A question frequently asked is how one goes about improving run ability, in particular the three determinants of performance: economy, lactate threshold, and VO2max. In this article, I will largely focus on improving running economy to further develop run performance. Running economy (RE) is defined as the energy expenditure (expressed as oxygen consumption, VO2) at a given running speed (1) and RE is a critical factor in distance running performance (22). A question that exercise physiologists and coaches have been attempting to answer is how to improve RE due to its significant role in performance.
Does one focus on increasing mileage, as we can often see where athletes are constantly adding on run mileage throughout the year or does one build intensity? Several papers of original research, meta-analysis, and review in nature have examined this question (10,14,15). What other methods can be used to improve run economy? In this paper, I will discuss three methods of improving run performance: high intensity interval training, strength training, and run gait analysis/run gait modification.
High Intensity Interval Training
The first method of improving run performance I will focus on is training that includes high intensity intervals. Let's start with a couple definitions, beginning with VO2max. VO2max is the maximum capacity of the body to transport and utilize oxygen for energy. This is one indicator of physical fitness and was previously considered the "gold standard" of fitness. I like to think of VO2max as the size of the engine an athlete has. As mentioned, the other determinant of endurance performance is lactate threshold. With increasing work intensity the body transitions from producing energy largely by physiological processes that utilize oxygen for energy to means that do not require oxygen to produce energy (anaerobic metabolism). As this transition occurs to anaerobic means of producing energy, a by-product called lactic acid is produced. Lactic acid is immediately converted to lactate. At lower exercise intensity levels, the body is able to remove lactate as it is produced; however, at higher intensity levels, the lactate is produced faster than it can be removed and blood lactate levels increase. This is the lactate threshold. Think of lactate threshold as the red line limiter on the engine tachometer. Two variables that are routinely investigated in high intensity run training research are vVO2max which is the velocity associated with maximal oxygen uptake (VO2max) determined by an incremental treadmill exercise test (9) and the run velocity associated with onset of blood lactate accumulation (vOBLA). The latter is sometimes called the run velocity at lactate threshold. Both vVO2max and vOBLA are important variables in middle and long-distance run performance (4,9,24). In this article, we will be focusing on the speed at lactate threshold (vOBLA) and the speed at VO2max (vVO2max).
One question that has been investigated is whether intervals at VO2max intensity should be short intense intervals with short recovery or whether the intervals should be longer in nature in an attempt to maximize the amount of time spent at VO2max. What has been found is that multiple short work intervals with short rest periods actually leads to more time spent at VO2max (5).
Billat et al (5) compared two different run protocols to examine the amount of time runners would spend exercising at VO2max intensity. One group of runners in the study performed an exercise session that consisted of alternating 30 second runs at 100% vVO2max and 30 seconds at 50% vVO2max. The other group of runners ran at an intensity halfway between the intensity associated with lactate threshold and VO2max. The reason for this intensity is that it would allow runners to exercise for a longer period of time compared to running at maximal intensity; however it is intense enough that the athlete would eventually attain VO2max due to what is called the slow component of VO2max. What is the slow component of VO2max? This is a physiological phenomenon where a person exercising at a constant high intensity (above lactate threshold, but below VO2max) will eventually reach maximal oxygen consumption even though the intensity (run speed) remains the same. It is the intensity where if it only lasted a few minutes would not normally be considered VO2max intensity. In other words, despite running at the same run velocity, oxygen consumption continues to increase and may eventually reach VO2max oxygen consumption. Thus, even though the run speed remains the same, the relative work intensity increases and the athlete can eventually be working at the maximal oxygen consumption (VO2max). An example will illustrate. Lets say an athlete has a vOBLA pace of 7:25 per mile pace and is setting out on a long run where he will be performing one mile repeats at a 6:41 per mile pace. This is an intensity that is faster than lactate threshold pace, but initially slower than VO2max pace. The first couple repeats will be hard, but will not lead the athlete to reach maximum oxygen consumption. However, as the repeats continue, the athlete may reach VO2max (maximal oxygen consumption), thus the relative intensity (in terms of oxygen consumption) has increased across intervals, despite the run pace remaining the same. However, elite athletes with a high VO2max (greater than 65 ml•min-1•kg-1) may not experience the slow component of VO2max at exercise intensities that leads to the slow component of VO2max in less highly trained athletes (5). In this study (5) it was found that the intermittent running protocol caused the athletes to spend more time at VO2max intensity compared to the continuous exercise session. So why is this important? It has been suggested that running at intensity level that is vVO2max leads to improvement in VO2max (7).
The findings of Billat, et all may be found to be in slight disagreement with an earlier study (12) which found that trained runners running at 92% of vVO2max took longer to achieve VO2max, but the intensity was sustained longer compared to the runners who ran at 100% vVO2max. Billat et al (5) suggest interval training (30 seconds at VVO2max + 30 seconds active recovery as the active recovery) will elicit and maintain VO2max and will also stimulate lactate removal while remaining close to maximal blood lactate steady state. The rest intervals allow the athlete to train longer before fatiguing. However, what may be more important than actually running at VO2max intensity (in terms of oxygen consumption) is the high velocity associated with running at vVO2max in order to maximize muscle contractions. Thus, it may be that speed is more important than the actual oxygen consumption and by maximizing muscle contractions; this may lead to neuromuscular adaptations that will lead to improved performance.
This very question was examined by Denadai, et al (10) where the research group investigated two different protocols that consisted of two high intensity training sessions (HITS) each week, one run session each week at vOBLA, and 3 continuous submaximal sessions at 60-70% vVO2max each week. The training sessions lasted for four weeks. Prior to the four-week training program, VO2max, vVO2max, and vOBLA were determined. vOBLA was considered the intensity that corresponded to 3.5 mmol lactate concentration. The authors also determined the time the athletes could hold the velocity that corresponded to 95% and 100% VO2max (ttim 95%vVO2max and ttim 100% VO2max, respectively), running economy, and each athlete underwent a 1500 meter and 5000 meter time trial. The runners underwent the same training protocol for the four weeks with the exception that one group of runners ran HITS intervals at 95% vVO2max and the other group ran intervals at 100%vVO2max.
The findings of the previous study were there were no significant differences between groups pre-and post-training in the values of VO2max, vVO2max, and vOBLA. However, there was a significant increase in vVO2max in the 100% vVO2max group compared to pre-training. There was also a significant improvement in running economy in the 100% vVO2max group post training compared to pre-training. There was a significant increase in vOBLA in both groups post-training compared to pre-training. In both groups there was a significant decrease in 5000 meter time compared to pre-training; however, only the 100% vVO2max group had a significant decrease in 1500 meter time. Finally, a very important finding of this study is that these improvements occurred without a significant increase in VO2max post-training compared to pre-training. The increased performance in the post-testing, particularly the increased performance in 1500 meter time trial performance and running economy of the 100% vVO2max group could be due to neuromuscular adaptations that occurred specifically in the 100% vVO2max group (10).
Resistance and Plyometric Training and Running Performance
It has been suggested that neuromuscular characteristics may be important for endurance running performance (19). Indeed over two decades ago it was proposed that failure of muscle contractility ("muscle power") limits maximal exercise performance (18).
A combination of heavy weight training (hamstring curl, leg press, parallel squat, leg extension, and heel raise) and endurance training (running) led to an improvement in running economy compared to endurance training alone in well trained triathletes. The combination of heavy weight and endurance training did not affect VO2max (16). A similar study (19) examined the effect of explosive-strength training in combination with endurance training. In this study two groups of runners were tested pre and post 9 weeks of training in which one group performed considerably more sport-specific explosive-strength training (sprints, jumping exercises, leg press, and knee extensor-flexor exercises). Pre and posttests included maximal anaerobic and aerobic tests, 5K time, running economy, maximal 20-meter speed, and 5-jump test. The groups were matched based on VO2max and 5K performance. Both groups engaged in the same training volume (time spent training) during the study. The results were a decrease in 5K time, improvement in running economy, and improvement in peak treadmill running performance in the experimental group that performed more explosive-strength training compared to the control group, which performed less explosive-strength training.
What I consider an important finding is that the control group showed an improvement in VO2max, but this did not lead to a change in 5K performance. Furthermore, the experimental group did not have any changes in VO2max or lactate threshold, yet exhibited improvements in running economy and 5K performance The experimental group showed improvement in the maximal 20 meter and 5 jump test, whereas the control group showed a decrease in performance. The results of this study suggest that lack of muscle power may be a factor that limits endurance performance and is more support for the role of strength training in an athletes overall training schedule.
A more recent study (23) examined the effects of a plyometric training program on running economy (among other measures) in elite endurance runners (average VO2max 71.1 ml/kg/min; run volume 107 km/wk). Plyometrics are exercises that are designed to improve the production of muscle force and power. In a rapid stretch, elastic energy in the musculotendinous components is increased and this energy is stored. When the muscle contracts the stored energy is released. This is one means by which plyometrics may improve power. The other means that plyometrics may improve muscle force and power, is by changing the force-velocity characteristics of the muscle's contractile components caused by stretch of the muscle contraction by use of the stretch reflex. In other words, the plyometrics are causing the nerve bodies involved in stretch reflex to increase power production (2). However, the muscles must contract immediately after the muscle is stretched (thus speed of movement is critical in plyometrics to maximize power production). Plyometrics are exercises characterized by fast powerful movements. An example of a plyometric exercise is a squat jump. In the current study being discussed (23) one group performed 3 X 30 minute plyometric sessions in their training schedule, whereas the control group continued with their current run training. Total training time was the same for both groups. After 9 weeks, running economy at 18 km/hour improved in the group that performed plyometric training, but remained unchanged in the control group. There was no change in VO2max in either group. The authors suggest the improved performance is related to improved muscle power development and better use of stored elastic energy (energy developed from the stretching of the muscles and tendons) from the plyometric training.
Gait Analysis and Changes to Run Gait Biomechanics
The final method of improving run performance I will address is altering run gait (how you run, including all movements of the body during the running action). While it is documented that more efficient runners have specific gait characteristics that differ from less efficient runners (25) and that faster runners tend to have less ground contact time and exhibit a mid-foot strike (11); there is very little research investigating altering run gait to improve performance. Studies that have altered gait include investigating a specific style of running, such as the "pose" method (8), which found a decrease in running economy in triathletes. Other studies included the experimental group self altering stride length during a 7 week training program with no changes in running economy (22) or compared changes in running economy in untrained runners as they complete a 6 week run training program that included guidance related to frequency, intensity, and distance; but no gait feedback (13). The latter study found those participants that engaged in run training had improved running performance compared to the control group that did not engage in run training; however, there was no change in run biomechanics. The improved running performance was likely due to improved fitness, as the control group did not participate in a running program. To the authors knowledge there are no studies that have looked at making long term changes in run gait to achieve the biomechanics of economical runners and how this will affect performance. This is an area that requires further research. What is known among knowledgeable coaches is there are certain gait mechanics that are preferable in order to have an effective run gait. In fact many of these are published in USA Triathlon coaching manuals and also reference the early study by Williams and Cavanagh (25).
Furthermore, many deficiencies related run gait have their origin in weak or imbalanced core strength. Numerous studies have examined the relationship between core strength and the incidence of running injuries (6,17, 20, 26). Furthermore, a recent study has shown that a program consisting of 4 core-training sessions per week for 6 weeks led to improved 5K run performance in marathon runners (21). In the gait analysis that I perform, one area that I focus attention is core stability, in particular hip movement, while the athlete is running. Furthermore, by adjusting an athletes gait to mimic economical runners I have had great success improving runner's performance and minimizing injury. This makes perfect sense, given that if you want to improve at something, you should model those that are better at that skill.
There is ongoing research to investigate methods to improve the determinants of running performance: economy, lactate threshold, and VO2max. In elite runners in particular, there becomes a point where attempting to improve VO2max becomes less important because these athletes have generally reached a ceiling in terms of oxygen consumption and competitors at the elite level generally have similar VO2maxvalues. Methods must be used to increase the actual speed at lactate threshold and VO2max. Research is showing that methods to improve economy involve alterations in neuromuscular adaptations and improving muscle power development. The two methods that can be used to improve these components are high intensity training and resistance/plyometric training. I will give an example of a high intensity training session for running. This workout would be conducted on the treadmill and the grade would be kept at 1% for this athlete (depending on the ability of the athlete and the top speed of the athlete, the grade may need to be increased to achieve the desired intensity of the interval). The athlete would warmup at a low intensity (zone 1 by the zones I use for my athletes) for 10 minutes and then run five minutes at a slightly harder intensity (zone 2) and then performs 4 X (4:00 @ 10.8 mph and then walk until HR recovers to 114 bpm) and then finish with an easy 10 minute cool down. Of course these numbers are based on the performance of this particular athlete and the numbers vary based on the athlete's test results.
More research needs to be performed to evaluate how changing running mechanics will increase running economy and thus performance. The limited research that is out there has focused on the athletes altering the run stride themselves, are short term, and/or only investigated changing one component of the run stride (stride length). What is known is that knowledgeable coaches are altering the run stride of their athletes with successful results. Furthermore, by evaluating core stability during the run stride, changes can be made to decrease the likelihood of injury and further improve running performance.
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Coach Brett is the owner and head coach of Petersen Performance Lab (PPL) based in the Chicagoland area. PPL offers individualized coaching that is unique to each athlete.
Coaching and competing are two of Coach Brett Petersen’s passions. Consistently expanding his knowledge in exercise science, Coach Brett brings a unique perspective to his multi-sport athletes. Brett’s academic and professional certifications include:
• Masters Degree in Movement Sciences (Combination of Exercise Physiology and Kinesiology)
• National Strength and Conditioning Association Certified Strength and Conditioning Specialist.
• Appointed USAT Mideast Team Elite Performance Coach
• Head coach for Team Ethos Multisport Team
• USA Cycling Level II Coach
• USA Triathlon Level II Triathlon Coach
• American Swim Coaches Association Level II Coach
• Serotta Certified Bike Fit Technician
• Completed all course requirements for a Master's degree in Psychobiology
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