As climbers, our sport demands a unique combination of strength and endurance. It's common to try to work on both qualities in our training routines, whether in the same session, the same day, or throughout the week. This practice is known as concurrent training, and while it can boost our performance, it can also generate a less desirable phenomenon: interference.

In this post, we'll unravel what concurrent training is, how it can affect us, and—most importantly—what strategies we can apply to maximize our benefits and minimize possible drawbacks, always thinking about our performance on the wall.

What is concurrent training and what are its effects?

Concurrent training is the combination of strength and endurance training within the same physical conditioning program. Its effects can be of two main types:

Potentiation: One type of training can enhance the results of the other, achieving positive synergies.
Interference: One type of training can diminish the benefits of the other, reducing the effectiveness of the time invested.

These effects are observed when the trainings are performed in close temporal proximity, whether in the same session, on consecutive days, or within the same microcycle.

The interference phenomenon: why does it occur?

Interference translates into a reduction in training effectiveness, where strength and endurance adaptations counteract each other. It is mainly attributed to two interrelated factors:

Opposing Adaptations:
- Endurance training stimulates mitochondrial biogenesis, increasing the muscle's ability to use oxygen (oxidative capacity).
- Strength training (especially oriented toward hypertrophy) increases the thickness of myofibrils. This muscle growth can, paradoxically, hinder the diffusion of oxygen and nutrients, compromising metabolic efficiency.
- Additionally, each type of training does not optimize the adaptations of the other; endurance does not generate significant muscle growth, and strength does not optimize the vascular and metabolic adaptations of endurance.
Residual Fatigue:
- Endurance training can generate metabolic fatigue that limits the ability to perform subsequent high-intensity strength training.
- Strength training can cause neuromuscular fatigue that affects performance in subsequent endurance activities, though to a lesser extent.

When and who experiences more interference?

Interference occurs when strength and endurance stimuli are combined in close proximity. However, it's crucial to understand that interference effects are more pronounced in high-level or trained athletes, while in untrained or beginner populations, they are barely noticeable. This highlights the importance of more careful planning for advanced climbers.

According to Docherty and Sporer (2000), there are degrees of interference:

Low interference: Occurs when combining moderate-intensity endurance (below 90% of VO2max) with high-intensity, low-volume strength, aiming for neuromuscular adaptations. Low-intensity, long-duration aerobic training barely affects strength adaptations.
High interference: Occurs when mixing high-intensity endurance (close to Maximal Aerobic Power) with strength training oriented toward hypertrophy (heavy loads with high repetition volume). Short-duration, high-intensity workouts like HIIT can also have a greater impact on strength adaptations.

In fact, interference is greatest in the expression of power (RFD) and less in the expression of maximal strength. Additionally, the volume of endurance training negatively affects interference.

Concurrent training in climbing: when does interference occur?

Although there is no specific scientific evidence in climbing regarding the effects of concurrent training, we can infer when this interference might occur based on other sports:

At the local level (especially in the finger flexors), interference would occur when simultaneously working on:

Hypertrophy stimuli: Characterized by high intensities (70%-80%), near muscle failure, and may include stretch-shortening cycles.
Non-oxidative glycolytic or fast oxidative endurance stimuli: These involve high-intensity contractions followed by brief rests, aiming to stimulate oxygenation and phosphagen replenishment.

This means that, for example, attempting a weighted hang session for hypertrophy and, shortly after, an intense circuit session for specific endurance in the same musculature could generate interference.

Strategies to minimize interference in your training plan

For climbers, planning is key to optimizing the benefits of concurrent training. Here are the main strategies:

Temporal Separation:
- If you do both types of training on the same day, a minimum interval of 6 hours between strength and endurance sessions is recommended.
- Ideally, sessions should be separated by 24 hours when possible.
Weekly Frequency:
- For high-performance athletes, it is suggested to limit concurrent sessions to 1-2 per week.
- In untrained or moderately active individuals, 2-3 concurrent sessions per week are acceptable.
Training Sequencing (Order):
- If your main goal is to develop strength: Do strength training before aerobic endurance training. This minimizes the catabolic effects of endurance training on hypertrophy.
- If your main goal is to develop endurance: Prioritize endurance training before strength training. Although this order does not seem to have as significant an impact on endurance performance, it can avoid the interference effects of prior high-intensity strength training.
Consider Muscular Specificity:
- Interference mainly occurs when the same muscle groups are worked in both types of training. For example, if you train shoulder hypertrophy and endurance in the finger flexors, interference would be low.
Avoid Double Specific Objectives:
- Avoid sessions with the dual goal of strength via hypertrophy along with non-oxidative glycolytic or fast oxidative endurance in the same muscle groups, such as the finger flexors.
Attention to Training Level:
- Recognize that at low-to-medium performance levels, interference effects are less pronounced, so they do not require as much attention as in elite athletes.

Conclusion: Train Smart

Concurrent training is a reality in climbing, but its effectiveness depends on how we plan it. Understanding the mechanisms of interference and applying strategies of temporal separation, proper sequencing, and control of volume and intensity will allow you to optimize your adaptations. This way, you can continue developing that explosive strength, endless endurance, and the ability to send that you long for, all in a more efficient and safer way!