All-too-often, however, triathletes forego strength training due to time constraints and the perception that it is less important than sport-specific training.

Better performance

Certain types of endurance activities benefit tremendously from the speed and power gained from strength training. These include: climbing hills, surging, closing gaps and sprinting for the finish line. In addition, research suggests that strength training can improve some aspects of endurance performance.

A study from the University of Illinois investigated the effects of a 10-week strength-training program on endurance-trained individuals. Parallel squats, knee extensions, knee flexions and toe raises were performed three days per week in conjunction with an existing cycling and running schedule.

The program elicited a 27-percent increase in strength from parallel squats, a 37-percent improvement from knee extensions and a 25-percent increase in strength from knee flexions. While no significant changes to VO₂max were seen after combining strength and endurance training, long-term cycling to exhaustion at 80 percent of VO₂max was increased from 71 to 85 minutes. Short-term performance increased by 11 percent in cycling and 13 percent in running.

A second investigation from the University of Illinois looked at the effects of strength training on aerobic power and short-term endurance. Untrained subjects undertook a 10-week, five-days-per-week strength-training program. Parallel squats, knee extensions and knee flexions were performed three days per week. Leg presses and calf raises were performed on alternate days.

The program elicited a 38-percent increase in strength from the parallel squats, a 50-percent improvement from knee extensions and a 42-percent increase in strength from knee flexions. Again, although no significant changes to VO₂max were recorded, short-term cycling performance increased by 47 percent and short-term running performance increased by 12 percent.

Researchers from the University of Maryland studied the effects of a 12-week strength-training program on endurance performance and lactate threshold in untrained healthy males. Subjects completed three circuits per session. Each circuit consisted of 10 exercises. There were no significant changes in maximum oxygen consumption on the bike or the treadmill. However, blood-lactate concentrations at all relative exercise intensities between 55 and 75 percent of VO₂max were significantly reduced.

Therefore, subjects were able to perform a greater amount of work at the same relative intensity. After training, cycling time to exhaustion increased substantially and was accompanied by a 12-percent increase in lactate threshold.

Injury prevention

The effects of strength training on injury risk are perhaps even more noteworthy. In part II of this article (in January), I will show you how to combine both triathlon-specific and injury-prevention exercises into your strength-training sessions to improve performance and decrease incidence of injury. The key lies in enhancing joint stability by improving strength balance in muscles on both sides of major joints.

In a survey of 155 British triathletes who kept a training diary for an eight-week period, 37 percent of the respondents reported suffering at least one injury during the survey period. Seventy-eight percent of the injured triathletes had to stop running, while 37 percent and 21 percent discontinued cycling and swimming respectively. Seventeen percent missed a planned competition.

Overuse was identified as the cause of at least 41 percent and as many as 90 percent of these injuries. The questionnaire showed 65 percent of the injuries to have occurred during running while 16 percent and 12 percent of injuries took place during cycling and swimming, respectively. While factors as diverse as body alignment, technique, equipment and training errors can lead to injury, training error may be the most significant risk factor for suffering an overuse injury.

Training errors include excessive mileage, a sudden change in training distance or intensity, an excessive amount of hard interval training, improper footwear and running on cambered surfaces. By incorporating a regular weight-training program into your training schedule, you can help protect yourself against many of the injuries commonly associated with high-volume triathlon training.

In summary

Though strength training might not lead to significant changes to VO₂max, it does enhance endurance performance through other means. From a performance-enhancement standpoint, strength training may be most beneficial for sprint and Olympic distances, but it should not be overlooked when preparing for half-Iron or Ironman-distance competition.

Therefore, the next time you contemplate doing an extra set of hill repeats, ask yourself: Is muscular strength or power my weakest link? Would it be more beneficial to spend more time under the squat rack?

When it comes to injury prevention, strength is a must regardless of competition distance. Lack of adequate joint stability contributes to many overuse injuries, and appropriate strength training can do wonders to increase the stability of your joints. Its tempting to skip strength training in favor of swimming, cycling or running, but this decision could render you unable to swim, ride or run at all.