Training distance runners typically focus on improving three main physiological variables: aerobic power (VO2max), lactate threshold, and running economy. The methods used to improve these variables are varied, and include everything from running long, slow distance to performing very short interval workouts. However, despite the attention given to interval training in the fitness and coaching industries, research has shown that elite endurance athletes do about 80 percent of their training at low intensity and only 20 percent at high intensity. Many athletes also incorporate strength training in their programs. With all of the different training methods, what is the best way to train?
Although it is very difficult, for a number of reasons, to answer this question, scientific research allows us to gain an understanding of the physiological processes that occur in improving performance, and can help the coach direct his or her training decisions. What does the scientific research have to say about endurance training?
- Understand the physiological factors that determine endurance performance.
- Summarize the research on endurance training.
- Describe the different methods of endurance training.
Aerobic Power (VO2max)
It is widely believed that having a high VO2max is important for success in endurance sports. Although a high VO2max alone is not enough to attain elite-level performances, it gains one access into the club. An athlete cannot attain a high level of performance without a high VO2max. Training VO2max is especially important for those who run the 1,500-meter/mile and 3,000-meter races. While VO2max is largely genetically determined, training can improve it between 5 and 20 percent, depending on initial fitness level.
VO2max plateaus after only about three weeks of daily training, and it has been suggested that the training stimulus needs to increase every three weeks if further improvements in VO2max are to be realized. With long-term training programs, VO2max tends to stabilize, with further improvements in fitness and performance resulting from improvements in lactate threshold and/or running economy. In fact, it is possible for VO2max to decrease over a period of years while racing performance continues to increase, lending support to the greater importance of the other two factors.
Long interval training (with work periods of 3-5 minutes) is the most potent stimulus for improving VO2max, likely because VO2max can be achieved during the work periods, with the repeated attainment of VO2max serving as the stimulus to improve it. However, as some studies have shown, it may not be necessary to elicit VO2max during the workout to cause it to increase. For example, similar increases in VO2max have been shown to occur between continuous training and interval training programs. Thus, increasing athletes’ weekly training volume will help increase their VO2max, at least initially. There does not seem to be any significant increase in VO2max when running more than 75 to 80 miles per week, unless more intense training is performed to supplement the mileage. Billat et al. (2002) found that elite male and female marathon runners increased VO2max after eight weeks of interval training was added to their weekly training volume. The high mileage that distance runners typically run may improve the ability to run more repetitions during the interval training sessions, thus allowing more time to be spent at a high intensity.
Short intervals (work periods of <30 seconds) also have the ability to improve VO2max when short, active recovery periods are used during the workout. Even short intervals have an aerobic component to them since it is very difficult to elicit exclusively anaerobic metabolism.
Speed at VO2max
When determining at what pace athletes should perform their interval workouts, the running velocity at which VO2max occurs (vVO2max) seems to hold the most promise. This velocity, which is very close to 3,000-meter race pace for good runners, is a variable that combines VO2max and running economy, and is another important determinant of distance running performance. Interval training at vVO2max allows VO2max to be sustained for the longest possible time. This has important implications for athletes in the middle distances (1,500 meters/3,000 meters/5,000 meters), events that are run at, or close to, 100% VO2max.
The lactate threshold is the intensity above which the rate of lactate removal begins to lag behind the rate of lactate production, causing a rapid accumulation of lactate in the muscles and blood. It is also described as the intensity above which oxygen-independent (anaerobic) metabolism becomes a significant contributor of energy. The lactate threshold can therefore be considered the upper limit of steady-state aerobic metabolism, or the greatest intensity that can be supported by aerobic means.
Although VO2max has historically been the criterion measure of cardiovascular fitness, the lactate threshold explains more of the variability in performance between runners, and is the best physiological predictor of distance running performance. Furthermore, the lactate threshold is more responsive than VO2max to training, and is thus more useful for training purposes. Even world-class runners can increase their lactate threshold, as shown by Jones (1998), who tracked marathon world-record holder Paula Radcliffe for five years and found the pace at her lactate threshold improved by 20 percent, from 6 minutes 25 seconds per mile to 5 minutes 20 seconds per mile. The intensity associated with the lactate threshold also increased from 80 percent VO2max to 88 percent VO2max in the five-year period, and her 3,000-meter performance improved from 9 minutes 23 seconds to 8 minutes 37 seconds.
Several researchers have suggested that the lactate threshold is the optimal intensity for improvement in endurance. Training the lactate threshold increases the speed at which lactate accumulates and acidosis occurs, thus allowing athletes to run at a higher percentage of their VO2max for a longer period of time. The longer the race your clients are training for, the more important it is to train their lactate threshold.
While the lactate threshold increases along with VO2max with interval training, specific training of the lactate threshold is accomplished through the use of steady “tempo” runs, which are run at, or slightly faster than, the athlete’s current lactate threshold pace. It has also been suggested that the pace should elicit a blood lactate concentration of 4 millimoles per liter, which approximates the blood lactate concentration at the lactate threshold. In the study by Jones (1998) on Paula Radcliffe, it was discovered that she incorporated a lot of steady runs close to, or at, her lactate threshold pace. Franch et al. (1998) found that runners who included tempo running (20-30 minutes at >90% max heart rate) improved their time to exhaustion during submaximal running (at 87% VO2max) by 94%, compared to only 67% and 65% for those who trained with long or short intervals, respectively. The ability to sustain a hard pace for a longer time is greatly influenced by the lactate threshold.
One of the major advantages to lactate threshold training is that the intensity represents the fastest pace at which athletes can train aerobically without acidosis or excessive fatigue. Doing workouts faster than lactate threshold pace causes a great deal of fatigue, which limits how often athletes can do those workouts.
Running economy is the oxygen consumption required to run at a given pace. Along with the running speed at the lactate threshold, running economy seems to be more important than VO2max in improving or predicting distance running performance. Runners with good economy can frequently perform better than those with higher VO2max values.
Volume of Training
Runners who perform greater volumes of endurance training tend to be more economical, which has led to the suggestion that running high mileage (>70 miles per week) seems to improve running economy. Furthermore, runners tend to be the most economical at the speed at which they train the most. It is possible that the greater repetition of running movements in those runners who run more weekly miles results in better biomechanics and motor unit recruitment patterns. Additionally, the lower body weight (and consequent lower oxygen cost) often associated with a greater volume of running may lead to improved economy. Thus, an improved economy may be the most significant attribute gained from running high mileage. However, not all studies have shown economy to improve with endurance training. The subjects in the study by Billat et al. (2002) were elite marathoners running over 100 miles per week in preparation for the Olympic Trials, suggesting that, if high mileage does improve economy, there is a limit to the volume of training that will elicit further improvements. It is not entirely clear whether runners who train with high volumes become more economical by running more miles or are innately more economical and can thus handle greater training volumes.
Interval training has been shown to improve running economy, albeit slightly. Franch et al. (1998) observed a three percent improvement in economy following both exhaustive distance training (20-30 minutes at >90% maximum heart rate) and long interval training (4-6 x 4 minutes with 2 minutes rest), performed 3 times per week for 6 weeks, but only a 0.9 percent increase in economy following short interval training (30-40 x 15 seconds with 15 seconds rest). The improved economy was correlated with a decrease in exercise ventilation following training, suggesting that improved economy may be the result of decreasing the oxygen cost of breathing.
It is very common for athletes in all sports to lift weights to supplement their sport-specific training. But, unlike most sports, which require strength, speed, and power to be successful, maximal endurance performance is primarily limited by the consumption and delivery of oxygen. There are no studies to show that strength training improves oxygen delivery from lungs to muscles, a variable that is largely controlled by the cardiac output. However, many (most) distance runners still lift weights, typically with light/moderate loads and a high number of repetitions, a program that is geared toward increasing muscular endurance with only small increases in strength. Is performing three sets of 10 to 15 repetitions going to increase muscular endurance any more than running greater than 50 miles per week? While some studies have found that strength training may lead to improved endurance performance in previously untrained subjects, other studies have shown it to be ineffective. It is possible that traditional strength training may enhance endurance performance in those untrained or in younger, less experienced runners, while more experienced, highly-trained athletes may not benefit from traditional strength training and may even be hampered by it, especially if it is performed at the expense of more sport-specific training.
Concurrent Strength and Endurance Training
Strength and endurance training programs elicit contradictory physiological changes that may lead to counterproductive results when these two types of training are performed concurrently. For example, strength training stimulates muscle fiber hypertrophy mediated by increases in protein (actin and myosin) synthesis. This increases body weight, which may impair endurance performance, since a greater amount of weight would have to be transported over a long distance. The larger muscles also have reduced capillary and mitochondrial densities, changes that are detrimental to endurance. Endurance training causes muscles to respond in an opposite fashion by increasing the mitochondrial volume and density and number of capillaries, and may even induce atrophy of muscle fibers. In addition, endurance training has a greater influence on left ventricular size and volume than does strength training, likely owing to the need for these athletes to have a large stroke volume and cardiac output.
Maximal/Explosive Strength Training and Plyometrics
Maximal and power-type (explosive) strength training and plyometric training have been getting increased attention as a means to improve endurance performance, as it has been recognized that anaerobic factors may also play an important role in the success of a distance runner. Recent studies have shown an improved running economy with the inclusion of heavy weight training (3-5 sets of 3-5 repetitions to muscular failure at >90% of the one repetition maximum) in the subjects’ training programs. Explosive strength training and plyometric training have also been shown to improve economy for running and cross country skiing, and may be the strongest evidence for improved economy following strength training. Paavolainen et al. (1999) had runners perform short sprints (5-10 x 20-100 meters), jumping exercises, and lower body weight training with low loads (0-40% 1RM) moved with fast speeds, while other studies had subjects perform 3 to 4 sets of 5 to 6 repetitions using a heavy load (85-100% 1RM), also moving the load with the fastest possible speed. In addition to the improved running economy following training, Paavolainen et al. (1999) found that the runners’ 5-kilometer time improved in the group that combined endurance and explosive strength training but not in the group that only performed endurance training. Spurrs et al. (2003) reported similar results, with an improvement in runners’ 3-kilometer time when endurance training was combined with plyometric training. Although racing performance was not measured following the strength training intervention, other studies have also found that endurance was improved, as measured by an increased time to exhaustion at maximal aerobic velocity. Furthermore, these studies found that neither VO2max nor lactate threshold changed. It is logical, then, to expect that endurance performance would be enhanced since economy improved while VO2max and lactate threshold remained the same. Another interesting finding is that, although the subjects got stronger as a result of the strength training, they did not gain weight, supporting neural adaptation, as opposed to muscle hypertrophy, as a valuable method for improving strength without weight gain.
Maximal, explosive strength training may improve running economy by improving the muscles’ rate of force development. Thus, just as in the initial development of strength, neural adaptation seems to be the stimulus for improved economy. In addition, increasing the strength of a muscle would reduce the percentage of maximal strength required for each contraction (e.g., hip extension at push-off), delaying the recruitment of Type II (fast-twitch) motor units and the associated inevitable fatigue.
Distance runners should focus their training on improving three main physiological variables: VO2max, lactate threshold, and running economy. The greatest changes in VO2max occur when the intensity of training is greater than 90% VO2max. The velocity at VO2max (vVO2max) is an effective intensity at which to perform interval workouts, approximating 3,000-meter race pace in good runners.
The lactate threshold is more sensitive to training than is VO2max. Lactate threshold training is best accomplished with steady runs, near the athlete’s current threshold pace.
Running economy seems to be improved with high weekly volumes of training and by heavy or explosive strength training. While traditional weight training with light weights and a high number of repetitions may be beneficial for untrained or inexperienced runners, it seems that this type of weight training is not beneficial for highly trained distance runners. However, maximal or explosive weight training that focuses on neural adaptation, such as lifting near-maximal loads, or near-maximal or light loads with fast movement speeds, may improve distance running performance in those who are highly trained.
There are still a number of unanswered questions for future research regarding the training of distance runners, including the amount of mileage that is necessary for high-level performance, and the mechanism(s) behind the improvements in lactate threshold and running economy. Future research should focus on the interplay between the different types of workouts, including their organization in the year-long training program.
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