Pressure in the eye increases during certain weightlifting exercises, and this could boost the risk for developing a type of glaucoma called normal-tension glaucoma, say researchers.
"Intra-ocular pressure goes up when you lift weights and even more when you hold your breath," said co-author Dr Robert Ritch, from the Department of Ophthalmology at the New York Eye and Ear Infirmary, New York City.
However, another expert said it's unlikely weightlifting poses any real threat to sight. "People who lift weights shouldn't be concerned," said Dr Richard Bensinger, a spokesman for the American Academy of Ophthalmology and chair of the Eye Department at Swedish Hospital, Seattle. The report was published in the September issue of the Archives of Ophthalmology.
Intra-ocular ("within the eye") pressures decrease after aerobic exercise and non-aerobic exercise, such as weightlifting. However, higher intra-ocular pressure is associated with the Valsalva maneuver - where air is forced against a closed windpipe and pressure goes up within the chest. This can occur during coughing, vomiting, playing wind instruments and weightlifting.
In the study, Ritch's team measured the intraocular pressure of 30 male weightlifters, none of whom had glaucoma. All tested as having normal intraocular pressure before working out.
The men then did four repetitions of a typical high-weight bench press. The first time, the researchers measured pressure in the right eye, and the weightlifters held their breath during the last repetition. Next, they measured pressure in the left eye while the men breathed normally during the exercise. Eye pressure was measured during the fourth repetition.
Ritch's team found that during the first round of exercise, intra-ocular pressure increased in 27 of the men by an average of 4.3 millimeters of mercury. During the second round, 18 men showed an average of 2.2 millimeters of mercury increase in pressure, the researchers found.
The rise in pressure could be due to the Valsalva maneuver or a similar motion performed during bench presses, the researchers said. The higher pressure during the first repetitions "may be due to greater intrathoracic [chest] pressure caused by the air retained in the lungs when the subjects held their breath during intraocular pressure measurement," they theorised.
So does lifting weights causes glaucoma?
Normal-tension glaucoma appears to be more common in people who experience frequent changes in eye pressure. However, whether weightlifting actually can cause glaucoma is not known. "Can you get glaucoma from lifting weights? Probably not," Ritch said.
However, "we don't know how many people who have been lifting weights for 20 years have glaucoma and if that is greater than one would suspect in the general population," Ritch said. "All we can say at this point is that lifting weights can increase [intra-ocular] pressure," he said.
People already diagnosed with glaucoma may be putting themselves at risk of further damage from weightlifting, however. "People with glaucoma probably ought to be very careful about weightlifting," Ritch said. Bensinger remains skeptical as to the findings' importance.
"Whatever effects they are seeing are very short-term," said Bensinger. "Whenever you do this stuff, the pressure in the eye goes up, and when you stop, it goes down." Glaucoma takes a long time to develop, Bensinger noted, so these minor ups-and-downs in intraocular pressure are unlikely to cause any damage.
"I don't believe that these temporary increases in pressure are anything serious," Bensinger said. "There are enough weightlifters out there that if there was a concern, we would have seen it already," he said.
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