SUHU TUBUH: HOMEOSTASIS DAN EFEK TERHADAP KINERJA TUBUH MANUSIA

Body temperature is defined as one of the vital signs that indicates the health status of a person. Compared with other primates, man has a greater ability to tolerate hot temperatures due to his many sweat glands, and that his skin is covered mostly by fine hair. In our bodies, heat energy is produced by muscles (mostly), sweat glands, fats, bones, connective tissues, and nerves. Heat energy is distributed to the whole body by blood circulation, but the temperatures are not the same in all parts of the body. There is a difference (around 40C) between core and surface body temperatures. The thermoregulator system has to obtain two suitable gradients: 1) between core and surface body temperatures, and 2) between surface and ambient temperatures. The gradient between core and surface body temperatures is the most important one to maintain optimum body function. Understanding from physics the aspect of body temperature and its influence on homeostatis mechanism, gives some valuable contribution to applied clinical sciences. Key words: core temperature, skin temperature, energy. Abstrak: Suhu tubuh didefinisikan sebagai salah satu tanda vital yang menggambarkan status kesehatan seseorang. Dibandingkan dengan primata lainnya, manusia mempunyai kemampuan yang lebih besar untuk mentolerer suhu tinggi oleh karena banyaknya kelenjar keringat, dan kulitnya hanya ditumbuhi oleh rambut halus. Di dalam tubuh energi panas dihasilkan oleh jaringan aktif terutama dalam otot, kemudian juga dalam alat keringat, lemak, tulang, jaringan ikat, serta saraf. Energi panas yang dihasilkan didistribusikan ke seluruh tubuh melalui sirkulasi darah, namun suhu bagian-bagian tubuh tidak merata. Terdapat perbedaan yang cukup besar (sekitar 4°C) antara suhu inti dan suhu permukaan tubuh.6,7 Sistem termo-regulator tubuh harus dapat mencapai dua gradien suhu yang sesuai, yaitu: 1) antara suhu inti dengan suhu per-mukaan, 2) antara suhu permukaan dengan suhu lingkungan. Dari keduanya, gradien suhu inti dengan suhu permukaan adalah yang terpenting untuk kelangsungan fungsi tubuh yang optimal. Pemahaman tentang besaran suhu dan pengaruhnya terhadap mekanisme homeostatis tubuh melalui pendekatan hukum-hukum fisika setidaknya memberi kontribusi yang berarti pada bidang ilmu klinis terapan. Kata kunci: suhu inti, suhu kulit, energi.

Design and Evaluation of a Modified Underwater Cycle Ergometer

An underwater cycle ergometer was designed consisting of an aluminum cycle frame in water connected with a 1:1 gear ratio to a mechanically braked standard cycle ergometer supported above the water. Three progressive maximal exercise tests were performed (n = 10): (a) the underwater ergometer in water (UEW), (b) underwater ergometer in air (UEA), and (c) a standard cycle ergometer in air (SEA). At submaximal power outputs, oxygen consumption [Formula: see text] and heart rate (HR) were generally lower in the SEA condition (p <.05), indicating that exercise in the upright position was more efficient. Exercise in water (UEW) resulted in lower total exercise duration, maximal HR, and maximal Tes than in air conditions. The upright position (SEA) resulted in greater total exercise duration and maximal power output than the semirecumbent positions. Because of positional differences between the standard and underwater ergometers, air-water comparisons should be made by using the underwater ergometer in water and on land. Key words: core temperature, esophageal temperature, skin temperature, exercise, resistance, work, power output, heat balance, heat loss, heat production, thermoregulation