How does strength training improve triathlon performance?
Research has shown that the completion of strength training in addition to endurance training can significantly improve cycling and running economy in triathletes. Additionally, strength training programs have shown significant improvements in other performance variables including time-trial performance, reduced heart rate at submaximal intensities, mean power output, peak power and velocity and power at V̇O2max in single mode endurance sports such as swimming, cycling and running.
Strength training can improve performance through the following proposed mechanisms:
- Improving overall maximal strength. As maximal strength increases, the submaximal forces produced during each pedal stroke and running stride will decrease to a lower percentage of maximal force values. This in turn can postpone the recruitment of the less efficient type II muscle fibers and therefore improve cycling or running economy. This delay in recruitment of type II muscles fibers may have a glycogen sparing effect, meaning there is more energy available, which can contribute to improved performance at the back end of a race. This is supported by research showing a significant improvement in a 5-minute all-out effort after a 3-hour submaximal cycle following a heavy strength training intervention.
- Improved musculotendinous stiffness. We can think of musculotendinous stiffness similar to that of an elastic band. Strength training is proposed to increase muscle co-activation and synchronisation which can result in improvements in the stiffness of the muscle-tendon system. This can have a positive flow-on effect increasing the athlete’s ability to utilise elastic energy and produce rapid forces during running. These changes can decrease ground contact time and reduce energy expenditure during running which can improve running economy and performance.
- Strength training can also improve the rate of force development. The rate of force development can be simply thought of as how quickly and athlete can develop force. By improving the rate of force development, this means there is a shorter contraction time of working muscles and therefore less constriction of the blood vessels. This can result in an increase in blood flow and therefore oxygen delivery to working muscles which may in turn improve performance.
- An increase in the proportion of the more fatigue-resistant type IIa muscle fibers and a reduced proportion of the less-efficient type IIx fibers which can be beneficial for endurance performance.
- Finally, an increase in lean body mass and muscle cross-sectional area has been reported from the implementation of strength training programs in endurance athletes. Research has shown a positive relationship between lean body mass and 1 hour all out cycling power output in well trained and elite cyclists. This research has suggested that there is an increased ability of the athlete to recruit a relatively large quantity of muscle mass during each pedal stroke which is associated with improved performance. Additionally, cyclists that are able to use a larger amount of their muscles mass have been observed to have a larger fractional utilization of VȮ2max, meaning they are able to train or race at a higher percentage of their VȮ2max for a prolonged time. It is important to note that the increases in lean body mass and cross-sectional area occurred without an increase in body mass, suggesting that muscle mass increased whilst body fat decreased in participants.
In summary, proposed mechanisms contributing to improved endurance performance include improvements in maximal strength, musculotendinous stiffness, rate of force development, muscle fiber composition, and an increase in lean body mass and muscle cross sectional area.
