What is Interval training?
Interval training is when you do short burst of exercise normally at high effort reps with rests in between. You can do low interval training but normally when people talk about interval training they talk about high-intensity interval training (HIIT) which is when you are working between 80-100% of your heart rate. You can also do sprint interval training which is when you go flat out an therefore at 100% of your VO2 max or effort for all the reps in the session. (Weston et al 2014) There are many different of types but a simple example is run for 2 minutes walk or rest for 2 minutes and repeat. The idea with interval sessions is to push yourself with each reps then allowing yourself the chance to recovery before having to repeat it again rather than just going continuously. Ideally you want to run the last rep at least as fast as the first one, so pacing is important. The intensity of the reps should be at least around 85% of your max on average obviously each rep may differ a little. Obviously it will be normal to fatigue as you progress through the session but the recovery in between should be long enough to allow your heart rate and breathing to return to normal.
Interval sessions can vary depending on your goals, fitness and the distances your training for, but the basic structure is the same. You can also alter the speed and the intensity with each rep as well as the rest that you have between each rep. There are two ways to structure your interval training you can either do it by distance or by time. Distance is easy if you have access to a running track or have a GPS watch. You can use a mobile apps if you are doing shorter intervals, however I am not convinced they are as accurate compared to the longer distances. I have used my Garmin for Fartlek and interval training before and it has worked very well there a separate setting where you can plug it all in. For more information look at my review post on my garmin to see how I use it. I have done all the examples in terms of running as I am primarily a runner and have the most experience in this sport. However you can adapt this structure for a range of other cardiovascular sports such as cycling or rowing.
You want to include a warm up before each session, for more information about the benefits of warming out look at my previous blog post. I train for middle distance running so my warm ups are around 1.5-2km but they will vary on what discipline and sport you are training for.
- Pyramid structure: 200m,300m,400m, 500m, 300m, 200m (As you can see the distances build up and then they drop down again)
- Two sets of x2 – 500m 3 minutes rest
- Three/four sets of 200m x3 with 100m walk recovery
Cycling: 60 seconds efforts at 85-90% of HR/ efforts with 60seconds recovery. (Weston et al 2014)
Different types of interval training:
Fartlek means “speed play” in Swedish and as it says on the tin it’s used to improve your speed in training. They are often a little less intense or can be than an average interval workout but that obviously depends on how far you push each rep and how little recovery you give in between. You can a fartlek session by either time or distance depending on whatever is easiest for you. It is then followed with a easy jog or walk in between the reps. The recovery for fartlek is either a walk or a jog, the difference between this and normal interval training is that you keep moving even in the recovery period. Therefore a for intense work out would have a jog in between the reps compared to a walk. The idea is to mix up the pace and intensity as well as increase your general cardiovascular fitness at the same time. The session can have less structure as you don’t have to stick to a certain pace for each rep and you can take longer or slower recovery if you need to as well.
- Warm up – 5 mins easy or 1.5 jog, 15-30 secs fast sprint X12 with a jog back to where you started as a recovery, then another 1.5km/ 5 min easy jog to warm down.
- Warm up: 1.5/2km, X4 – 200m sprint with 100m walk recovery then 400m walk/jog, then repeat the X4 – 200m sprint with 100m walk recovery then warm down 1.5/2km.
- Coach to 5km: Many people would have heard of this 9 week plan and it is very much structured round and interval training structure. It starts with a 5 min walk up and reps of 60 secs jogging then 90 seconds walking for 20 minutes as you go through the programme it will build up to running continuously but not till the end of the 6th week.
The reps can vary if you are training for shorter distances you can vary the reps between 1 min- 15 sec intervals. If you are training for longer distances you can do longer reps with the total mileage for the session ranging from 6-10 miles. You can also change the jog recovery to walks as well depending on your fitness and the intensity of your reps.
Hill reps are normally done in a fartlek structure as generally you use the recovery to come down the hill before climbing back on it. The structure of the session will obviously depend on the hill itself, the incline as well as the length of the hill. You can also incorporate hills into your normal interval runs rather than just doing a straight hill session.
Warm up and warm down of: 1.5km easy pace
- Short Hills (50-80m): Two sets: 6 runs up the hill when a jog recovery. You can take a short break in between the different sets.
- Long Hills (100-120m): 8-10 runs up the hill with a jog recovery.
Spin classes are a form of HIIT on an indoor bike run by an instructor the class will also be set to music. It is accessible for all levels of fitness you don’t have to be uber fit to join as you can go at your own pace and control the resistance on the bike. The research points to cycling on average 15-30 miles and burning around 400-600 calories in a 40 minute class. The classes have grown in popularity and are a very good way of increasing your fitness. I often use spin classes as a way of cross training for running as it allows me to have a good work out without putting as much stress on my muscles.
What are the benefits to interval training?
There is many benefits to interval running and they range from physiology effects to the muscles themselves as well as increasing the cardiovascular fitness, other benefits include the shorter length of sessions without losing the benefits. There is a study by Bartlett et al 2011 that states despite it being perceived as a more intense and challenging workout HIIT running is actually more enjoyable than continuous running.
Length of time:
Interval training at both low and high intensity is a very time efficient way of training and can mean that you can get tough workout done a lot faster than the equivalent mileage if you were to do it continuously. (Gibala et al 2014) McMaster University, Canada found that a session of 20 minutes three times a week would be equal to 10 hours of steady exercise in two weeks. So in a world where time is of the essence HIIT is defiantly a good option in order to still get a good training session in. The recommended guidelines by the ACSM (American College of Sports Medicine) is that you do 150 minutes of moderate exercise per week however if you do exercise at a high intensity then the figures are actually halved to 75 mins instead.
Increasing cardiovascular Fitness:
While weights training is normally split into intervals in terms of reps and rests in this article I am mostly talking about interval training in terms of cardiovascular exercise whether it be swimming, cycling, rowing, running ect. Therefore one main feature will always be to increase your cardiovascular fitness.
One way of measuring your cardio fitness is through your VO2 max you can read more about VO2 max on my other blog post. The study by Bacon et al 2013 showed that interval training does increase your VO2 max and research points to it being more efficient than just going for a continuous session. It on average can increase your VO2 max around 0.51 L a min or 19% after 4 weeks of interval training. Ma et al. (2013) It seems the general rule that the longer the intervals the more effective.
Another main reason to do interval work is to work on your speed as you will be working at a faster and high intensity. It will train your body to work more efficiently and get used to working at higher speeds. In turn this should mean that that your continuous paced sessions should feel a lot easier. Speed intervals at 100% effort for 30 secs has been shown to be just as effective in terms of cardiac capacity as training sessions that consist of training at a moderate but continuous level. Gist et al 2014.
Affects on skeletal muscle:
It was found that HIIT in cycling produced the same effects as continuous training session in regards to the increasing the efficiency of oxygen uptake to muscle as well as increasing the muscle buffering capacity, which is the rate at which our bodies are able to get rid of the build up of lactic acid from exercise. A study by Terada et al. (2001) in swimmers has also shown similar levels of improvement in muscle adaptation in low intensity interval training. One study by Edge et al (2006) suggested an increase of around 25% in muscle buffering capacity as well as the amount of lactate acid the muscle can deal with through 5 weeks of interval training.
Weight loss and insulin resistance:
Obviously any cardiovascular exercise will burn calories and fat however there have been studies that show that HIIT is more efficient at decreasing your overall body fat as well as abdominal fat. In a session with 60 reps of 8 seconds you actually burning more fat than 40 mins of cycling. (Trapp et al 2011) This study is not alone there are many others to support theres claims. HIIT has been proven to lower your insulin resistance, which is great news for anyone, that is worried about developing type 2 diabetes. However the effect of decrease insulin resistance doesn’t stop there it actually causes increased fat oxidisation in the skeletal muscle which means you will be burning more fat even though your working out for less time. Boutcher (2011) It has also been speculated that HIIT has the ability to temporarily suppress your appetite however whether this is just an effect of hard exercise rather than the structure of HIIT is still in question. Bilski et al (2009)
How often and who should do interval training?
I have touched on a lot of benefits to interval training however high intensity interval training isn’t for everyone as it can put significant strain on your heart and cardiovascular system and therefore may not be suitable for everyone. It is recommended that you consult a health professional if you are worried about starting HIIT especially if you are over the age of 60 or suffer from heart disease.
While interval sessions are often shorter than your normal sessions they are often more intense consequently don’t underestimate them. The recommendation is to have 24 hours recovery between the HIIT, my rest day for my running is the day between my two interval track sessions. There is no point doing the session and working 100% if you aren’t able to recover and get the full benefits from the session, look at my blog post on recovery for more details. The guidelines is to do HIIT training between 1-3 times a week obviously it depends on the individual as well as the intensity of the HIIT, at then end of the day its important to listen to your body and know when its too much. In a normal training week I will do 3 interval sessions: two running sessions and a spin class.
Terada S, Yokozeki T, Kawanaka K, Ogawa K, Higuchi M, Ezaki O, Tabata I (2001) Effects of high-intensity swimming training on GLUT-4 and glucose transport activity in rat skeletal muscle. Journal of Applied Physiology
Bartlett JD, Close GL, MacLaren DP, Gregson W, Drust B, Morton JP. (2011) High-intensity interval running is perceived to be more enjoyable than moderate-intensity continuous exercise: implications for exercise adherence. Journal of Sports Science.
Ma JK, Scribbans TD, Edgett BA, et al. (2013) Extremely low-volume, high-intensity interval training improves exercise capacity and increases mitochondrial protein content in human skeletal muscle. J Mol Integr Physiol.
Weston, M., Taylor, K. L., Batterham, A. M., & Hopkins, W. G. (2014). Effects of Low-Volume High-Intensity Interval Training (HIT) on Fitness in Adults: A Meta-Analysis of Controlled and Non-Controlled Trials. Sports Medicine