Concurrent training: Building the hybrid athlete

Most sports require athletes to possess well developed
aerobic systems as well as high levels of strength and power. Training for both
of these systems at once is referred to as concurrent training and with poor management,
this can lead to lack of recovery, overtraining and an interference effect where
training for one system hinders performance of another system. Early research from
Hickson (1980) found that strength performance was hindered during concurrent training
programs and this has since been backed up both anecdotally and through further
research. This interference effect explains why historically, a large amount of
gym goers avoid cardio and why many endurance athletes view strength training
as detrimental to performance. Other studies however, have found no evidence of
interference. It appears that factors within a study such as; mode of exercise,
frequency of training, recovery, and background of participants play a large
role in whether an interference effect is observed (2).

This concurrent training model isn't just for athletes with
a direct requirement for both systems. A solid foundation of aerobic capacity
will benefit those training for strength and size with improved recovery and general
athleticism, whilst strength training will add to the robustness and movement
efficiency of the endurance athlete. In this article we will explain why this interference
effect occurs and how you can minimise this effect to get the most out of both strength
and aerobic systems.

Mechanisms of the
interference effect

Whilst research on
the interference effect is not conclusive, a number of potential mechanisms
have been proposed.

Motor unit recruitment: Endurance training has been shown to hinder the neural pathways utilised
within strength and power activities.

Overreaching:
A common mistake is to simply add aerobic training to a training program
without making adjustments to strength training. This results in a higher total
stress and workload, therefore, increasing the risk of overreaching.

Enzyme activation: Resistance training triggers the activation of mTORC1, an enzyme
responsible for regulating protein synthesis. Endurance training activates
enzyme AMPK, which inhibits the activation of mTORC1, therefore, limiting
protein synthesis.

Key considerations

When it comes to building the hybrid athlete, two of the key
programming considerations include recovery and mechanical stressors.

Recovery

When designing your concurrent training program, careful
consideration of training loads and training frequency will allow you to recover
between sessions, manage training stressors and maximise adaptive response to
training. Fatigue from endurance training has been shown to limit strength
performance through an acute reduction in motor unit recruitment, protein
synthesis, and a depletion of glycogen stores (2).

To reduce the negative effect of fatigue, athletes should
aim to separate sessions by as much time as possible. This allows time for
glycogen replenishment and for AMPK activation to ‘switch off' avoiding any hindrance
to protein synthesis. Ideally endurance and strength sessions should be
completed on separate days however this is not always practical. In this case it
is recommended that at least 6 hours gap is provided between sessions (3).

Mechanical stress

When choosing your mode of aerobic exercise it is important
to look at your current lifting routine to allow for a variety of mechanical
stressors. Different types of cardio will lead to different levels of trauma to
muscles, tendons and bones which must be considered. Keeping this in mind,
lifters should look to include cardiovascular activity which applies a
different type of mechanical stress. For example; hill sprints on day 1 will likely
decrease performance in a squat on day 2, whilst a swim or cycle on day 1 may
allow for more total work to be completed.

Practical implications

When looking to design a concurrent training plan in order
to minimise the interference effect, it is important that our plan prioritises
recovery. Whilst there are many training models that one may implement, when it
comes to optimising recovery and categorizing training based on stress, I
favour the high-low method popularised by sprint coach Charlie Francis. Within
this method, high intensity stimuli and low intensity stimuli are performed on
separate days while similar stimuli are grouped together. For example, one day
may include sprints and heavy lifting, while low stimuli days may include tempo
runs and light circuit work. As a general rule, methods completed on high days
require 48-72 hours for full recovery. The idea behind this model is that ‘medium’
sessions are not intense enough to stimulate adaptation, yet too intense to
facilitate recovery.

The model (shown below) proposed by Docherty & Sporer
(2000), identifies complimentary modes of training and attempts to predict whether
certain protocols are likely to be affected by the interference effect (4).

Within this model we see that interference is most likely
when both cardio and resistance training target the peripheral system and place
large metabolic demands on the muscle. High intensity cardio and neural focused
(<5RM) resistance training are seen as compatible, while continuous cardio at
less then 80% VO2max should not affect strength regardless of rep range.

Taking these models, one can then plan their training week
to ensure complimentary stressors are paired together and plan for recovery
time between sessions. Below is a simple 4 day training week which allows plenty
of time for rest and regeneration between sessions.

Those wishing to train more frequently should allow a
minimum of 6 hours between training conflicting systems and focus on rest and
nutritional replenishment.

In summary, those looking to implement a concurrent training
program should consider timing between sessions, nutritional replenishment and complimentary
modes of training as 3 of the most important factors to minimise the interference
effect.

References

1. Hickson,
   R. C. (1980). Interference of strength development by simultaneously training
   for strength and endurance. European journal of applied physiology and
   occupational physiology, 45(2-3), 255-263.

• Blagrove,
  R. C. Programmes of concurrent strength and endurance training: How to minimise
  the interference effect. Part, 1, 7-14.

• Robineau,
  J., Babault, N., Piscione, J., Lacome, M., & Bigard, A. X. (2016). Specific
  training effects of concurrent aerobic and strength exercises depend on
  recovery duration. The Journal of Strength & Conditioning Research, 30(3),
  672-683.

• Docherty,
  D., & Sporer, B. (2000). A proposed model for examining the interference
  phenomenon between concurrent aerobic and strength training. Sports
  medicine, 30(6), 385-394.