|
|
 |
Vol. 5 nr.1 |
EXCERPTS ON HUMAN COLD SURVIVAL
JOHN E. GREENLEAF1, JODIE M. STOCKS2, HANNA KACIUBA-UŚCIŁKO3
1 Laboratory for Human Environmental Physiology, NASA, Ames Research Center, Moffett Field, California, U.S.A
2 Eli Lilly Pty Ltd, Macguarie Park, N.S.W., Australia
3 Department of Applied Physiology, Medical Research Center, Polish Academy of Sciences, Warsaw, Poland
To understand fully the mechanisms of homeostasis in humans, especially during exercise and environmental challenges, one must also probe their physiological and psychological limits commensurate with survival. All elements of the Earth, air, fire and water quadruple are involved, especially during environmental cold exposure. The major body heat defense mechanisms against cold are reduction in peripheral (skin) blood flow via vasoconstriction, and increased metabolic heat production via muscular exercise and shivering; both can be enhanced by good nutrition and increased body fat content to facilitate avoidance of hypothermia, frostbite, and frozen tissue. Included in this brief review are data on incidence of hypothermia cases in Antarctica, Alaska, and during athletic events; as well as excerpts from human survival scenarios in cold water (Dachau experiments), in cold air on the ground (Etienne’s trek, Napoleon’s retreat), in cold air on cold water (Shackleton’s ordeal), and in cold air at high altitude (airplane wheel-well passengers). These excerpts testify to the inherent redundancy of the homeostatic mechanisms that facilitate human survival in cold environments.
Key words: cold survival, heat defense mechanisms, hypothermia, frostbite, immersion
Artykuł w PDF
EVIDENCE BASED CLINICAL PRACTICE IN SPORT AND EXERCISE MEDICINE
DOMHNALL MACAULEY, IAN RYANS, CHRIS BLEAKLEY
Institute of Postgraduate Medicine and Health Science, University of Ulster, Ireland
ABSTRACT
Much of our sports medicine practice has developed empirically and we treat many conditions without knowledge of the quality of the evidence base. If we examine the evidence supporting some aspects of sport and exercise medicine we find major deficiencies. This is in contrast to other medical disciplines with a long history of quality research where clinical practice is supported by a strong literature. If we are to promote sport and exercise medicine as an academic discipline we should be able to support our treatment plans, guidelines, and preventive strategies, with quality research evidence and to measure ourselves against the standard measurement criteria of any academic discipline. Developing an evidence based approach is a key component of our evolution as a clinical discipline.
Key words: systematic, review, appraisal, diagnosis, injury, treatment
Artykuł w PDF
IMPROVING PERFORMANCE IN HIGH-POWER ATHLETES
THOMAS D. FAHEY
Exercise Physiology Laboratory, Department of Physical Education and Exercise Science, California State University, Chico, CA, USA
ABSTRACT
Coaches and athletes must consider four elements when attempting to develop performance in high-power sports: muscle hypertrophy, neuromuscular activation, stretch-shortening cycle, and skill. Performance in high-power activities, such as sprinting, jumping, and throwing are moderately related to basic measures of strength, such as the bench press and deadlift. Muscles hypertrophy when subjected to tension. The training program must be structured to maximize tension during workouts, which requires the proper combination of training and rest. High-power athletes should include presses, pulls, and squats in their programs. Neuromuscular activation training turns of larger, stronger motor units and activates them more quickly. This fitness component is best developed through plyometric and speed exercises. These training techniques transfer fairly rapidly to motor skills. Activation of the stretch-shortening cycle is central to performance in high-power sports. While elastic facilitation of movement can be developed through plyometrics, it is best made through proper execution of skills. Skill is an essential factor contributing to power formation. Skills are highly specific. Small improvements in technique can often result in large changes in power output on the playing field. This paper explores the association between muscular power and performance and reviews the research on how to train to improve muscular power expression in high-power sports.
Key words: skill, jumping, sprinting, weight training, plyometrics
Artykuł w PDF
EFFECT OF EXHAUSTIVE ENDURANCE EXERCISE ON CARDIAC CATECHOLAMINE METABOLISM IN TRANSGENIC MICE
MICHAEL KALINSKI1, HYUNSIK S. KANG1, MATTHEW S. KERNER2,
ELLEN GLICKMAN-WEISS1
1 Exercise Sciences Laboratories, Kent State University, Kent, OH, USA
2 Division of Sports Sciences, School of Health Professions, Long Island University, Brooklyn, NY, USA
ABSTRACT
Purpose. Neurotrophin-3 (NT-3) is required for proliferation, differentiation and survival of sympathetic neurons. A NT-3 transgenic mutant mouse strain was used to determine whether disruption of one NT-3 gene can maintain increased cardiac sympathetic response during stress of exhaustive endurance exercise.
Methods. Ten NT-3 mutant (+/-) and 10 wild type (+/+) adult mice were randomly assigned into four groups: mutant sedentary control (MUT, +/-, CON), mutant exercise (MUT, +/-, EX), wild type sedentary control (WT, +/+, CON) and wild type exercise (WT, +/+, EX). Exercise groups ran until exhaustion on a motor-driven treadmill, while control groups remained in their cages. Mice were euthanized immediately after running or resting. Left ventricles (LV) were excised and homogenized in 0.1M percholoric acid and catecholamine concentrations were measured by HPLC. Norepinephrine (NE), 3-methoxy-4-hydroxyphenylglycol (MHPG), dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) concentrations were measured in the LV.
Results. Data showed that stress of exercise could uncover an effect of NT-3 gene disruption on the LV NE concentration and its turnover. Exercising WT mice demonstrated higher cardiac sympathetic activity. NE and MHPG concentrations and MHPG/NE ratios significantly increased in the LV of WT-EX. Mice with disruption of one NT-3 gene (MUT, +/-, knockout mice) could not maintain increased sympathetic response at the same level. There was no significant increase in NE and MHPG concentrations or MHPG/NE ratios in MUT (+/-) mice under stress of exercise. There were no significant differences in the concentration of dopamine’s metabolite DOPAC in the LV among any group.
Conclusion. MUT (+/-)-knockout mice could not maintain increased cardiac sympathetic response of the LV during exhaustive endurance exercise at the same level as wild type mice.
Key words: neurotrophin-3, knockout mice, exercise, cardiac norepinephrine
Artykuł w PDF
LUMBAR BONE MASS OF ADULT MALES AND FEMALES IS POSITIVELY RELATED TO PHYSICAL ACTIVITY PATTERNS IN ADOLESCENCE AND YOUNG ADULTHOOD
HAN C.G. KEMPER, INGRID BAKKER, WILLEM VAN MECHELEN,
G. BERTHEKE POST, JOS W.R. TWISK
Institute Research in Extramural Medicine (EMGO), The Netherlands
ABSTRACT
The purpose of this study was to investigate the relation of daily physical activity during adolescence (age 13-17) and young adulthood (age 21-27) on the lumbar bone mass (LBM) at age 32.
LMB was measured with dual X-ray absorptiometry (DXA) in the lumbar region in 163 males and 139 females at age 32.
Physical activity was measured longitudinally from age 13 till age 27 by an interviewer administered activity questionnaire. From this a metabolic (METPA) and a mechanic physical activity score (MECHPA) were derived. Regression analyses were performed with gender, height, weight, body fatness and calcium intake as covariates.
Both aspects of physical activity (METPA and MECHPA) during adolescence and young adulthood are positively related to the LBM at age 32 in both sexes.
This longitudinal study shows that physical activity during youth can increase peak bone mass.
Keywords: peak bone mass, physical activity, longitudinal study, lumbar bone mineral density
Artykuł w PDF
HEART RATE VARIABILITY FOLLOWING 5 WEEKS OF DETRAINING IN COMPETITIVE SWIMMERS
ROBERT H. WOOD, SARA LELEUX, MICHAEL A. WELSCH, ARNOLD G. NELSON, HEIDI A. KLUESS, AMELIA M. LEE
Department of Kinesiology, Louisiana State University, Baton Rouge, LA, USA
ABSTRACT
The purpose of this investigation was to evaluate HRV following a period of detraining. Therefore, six elite collegiate swimmers were examined for heart period (RR) and HRV (i.e., standard deviation of normal R-R intervals (SDNN), and normalized high- and low-frequency spectral power), and maximal oxygen consumption (VO2max) during incremental arm-ergometry. ECG data were collected for 5 minutes in the supine position under conditions of spontaneous and paced (0.20 Hz) breathing. The athletes were examined 2 weeks prior to the end of the season, at end season, and 1, 2, 3, and 5 weeks post-season. During the first 2 weeks of the post-season period the swimmers reduced their training duration from 20 to 10 hours per week, and during the 3rd through 5th weeks post-season the swimmers did not swim-train. VO2max was significantly reduced by the 2nd week of the post season (34.0 + 8.3 vs. 28.2 + 6.9 ml•kg-1•min-1, respectively) and did not change thereafter. RR intervals were 60-100 msec shorter at the 5th week of detraining than at the other observation periods (regardless of breathing condition), but HRV did not change across the observations. Paced breathing was consistently associated with shorter RR intervals and greater SDNN, but no differences in normalized units of low-and high-frequency power. The results of this investigation are consistent with differential effects of detraining on aerobic power and autonomic modulation of the heart, and provide further indirect evidence for the use of HRV as an index of autonomic modulation of the heart.
Key words: detraining, heart rate variability, exercise, autonomic, cardiovascular
Artykuł w PDF
HEART VALVES FUNCTION IN CHILDREN INTENSIVELY TRAINING SPORT
WŁADYSŁAW ROKICKI, JAN SZEWIECZEK, GRAŻYNA MARKIEWICZ-ŁOSKOT, EUGENIUSZ FOJT, KATARZYNA MICHALAK
Silesian Medical University, Katowice, Poland
ABSTRACT
Little is known about athlete’s heart in children. The aim of the study was to assess the incidence and significance of heart valve regurgitation in the children - pupils of so called sport mastership schools. There were 31 healthy subjects (16 girls and 15 boys) included in the study protocol and observed for three consecutive years. Their mean sport training time was 14,7 hours per week (girls training predominantly gymnastics) and 8,9 hours per week (boys training predominantly handball). The children were studied on three occasions, after about 1, 2, and 3 years of sport mastership school attendance. Their mean age during the first study was about 8,8 years (girls) and 11,2 years (boys).
Regurgitant flow of any heart valve was detected by Doppler color echocardiography in 11 children during the first study (35%), in 10 subjects after two years of sport training (32%), and after three years - in 12 young athletes (39%). Described regurgitations were predominantly negligible. In some children valvular insufficiency which was observed during the first examination disappeared after one or two following years of sport training and in not one case was significant progression observed. On the other hand, there were some children in whom valvular regurgitation was found for the first time during the second or third examination.
It was concluded that 3 years of sport training in children without heart disease is not associated with an increased risk of heart valve regurgitation.
Key words: child, sport, heart valves regurgitation
Artykuł w PDF
|
|
