锻炼虽好，过犹不及！

美国心脏病学会杂志2月10刊发了一项研究，该研究是哥本哈根心脏研究的一部分，随访了1098例健康的跑步者和3950例健康的非跑步者，旨在评估跑步和死亡率之间的关系。研究发现，最低的死亡率与每周慢速至中速跑步至多3次、每次1至2.4小时相关。将这些跑步者按照每次跑步的时间长度、频率和跑步速度分为轻度、中度或重度跑步者后，结果发现轻度跑步者的死亡率最低，其次是中度跑步者。重度跑步者的死亡率与惯于久坐的非跑步者并无显著差异。

轻至中度跑步者与久坐但健康的非跑步者相比，死亡率较低。而重度跑步者与非跑步者的死亡率统计相似。美国哈特福德医院的Paul D Thompson博士对此进行了点评。

哈特福德医院Paul D Thompson博士

哥本哈根心脏研究的早期结果显示，跑步者比更惯于久坐者寿命延长，男性跑步者延长6.2年，而女性跑步者则延长5.6年。尽管这种结果令人振奋，但是近期的几项研究则提示，锻炼可能会存在过犹不及的问题。研究表明，终身耐力运动员右心室钆对比剂延迟强化显像示斑块状影像，而参加过多次马拉松比赛的男性中冠脉粥样硬化发生率较高。所以关键问题是，运动量增加是否会导致获益减少，或者甚至会增加风险？

为确定是否存在这种可能，哥本哈根心脏研究的人员重新评估了其研究数据。他们调查了丹麦国家死亡记录，并确定了自2001年来1098例跑步者和413例非跑步者的死亡数据。研究结果显示，锻炼较少时结果更好。与非跑步者相比，每周跑步1至2.4小时者死亡率最低，而每周跑步2.5~4小时以及多于4小时者死亡率依次增加。从跑步频率上看也是如此，每周跑步3次以上比每周跑步2~3次者死亡率更低；此外，慢速跑步者的死亡率比中速和快速跑步者死亡率低。

目前已有许多研究就锻炼是否会过量展开激烈讨论，这一报告则使讨论更加深入。值得注意的是，一些研究表明，最大的心血管风险来自于久坐，而仅仅是站立就可降低风险。而哥本哈根心脏的研究数据支持“极少量的锻炼可使人们获益最多”这一理念；其并未指明过量锻炼会导致风险，只是会减少获益。然而，当前哥本哈根研究及许多类似研究的主要问题在于，高强度锻炼类的个体较少，所以可供分析的案例较少。例如，当前哥本哈根研究中，每周锻炼少于1小时组中仅有20例死亡；1~2.4小时组有4例，2.5~4小时组有3例，而每周锻炼大于4小时组中仅有1例患者死亡。这意味着数字稍有变化便会对结果产生重大影响。

尽管研究存在样本上的局限，过多锻炼未必是好事也值得我们仔细考虑，毕竟事出必有因。 

独家授权，未经许可请勿转载！

The association between jogging and mortality was evaluated by following 1098 healthy joggers and 3950 healthy non-joggers. Lowest mortality was associated with 1 to 2.4 hours of jogging per week, no more than three times per week, and slow and average pace. When grouped into light, moderate, or strenuous joggers based on quantity, frequency, and pace, light joggers were associated with lowest mortality, followed by moderate joggers. Strenuous joggers were not statistically different from sedentary non-joggers.

Light to moderate joggers had a lower mortality compared with sedentary but healthy joggers. Conversely, strenuous joggers are statistically similar in mortality to non-joggers.

Expert Comment

Can lots of exercise be too much of a good thing?

Earlier results from the Copenhagen Heart Study1 demonstrated that men who classified themselves as joggers lived 6.2 years longer than their more sedentary counterparts and that women joggers lived 5.6 years longer. Despite such positive results, several recent studies have suggested that with exercise there may be a point of too much of a good thing. Investigators have shown patchy late gadolinium enhancement in the right ventricles of lifelong endurance athletes2 and have even found increased coronary atherosclerosis in men who have run multiple marathons over their lifetimes.3 The key question is whether increasing amounts of exercise have diminishing returns or even increased risk.

Researchers from the Copenhagen Heart Study reexamined their data to look at this possibility. They examined Danish national death records to determine mortality in 1098 joggers and 413 non-joggers followed since 2001. They divided the joggers by hours per week, days per week, and the speed of their jogging. The results suggest that less is better. Jogging 1 to 2.4 hours weekly had the lowest mortality rate compared with that of the non-joggers, but the rate increased progressively with 2.5 to 4 hours and >4 hours of jogging. Similarly jogging 2 to 3 times per week had a lower mortality rate than >3 times weekly, and slow jogging had a lower mortality rate than moderate and fast jogging.

This report adds to other provocative papers on the subject of whether or not one can get too much exercise. Interestingly, some studies suggest that the greatest cardiovascular risk comes from sitting and that just standing reduces risk. These data from the Copenhagen Heart Study support the idea that one gets the most benefit from very low doses of exercise. The Copenhagen results do not indicate risk from too much exercise, but rather lack of benefit. The present Copenhagen study and many similar studies have one major flaw: there are few individuals in the highest exercise groups, leaving few cases for analysis. For example, in the present Copenhagen study, there were only 20 deaths in the <1-hour group, 4 in the 1- to 2.4-hours group, 3 in the 2.5- to 4-hours group, and 1 in the >4-hours per week group. This means that small changes can have a profound impact on the results.

Despite this limitation, the possibility that too much exercise might be too much of a good thing deserves consideration. Where there is smoke, there is usually some fire. 

Journal of the American College of Cardiology

Jogging and Long-Term Mortality: The Copenhagen City Heart Study

J Am Coll Cardiol 2015 Feb 10;65(5)411-419, P Schnohr, JH O’Keefe, JL Marott, P Lange, GB Jensen