Cardio and all its forms are a phenomenal source of fitness.
Treadmills, stationary bikes, rowing ergometers; their variety is just as numerous as their health benefits. However if you’ve ever felt your progress with cardio has run its course, that you’ve hit the proverbial wall- then you’re not alone. To reap the benefits of aerobic training, the body has to continue to adapt and grow— but first the plateaus have got to go.
One of the best kept secrets for progressively improving aerobic performance is through interval training.
When talking about aerobic training, it’s usually in direct reference to cardiovascular fitness. Aerobic means “with oxygen”, and throughout an aerobic workout, the body uses oxygen as a main ingredient for energy. All of this works the heart and lungs to provide oxygen-rich blood to slow twitch muscle fibers- enabling athletes to trek further distances in better time.
What Does It Take To Improve Cardiovascular Performance?
We all know what better cardio looks like, but what internal systems aid in better performance? Their are quite a few, but here are the main ones:
- VO2max and aerobic capacity. The body is constantly producing energy (ATP) to power it’s physical functions, but for long term activities it needs a steady stream of oxygen to aid in the chemical process of ATP production. This is why VO2max and aerobic capacity are both so important. When the body can efficiently process more oxygen, it can maintain energy production, thus allowing people to exercise for longer periods of time.
Increasing oxygen uptake (VO2max) is essential for all athletes and gym-goers looking to improve their distance running and limits of tolerance.
- lactate threshold: To improve cardio the body’s lactate threshold has to increase. As exercise intensifies the body builds up lactate, the by-product of pyruvate during aerobic glycolysis. The lactate threshold is the maximal effort or intensity that an athlete can maintain for an extended period of time with little or no increase in lactate in the blood. It is an effort or intensity and not a specific lactate level.
Interval Training Benefits
Not only can aerobic interval training improve performance, it can do it better than steady state training. We all come across people who hit the ceiling in their training. Many of them believe that progressively running longer distances will level up their cardio, but this isn’t the best approach.
The body is conditioned to adapt to the continuous stress of distance running very quickly. It’s only a matter of time before the benefits of this training become less and less potent. Therefore new challenges are necessary to overcome the plateaus in training and performance.
Quick, intense intervals boost maximal oxygen uptake, oxygen transportation (heart), oxygen capacity (lungs), oxygen utilization (cells), etc. All of these factors work together to optimize energy usage and ultimately improve performance.
Studies also attest to the long term affects of this form of training. While Vo2peak improved in both aerobic interval and moderate continuous training groups during the first 4 weeks of a conditioning study, Vo2peak continued to rise for aerobic interval training after 6 months(3). This means that as the program progressed, the subjects’ limit of tolerance continued to expand, enabling them to out-perform those using moderate continuous cardio.
Like any system of the body, growth happens when the body is pushed to extremes. Adaptation requires a level of intensity that moderate-state cardio can’t offer. That’s not to say it doesn’t offer health benefits, however if your goal is to rise above your plateaus, you’ll need interval training.
The Problem With Low Intensity Interval Workouts
Here’s the thing: the term “interval” has no standard definition, so long as it has bout of brief intermittent exercise. It’s generally assumed to be high intensity, but for effective training, it must always be there. No exceptions.
Just having cardio “interval training” isn’t going to cut it. While some low intensity training like endurance training has produced similar results to low volume HIIT, this is only accomplished over a much longer period of time, which can be impractical to the average gym-goer.
Aerobic Capacity
The number one aspect that intervals improve is aerobic capacity.
As the highest amount of oxygen consumed during maximal training, greater aerobic capacity will take any form of cardio to the next level.
In a study comparing aerobic intervals and continuous state cardio, the difference in results couldn’t be clearer. AIT and CME increased V̇O2max by 35% and 16% (P<0.01), respectively (group difference, P<0.01; Figure 2A). Only aerobic interval training had a significantly increased peak O2 pulse (P<0.05; between-group difference, P<0.001; Table 2).
Interval Training Sprints
If interval training works, what about specific types like sprint interval training? The good news– they actually improve performance, and in less time than you may think!
Multiple studies show how sprint interval training is a game-changer in performance. Activities where strength, power, and speed are needed (countermovement jumps, 10-30 sprints, etc.) sprint intervals have brought small and large improvements. Researchers suggest that in some cases, repeated sprints are even more effective at improving short-sprint performance than methods like plyometric training.
16 trained runners completed 2-week trials of 4-7 bouts of 30 seconds at maximum effort between 4 minutes of rest, 3 times a week. During testing 3 things were measured before and after training:
- maximal aerobic speed (MAS)
- time to exhaustion
- 3,000-m timed trial
Maximal aerobic speed improved by 2.3%, whereas peak power (PP) and mean power (MP) increased by 2.4%. The 3,000-m time was reduced by 6% while time to exhaustion at 90% MAS was 42% longer.
These results are impressive for such a short amount of time. A few weeks of sprint interval training cause changes on a musculoskeletal level that adapt enzymes used in energetic systems. The increase in glycolytic enzymes and increased markers of aerobic metabolism may lead to improved running economy, and by extension, performance.
Do you know what the best part is about sprints? You don’t have to be an hardcore athlete to see improvements in performance!
That’s right- average, untrained individuals can reap the benefits of this training type.
There has been a consistent association with sprint interval training and better cardio performance. SIT produced improvements of 4%, 8-10%, and 15% after only 1, 2, and 6 weeks respectively(2).
Sprint Intervals VS. Endurance Training
Aerobic fitness encompasses many facets of bodily health; aerobic and anaerobic power, muscular strength, sprint time, all of which was compared between sprint intervals with active rest and endurance training. Results showed a significant improvement in absolute and relative V̇o2max, anaerobic treadmill run, and sprint time in both groups. Only SITAR showed significant improvements in isokinetic leg extension and flexion and decreases in body mass. Sprint intervals also showed much greater improvement over endurance training in anaerobic treadmill run and 50 m sprint time. So intervals are a time-efficient strategy that creates rapid adaptations in V̇O2max with added improvements in anaerobic power, isokinetic strength, and sprint time not observed with endurance training(4).
Interval Training Examples
One of the best things about aerobic interval training is the wide range of diversity. There are so many different forms of cardio, and with it comes numerous ways to personalize your training. Here are a few examples:
Shuttle Sprints
One of the above studies used shuttle sprints to produce significant results in very little time. This method is great if you’re a fan of the outdoors and has been shown to deliver results even for professionals.
Using a track, begin 30 seconds of all out sprints running to and from the 5, 10, and 15m mark, returning to the start-line after reaching each point. Keep running with maximal effort until the 30 seconds are up and once finished begin a light jog rest interval for 4 minutes. Repeat this for 7 rounds to complete the workout.
Cycling Intervals
If you’re familiar with spin classes then you may know how intense an cycle interval workout can be. Similar to the their format, you’ll need bouts of extreme effort with recovery periods of low intensity cycling in between.
I recommend using a structure similar to HIIE (high intensity intermittent exercise) in which you complete 8 second sprints followed by 12 second low intensity cycling. It’s theorized that maintaining a near 1:1 ratio of work-to- recovery improves overall results compared to training with longer rest periods.
14 rounds of this would add up to as little as 8 minutes, yet produce greater results than far longer steady-state programs.
A Tremblay study found that HIIE training compared to steady-state aerobic training not only improved short term results, but also reduced fat mass (<2.5 kg) and abdominal fat in participants.
Row Machine Training
The rowing ergometer is my personal favorite piece of equipment for interval training. Rowing is in the highest tiers of difficulty for cardio activities, which means it’s one of the most rewarding! Rowers are generally the best conditioned aerobic athletes due to power outputs that place tremendous stress on the muscles.
This is not speculation, this is fact. When testing the power output and physiological response, rowing ranked highest among all of the usual forms of cardio (treadmill walking, running, cycling, etc.). Switching to a rowing ergometer alone would likely improve your aerobic performance, but give this interval a try:
Begin the session with a 5 minute warm up. Once your body has adjusted go straight into alternating bouts of 40 seconds of hard rowing and 20 seconds of light rowing for a total of 10 minutes. After this, set aside 5 minutes of light rowing to serve as your cooldown, and your workout is compete!
Whichever form of cardio you choose, the most important aspect is that you add intervals. Having alternating periods of high and low intensity will skyrocket your results while keeping you motivated on your fitness journey.
