Appeal by the employer and carrier from an award for disability due to a heart attack. Appellants contend that there is no substantial evidence that claimant’s disability was the result of an industrial accident. Claimant was a route man delivering and picking up industrial uniforms and coveralls with a truck. There is evidence that the bundles which claimant had to carry weighed from 40 to 50 pounds. On August 12, 1958, while making his deliveries, claimant felt pains in his chest at about 10:30 a.m. After resting in his truck for a time he continued to work, and the chest pains continued. At about 1:30 p.m. he collapsed and was taken to a hospital. It was a hot day, and the heater in the truck was out of order and could not be turned off. The undisputed cause of claimant’s disability was an acute myocardial infarction. There is medical evidence that the conditions and efforts of the work were the cause of claimant’s attack. The board has so found, and substantial evidence supports the finding. Award unanimously affirmed, with costs to the Workmen’s Compensation Board.