Individualizing Aerobic Training Intensities

According to the CDC, heart disease is the leading cause of death in the United States today.  Considering the widely-known connection between obesity and heart disease, the need for Americans to engage in exercise that improves cardiovascular health has never been so apparent and urgent (Yoshino & Klein, 2015).  Despite this clear need for endurance exercise, it has been reported that 75% of American adolescents do not get 60-minutes of moderate-to-vigorous activity on most days; the established guideline for physical activity (Fakhouri et al, 2014).  This statistic appears to have a connection to another; 34% of adolescents in the U.S. are overweight or obese (Ogden, Carroll, & Flegal, 2014). What can be done to put this young generation of Americans on a path toward long, healthy lives with reduced risk of heart disease?

As professionals in the fields of health and fitness, we are in a pivotal position to make a difference by prescribing endurance exercise to improve cardiovascular fitness.  As a cross country and track and field coach, and biology educator to young people, I am thankful for the opportunity to provide education and influence the overall health of the kids in my community.  I place a strong emphasis on making running enjoyable for the hundreds of athletes I work with through the course of a school year in an attempt to change perceptions about the enjoyability of endurance exercise. My overall goal is to help young athletes meet the established health recommendations. Beyond this, my secondary goal is to help athletes who have dedicated themselves to improving race performances carefully meet established fitness recommendations (Rhea, 2014).

The athletes I coach are distance runners; they compete over distances ranging from 400m to 5,000m.  A significant part of my role is to prescribe their training to improve the measures associated with endurance performance, such as VO2max and anaerobic (lactate) threshold (Rhea, 2014).  However, one of the greatest challenges I face, is the task of appropriately individualizing and optimizing the training for sixty to eighty athletes I am coaching during any one season.  Individualization has the power, I believe, to instill a sense of belonging for young athletes, and learning how to enjoy training for aerobic capacity can empower them to continue enjoying endurance training for years to come, thereby reducing health risks that lead to heart disease.

Again, individualization with a large group of athletes is a challenge. I have a number of athletes in my care who struggle to jog continuously for one mile, and a handful of others who can comfortably run 12-15 miles under seven minutes per mile.  When I first began coaching, I would prescribe workout intensities based upon perceived effort. Later, when heart rate monitors became more accessible, I placed an emphasis on training by percentage of maximum heart rate (HRmax) for the relative few athletes who were fortunate enough to have a monitor. Today, I place an emphasis on a combination of perceived effort, percent of HRmax, and GPS-guided pace feedback that corresponds to Jack Daniels’ VDOT values based upon maximum effort performances. How do these three measures interact to help athletes reach their particular daily prescribed training goals?

Perceived effort can be given values in a number of ways.  Effort can be qualitative (e.g. “comfortably difficult,” or “very difficult”), or can be quantitative (e.g. using the Borg 6-20 scale, where an athlete quantifies a “somewhat hard” effort as a “13” on this 15-point scale from 6 to 20 (Kilpatrick et al., 2009)). While this is a highly subjective way to gauge an athlete’s effort, without a heart rate monitor, a marked running path with a known distance (like a 400m track), or a satellite-guided GPS device, it may be the only way to prescribe and monitor running intensity. However, as it turns out, perceived effort, as simple as it may be, is quite possibly the best method for intensity determination.

As pointed out by Robergs and Landwehr (2002), all known formulas for predicting an athlete’s HRmax are insufficient for doing so, as variability among individuals is too great to make accurate predictions (Robergs & Landwehr, 2002; Rhea, 2014).  If HRmax and HRmin are known, and not predicted or estimated, then a heart rate monitor can be an incredibly valuable tool for determining training intensities.  According to Dr. Jack Daniels, running at anaerobic threshold, for example, corresponds to a heart rate between 88% and 92% of HRmax (Daniels, 2014).  This is very specific and not subjective in the way that perceived effort is; on the contrary, working at a percentage of HRmax is completely biometric and linked to physiological intensity.

The final measure I use to determine training intensities is Dr. Daniels’ “VDOT” scale.  In his book, Daniels defines a value he calls “VDOT” which accounts for an athlete’s VO2max and running economy. Once an athlete has completed a maximum-effort performance of a mile run or longer, a formula can be used to quantify aerobic fitness. This numeric value is Daniels’ “VDOT” value which roughly corresponds to VO2max values.  An athlete’s VDOT can be determined using Dr. Daniels’ free calculator found on his website ( ). Armed with VDOT values for each athlete, I can determine the exact pace the individual athletes should run to elicit specific training responses. For example, I know that an athlete with a VDOT of 58 (capable of running a 17:30 for a maximum-effort 5k race) needs to run 5:35/mile (1:23 per 400m) in order to be running at the velocity that elicits VO2max (Daniels, 2014).  This system is trusted by athletes and coaches all over the world and is founded upon sound scientific principles.  Some of the problems with this method of intensity determination is that athletes need to have steady feedback about their running pace (which likely requires a GPS-watch) and that it doesn’t account for environmental factors like excessive air temperatures, humidity, altitude, and hilly running paths.

There are strengths and weaknesses inherent to each of these methods for prescribing and monitoring an athlete’s aerobic exercise intensity, thus, the best way I’ve found to prescribe and monitor intensity is to allow athletes to utilize as many of these methods as possible at once.  If the goal of a particular workout is to improve anaerobic (lactate) threshold, for example, the athletes can be prescribed to run at a pace that feels “comfortably difficult” (roughly a 13 on the Borg 6-20 scale), run at whatever pace elicits a heart rate between 88% and 92% of HRmax (if the athletes know their HRmax and HRmin and have a heart rate monitor), and/or run a highly specific pace (if the athletes have completed a timed all-out effort in a race one mile or longer, have a calculated VDOT, and access to a GPS-watch).  A combination of all three of these guides can give an athlete and their coach a very good target for which to aim, in attempt to accomplish a particular training goal related to intensity.

Individualizing workouts in this manner can give athletes that are part of a larger training group a sense of belonging, and a sense that their needs are being met by their individual coach. Having greater confidence that athletes are accomplishing the metabolic goals of an aerobic workout can translate to improved race performances and increased overall enjoyment with the process and its outcomes.  Ultimately, this may bring more young athletes into the sports of cross country and track, which can in turn create a population of people with the tools necessary to continue to enjoy aerobic exercise and maintain healthy weight, and therefore reduce their risk of death by heart disease.


Daniels, J. T. (2014). Daniels' running formula. Champaign, IL: Human Kinetics.

Fakhouri, T. H., Hughes, J. P., Burt, V. L., Song, M., Fulton, J. E., & Ogden, C. L. (2014). Physical activity in U.S. youth aged 12-15 years, 2012. NCHS Data Brief, 141, 1-8.

Kilpatrick, M. W., Kraemer, R. R., Quigley, E. J., Mears, J. L., Powers, J. M., Dedea, A. J., & Ferrer, N. F. (2009). Heart rate and metabolic responses to moderate-intensity aerobic exercise: A comparison of graded walking and ungraded jogging at a constant perceived exertion. Journal Of Sports Sciences, 27(5), 509-516.

Ogden, C. L., Carroll, M. D., & Flegal, K. M. (2014). Prevalence of obesity in the United States. Journal of the American Medical Association, 312, 189-190.

Rhea, M. [CGHSdesigners]. (2014, November 20). Cardiovascular exercise program design [Video file]. Retrieved from

Robergs, R. A., & Landwehr, R. (2002). The surprising history of the "HRmax=220-age" equation. Journal of Exercise Physiology Online, 5(2), 1-10.

Yoshino, M., & Klein, S. (2015). Endurance exercise: More pain, more metabolic gain. Annals of Internal Medicine, 162(5), 385-386.