Low-intensity training, also known as base endurance, deserves special attention. It is clear that achieving high performance in triathlon requires sessions at race pace or higher. However, it may seem paradoxical to train at a slow pace to improve competitive performance.
This article explores how these sessions, while less spectacular, lay the foundation for sustainable performance by optimizing athletic potential in the long run.
Published in Trimax Magazine – March 2020, written by Jean-Baptiste Wiroth
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Definition of Very Low-Intensity Training
Very low-intensity training involves exercising at an intensity below the first ventilatory threshold (VT1), which roughly corresponds to the first lactate threshold. In terms of heart rate, this training zone typically falls between 60–70% of maximal heart rate for most athletes.
From an aerobic power perspective, training at a slow pace aims to produce an effort equivalent to 50–60% of maximal oxygen consumption (VO₂max)—a level far from peak performance!
For athletes who prefer to rely on their sensations, very low-intensity training is characterized by easy and relaxed breathing—you should be able to have a conversation effortlessly while running or cycling. On a muscular level, these sessions cause no peripheral discomfort, at least for the first two hours.
Why Train at a Slow Pace?
The benefits of low-intensity training are numerous, especially at the beginning of the season when most athletes are building their foundation for triathlon performance.
1. Faster Recovery
These sessions generate relatively little fatigue, allowing for consistent daily training and even twice-daily workouts without excessive strain.
2. Improved Capillary Network
From a vascular perspective, low-intensity training promotes the growth of capillaries through a process called angiogenesis. As blood flow increases, these tiny blood vessels multiply, enhancing the delivery of oxygen and nutrients to muscle fibers deep within the tissues. A well-developed capillary network also facilitates the efficient removal of metabolic waste products such as lactate.
3. Increased Stroke Volume & VO₂max
On a cardiac level, low-intensity training increases stroke volume (SV)—the amount of blood ejected by the heart per beat. Since cardiac output (CO) is the product of stroke volume and heart rate (CO = HR x SV), a higher stroke volume leads to an increased VO₂max, meaning better oxygen delivery and improved endurance capacity.
4. Enhanced Metabolic Efficiency
Low-intensity training stimulates the growth of mitochondria, the tiny energy powerhouses within muscle cells. Over time, your body becomes more efficient at using fat as fuel while preserving its limited glycogen stores—a crucial factor in endurance performance.
5. Low Risk of Overtraining
Since these sessions generate minimal fatigue, the risk of overtraining is low, as long as the training duration remains within typical limits:
- 1–1.5 hours for swimming or running
- 1.5–3 hours for cycling
By integrating low-intensity training into a structured plan, endurance athletes can build a strong foundation for long-term performance while reducing the risk of overtraining and injury.
Which Exercises?
Base endurance training can be implemented in various ways:
- Long sessions are the cornerstone of endurance training. They apply to open-water swimming and running but are particularly crucial in cycling, where sessions can last up to 5–6 hours.
- Warm-up phases should always include 20–30 minutes of progressive effort in a base endurance zone before moving on to more intense work. 30 minutes is the minimum time required to activate lipolysis (fat metabolism) and prepare the body for higher exertion.
- Active recovery and cool-down phases after interval sessions should include 10–15 minutes of very easy movement in the base endurance zone. This helps to optimize muscle recovery and brings body temperature back to a relatively normal level.
- Technical training sessions should always be built on a foundation of base endurance. This is especially true in swimming, where the body is supported by the water, allowing for focused and controlled effort without excessive fatigue.
Conclusion
Very low-intensity training is a fundamental element in triathlon preparation, particularly for long-distance specialists and high-performance athletes. However, to fully maximize its benefits, it should be combined with other training methods, including:
- Interval training
- Strength training
- Stretching and mobility work
- Altitude training
By integrating these elements strategically, athletes can optimize their endurance potential and long-term performance.
The Expert Answers
“I’m considering commuting to work by bike (5 km each way) starting in the spring. Does this count as part of my training volume?”
While commuting by bike or walking isn’t technically structured training, active transportation plays a valuable role in building endurance foundations.
In your case, covering 10 km per workday would amount to approximately 250 km per month, which is statistically significant in terms of accumulated mileage! Maintaining this routine throughout the year (excluding holidays and off-days) would result in around 2,500 km annually, which is a substantial contribution to your physiological endurance capacity.
References
- Olfert IM et al. Advances and challenges in skeletal muscle angiogenesis. Am J Physiol Heart Circ Physiol. 2016 Feb 1;310(3):H326-36.
- Romijn, J. A., Coyle, E. F., Sidossis, L. S., Gastaldelli, A., Horowitz, J. F., Endert, E., et al. (1993). Regulation of endogenous fat and carbohydrate metabolism in relation to exercise intensity and duration. Am. J. Physiol. 265, E380–E391.