Monday, January 21, 2013

Hill Sprints and Running Economy: Review (Part 2)

   As promised for this week's post -- more on hill sprint training and its potential to improve running economy. Below I have included tid-bits from my review of literature. Yes, the text may be a bit redundant, especially if you read last week's post, but that is the nature of a proposal. I hope this information allows us all to further evaluate the training's potential.

Chapter 2
Review of Literature

Introduction

...Research has shown running economy (RE) to be a critical factor in determining distance running performance in highly trained runners. (J. T. Daniels, 1985Midgley et al., 2007Noakes, 1988Spurrs et al., 2003).  Further, research shows running economy can be improved with traditional heavy-weight resistance training and/or plyometric training (Jung, 2003McCann & Higginson, 2008Midgley et al., 2007Paavolainen et al., 1999Saunders et al., 2004aSaunders et al., 2006Spurrs et al., 2003). Yet, no research has studied the effects of added resistance specifically to the running gait on RE.  Midgley et al. (2007) suggests one way off adding resistance to the running gait is by running uphill.  Adding resistance to movement could potentially improve running economy through the same mechanisms as resistance training and plyometric training...



The Importance of Running Economy

Numerous studies have found RE and performance to be closely associated with one another (Jung, 2003Midgley et al., 2007Paavolainen et al., 1999Saunders et al., 2004a).  RE may be  particularly important to highly trained runners because these athletes have similar VO2max values. In highly trained distance runners with similar VO2max values, differences in RE are likely to explain a large portion of the variability in performance times between elite distance runners.  Daniels (1985) reports running economy can vary by as much as 30% among runners with similar VO2max values.  Further, Noakes (1988) states, VO2max is a poor predictor of performance when considering athletes of similar ability and RE is a better predictor of running performance.  Many others also suggest that RE is better predictor of running performance than VO2max alone in runners with similar VO2max values (Costill, Thomason, & Roberts, 1973Paavolainen et al., 1999Spurrs et al., 2003).

Evaluating Running Economy

Running economy has been evaluated with different protocols using both treadmill and over ground running.  Saunders et al. (2004a) state that while treadmill running is slightly different from over ground running, it can still be a reliable indicator of a runner’s economy and RE on a treadmill is still highly correlated with over ground RE.  A major advantage of using treadmill running is that variables in the laboratory such as temperature, humidity, and wind can be controlled for.  Saunders et al. (2006) tested RE at three different steady state running speeds on a treadmill.  After a standardized warm-up the subjects completed three four minute long stages at 14, 16, and 18 km/h. O2 uptake (VO2) was measured in the final minute at each speed.  By testing VO2 at multiple speeds, Saunders et al. were able to evaluate whether a 9 week plyometric training program changed RE at the different speeds tested.  Interestingly, the improvements in RE at higher speeds (16 and 18 km/h) were greater than those observed at slower speed (14 km/h) and the change increased with each increase in speed. In this study, the only statistically significant change in RE was seen at 18 km/h.  A trend found showing greater gains in economy with increased velocity. While it would have been interesting to see whether the changes in RE continued to increase at speeds of 20 km/h and higher, Saunders et al. chose to stop testing at a maximal speed of 18 km/h. This speed was chosen because it is a steady state speed for the athletes. This means that there is a negligible contribution of energy from anaerobic metabolism.  Saunders et al. (2004a) also suggest that RE of highly trained distance runners be tested at speeds eliciting no more than 85% of VO2max to minimize energy contribution from anaerobic metabolism.  Spurrs et al. (2003) used a protocol similar to Saunders et al. (2006) to test highly trained runners, but utilized three minute stages, an incline of 1%, and speeds of 12, 14, and 16 km/h. Interestingly, the results were not consistent with those of Saunders et al.  Spurrs et al. found that largest change seen in RE was at the slowest speed of 12km/h. Paavolainen et al. (1999) used over ground running and a portable O2 analyzer. Pace was controlled using a “light rabbit” on the track and the athletes completed two five minute stages at 3.67 and 4.17 m/s (13.2 and 15.0 km/h). RE was calculated as VO2 over the last minute of each stage.  A major limitation of the study by Paavolainen et al. is having the resources such as an indoor track, a portable VO2 analyzer, and a “light rabbit” to conduct the study.  Mojock et al. (2011) evaluated RE in moderately trained female distance runners, having them run on a treadmill for 30 minutes at 65% VO2max.  RE was determined by measuring total caloric expenditure and VO2 over the thirty minute trial.  Obviously, a limitation to this protocol is the use of only one running speed. This protocol may accurately assess RE at that one speed, but as Saunders et al. (2006) have shown, changes in RE may vary at different running speeds.  By utilizing a protocol that tests RE at multiple speeds, the likelihood of finding a statistically significant difference may be increased and the risk of committing an error decreased.... Others have also utilized performance time trials such as a 5000m run (Paavolainen et al., 1999).  Time trials may be a practical application assessing the training's effect on performance, but performance tests cannot isolate the variable of running economy.  A 5000m time trial would not be able to assess running economy (VO2) because a considerable amount of energy in a 5000m run between 13 and 16 minutes (18.8 to 23.1 km/h) comes from anaerobic metabolism.  Therefore improvements in 5000m time could be the result of improved VO2max, anaerobic capacity, or other variables involved in running performance.  Additionally, performance tests are limited in their ability to eliminate other variables that may also affect performance, e.g., temperature, wind, humidity, pacing.

Training Running Economy – Current Understanding

Running economy can be improved as a result of different training stimuli, and there are multiple mechanisms that influence RE. Altitude training, training in hot climates, resistance training and plyometric training have all been shown to improve RE (Saunders et al., 2004a).  Saunders et al. (2006) is one of many studies that found plyometric training to significantly improve RE.  The authors conclude that plyometric training may improve muscle power characteristics and/or increase the stiffness of the muscle-tendon system, enabling the body to better utilize stored elastic energy. This study is particularly important because it increased RE in highly trained, elite level distance runners.  Spurrs et al. (2003) and Paavolainen et al. (1999) have also demonstrated that that plyometric training improved RE.  A review by Jung (2003) investigated the impact of resistance training on RE,  and concluded that traditional heavy weight resistance training also improves RE – but the effect of long term resistance training has not been studied and may result in hypertrophy and weight gain which could negatively impact RE.

Could uphill running induce similar effects as resistance or plyometric training?

Jung (2003) states resistance training exercises that closely mimic a particular skill result in greater improvements in that particular motor skill. This is known as the rule of specificity.  Following the rule of specificity, performing exercises that most closely mimic the action of running should result in the most favorable improvements in running performance. Therefore, applying resistance to the running stride has the potential to improve running performance. Midgley et al. (2007) states that hills effectively add resistance to running and suggest that high-velocity running exerts similar training effects as resistance training in distance runners.  Potentially, by running at or near maximal velocities with the added resistance of running uphill, one could mimic the stimulus of resistance and/or plyometric training with a very specific application to the running gait and see improvements in RE.  However, no research exists investigating the effects of high-velocity uphill running on RE.  There is only speculation and anecdotal evidence from coaches and athletes on the effectiveness of running uphill intervals improving running economy. Some speculate it may improve anaerobic capacity, but is not applicable to training economy.  Arthur Lydiard was an advocate of hill running in the 1950’s and 60’s.  Lydiard’s athletes were well known for setting world records in 800 and 1500m and winning multiple Olympic gold medals.  Likewise, Jack Daniels, a world renown running coach and physiologist states in his book, Daniels’ Running Formula, that uphill running does indeed improve running economy (J. Daniels, 2005). Despite there being no scientific studies to support the theory, many coaches today still utilize uphill running; believing it strengthens their runners’ legs and improves RE.

Summary

RE is a critical component of distance running performance. Plyometric and resistance training have been proven to effectively increase RE by improving muscle strength and power and also through stiffening of muscles and tendons improving elasticity.  Hills effectively add resistance to running and high-velocity running may induce similar responses in muscles and tendons as resistance training. Logically, high-velocity uphill running may possess the potential to improve RE.  To date, no research has investigated the effects of high-velocity uphill running on RE.

References



Costill, D. L., Thomason, H., & Roberts, E. (1973). Fractional utilization of the aerobic capacity during distance running. Medicine & Science in Sports & Exercise, 5(4), 248-252.
Daniels, J. (2005). Daniels' Running Formula, Second Edition: Human Kinetics.
Daniels, J. T. (1985). A physiologist's view of running economy. Medicine & Science in Sports & Exercise, 17(3), 332-338.
Foster, C., & Lucia, A. (2007). Running Economy. Sports Medicine, 37(4/5), 316-319.
Jung, A. P. (2003). The impact of resistance training on distance running performance. . Sports Medicine, 33(7), 539-552.
McCann, D. J., & Higginson, B. K. (2008). Training to Maximize Economy of Motion in Running Gait. Current Sports Medicine Reports (American College of Sports Medicine), 7(3), 158-162.
Midgley, A. W., McNaughton, L. R., & Jones, A. M. (2007). Training to Enhance the Physiological Determinants of Long-Distance Running PerformanceSports Medicine, 37(10), 857-880.
Noakes, T. D. (1988). Implications of exercise testing for prediction of athletic performance: a contemporary perspective. Medicine & Science in Sports & Exercise, 20(4), 319-330.
Paavolainen, L., Hakkinen, K., Hamalainen, I., Nummela, A., & Rusko, H. (1999). Explosive-strength training improves 5-km running time by improving running economy and muscle power. Journal of Applied Physiology, 86(5), 1527-1533.
Saunders, P. U., Pyne, D. B., Telford, R. D., & Hawley, J. A. (2004). Factors affecting running economy in trained distance runners. Sports Med, 34(7), 465-485.
Saunders, P. U., Telford, R. D., Pyne, D. B., Peltola, E. M., Cunningham, R. B., Gore, C. J., & Hawley, J. A. (2006). SHORT-TERM PLYOMETRIC TRAINING IMPROVES RUNNING ECONOMY IN HIGHLY TRAINED MIDDLE AND LONG DISTANCE RUNNERS. Journal of Strength & Conditioning Research (Allen Press Publishing Services Inc.), 20(4), 947-954.
Spurrs, R. W., Murphy, A. J., & Watsford, M. L. (2003). The effect of plyometric training on distance running performance. European Journal of Applied Physiology, 89(1), 1-7.



     In summary, resistance and plyometric training has been shown to improve RE. Hill sprints could potentially mimic the stresses of resistance/plyometric training, while maximizing specificity and minimizing hypertrophy. Of course, this is theoretical physiology -- and theoretically physiology will not hold much clout in academia.

     Take note of the differences seen in running economy at different speeds in the Saunders study from 2006. This study used a 9 week long plyometric training protocol with highly trained nationally and internationally competitive middle and long distance runners. RE was evaluated at 14, 16, and 18 km/h. They found that RE was significantly increased only at 18 km/h. This equates to a 5:22 mile. But perhaps the most interesting thing was the decrease in VO2 slope with increasing running speed after training. What this means is that as the speed running increased, greater changes in RE were observed. Of course, it would be interesting to see if the trend continued out to 20, 22, 24 + km/h. But... the major limitation to the RE evaluation (steady state VO2 at a certain speed) is that it has to be an aerobic pace to evaluate VO2. So, running at 18 km/h (5:22 mile), these athletes were able to supply all the energy they needed through aerobic metabolism -- this is also consistent with their lactate analysis.

     But, who knows -- If we were somehow able to evaluate RE at non-steady state VO2 paces (20+ km/h), would we see this decreased VO2 slope continue? If so, this type of training could be particularly important to elite level middle distance runners who often complete 5000m in 13:15 at a rate of 22.6 km/h or 800m in 1:45.0 at 27 km/h. But even today, most major marathons are completed in under 2:08 which is 19.8 km/h -- faster than was tested in this study.

     Finally, the decreased VO2 slope after training is consistent to the findings of Cavagna (1964), who concludes that elastic mechanisms prevail at higher speeds.

     In the end, we have no studies to say whether or not hill sprint training improves running economy. We do have anecdotal evidence to suggest running hills improves running performance -- in the past and present some of the greatest coaches and athletes have incorporated some sort of hill training into their regime. I also do hill sprints, and have my athletes perform them. Why? Maybe it improves running economy by improving power/recruitment, maybe it improves lactic capacity (one's ability to create lactate). Either one, or a combination of the two could lead to an improvement in performance. And theoretically...

     This leads me to my next post: Next week I hope to discuss topics like lactate, lactate threshold, acidosis and why lactate capacity/threshold training is crucial to middle and long distance running performance from 800m to the marathon.

Feel free to leave me a question or comment. I'll need some topics for future blog posts...

Sunday, January 13, 2013

Hill Sprints and Running Economy: Review (Part 1)

     Last semester I started working on a project proposal that would investigate what effect 10 weeks of uphill sprint repetition training (hill sprints) would have on running economy. This will be a two-part post. My introduction is below, followed by a few (hopefully) thought provoking comments. Next week I will be posting my review of literature.

Chapter 1
Introduction

Distance running performance relies upon many variables.  For trainable attributes, coaches and athletes often assume the variables of maximum oxygen consumption (VO2max), anaerobic capacity, and lactate threshold are the major determinants of an athlete’s performance.  As stated by Noakes (1988), VO2max is so frequently discussed in lay articles that it seems most runners, swimmers, triathletes and cyclists believe that it is the most important predictor of athletic ability.  Indeed, VO2max and the other aforementioned variables are important for distance runners, but there is another critical component that contributes to an athlete’s performance; the variable of running economy (RE).  RE is defined as the steady state VO2, or energy demand, for a given velocity of submaximal running. RE is quantified by calculating the steady-state VO2 with respect to body mass and time for any given submaximal running speed (Morgan, Martin, & Krahenbuhl, 1989).  An improvement in RE would be indicated by a reduction of steady state oxygen consumption at a certain velocity of running.  Therefore, more economical runners are able to maintain a greater velocity while consuming less O2 and expending less energy.  The more economical runner may also be able to utilize fatty acids as fuel at high work rates, sparing carbohydrate (J. T. Daniels, 1985; Philo U. Saunders, D. B. Pyne, R. D. Telford, & J. A. Hawley, 2004a).  This would allow an athlete to not only run faster, but also extend that faster pace over a longer distance.

Significance of Running Economy
A strong association has been found between running economy and distance running performance.  In fact, research suggests that RE is a better predictor of performance than VO2max alone in runners with similar VO2max values (J. T. Daniels, 1985; McCann & Higginson, 2008; Noakes, 1988; Saunders et al., 2004a).  Because VO2max values of elite runners are generally similar, a difference in running economy between athletes could be the deciding factor in the outcome of a race.  Despite evidence demonstrating running economy’s importance to performance, to date there are few studies documenting training methods that improve running economy in highly trained distance runners.

Improving Running Economy
Some evidence indicates that running economy can be improved with resistance and/or plyometric training but the exact mechanism(s) behind the improvement is unknown (Foster & Lucia, 2007; Jung, 2003; McCann & Higginson, 2008; Saunders et al., 2004a).  It has been proposed that improvements in economy from resistance training are the result of improved neuromuscular characteristics such as motor unit recruitment and decreased ground contact time (Jung, 2003).

Resistance Training
While traditional resistance training has been shown to improve running economy, the techniques and lifts often employed (e.g. squats, leg extension, leg press, leg curls) cannot mimic the running stride.  Specificity of resistance training has been well documented.  It is known that resistance exercises will elicit effects on the specific muscles activated at or near the specific speeds and ranges of motion which the resistance exercises are performed (Morrissey, Harman, & Johnson, 1995).  Therefore, the more running specific a resistance training program, the better the results for running. Additionally, resistance training may improve RE in short term studies, but long term effects have not been investigated.  It is possible that weight gain associated with hypertrophy from long term resistance training could negatively impact RE (Midgley, McNaughton, & Jones, 2007).

Plyometric Training
In comparison to resistance training, plyometric training may be able to better simulate the kinematics of running and elicit a more specific response for the runner.  A number of studies have found plyometric training to improve RE (Paavolainen, Hakkinen, Hamalainen, Nummela, & Rusko, 1999; Saunders et al., 2006; Turner, Owings, & Schwane, 2003).  Like resistance training, plyometric training is also thought to improve neuromuscular motor unit recruitment but plyometric training may also increase the stiffness of the muscle-tendon system.  This allows the muscles to store and utilize elastic energy more effectively (Saunders et al., 2006; Spurrs, Murphy, & Watsford, 2003).  While plyometric training has shown to effectively improve RE in highly trained runners, and the movements used (e.g. bounding, hopping, and jumping) are more specific to running than traditional resistance training, there is no movement more specific to running than running itself.

Statement of the Problem 
Uphill running effectively adds resistance to movement, adding resistance very specifically to the running stride.  Uphill bounding and running have been used by coaches and athletes in attempts to increase distance runners’ strength and economy.  It has been suggested that high-velocity running exerts similar training effects as resistance training in distance runners such as improved motor unit recruitment (Midgley et al., 2007).  Potentially, adding resistance in the form of a hill to very high effort running could result in a response similar to that seen after plyometric and resistance training in the specific muscles used during running. While a number of lay publications and coaches today advocate the use of uphill running for strength their rationale is based solely on anecdotal evidence.  To date, no research has investigated the effects of high intensity uphill sprint training on RE.  Therefore the purpose of this study is to determine the effect of high intensity uphill sprints on RE in highly trained runners.

Significance of this Study
Relatively few interventions have been shown to improve RE in highly trained runners. If uphill sprint repetitions are found to improve RE, this will give coaches and athletes another means of potentially improving running performance. Further, this study will serve to justify or reject the current use of uphill sprint repetitions by coaches and athletes.  Further research would be necessary to confirm what distance, intensity, frequency, and grade of uphill work best for improving RE.



References


Daniels, J. T. (1985). A physiologist's view of running economy. Medicine & Science in Sports & Exercise, 17(3), 332-338.
Foster, C., & Lucia, A. (2007). Running Economy. Sports Medicine, 37(4/5), 316-319.
Jung, A. P. (2003). The impact of resistance training on distance running performance. . Sports Medicine, 33(7), 539-552.
McCann, D. J., & Higginson, B. K. (2008). Training to Maximize Economy of Motion in Running Gait. Current Sports Medicine Reports (American College of Sports Medicine), 7(3), 158-162.
Midgley, A. W., McNaughton, L. R., & Jones, A. M. (2007). Training to Enhance the Physiological Determinants of Long-Distance Running Performance. Sports Medicine, 37(10), 857-880.
Morgan, D. W., Martin, P. E., & Krahenbuhl, G. S. (1989). Factors affecting running economy. Sports Medicine, 7(5), 310-330.
Morrissey, M. C., Harman, E. A., & Johnson, M. J. (1995). Resistance training modes: specificity and effectiveness. Medicine & Science in Sports & Exercise, 27(5), 648-660.
Noakes, T. D. (1988). Implications of exercise testing for prediction of athletic performance: a contemporary perspective. Medicine & Science in Sports & Exercise, 20(4), 319-330.
Paavolainen, L., Hakkinen, K., Hamalainen, I., Nummela, A., & Rusko, H. (1999). Explosive-strength training improves 5-km running time by improving running economy and muscle power. Journal of Applied Physiology, 86(5), 1527-1533.
Saunders, P. U., Pyne, D. B., Telford, R. D., & Hawley, J. A. (2004). Factors affecting running economy in trained distance runners. Sports Med, 34(7), 465-485.
Saunders, P. U., Telford, R. D., Pyne, D. B., Peltola, E. M., Cunningham, R. B., Gore, C. J., & Hawley, J. A. (2006). SHORT-TERM PLYOMETRIC TRAINING IMPROVES RUNNING ECONOMY IN HIGHLY TRAINED MIDDLE AND LONG DISTANCE RUNNERS. Journal of Strength & Conditioning Research (Allen Press Publishing Services Inc.), 20(4), 947-954.
Spurrs, R. W., Murphy, A. J., & Watsford, M. L. (2003). The effect of plyometric training on distance running performance. European Journal of Applied Physiology, 89(1), 1-7.
Turner, A. M., Owings, M., & Schwane, J. A. (2003). Improvement in running economy after 6 weeks of plyometric training. J Strength Cond Res, 17(1), 60-67.





     The basis of this study came from reading Brad Hudson and Matt Fitzgerald's book, Run Faster: From the 5k to the Marathon. I'd done hill sprints in my years running cross country and track at Berry College and had never given them any more thought than what my coach and Hudson had said or written about them. Hudson, a former coach of Dathan Ritzenhein and founder of Hudson Training Systems states, " [Hill sprints] increase the power and efficiency of the stride, enabling the runner to cover more ground with each stride with less energy in race circumstances." In a roundabout way, Hudson claims that hill sprints improve running economy. Hudson goes on the state that hill sprints are, "not much different from a set of explosive Olympic weightlifting exercises... except more running specific."

     Hudson is not the first to incorporate hill sprints into his athletes' training. The Italian coach Renato Canova, who now coaches some of the world's best marathoners, has long been an advocate of hill sprints. And Canova admits he got the idea of hill sprints from the American sprint coach Bud Winter who began using hill sprints in the late 1960's. The Kiwi Arthur Lydiard was also using hill training in the 60's. My point being, using hills as a means of increasing a runner's strength is not a new concept. However, to my knowledge, no studies have assessed hill sprint training's effectiveness at increasing strength or economy. All the information we have is anecdotal. 

     Despite the lack of controlled studies, hill sprint training is quite popular. A quick Google search will turn up hundreds, if not thousands, of results touting the benefits of hill sprints from sites like Joggers Runners' World and Competitor -- they're the best thing since sliced bread, they increase strength, power, and running economy. So, you see the problem... All of these claims with no evidence to back them. Clearly, there is a knowledge gap between the coaches/athletes and the academic arena.

There are other aspects of hill training and I hope to address those in the weeks to come. I'd appreciate any comments on the topic or suggestions for new blog posts.