Category Archives: Interval training

High-Intensity Workouts and the 6 Damaging Effects it has on our Metabolic System

By: Geoff Rubin, Fitness Propelled, CPT/CIFT/TRX II

High intensity training has reached an all-time high in popularity, mostly because it provides people what they want = results! As a trainer, I constantly hear about high intensity training and all the questions that surround it. Is high intensity training right for me?, is it damaging to the body?, will it help me get that chiseled Tony Horton six pack? Personally, I am a non-believer in the “high-intensity” model and feel that it has narrowed the general public’s view on understanding effective training options. Such options include specific cardiovascular programs with regulated HR monitoring, anaerobic conditioning programs built for hypertrophy / muscle development and core conditioning programs to name a few.

While “high intensity” programs often do deliver the results it is important to understand that these programs can also lead to the following six types of metabolic damage which could keep you from reaching your fitness goals:

1) Elevated blood lactate:

When muscles involved in exercise can no longer meet energy demands through aerobic metabolism they will tap into the ATP-PC and Glycolysis energy pathways to produce ATP anaerobically (without oxygen). One by-product of anaerobic metabolism is lactic acid, which can accumulate quickly during high intensity exercise. The Onset of Blood Lactate (OBLA), commonly called the lactate threshold (LT), is a physiological marker that indicates an elevation in blood acidity, which can inhibit energy production and the ability to do physical work, leading to fatigue. When you feel that burning sensation in your muscles, it’s an indication of OBLA and a sign that it is time for a lower-intensity active recovery interval.

2) Acidosis:

Anaerobic exercise also elevates levels of hydrogen ions (H+), both of which increase blood acidity reducing the levels of oxygen and other nutrients available for aerobic energy production. In extreme cases acidosis can cause severe damage to muscle tissue resulting in a breakdown of muscle protein called myoglobin. When myoglobin is broken down and subsequently enters the blood stream this could ultimately lead to rhabdomyolysis. Rhabdomyolysis can inhibit normal function of the kidneys, potentially leading to hospitalization or possibly death, so it is extremely important to listen to your body and not push physical exertion past your normal comfort levels.

3) Gluconeogenesis:

Protein is normally used to repair tissue damaged during exercise and promote the growth of new muscle. Carbohydrates are converted to glycogen and used for ATP production during anaerobic exercise. Fatty acids require oxygen and take longer to convert to ATP, making them an inefficient energy source for high intensity exercise. When high intensity exercise lasts for extended period of time, the body will convert protein to ATP in a process callused gluconeogenesis, reducing the amount of protein available for muscle growth. The process of converting amino acids (the building blocks of protein) to ATP elevates levels of ammonia, further increasing blood acidity and the risk of acidosis.

4) Increased levels of human growth hormone (HGH):

When muscle damage occurs due to exercise,  the body will produce higher levels of HGH to repair this damaged muscle. This is the metabolic response that most body builders hope for because this increase in HGH can lead to an increase in muscle size. So if your goal is to add lean muscle mass, this is a good thing and one of the most important benefits of high intensity training. But if your goal is to simply lose weight, then all of that high intensity exercise could be having an opposite effect, increasing both muscle size and net bodyweight. One thing to keep in mind is that as you add lean muscle mass, you can increase your resting metabolism, elevating the amount of calories you burn at rest.

5) Increased glycogen storage in muscle tissue:

High intensity exercise frequently relies on muscle glycogen to produce ATP. As a result of extended exposure to high intensity training, muscles become more efficient at storing glycogen for future use. But it’s important to note that when stored in muscle tissue, one gram of glycogen holds approximately three to four grams of water. If weight loss is your goal then training your muscles to store glycogen (and water) may have an impact on the scale that you weren’t hoping for. Remember that weight is one number, but body composition may be a more important measure of overall health.

6) Over-training:

Excessive exposure to high intensity exercise without sufficient rest periods can lead to Overtraining Syndrome (OTS). Signs of OTS include reduced immune system function (leading to lingering colds or flu-like symptoms), elevated heart rate, sleeplessness, increased irritability, weight gain (despite exercise) and a significant decrease in physical performance. It can take anywhere from 24 to 96 hours to fully recover from a metabolically demanding high intensity exercise session.

We know that “High – Intensity” training is here to stay, however, it is important to know the impacts that certain styles of training can and does have on our bodies. It’s always best to be informed.

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Why Integrate heart rate training into your running program?

ImageBy: Geoff Rubin, Fitness Propelled (CPT/CIFT/TRX II)

I am a runner; however I am not one with a strap tightly fastened across my chest. However, more recently as I progress in my running distances and pace, I wanted to garner an understanding of the basic rationale for wearing a heart rate monitor while running. Heart rate monitors are not essential tools for training, but when used properly, they can be a valuable training aid.

Wearing a heart rate monitor while running provides an indicator of exercise intensity. A heart rate monitor, therefore, allows you to monitor and control the intensity of your running. Starting runners often make the mistake of not sufficiently varying the intensity of their running pace. A heart rate monitor can help you accomplish this variation through monitoring.

To do this, you first need to determine your individual heart rate response to running intensity. Step one is to determine what is called your lactate threshold heart rate. Lactate threshold is a moderately high running intensity — the highest intensity that can be sustained without significant discomfort. At exercise intensities below the lactate threshold, your breathing is controlled. When you exceed lactate threshold intensity, there is a sudden increase in breathing rate.

Strap on your heart rate monitor and jog for two to three minutes at a very comfortable pace. Then increase your pace moderately and sustain the new pace for two to three minutes. Continue this pattern, noting your heart rate at each pace, until you reach a pace at which your breathing rate spikes. You are now above your lactate threshold. Your lactate threshold heart rate is the heart rate you noted at the preceding pace.

Heart rate-based training involves targeting different heart rate zones in different workouts. The most popular zone system is the following:

Zone 1

Active Recovery

<80% lactate threshold heart rate (LT HR)

Zone 2

Aerobic Threshold

81-89% LT HR

Zone 3


90-95% LT HR

Zone 4

Sublactate Threshold

96-99% LT HR

Zone 5a

Lactate Threshold

100-101% LT HR

Zone 5b

Aerobic Capacity

102-105% LT HR

Zone 5c

Anaerobic Capacity

>106% LT HR

Each zone holds its own benefits and is appropriate for different types of workouts. Zone 1 is so light it barely qualifies as exercise, and is appropriate on days when you are especially fatigued from prior days’ running and for “active recoveries” between high-intensity intervals. Zone 2 is very comfortable and quite useful for building aerobic fitness, fat-burning capacity, and endurance. Running in Zone 2 more than in any other zone is recommended.

Zone 3 is just a bit faster than your natural jogging pace — that is, the pace you automatically adopt when you go out for a run without even thinking about the intensity. It is useful for extending the benefits of training in Zone 2. Zone 4 is a running intensity that requires a conscious effort to go fast but is still comfortable. It is close to the intensity that is associated with longer running races, and should be incorporated into your training in moderate amounts to get your body used to that intensity.

Zone 5a is your lactate threshold intensity. It is more stressful than the lower zones, so you can not do a lot of running in this zone, but it is a powerful fitness booster, so you will want to do some Zone 5a running each week. The typical Zone 5a workout contains one or more sustained blocks of Zone 5a running sandwiched between a warm-up and a cool down. For example: 10 minutes Zone 2 (warm-up), 20 minutes Zone 5a, 10 minutes Zone 2 (cool-down).

Zone 5b is very intense, but when incorporated into your training in small amounts it will elevate your running performance significantly. Zone 5b is too intense to be done in sustained blocks, so instead it is incorporated into interval workouts featuring multiple short segments of fast running separated by active recoveries. For example, you might run 5 x 3 minutes @ Zone 5b with 3 minutes @ Zone 1 after each Zone 5B interval.

Zone 5c covers everything between the fastest pace you could sustain for a mile or so and a full sprint. It is incorporated into very short intervals and should be used very sparingly in your training because it’s so stressful. You will not want to make the mistake of avoiding it, though, as it is a great way to boost speed and running economy.

The content above contains some basic guidelines for using heart rate to monitor and control the intensity of your running. The biggest limitation of heart rate-based training is that, while heart rate is a good indicator of running intensity, it is not a perfect indicator. Heart rate is affected by a number of other factors, including fatigue level, sleep patterns, psychological state, hydration status, and diet, which make it somewhat unreliable in certain circumstances.

For example, while heart rate tends to be lower at any given pace on a treadmill than it is outdoors, running at any given pace actually feels easier outdoors, and one can also sustain higher heart rates outdoors, possibly for psychological reasons. The relationship between heart rate and running intensity also changes continuously as your fitness level changes, so you need to repeat the lactate threshold test frequently to keep your target zones accurate.

Many experienced runners, including elite runners, train without heart rate monitors, instead they rely on a combination of perceived exertion and pace to monitor and control the intensity of their workouts. The success of these runners is proof that a heart rate monitor is not needed to realize your full potential as a runner.

The most comprehensive indicator of running intensity is perceived exertion, or how hard running feels. Perceived exertion attributes for not only heart rate but also all of the other physiological and psychological factors that influence exercise intensity. You will always want to pay more attention to how hard running feels than you do to your heart rate when running.

Heart rate monitors provide users with important data that can be used towards improving running intensity, duration and speed; just do not use it as an end all.


Matt Fitzgerald -Running 101: Training With A Heart Rate Monitor


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Interval training, a must for reaching greater heights as a runner

Image “If you ever want to be a successful runner, you have to consider everything.” (Arthur Lydiard) All the more reason that just running more or longer simply doesn’t cut it in today’s ever growing popularity with running. Well, you must be asking, what am I supposed to do instead?   It is time for us to understand and implement the benefits of “Interval Training”.

 Interval training is defined as training in which an athlete alternates between two activities, typically requiring different rates of speed, degrees of effort. The University of Western Ontario, showed that with just six weeks of sprint interval training participants elicited jumps in VO2 max, running performance and lower heart rates as compared to regular endurance training.“You can train all the energy systems with interval training, including stamina, threshold, strength and improve your mental discipline” (Ken Rickerman). When you have the chance to get more bang for your buck, why wouldn’t you consider ramping up the intensity occasionally?

 Let’s put interval training into practice. Training intensity should follow the widely cited rule for endurance athletes, which is to do 80% of your training below your lactate threshold and 20% at or above it. In more simplistic terms, your lactate threshold is the intensity at which lactic acid begins to build up in your blood stream. As runners world puts it and I agree, “it’s all about pushing yourself out of your comfort zone, but generally at a controlled pace”.

Examples of implementing interval training into common mileage distances:

  • 1 mile: .25 @ 4mph / .25 @ 4.5mph / .25 @ 5mph / .25 @ 4mph
  • 3.2 miles: 1mile @ 5mph / .50 @ 6mph / .25 @ 6.5mph / .25 @ 7mph / 1mile @ 6mph / .20 @ 5.5mph

  • 6.0 miles: 2miles @ 4.5mph / 1mile @ 5.5mph / 2 miles @ 4.5 / 1 mile @ 6mph


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