高溫作業作息時間與工作負荷量對心率之影響研究

Effect on Heart Rate of Performing Workload in Hot Environment

為瞭解我國高溫作業作息時間標準對國人生理之影響，本研究從心率這一項最敏感的指標來進行探討。本研究對象是六名（男性四名，女性二名）25〜30 歲之年輕人，首先，利用能量消耗值、心率及相對代謝率之測定，將履帶跑步機依速度及坡度標準化為輕、中度、重工作之分類，再依高溫作業作息時間標準設定實驗環境WBGT 值，令經過熱適應之受測者接受不同的工作負荷及作業休息時間的安排，同時連續記錄其心跳。結果顯示，受測者工作負荷之輕、中度、重工作的分類，依序為在履帶跑步機上以坡度10％，每小時1.2，2.4 及3.0 英里的速度行走。輕工作且環境WBGT 在30.7℃〜33.1℃之間時，受測者作業中之平均心率介於113.6〜121.8 bpm；中度工作且WBGT 在28.3℃〜32.7℃之間時，則為133.6〜139.4 bpm；重工作且WBGT 在26.0℃〜32.1℃之間時，則為134.9〜148.3 bpm。亦即，工作負荷對心率之影響比環境熱壓力為大，同時，從事重工作之後，心率回復所需的時間亦較長。受測者按我國之標準作業時，任何時間均未超過安全限值180 bpm，但是，中度及重工作當中，部份受測者之作業時平均心率超過150 bpm，值得注意。

The aim of this study is to explore the physiological strains resulting from work condition which is designated in “The Standard of Work/rest Regime to Hot Environment, Republic of China.” Six volunteers, 4 males and 2 females with age between 25 and 30, participated in this study. Work load was classified into three categories, in which walking on a treadmill with 10％of acclivity and speeds of 1.2, 2.4, and 3.0 miles/hour were defined as mild, moderate, and heavy workload, respectively. After heat acclimatization, subjects exercised on the treadmill and exposed to a simulated hot environment, simultaneously, in a work/rest schedule. Their heart rates were monitored continuously. Results show that subjects’ heart rates range from 113.6 to 121.8 bpm for performing mild workload with WBGT 30.7℃-33.1℃. For moderate workload with WBGT 28.3℃- 32.7℃, the heart rates range from 133.6 to 139.4 bpm. Furthermore, the heart rate presents the highest, ranging from 134.9 to 148.3 bpm, for heavy workload with WBGT 25.7℃- 32.1℃. It indicates that heart rate is influenced more profoundly by workload than heat stress. In addition, the recovery of heart rate takes longer time to normal level after heavywork load than that of moderate or mild workload. The safety limit, 180 bpm, is not exceeded for all of the subjects performing the designated work condition of the standard. However, it’s noteworthy that some subjects present an average heart rate over 150 bpm during their performing moderate or heavy workload.