目前已累積非常多的研究證據證實運動有利於改善代謝疾病，由於證據結果的一致性很高，目前已沒有什麼爭論，代謝疾病通常是人類與動物死亡的重要前兆，運動可延長壽命，為下一個重要研究假設。有關壽命的研究，在二十年前規律運動是否可延長壽命的證據仍然相當缺乏，無法作出結論。當時動物研究均以較短命的齧齒類動物為主，採用自主運動 (voluntary exercise) 的方式，發現在動物開始老化到大量死亡的初始期，確實自發性運動量高的動物平均壽命較長。平均壽命指接受該實驗組的動物群存活剩下 50% 的對應時間長度（介入日開始計算）。然而，自主運動有先天的研究限制，即在生命後期由於好動的動物與少動的動物活動量趨於一致，無法判別最高壽命是否可被運動延長，最高壽命係指該介入組最後 10% 存活者壽命的平均。動物研究的限制，使得我們一直無法很有把握的回答運動是否可延長壽命這個問題。直到最近有幾個大樣本人體研究與統合分析(meta-analysis) 顯示：一、增加身體活動量確實與未來死亡率的降低有關 (Samitz, Egger, &Zwahlen, 2011)；二、運動強度愈高者，未來死亡率愈低，即使 50 到 60 歲間改變習慣將中低強度改為高強度，也能在未來十年後顯現減少死亡率的效果 (Byberg et al., 2009)；三、對超過 50 歲以上的高血糖者，較易造成肌肉損傷的肌力訓練對改善老人代謝指標的效果，遠比造成肌肉損傷少的有氧訓練好 (Cauza et al., 2005)；四、年齡超過 50 歲以上者，有氧訓練的代謝改善效果逐漸消失 (Short et al., 2003)。這些重要研究結果除了證明運動可抗老化，也打破大部分人認為中低強度運動（走路或慢跑）可能較適當的猜測。因此，基於這些較新的證據，對於中高齡人口應建議的運動處方，不再適用學生的 333 原則。目前大部分專家的猜想是運動強度應訂在中低強度即可，儘量避免劇烈運動，但根據研究證據顯示中低大專體育學刊第18卷 第1期，i-iv頁（2016年3月）DOI:10.5297/ser.1801.editoriali大專體育學刊18(1)-00 1 前頁.indd 1 2016/4/12 上午 09:50:47ii 郭家驊強度運動雖然有些許效果，但效果不強。因此專家給予正確建議時必須回歸科學證據來給予個人能承受的高強度的運動，未必要長時間耐力運動。至於為什麼愈易造成肌肉損傷的高強度運動，反而愈能改善代謝功能延長壽命。最可能的原因在於人類是多細胞生物，而多細胞生物應被視為「由眾多具有合作能力的單細胞構成的社會」。在一個社會中，運動挑戰造成自然篩選 (natural selection) 的結果，適者生存不適者淘汰，存活下來的細胞與新生細胞重新建構新的社會合作體，除能適應新環境，也使得全身細胞平均年齡下降。下次承受相同挑戰，一樣能安然存活度過。運動強度愈高，淘汰篩選門檻愈高，雖恢復時間增長，更能作大幅度的汰舊換新。目前已有完整的研究發現可殺死動物身上的老細胞即可明顯增加壽命 (Baker et al., 2016; Tsygankov, Liu, Sanoff,Sharpless, & Elston, 2009)。最近的這些新的證據也給我們帶來新的研究主題，例如：人體如何辨認運動後不健康的細胞給予破壞？破壞後的訊息如何啟動細胞再生機制？恢復時間應該多長？我們希望透過這些新發現，提供給《大專體育學刊》的讀者最新的研究方向，期望產生出對於社會大眾有益的新知識。
A large body of evidence from well-designed studies has repeatedly validated the beneficial effect of exercise training on metabolic health in animals and humans. Metabolic disorders are generally known as early signs of death during aging. However, insufficient research effort in the past 20 years limited us to conclude the life-prolonging effect of exercise training. One of the reasons accounted for this uncertainty comes from the difficulty to conduct human trial for entire life. Furthermore, most of animal studies use voluntary exercise as an experimental model. During early life, physically active animals tend to have longer average lifespan compared to less active counterparts. Average lifespan defined by the time length when 50% of the cohort can no longer survived. But during the time period when animals are rapidly dying, voluntary physical activity drops as well. It is thus hard to distinguish the causal relationship between physical activity level and maximum lifespan on such kind of studies. Maximum lifespan is often defined as the mean lifespan of the most long-lived 10% of a given group (i.e., exercise training or sedentary cohort). Such limitation of animal studies prevents us from making clear-cut conclusion on the question whether exercise training can prolong lifespan. Until recently, data from several longitudinal studies and meta-analysis provide answer for the question. First, life expectancy is relatively higher among those people who participated in high intensity than low intensity of exercise (Samitz, Egger, & Zwahlen, 2011). The surviving chance during aging appears to be positively correlated with exercise intensity in humans. Second, for those individuals aged around 50 ~ 60 years, increasing exercise intensity from moderate to high levels significantly increases survival rate 10 years later to a level similar to the high intensity cohort (Byberg et al., 2009). Third, muscle-damaging exercise like strength training, has much better improving effect on metabolic measures compared to aerobic training with much less muscle damage in hyperglycemic participants aged around 57 years (Cauza et al., 2005). Aforementioned evidence denies speculation and current belief of most experts who consider moderate aerobic exercise is the best for improving human survival (Short et al., 2003). Based on these data, “333” exercise guideline suggested by Taiwan government may need to be modified for adults. “333” represents exercise duration of 30 min, intensity of 130 beat per min, and frequency of 3 times per week. This guideline may be slightly helpful in health among sedentary people, but we do not expect an impressive health outcome according to aforementioned empirical data. Here we recommend an individual to push their exercise intensity to the highest tolerable level for improving survival. A major question remains that is why the exercise producing greater damage offers better benefit for survival compared to those moderate intensity exercise? The most likely answer accounts for the dose-dependent lifeprolonging effect is that human should be regarded as a "society" instead of "an individual." To be more specific, human body is a society of cells where natural selection is taking place among cells in a society at different agelevel. Exercise provides acute challenge to select the cells that has the best capability to cooperate with other partner cells for survival. Advantage of multicellular organism to be existed is achieved by natural selection on cooperativity among specialized cells. Thus, increasing exercise intensity will kill greater number of impotent (less cooperative) cells in human body, which in turn results in reduced average age of cell population in human body, and strengthen our capability against the life-threatening challenge. In consistent with this thought, recent new evidence has found that increasing killing mechanism to eliminate unhealthy population of cells can increase lifespan in animals (Baker et al., 2016; Tsygankov, Liu, Sanoff, Sharpless, & Elston, 2009). Aforementioned evidence collectively gives us a new area of future study, such as how those unhealthy cells are recognized, and how many destructive signals are involved to trigger cell renewal. The message of the paper is hereby to offer readers of the Journal for further investigation to benefit our own survival, as the primary goal of human life.