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Why exercising on polluted city streets does more harm than good



*Inhaling toxic fumes cancels out benefits of keeping fit, stiffens arteries, reduces lung function
*Working out changes gut bacteria in just six weeks, could prevent bowel tumour
*Women naturally fitter than men, process oxygen 30% more efficiently than male counterparts
*Additional steps taken by patient after surgery reduces hospital readmission risk by nearly 20%

Exercising on polluted city streets does more harm than good, research suggests. The damage done by breathing in traffic fumes outweighs the benefits of physical activity, scientists found.

Inhaling polluted air even for two hours was seen to stiffen arteries and reduce lung function, countering all the good done by a workout.

But the researchers, from Imperial College London and Duke University in the United States (U.S.), also discovered that air pollution is very localised – so leaving a busy street and exercising in a park instead was enough to reverse the trend.


The study, in the Lancet medical journal, warned breathing in pollution from diesel cars is particularly dangerous.

Also, new research suggests that a Fitbit could save your life.

Every 100 additional steps certain cancer patients take after surgery to remove their tumor reduces their risk of hospital readmission by up to 18 percent, a study found.

Fitbits are inexpensive, wearable devices that monitor users’ step counts and overall activity levels.

The findings were published in the journal Annals of Behavioral Medicine.

Also, new research reveals that exercise changes gut bacteria in just six weeks.

Previously inactive people who exercise for at least 30 minutes a day three times a week experience increased levels of gut bacteria that produce butyrate, a study found.

Butyrate is an anti-inflammatory acid that has been linked to protection against bowel cancer, as well as weight loss and stronger immunity.

The same findings were previously found in mice, who became less likely to develop the inflammatory bowel disease ulcerative colitis if they were active.

The current study’s results were published in the journal Medicine & Science in Sports & Exercise.

Also, new research reveals that women are naturally fitter than men. Females process oxygen 30 percent more efficiently than their male counterparts, a study found.

Quick oxygen uptake is a measure of fitness and associated with a reduced risk of muscle fatigue.

The findings were published in the journal Applied Physiology, Nutrition, and Metabolism.

The Imperial College London and Duke University scientists tested 119 over-60s as they walked for two hours in central London. Half walked on Oxford Street and the other half through a quiet section of nearby Hyde Park.

The study found everyone in the park group benefited, with lung capacity improving within an hour and persisting for 24 hours.

Blood flow increased, blood pressure fell and arteries became 24 per cent less stiff.

But for those in the Oxford Street group there was only a tiny increase in lung capacity, and arterial stiffness got seven per cent worse.

Researchers said this was linked to the black carbon soot and ultrafine particles from diesel fumes, which have been linked to higher risk of cardiovascular disease, asthma and death.

Lead author Professor Jeffrey Woods from the University of Illinois, US, said: “These are the first studies to show that exercise can have an effect on your gut independent of diet or other factors.”

Yet, the catch is exercise’s positive impact on gut bacteria is reversed if people revert to being inactive.

The researchers analyzed 18 lean and 11 obese women.

All of the study’s participants were previously sedentary before undergoing six weeks of endurance-based activity for three days a week that progressed from 30 minutes of moderate exercise a day to one hour of vigorous activity.

The participants then went back to a sedentary lifestyle for six weeks. Their diets were consistent throughout the study.

Faecal samples were collected before and after the participants became active.

Results reveal exercise changes gut bacteria, which is largely reversed if people revert to being inactive.

In particular, species that produce an anti-inflammatory acid known as butyrate increase, which has previously been linked to bowel-cancer protection, weight loss and stronger immunity.

For unclear reasons, the findings are greater in lean people than those who are obese.

The same findings also previously occurred in mice, who become less likely to develop the inflammatory bowel condition ulcerative colitis if they exercise.

The author of the journal Applied Physiology, Nutrition, and Metabolism study, Prof. Richard Hughson from the University of Waterloo in Ontario, said: “We found that women’s muscles extract oxygen from the blood faster, which, scientifically speaking, indicates a superior aerobic system.”

Lead author Professor Thomas Beltrame added: “While we don’t know why women have faster oxygen uptake, this study shakes up conventional wisdom.”

The researchers analyzed 18 healthy, active adults, half of which were men and the remainder women.

All of the study’s participants completed four moderate-intensity treadmill tests.

Their heart rate and oxygen tissue content were assessed, as well as the difference in oxygen levels between their veins and arteries being investigated.

Results reveal women process oxygen more quickly than men when exercising.

For unclear reasons, females are around 30 percent more efficient at processing oxygen than their males counterparts.

Quick oxygen uptake is a measure of fitness and associated with a reduced risk of muscle fatigue.

Past research reveals being active can help cancer patients recover by boosting their mental health, preventing fatigue and strengthening bones.

Previous studies also show exercise reduces the risk of cancer by keeping hormone levels healthy, which affects how cells multiply.

Up to 50 percent of patients are readmitted to hospital within 30 days of having major surgery to remove abdominal cancer, which was the form of the disease investigated in this study.

Hospital readmission is associated with poor long-term health outcomes, including premature death.

Researchers from the University of Pittsburgh analyzed 71 patients with an average age of 57 who had advanced peritoneal cancer between July 2014 and October 2016.

Peritoneal cancer affects the tissue that lines the abdomen, rectum, uterus and bladder.

The patients underwent surgery to remove part or all of the affected area before having Fitbits placed on their wrists upon transfer from intensive care.


They wore the Fitbits for the remainder of their hospital stay, which on average lasted 12 days.

Information regarding hospital readmission was gathered from electronic medical records.

Results reveal recording more steps on Fitbits statistically reduces a cancer patient’s risk of being readmitted to hospital 30 and 60 days post-discharge after surgery.

For every additional 100 steps taken every day, the risk of hospital readmission after 30 days reduces by 17 percent and 60 days by 18 percent.

The researchers believe their findings may help doctors identify patients at risk of being readmitted to hospital.

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