2. does carbohydrate ingestion during exercise slow down muscle glycogen depletion? does it improve performance?

Yes, it does slow down glycogen depletion and improves performance.

Explanation:

Carbohydrates are important substrates for contracting muscle during prolonged, strenuous exercise, and fatigue is often associated with muscle glycogen depletion and/or hypoglycaemia. Thus, the goals of carbohydrate nutritional strategies before, during and after exercise are to optimise the availability of muscle and liver glycogen and blood glucose, with a view to maintaining carbohydrate availability and oxidation during exercise.Taking carbohydrate energy giving food in advance of any energy sapping exercise is known to accelerate the depletion of muscle glycogen.

However, taking carbohydrate during such physical activities  delays overall fatigue and increase performance. Carbohydrate ingestion during prolonged, strenuous exercise, where performance is often limited by carbohydrate availability sees delay in  fatigue due to maintenance of blood glucose levels and a high rate of carbohydrate oxidation, rather than a slowing of muscle glycogen utilisation, although liver glycogen reserves may be spared. During recovery from exercise, muscle glycogen resynthesis is critically dependent upon the ingestion of carbohydrate.The delayed fatigue is an evidence of reduction in the rate of depletion of glycogen levels in the muscles.