Some Physiology: Preload, Mitochondria and Endurance

Gorge-Paddle-Challenge-2013-3Like most of you I don’t have time this week (or many weeks) to put in the miles of training that could definitely build my endurance. I understand the correlation between heart rate (and the underlying volume and force of blood flow) and endurance training. During the next 8 weeks before the Colombia Gorge Paddle Challenge (8 miles down wind and a 5 mile course race) training I hope to enhance additional variables – the preload and mitochondria.

For example, when your muscles contract, they propel the flow of blood traveling through your veins and back to heart, which increases the amount of blood filling your heart (this is called a preload). This preload actually enhances the heart’s stroke volume during exercise, making adequate contraction and strength of your skeletal muscle a major determinant of your endurance performance . I’m gonna need that for both the down wind and the course race.

gorge-downwindThat’s not all. Tiny powerhouses in your cells called mitochondria use oxygen to manufacture high levels of ATP energy via the breakdown of carbohydrates or fat. So if you increase your mitochondrial density, more energy becomes available to your working muscles, which allows you to produce higher amounts of force for longer periods of time. In addition, your actual VO2max (the maximum amount of oxygen you can deliver to your muscles in a given amount of time) is a result of two variables:

1) how much blood your heart can send to your muscles (a combination of the heart rate, stroke volume and heart contractility you already learned about)

2) how much of the oxygen sent to your muscles is actually extracted from the blood and used by the muscles before the blood heads back to your heart.

Whole body (panaerobic) strength-endurance - 1987

Whole body (panaerobic) strength-endurance – 1987

In the 1980’s I was the national education director for a program called Heavyhands. It was a method of using light handweights in a variety of movement patterns that engaged about 80% of trunk, arm and leg muscles in an aerobic level. When such a large percentage of muscles were engaged and moving blood and oxygen in the body the perceived exertion at high intensity levels was less than the same intensity with fewer muscles involved (like running or cycling).

In one study (1) 4 repetitions of 4-minute runs at 90%–95% of heart rate maximum, followed by 3 minutes of active recovery, performed 3 days per week for 8 weeks resulted in a 10% greater improvement in stroke volume compared to long, slow distance training 3 days per week for 8 weeks. This is good for me because that series takes about 40-45 minutes including a cool down. It’s an easy lunch hour session 3 days a week.

Another study (2) showed that that high-intensity intervals performed at 90%–95% of VO2 max increased left-ventricle heart mass by 12% and cardiac contractility by 13% – and these are two other significant determinants of cardiovascular capacity and oxygen delivery during exercise.

Good paddling technique requires the engagement of trunk and legs in addition to arms, so it is an ideal exercise to build the fitness described above – and it is my sport! On non-paddle days I will use TRX system and a variety of Heavyhands workouts (link to come) and 3-4 days of yoga.

Engaged core and controlled movement protects back

Engaged core and controlled movement protects back

My plan for 3 times this week: (Building and mixing it up throughout the next 7 weeks until my event

-Start @ 4 x 30 seconds maximum sprints, with two to four minutes easy paddling after each sprint working on a good reach and catch,

Next I will do @4 X 90 second paddles at 85-90% HR max with 60 seconds of easy paddling after each sprint


  1. Helgerud, J., et al. 2007. Aerobic high-intensity intervals improve VO2max more than moderate training. Medicine and Science in Sports and Exercise, 39 (4), 665-71.
  2. Slørdahl, S.A., et al. 2004. Atrioventricular plane displacement in untrained and trained females. Medicine & Science in Sports & Exercise, 36 (11), 1871-75.

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