Please choose the correct ending to complete the given sentence: Computers and Electronics: [header] How to build up to long runs [title] Do one long run a week. [step] Take good note of that-don't make all of your runs longer. If you've been running 3 miles (4.8 km) a day (for example) 3-4 times a week, don't suddenly make all your runs 4 miles (6.4 km).

Ending1: Instead, spend 3 or 4 days training to do a longer run. Of course, if you're just starting to train, it doesn't hurt to set aside a day or two each week to train. Ending2: Increase speed gradually, and you will notice improvement in less than 1 mile (4.8 km). Also, increase the amount of activity you do to break up any old habits. Ending3: Besides adding additional 10 minute runs to your workout you'll be wasting your time, and doing a long run mainly on rest days like the weekends is useless. [substeps] Keep in mind that duration is generally not a good thing to do. Ending4: Just pick one day a week to go longer. [title] Gradually increase that long run by half a mile to a mile each week.

Answer format: ending1/ending2/ending3/ending4