Lee DC, Pate RR, Lavie CJ, et al.
J Am Coll Cardiol. 2014;64(5):472-481. doi:10.1016/j.jacc.2014.04.058

Background

Although it is well established that physical activity has substantial health benefits, it is unknown how much exactly is good, and whether there is such a thing as too much. The World Health Organisation and the U.S. government have released evidence-based Physical Activity Guidelines, which recommend at least 150 minutes of moderate intensity of 75 minutes of vigorous-intensity aerobic activity per week, or a equivalent combination of both [1,2].
It is unclear whether vigorous-intensity activity, like running, for less than 75 minutes per week, also confers benefits. This study aimed to determine whether leisure-time running is associated with all-cause and cardiovascular disease (CVD) mortality risks, and whether a dose-response relation between running and mortality exists. Data of over 52000 individuals from the Aerobics Center Longitudinal Study cohort were used.

Main results

• Runners had a 30% lower risk of all-cause mortality, and 45% lower CVD mortality than non-runners, after correction for potential confounders.
• When population attributable fractions (PAFs) were estimated, not running was almost as important as hypertension, accounting for 16% of all-cause and 25% of CVD mortality.
• All quintiles showed similar mortality benefits as compared with non-runners, including the lowest quintile of <51 min/week. No significant differences were seen between HRs for all-cause and CVD mortality of all quintiles of weekly running time.
• Running quintiles based on other running characteristics such as weekly distance, frequency, amount (MET-minutes) and speed, showed similar lower risks of all-cause mortality (including the lowest quintile) than non-runners.
• Persistent runners over an average of 5.9 years, showed most benefit, with 29% and 50% lower all-cause and CVD mortality, respectively, as compared to individuals who stopped or started running during follow-up.  

Conclusion

Runners consistently had a lower risk of all-cause and CVD mortality, as compared to non-runners, even at lower doses or speeds, below what guidelines recommend. This finding may motivate people to start running. Vigorous-intensity activity like running may be a time-efficient option, with similar mortality benefits with 5-10 min/day, for sedentary people who find 15-20 min/day of moderate-intensity activity too time consuming.

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Life-Threatening Events During Endurance Sports
Is Heat Stroke More Prevalent Than Arrhythmic Death?

Yankelson L, Sadeh B, Gershovitz L, et al.,

Background

In the same issue of J Am Coll Cardiol another publication addressed the observation that long distance running involve an increased risk of sudden death [3]. Two important causes of sudden death during endurance races like half and full marathons are arrhythmic death and heat stroke (in the context of exercise defined as a core body temperature of 40.0 to 40.5°C associated with multiorgan dysfunction, with cerebral dysfunction as an essential symptom for diagnosis[4]).
Initial symptoms of heat stroke may go unnoticed, after which rapid deterioration may occur, culminating in cardiac arrest [5] and ventricular fibrillation [6]. The diagnosis will furthermore be missed if the core body temperature is not immediately measured correctly (rectally). A primary cardiac disorder may then be suspected.
This retrospective study looked at all long distance races that took place in Tel Aviv between March 2007 and November 2012, and data was collected prospectively for the 2013 races.

Main results

• Among 137.580 runners, two athletes died as a result of participation in a race, yielding a sport-related mortality rate of nearly 1 in 69.000 (95%CI: 0.4-5.3 per 100.000).
• Two hospitalisations for cardiac events were documented.
• Over the same time period, 21 cases of serious exertional heat stroke were identified, of which 2 were fatal and 12 were life-threatening. 
• Another 42 cases of heat exhaustion requiring hospitalisation, but not in intensive care units, were identified.

Conclusion

This study shows that life-threatening events during endurance races that take place in warm climates are more likely to be caused by heat stroke than by cardiac arrhythmias. On average, for every serious cardiac event, 10 serious and at least 5 life-threatening or fatal heat stroke events were observed during 14 endurance races in Tel Aviv over the past 7 years.
Heat stroke also strikes in areas with a generally mild climate, and is not limited to endurance races. Since core (rectal) temperature is often not measured promptly, correct diagnoses likely are missed, and events may erroneously be attributed to cardiac conditions.

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References

1. Global Recommendations on Physical Activity for Health. World Health Organization. Available at:
http://www.who.int/dietphysicalactivity/factsheet_recommendations/en/. Accessed December 1, 2013.
2. Physical Activity Guidelines for Americans. U.S. Department of Health and Human Services. Available at: http://health.gov/paguidelines. Accessed December 1, 2013.
3. Kim JH, Malhotra R, Chiampas G, et al. Cardiac arrest during long-distance running races. N Engl J Med 2012;366:130–40.
4. Zeller L, Novack V, Barski L, et al. Exertional heatstroke: clinical characteristics, diagnostic and therapeutic considerations.Eur J  InternMed2011;22:296–9.
5. Casa DJ, Armstrong LE, Ganio MS, et al. Exertional heat stroke in competitive athletes. Curr Sports Med Rep 2005;4:309–17.
6. Ryan JF, Tedeschi LG. Sudden unexplained death in a patient with a family history of malignant hyperthermia. J Clin Anesth 1997;9:66–8.