As I write this blog, we seem to be rapidly heading towards the end of the year and you’ll no doubt be starting your winter training ready for next year. Although most of us approach those cold, wet winter training sessions with a sense of foreboding, this is arguably, the most important phase of your training. It will help lay those strong foundations for you to build on as the new year and spring arrives.

This initial phase of your training tends to be called AEROBIC BASE TRAINING and can last 2-5 months depending on your own fitness levels and the event you’re training for next year.

It doesn’t matter whether you’re a runner, cyclist or triathlete, your aerobic base training period will share the following characteristics:

  • Develop your aerobic fitness and improve endurance

  • The training volumes are likely to be high (but controlled)

  • The majority of your training will be at an easy/moderate training intensity

  • Predominantly involves the recruitment of slow twitch (type I) muscle fibres

  • You will get cold and wet!


There are a number of good reasons why these long, slow sessions should form the bedrock of your training. Your body is truly amazing and will initiate a number of physiological changes designed to improve your aerobic energy system and help your body cope with the higher intensity training (i.e. threshold training) as your event or race season approaches. Some of these adaptations include:

A big heart!

  • An increase your maximal oxygen uptake (VO2max) – this increases the amount of oxygen available for the aerobic production of energy which is key for endurance performance

  •  Increase in total blood volume – this results in a greater amount of blood pumped out by the heart in each beat

  •  Increased haemoglobin content – this improves the oxygen carrying capacity of the blood

Become a lean, mean efficient endurance machine

  • Increased ability of the muscles to extract oxygen from the blood

  • Fuelled by fat – develop an improved ability to utilise fat as an energy source which helps spare your stores of muscle glycogen

  • Possible improvements in biomechanics – long training sessions result in continued repetitions of complex neuromuscular movement patterns. For runners, this will utilise the majority of major muscles and joints within the body and could make you a more efficient runner. For cyclists, this may mean experimenting, and becoming more comfortable working at a higher cadence. Either way, the outcome means you use less oxygen at a given speed or pace.

  • Stronger connective tissues and increased muscle stiffness - increases the energy stored by the tendons resulting in more energy returned on each step and making you a more efficient runner

Keep cool when the going gets tough!

  • Long duration training can also help improve thermoregulation - this is the way in which your body copes with the increasing internal body temperature which occurs during long duration exercise.

  • Mental toughness – running for prolonged periods of time can help you develop psychologically as well as physiologically. Learning how to train your mind into coping with the increasing distances is very important as well as learning how to control your pace so you don’t utilise your stores of muscle glycogen too quickly.


So, you can see from the above that this aerobic base training phase is really important. It may not be exciting or very glamorous…..and to quote Winston Churchill:



 Seriously though, this phase of your training is important. Going long, and going slow will allow you to complete high training volumes whilst mitigating the risk of accumulating fatigue and over-training. Your current fitness and experience will dictate the starting level of any aerobic base training and so ‘long duration training’ is a relative term.

Going forward, this long, low intensity training will still make up 70-80% of your overall training load in order to provide the optimal stimulus for endurance adaptation. The remaining 20-30% will be higher intensity and threshold training. 

I’m here to guide and support you through this training phase so if you have any questions then please feel free to contact me. Good luck with your training this autumn and winter.