A training log can help you get more from your workout. It will help you organize and save information about your exercise routine so you can work toward a specific goal.
For example, if you're training for a marathon, keeping a log can help you track how you run under various weather conditions or when you're following a special diet. You can record information about the prettiest routes if you're walking to enjoy the scenery.
Your log also can push you to work out on those days when you're too tired or you think you're too busy.