Revista de Medicina Desportiva (English) September 2018 - Page 28

Physical Activity and Mortality: the Potential Impact of Sitting Peter T. Katzmarzyk, Russell R. Pate Translational Journal of the ACSM, 2017; 2(6):32-33. Summary: Dr. Basil Ribeiro The Physical Activity Guidelines for Americans, published in 2008, refer that for obtaining health benefits it is necessary to carry out 150 minutes per week of physical exercise of moderate to intense intensity. It is a magical number that applies to everyone, regardless of the time spend seated in the day- time. The authors of this comment add a very important information and also, somehow, challenge this value. Based on published studies, the average self-reported time the Americans spent seated is equal to 4.7 hours/day (2014), which is under- estimated, because the objective measurement with the accelerom- etry indicated the value of 7.7 hours/ day (2008). For the Australians it was found the value of 8.8 hours/day (2015). Regardless of these values, it is known that there are jobs that require the sitting position for many hours a day, but it is also realized that after the job, in all professions, the sitting time is high. The authors wanted to interpret on their own way the results pub- lished at the Lancet, in 2016 by Eke- lund, U. et al, from a meta-analysis (13 studies), where 1005791 people participated, were followed between 2 and 18 years, and the mortality was considered for all causes. In this period, 8.4% of the people died. Of course, and according to common knowledge, the negative effect of sitting was directly attenuated with the increase of the physical exercise levels. The practice of moderate- intensive physical exercise during 60 – 70 minutes/day effectively eliminated the risk of death from all causes. These results are not surpris- ing and are in accordance with the current sports medicine wisdom. But the authors wanted to know more and questioned whether the levels of sedentary life would influence the relationship between the practice of physical exercise and the mortality, Figure 1 – Association between the weekly levels of physical exercise of moderate intensity-intense according to the seating levels (2.5, 16, 30 and 35.5 MET.h.week-1 correspond approximately to 5, 25-35, 50-65 and 60-75 minutes of moderate-intensive physical exercise). 26 september 2018 www.revdesportiva.pt that is, if the relationship is the same on the subjects belonging to groups with different hours of daily sitting. From the data of the meta-analy- sis of Ekelund, U. et al, these authors worked the numbers differently and produced this figure/graph. Again, and very naturally, it was found a relationship between the practice of physical exercise of moderate intensity-intense and mortality from all causes, that is, the higher the volume, the lower the risk of death. But the graph, stratified by the number of hours of daily sitting, has another reading. The authors refer to the example of the person who performs 25-35 minutes a day (16 MET·h·week −1 ) that still have an increased risk of death, which is higher than the reference value for all levels of sitting time, even for values less than 4 hours per day. What the authors intend to say is that “people who remain seated for long periods on a desk during the working day should have a strong incentive, not only to get up, but also to substantially increase the volume of physical exercise of moderate- intense intensity”. They also men- tion that complying with such 150 minutes/week substantially decreases the risk compared to the person who performs little exercise weekly, but the 150 minutes will not minimise the risk (Hazard Ratio). The comment ends with two very strong opinions: 1. Moderate-intensive physical exercise levels shall be increased, irrespective of the number of daily hours remaining seated; 2. Persons who are obliged to sit for a long time must strive the higher levels of physical exercise and not the lower ones (the 150 min- utes will certainly not be enough).