. Cardiorespiratory fitness was measured by a 4-min step test and muscular fitness by tests of maximal isometric handgrip and isometric trunk extension. Information on occupational and leisure-time physical activity and smoking was obtained by questionnaire, and body height and weight were measured during medical examination. The data were analyzed by analysis of variance and Cox regression. RESULTS: Men doing heavy physical work scored better in cardiorespiratory fitness, handgrip strength, and trunk muscle endurance than men doing lighter work; the finding for cardiorespiratory fitness was similar in women. The associations were independent of leisure-time physical activity, body weight and height, and smoking. CONCLUSION: A positive association was found between heavy physical work and a high level of fitness in young workers. Due to limitations of the study setting, causality cannot be asserted, but a training effect of heavy work would not seem unreasonable. Previous studies have suggested a reversal of the positive effect of heavy work on fitness with advancing age. Therefore, regular monitoring of workers' fitness at an early phase is justified to enable assessment of workers' capacity for heavy jobs and any possible need for fitness-improving activities.

Adult↗
PubMed2002

Combined effect of repetitive work and cold on muscle function and fatigue.

This study compared the effect of repetitive work in thermoneutral and cold conditions on forearm muscle electromyogram (EMG) and fatigue. We hypothesize that cold and repetitive work together cause higher EMG activity and fatigue than repetitive work only, thus creating a higher risk for overuse injuries. Eight men performed six 20-min work bouts at 25 degrees C (W-25) and at 5 degrees C while exposed to systemic (C-5) and local cooling (LC-5). The work was wrist flexion-extension exercise at 10% maximal voluntary contraction. The EMG activity of the forearm flexors and extensors was higher during C-5 (31 and 30%, respectively) and LC-5 (25 and 28%, respectively) than during W-25 (P < 0.05). On the basis of fatigue index (calculated from changes in maximal flexor force and flexor EMG activity), the fatigue in the forearm flexors at the end of W-25 was 15%. The corresponding values at the end of C-5 and LC-5 were 37% (P < 0.05 in relation to W-25) and 20%, respectively. Thus repetitive work in the cold causes higher EMG activity and fatigue than repetitive work in thermoneutral conditions.

Adult↗