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January 19, 2021

Understanding Maximum Heart Rate

The modern fitness era has brought a host of wearable technologies that can track extraordinary amounts of biological and physiological data. Perhaps the most commonly measured variable we see today is one’s heart rate.

Understanding Maximum Heart Rate - Fitness, fitness, VO2 Max, aerobic exercise, obesity, weight loss, heart rate, aerobic fitness, heart health, wearables, fitness technology, obesity crisis, heart rate variability

This is certainly nothing new, as brands like Polar and Garmin have been around for decades providing wearable chest straps and watches for their users. We have always taken two fingers to locate our carotid (our neck) or radial (our wrist) pulses with ease.  

Today, nearly everybody wears some Apple watch or Fitbit around their wrist to track changes in their pulse whether they are working out, sitting at their desk, or just asleep.

Heart Rate Affects Health and Performance

Understanding one’s heart rate can be rather useful, both from a health and performance standpoint.

  • Resting heart rate can provide medical professionals insight into one’s health status for age and gender.
  • In contrast, increases or decreases in exercise response provide fitness professionals feedback on one’s general fitness levels.
  • Furthermore, we can use heart rate to set training zones and prescribe programs for increased aerobic fitness.
  • Perhaps the most difficult part of the entire equation is understanding the maximum heart rate (MHR).

Even when wearing technology, MHR must often be manually entered to set proper training zones moving forward. It will track your heart rate and tell you if you’ve established a new MHR through training. 

But it is extremely strenuous to train at or near MHR, and you can never be sure that the numbers provided aren’t some anomaly.

Source:  The Redline: Getting Comfortable With Being Uncomfortable

Find Your Maximum Heart Rate?

The most commonly used method to determine MHR is by taking 220 and subtracting your age.

If you are 40 years old, then your estimated MHR would theoretically be 180 bpm.

Although some technologies are implementing more advanced methods for determining this variable, many still rely on this simple equation to predict.

While it is useful in the sense that it provides a quick and no-cost method to predict MHR, it does have some issues.

It does not account for one’s:

People often get frustrated with this estimate because it does not align with their training or expectations of how their bodies should be responding when exercising.

Still, in reality, they should use it as a guiding compass. It is not the end all be all. In fact, there are other ways to estimate MHR

Measuring Tools for  MHR 

The most accurate way to determine MHR is through a VO2 peak treadmill test, but unfortunately, it is rather time-consuming, and not everybody has access to that technology.

Fortunately, some other methods and equations appear more accurate than 220 minus age for the MHR estimate.

A 2012 research study in the Journal of Strength and Conditioning Research1 compared the relative accuracy of three equations against a VO2 peak treadmill test in overweight or obese adults, including three equations:

  1. 220 – age 
  2. 208 – 0.7 x age 
  3. 200 – 0.48 x age 

The researchers found that the 220 – age equation overestimated MHR by an average of 5 bpm, while the 200 – 0.48 x age equation estimated MHR within 2 bpm, and the 208 – 0.7 x age equation proved most accurate.

We must understand that although the research I’ve discussed used a relatively large sample size (n = 132), it is only one study and did not look at athletic populations, therefore it is still difficult to say which equation is the best one of all.

There are methods to determine training heart rate (THR), such as the Karvonen method, and we know that a VO2 treadmill test will provide us with the best results of all, but we must accept the fact again that these are all estimates.

MHR and Response to Physical Training 

My suggestion to anybody struggling to nail down their MHR truly is to use multiple methods and monitor your training results.

One formula may prove to be more accurate than another in your case, but how you respond to training will give you the greatest insights into your aerobic capacity and unique heart rate.

Lastly, if you are still truly interested in being as accurate as possible, research nearby exercise physiology laboratories and see if you can schedule an appointment to do a treadmill test.

It could be worth the investment.

References

1. Franckowiak, Shawn C., Dobrosielski, Devon A., Reilley, Suzanne M., Walston, Jeremy D., Andersen, Ross E., “Maximal heart rate prediction in adults that are overweight or obese,” Journal of Strength and Conditioning Research: May 2011, Volume 25, Issue 5, p1407-1412.

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November 12, 2020

Vitamin D Deficiency in Athletes

Vitamin D is often referenced as the sunshine vitamin since the vitamin’s primary source is attained through sun exposure. Yet, many people are vitamin D deficient.

Vitamin D is a fat-soluble hormone that plays a critical role in bone health, muscle function, adaptive immunity, and many human diseases like cancer, diabetes, and musculoskeletal health.2

Vitamin D Deficiency

In fact, vitamin D deficiency is a global public health issue.

About 1 billion people worldwide have vitamin D deficiency, while over 77% of the general population is insufficient.1 So, what does that mean if you are an athlete who plays an indoor sport, trains indoors year-round, and rarely gets outside during the day?

What if you also live in the northern hemisphere? Odds are you are not getting enough vitamin D. Insufficient sun exposure can dramatically increase your risk of vitamin D deficiency. It can lead to a variety of negative health implications and hinder athletic performance.

Research has illustrated that vitamin D significantly affects muscle weakness, pain, balance, and fractures in the aging population.1

Vitamin D plays a key role in:1

Vitamin D deficiency occurs as blood levels drop to less than 20 ng/mL (< nmol/L), while vitamin D insufficiency for athletes is defined as blood levels reaching between 20-32 ng/mL (50-80 nmol/L).

Research has indicated that 40-50 ng/mL (100-125 nmol/L) seems ideal for optimizing athletic performance.1

Who’s at High Risk?

The people at high risk for vitamin D deficiency:1,5

  • Decreased dietary intake: Certain malabsorption syndromes like celiac disease, short bowel syndrome, gastric bypass, inflammatory bowel diseases
  • Decreased sun exposure. Roughly 50% to 90% of vitamin D is absorbed through the skin. Twenty minutes of sunshine daily, with 40% of skin exposed, is required to prevent deficiency.
  • Aging adults: The ability to synthesize vitamin D decreases by as much as 75% as we age.
  • Overweight and obese individuals: Those who carry excess body fat can increase their risk of up to 55% due to vitamin D being trapped in adipose tissue and being unavailable in the bloodstream.

See the previous blog on factors that influence vitamin D levels.

Athletes Who Play Indoor Sports

Athletes who play indoor sports are at a greater risk of vitamin D deficiency.

Hockey players specifically spend a great deal of their time training, conditioning, and competing indoors, making it difficult to attain vitamin D through sun exposure. To add to the statistics, another study found that as much as 88% of the population receives less than the optimal amount of vitamin D.3

Several studies link vitamin D status to bone health and the overall prevention of bone injuries in the athletic population.

Research and Vitamin D Deficiency

Studies have illustrated that inadequate vitamin D levels are linked to a greater risk of stress fractures in young men and women published in the Journal of Foot & Ankle Surgery.4

A study published in the journal, Nutrients assessed vitamin D status among college men and women basketball players in the season. The players were either allocated a high-dose, low dose, or no vitamin D depending on their circulation 25-hydroxyvitamin D levels at the beginning of the study to identify the optimal dosage of vitamin D3 supplementation optimal status.

The findings demonstrated that 13 of the 20 participants were vitamin D insufficient at baseline. Another finding was that of the athletes sampled, and the darker skin pigmentation increased the risk of vitamin D insufficiency at baseline.

Researchers found that most athletes who were vitamin D insufficient benefited from supplementation of 10,000 IU to improve their status.5

Another study concluded black professional football players have a higher vitamin D deficiency than white players.6

The study also suggests that professional football players deficient in vitamin D may also have a greater risk of bone fractures.7

Increasing power output is every athlete’s desire as it can translate into improved performance on the field. Your muscle tissues have several key receptor sites for vitamin D, and they will help support power production.1

A study in soccer players found that increasing baseline vitamin D status over an 8-week period leads to increased vertical jump and 10-meter sprint times.9

Of course, we need further research in this area to identify the relationship between vitamin D levels and power output.

Still, the current literature is promising and that, at minimum, baseline vitamin D levels should be desired.

Sources of Vitamin D

The best vitamin D sources include egg yolks, mushrooms, fortified milk, yogurt, cheese, salmon, mackerel.8

Vitamin D rich food sources:

  • 6 oz. fortified yogurt = 80 IU
  • 3 oz. of salmon = 794 IU
  • 1 cup of fortified cereal = 40 IU
  • 1 cup of fortified milk = 120 IU
  • 1 egg yolk = 41 IU
  • 1 cup of fortified orange juice = 137 IU

Practical applications

Athletes who train indoors, consume little vitamin D rich sources and live > 35 degrees north or south may benefit from a vitamin supplement of 1,500 – 2,000 IU per day to keep vitamin D concentrations within a sufficient range.

Athletes who may have a history of stress fractures, frequent illness, pain or weakness, or overtraining signs should have their vitamin D status evaluated.

Vitamin D is best absorbed when taken with a meal that contains fat.

It is important to follow up with a physician to assess vitamin D levels further and meet with a registered dietitian to discuss nutrition intervention further.

References

1. Ogan, D., & Pritchett, K. “Vitamin D and the athlete: risks, recommendations, and benefits.” Nutrients, 5(6), 1856–1868. 2013.

2. Umar, M., Sastry, K. S., & Chouchane, A. I., “Role of Vitamin D Beyond the Skeletal Function: A Review of the Molecular and Clinical Studies.” International Journal of Molecular Sciences, 2018,19(6),1618.

3. Bendik, I., Friedel, A., Roos, F. F., Weber, P., & Eggersdorfer, M. “Vitamin D: a critical and essential micronutrient for human health.” Frontiers in Physiology, 5, 248, 2014.

4. Elsevier Health Sciences. (2015, December 14). “Low levels of vitamin D may increase risk of stress fractures in active individuals: Experts recommend active individuals who participate in higher impact activities may need to maintain higher vitamin D levels.” ScienceDaily. Retrieved October 19, 2020.

5. Sizar O, Khare S, Goyal A, et al. “Vitamin D Deficiency.” [Updated 2020 Jul 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-.

6. Sekel, N.M.; Gallo, S.; Fields, J.; Jagim, A.R.; Wagner, T.; Jones, M.T. “The Effects of Cholecalciferol Supplementation on Vitamin D Status Among a Diverse Population of Collegiate Basketball Athletes: A Quasi-Experimental Trial.” Nutrients, 2020, 12, 370.

7. National Institutes of Health – Office of Dietary Supplements – “Vitamin D – Fact Sheet for Health Professionals.” [accessed October 19, 2020].

8. Maroon JC, Mathyssek CM, Bost JW, Amos A, Winkelman R, Yates AP, Duca MA, Norwig JA. “Vitamin D profile in National Football League players.” Am J Sports Med. 2015 May;43(5):1241-5. Epub 2015 Feb 3. PMID: 25649084.

9. Close, G. L., Russell, J., Cobley, J. N., Owens, D. J., Wilson, G., Gregson, W., Fraser, W. D., & Morton, J. P., “Assessment of vitamin D concentration in non-supplemented professional athletes and healthy adults during the winter months in the UK: implications for skeletal muscle function.” Journal of Sports Sciences, 31(4), 344–353. 2013.

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