Masters endurance athletes more at risk of heart arrythmias

Introduction

Over the last 5-10 years I have become aware of a number of former elite endurance athletes having heart issues. This is counter intuitive given endurance athletes are considered to have strong hearts. However, over the last 10 years research is increasingly showing that the incidence of arrhythmias is higher in athletes, especially in elderly athletes with a lifelong training history in marathons, ultra-marathons, ironman distance triathlons and long distance bicycle races. An arrhythmia is any change from the normal sequence of electrical impulses in the heart. The electrical impulses may happen too fast, too slowly (bradycardia), or erratically so that the heart can’t pump blood effectively.

Bradycardia, defined by a resting heart rate <60 beats min−1, is the most frequent rhythm disturbance in response to endurance training where the resting heart rate can be ~30 beats min−1 and even lower at night. Cyclists Sir Chris Hoy and Tour de France winner Miguel Indurain reportedly had resting heart rates of 30 and 28 beats per minute. Although the bradycardia is usually a harmless adaptation to endurance training, it can become a pathological condition. It was previously thought to affect the electrical activity of the heart that starts in what is called the sinus node (see photo) which is an area of specialized cells in the upper right chamber of the heart that controls the rhythm of your heart.

The most compelling evidence of a link between endurance training and sick sinus syndrome comes from a study of former professional cyclists. Their average heart rate was lower, sick sinus syndrome was more frequent, and pacemaker implantation for bradyarrythmias was more frequent relative to a control group with matched cardiac risk factors. Similarly, a high incidence of pacemaker implantation has been reported in elderly marathon runners.

Historically, this slowing of the heart rate was thought to be the result of a change in the nervous system stimulation of the heart muscle through the sinus node, the pacemaker structure in the heart muscle itself. However, a recent animal study is the first to show that the heart rate adaption to exercise training is not the result of changes in this nervous system control of the heart, and instead is primarily the result of a training-induced remodelling of the sinus node within the heart itself.

Methods

Rats were trained for 12 weeks (1 hour per day, 5 days per week) by aerobic interval training (uphill running) alternating between 4 min at 85–90% of the maximum oxygen uptake and 2 min active recovery at 50% of maximum oxygen uptake. Experiments were also carried out in mice that were trained for 4 weeks (1 hour per day, twice a day, 7 days per week) by swimming. Resting heart rates, electrical activity of the heart, as well as actual tissue samples from the sinus node of sedentary and trained animals were analyzed.

Results

The resting heart rate of the trained rats and mice was ~26% and ~20%, respectively, lower than the heart rate of untrained animals. The resting heart rate of exercise-trained human subjects in various studies varies between ~17–26% lower than the heart rate of inactive people, a reduction similar to that observed in the animal models in the present study. This decrease is less than in elite human athletes. However, severe bradycardia or heart rate slowing in human athletes is uncommon. A protein found in the sinus node (the heart’s pacemaker) changed in response to training with a decrease in an important pacemaker protein, known as HCN4, a protein that is responsible for the low heart rate seen in fit animals.

So What?

With lifelong endurance training, research has consistently shown that veteran endurance athletes have a higher incidence of sinus node disease and artificial pacemaker implantation than normal individuals. Historically, we always believed this was due to changes in the nervous system stimulation of the heart. The present study, although done on rats and mice, suggests the slowing of the heart rate may be due to actual remodeling of the sinus node in the heart wall that actually stimulates the heart muscle to beat. The researchers believe that this finding may also help explain syncope (fainting) in the young athlete as well as other heart rhythm disturbances in older athletes including atrial fibrillation, heart block, bundle branch blockand even sudden cardiac death.. They suggest that it is likely that these disturbances may be the consequence of an actual remodeling of other parts of the heart that are responsible for electrical activity in the heart and perhaps in combination with a pre-existing heart condition in the case of sudden cardiac death.

Critically, the researchers suggest endurance exercise is undoubtedly beneficial for the cardiovascular system, but at the same time intense endurance training over many year can have harmful effects, especially in elderly athletes with a lifelong history of training and competing in endurance events like marathons, triathlons and ironman. They conclude that although endurance exercise training can have harmful effects on the heart, it is more than outweighed by the beneficial effects. Importantly, the researchers also know that this animal study’s findings need to be reproduced in humans and that more research is needed before we could draw conclude that too much endurance training is bad for the heart health of veteran athletes who have undertaken years of endurance training.

Source: D’Souza, A. and others (2014). Exercise training reduces resting heart rate via downregulation of the funny channel HCN4. Nature Communications, 5, Article 3775.

Rain affects performance in the cold

Introduction
Environmental factors such as heat and cold, humidity, wind and altitude influence the performance of athletes young and old, especially endurance athletes. While their have been plenty of studies examining the effects of these factors on performance, little research has ever been done to examine the effects of rain on performance, especially in the cold. The present study aimed to determine energy metabolism while running in cold, wet conditions using a climatic chamber that precisely simulated rainy conditions.

The Research

Seven healthy (trained 3 times per week) men (23.3 ± 2.9 years; 168.6 ± 7.5 cm; 65.9 ± 8.1 kg; VO2max 52.0 ± 5.7 mL/kg/min) ran on a treadmill at 70 % VO2 (about 82% max heart rate) intensity for 30 min in a climatic chamber at an air temperature of 5°Celsius in the presence or absence of 40 mm/hr of very heavy rain. Expired air, oxygen consumption, oesophageal (down the throat and into the gut) temperature, heart rate, skin temperature, rating of perceived exertion and blood samples (lactate, glucose, adrenalin [stress hormone] and noradrenalin [increases heart rate]) were measured before the 30 min run and every 10 minutes of the 30 min test.

The Results

Oesophageal (body) temperature and average skin temperature were significantly lower in the rain condition than in the non-rain run. The amount of air breathed per minute, oxygen consumption used during the run, and levels of blood lactate and noradrenalin were significantly higher in rain. In conclusion, the higher oxygen consumption and plasma lactate in rain indicated that energy demand increases when running in cold and wet conditions.

So What?

This study is one of the first to suggest that rain has a strong effect on endurance performance, especially in the cold. The higher blood lactate, higher oxygen consumption and ventilation volumes all suggest that glycogen energy stores will be used up more quickly too. This suggests making sure that if we race or train hard in the cold (and wet), that we carbohydrate load well before training or racing, replace carbs during longer (> one hour) training and racing, and ensure we replace carbs more aggressively after training and racing to recover.

For more specific ‘bridging the gap’ tips on training in the cold or heat see chapter 11 of my book The Masters Athlete. For more on carbohydrates before, during and after training or racing, see chapter 16 of The Masters Athlete.

Source: Ito, R. and others (2013) Effects of rain on energy metabolism while running in a cod environment. International Journal of Sports Medicine, 34(8): 707-711.

Fitter Men Live Longer

Introduction

It pays to invest in aerobic fitness into older age with the dividend being extra years added to your life. A long-term study from the USA has just found that men who scored highly on aerobic fitness while in their 40’s and stayed fit into their 50’s were 30% less likely to die over the next decade than their unfit mates. The same study also found that men who improved their endurance fitness over that time lowered their risk of death by 40%.

The Research

The researchers examined the separate and combined relationships of changes in endurance fitness and body mass index (BMI)  with death rates from both all causes and death rates from cardiovascular disease (CVD) in 14,345 men (average age 44 years). Fitness was estimated from maximal treadmill test. Changes in fitness and BMI were tested after 11 years and the men were classified into loss of fitness, stable fitness, or gain in fitness groups.

The Results

At the time of the last test, 914 of the men had died from all-causes and 300 from CVD. The men who had maintained fitness showed a 30% lower risk from all causes and 27% lower risk of dying of CVD. However, the men who improved their endurance fitness lowered their risk of all-cause death by 40% and CVD death risk by 42% compared to the men who lost fitness. Crucially, for every 5-10% improvement in aerobic fitness, the risk of death dropped 15% and 19% for all-cause and CVD death, respectively. Moreover, aerobic fitness was far more important than BMI change in determining the risk of death.

So What?

Yet more evidence that we masters athletes need to stay active into older age. Masters endurance athletes know how important aerobic exercise is for both quality and quantity of life. Interestingly, our power / strength and team playing colleagues also benefit from the relatively smaller changes these type of training have on aerobic fitness.  So stick with it team!

For more information on successful aging and what science says are the keys to successful aging, see Chapter 1 of my book The Masters Athlete.

Source: Lee, D.C. and others (2011). Long-term effects of changes in cardiorespiratory fitness and body mass index on all-cause and cardiovascular disease mortality in men: the Aerobics Center Longitudinal Study. Circulation 124(23): 2483-2490.

Running injuries – what does the science say about preventing them?

Concensus on Short-Term Endurance Training Methods?

Introduction

In late 2009, the University of Copenhagen in Denmark and Team Danmark bought together the leading sport scientists in the world that were focused on high-intensity sport events lasting less than eight minutes in duration or team sports where frequent bursts of high intensity were needed. Such events require training that is a balance between high volumes and high intensity but is also technical as well. The objective was to develop consensus statements on preparing athletes for such events or sports. This article summarises the recently published outcomes of the three-day meeting of the minds.

The Consensus Statements

The meeting focused on high intensity sports lasting less than eight minutes (e.g. track running and cycling, 200 and 400m swim events, rowing, kayaking etc). Here is a summary of what they decided:

  1. Athletes should perform high–intensity interval training.
  2. These intervals should consist of repeated bouts of exercise performed close to or well above the intensity requiring maximal oxygen uptake (VO2max).
  3. Athletes should taper before major competitions by emphasising intensity of training at the expense of training volume.
  4. Heavy resistance strength training enhances performance in high-intensity sports.
  5. Heavy resistance strength training without muscle growth enhances endurance capacity in high-intensity sports or events lasting from a few minutes to several hours.
  6. Concurrent strength and endurance training prevents muscle growth but facilitates improved endurance capacity.
  7. Heavy training loads of 4-12 repetitions of 70-95% of maximum load are suggested.
  8. Adequate dietary carbohydrate and energy intake are essential for high-intensity training sessions.
  9. Small amounts of high-quality protein should be consumed soon after high-intensity training or events to enhance recovery and adaptation.
  10. Promote and monitor non-sport recovery strategies to enhance physical and mental recovery.
  11. Focus on long-term athlete development rather than short-term success.
  12. Create a social environment with open communication and a cohesive training group.
  13. Support athletes to balance sport, education, family and personal life.

Reference: Bangsbo, J. and others (2010). Performance in top sports involving intense exercise.  Scandinavian Journal of Medicine and Science in Sports. 20 (Supplement 2): ii-iv.