Overload endurance training

Overload endurance training is the third level of endurance training and it should be done at speeds exceeding those at which the anaerobic threshold occurs. This sort of training is highly anaerobic and produces severe levels of acidosis. What I just said may cause you wonder why it is in the category of endurance training. It is placed in this category because of it's training effects which are:

• An increase in the maximal oxygen consumption of all trained muscle fibers including FTb fibers
• An increase in the number of capillaries around all trained muscle fibers including FTb fibers
• An increase in the amounts of myoglobin and mitochondria in all trained muscle fibers including FTb fibers
• An increase in the rate of lactate removal from all trained muscle fibers including FTb fibers
• An increase in the buffering capacity of all three categories of muscle fibers

The following guidelines can be used when creating overload endurance repeat sets:

• Set distance. 500 yd or m or 6 min and longer. Set distances of 1200 to 2000 yd or m or 15 to 20 min are recommended.
• Repeat distances. Any distance up to 2000 yd or m can be used effectively.
• Rest intervals. 5 to 30 sec for short repeats, 15 to 60 sec for middle distance swims, and 30 sec to 2 min for longer repeats.
• Training speed. Faster than threshold speed. Times 1 to 2 sec per 100 yd or m faster than threshold speed usually indicate that FTb fibers are activated. Heart rates should be at maximum, and perceived efforts should be 18 to 20 on a scale of 1 to 20.

As with threshold training, swimming is the best method for overload endurance training because it is the only way to be sure that the same muscle fibers used in competition are being trained in practice. Swimmers should perform some overload endurance training during all phases of the swimming season so that the aerobic capacity of FTb muscle fibers can improve concurrently with that of the other fiber types. Major emphasis on overload endurance training should occur after athletes have significantly improved their aerobic capacity with basic and threshold endurance training. This emphasis should begin 4 to 6 weeks before most of the important competitions will occur so that swimmers will have sufficient time for the desired training adaptations to take place before they compete. The quantity of overload endurance training should decrease during the final 3 to 4 weeks before the taper to provide time for FTb fibers to regain some of their anaerobic capacity. Because overload endurance training can deplete the glycogen supply of muscle as quickly as threshold endurance training  reduces it, 1 1/2 to 3 days of easier training should follow after one or two consecutive sets of overload endurance training.

In contrast with the methods used for threshold endurance training,  the usual methods for overloading, increasing volume, increasing speed, and reducing rest work well for applying progressive overload to overload endurance training. When athletes can swim faster during one of these sets, they are getting betterand it is time to apply an overload in some manner. Blood testing has also been used to monitor improvements resulting from overload endurance training. Monitoring heart rates and perceived effort will not be effective for determining improvements from overload endurance training. Athletes should have maximum heart rates when they perform these sets, and they should experience maximum levels of perceived exertions.