Your body is able to make L-arginine, but during times of illness and stress, you may not be able to make enough to support needs, which makes this amino acid a conditionally essential one (see reference 1 under Conditional amino acids). However, the evidence to support supplementation of the amino acid before a workout is not sufficient and you may be better off getting your L-arginine from natural sources rather than a supplement. Consult your doctor before adding any dietary supplements to your daily routine.
L-Arginine and Exercise
For exercise, L-arginine supplements may be taken to improve performance (see reference 2 under What Is It para 4). According to MedlinePlus, the evidence to support L-arginine supplementation for exercise performance has been mixed. Some studies indicate that taking the supplement improves performance time, while others show no benefit at all (see reference 2 under Insufficient evidence to rate effectiveness for... under Exercise Performance). More research is necessary to determine the benefits, if any, of L-arginine supplementation before you workout before dosage recommendations can be made.
Under normal circumstances your body is able to make enough L-arginine to meet your daily needs (see reference 3 pg 594 para 2). However, when your body is under stress from an illness or injury or in a catabolic state, your body may not be able to make enough to support demands, and the amino acid becomes essential, which means it's necessary that you get it from food (see reference 3 pg 594 para 2). While there is an essential need for L-arginine during these times, the amount you need from your diet has not been determined, according to the U.S. Department of Agriculture, and may vary depending on the cause (see reference 3 pg 594 para 2).
Since the evidence to support L-arginine supplementation is insufficient, you may be better off getting the amino acid from the food you eat instead of a supplement. Good food sources include meat, poultry, fish, dairy foods, soy foods, seeds and nuts (see reference 2 under What Is It para 1, reference 4). Some of the top food sources include turkey, pumpkin seeds, soy beans, peanuts and chickpeas (see reference 4 pgs 1,2).
A healthy pre-workout snack rich in L-arginine might include a turkey sandwich on whole-wheat bread, a handful of soynuts or peanuts or hummus with carrot and celery sticks.
The Cardiac Exception
If you have heart disease, you know how it important it is that you get regular exercise to improve health and overall well-being. However, you may find exercise difficult if you have angina, which is a condition that causes chest pain when your heart is unable to get enough oxygen (see reference 2 under Possibly effective for... under Chest Pain, reference 5 para 1). L-arginine supplementation may help improve exercise tolerance for people with angina, according to MedlinePlus (see reference 2 under Possible effective for under Chest Pain). However, supplementation with L-arginine for exercise and angina should be based on your doctor's recommendation, including dose.