What Is High intensity resistance Training (HIRT)?
In the year 2005, the McMaster University research group made some startling discoveries. In a randomized clinical trial, experimental subjects underwent a 3x/week high-intensity aerobic exercise program that required subjects to perform 4-7x 30 second bursts of “all out” cycling on a stationary bike for a total time of 2-4 minutes, including recovery time. After testing the test subject’s muscle enzyme concentrations, significant increases in enzyme levels were found that indicated improved oxygen uptake. This shows that the muscle were able to utilize oxygen more effectively, translating into improved muscle performance. These remarkable findings showed that small amounts of very high intensity exercise could bring about significant exercise adaptations and that less exercise volume is needed for positive training adaptations than previously thought.
Following the McMaster studies, more research was performed on the benefits of high-intensity training. It was around this time when high-intensity resistance training became increasingly more popular. High intensity resistance training (HIRT) is a short, intense form of strength training that can be performed within only 10 minutes of your time. That being said, HIRT routines typically do not have to be performed more than 1-3x/week, depending on how far you can push your limits during your workout. Exercises should alternate between push and pull, focus on multi-joint muscle groups, are performed at very slow speeds.
High Intensity Interval vs. High Intensity Resistance Training
You may have heard of High-Intensity Interval Training (HIIT) in the past, a current new fitness trend that appears to have taken over the world in no time. If you have not heard about it, you can find more information about HIIT here.
Both training methods use high-intensity stimulus during workouts, however are quite different in their training methods and what you can get out of them. Let us dive deeper into the differences between HIIT and HIRT is.
1. Frequency:
- HIRT workouts are typically performed 1-2x per week. Individuals that are new to HIRT may want to start out with 3x/week to gradually get used to the feelings of severe muscle exhaustion. However, once you are past this stage and realize that the short-lasting feelings of panic at the end of your set will translate into improved muscle strength, mood and heart health, 1-2x/week are sufficient. Due to the fact that you fatigue your musculature to a deeper level, greater rest periods in between workouts are needed to fully recover and prevent muscle breakdown from occurring. Older adults are recommended to perform 2 workouts per week to combat the effects of sarcopenia (age-related muscle loss).
- HIIT workouts on the other hand are typically performed 2-3x per week. Normal rest periods in between workouts are 24-48h, depending on how far you can push yourself for the same reasons as mentioned above.
2. Intensity:
- HIRT workouts tend to be of even higher intensity than HIIT workouts. This is because of the fact that with HIRT training you specifically target one-two muscle groups at a time and perform the exercise to the point of muscular failure, a point where you are unable to perform a full repetition as a result of deep muscular fatigue (more about this later). The slow-speed technique and gradual fatiguing of muscle fibres in HIRT allows you to fatigue your muscles to a deeper level than you would with a dynamic HIIT workout.
3. Type:
- HIRT workouts tend to be much more static, are performed slower and more controlled than HIIT workouts. The only joints you are moving are dependent on the muscle groups you are attempting to fatigue (e.g. during a chest press you would only be moving your shoulder and elbow joints). The focus here lies on effectively fatiguing each individual major muscle group at a time. Your heart rate would likely not go up as high as during a HIIT workouts, however may stay elevated for longer after you finish your workout due to the effects of excess post-exercise oxygen consumption.
- HIIT workouts tend to be much more dynamic and less controlled. The workouts are faster and more strenuous on multiple muscle groups at once. Your peak heart rate will likely be higher during HIIT workouts, as you are engaging more musculature at once that require a sudden significant increase of blood to supply the muscles with oxygen.
4. Time:
- Full-body HIRT workouts typically take anywhere from 6-15 minutes to complete, depending on the amount of exercises and the rest periods in between exercises (which should be kept to a minimum)
- Full-body HIIT workouts typically take around 15-30 minutes to complete. Again, the exact time depends on the amount of exercises that are part of the workout, the intensity of the workout, as well as the rest periods in between exercises.
Sample Workouts
High intensity Resistance Training
high intensity interval training
Exercise Euphoria – High Intensity Resistance Training
High intensity resistance training typically does a great job at up-regulating hormones that are involved in stress relief, feelings of euphoria and happiness (including endorphins, serotonin, dopamine and others). Previous studies have shown us that you will receive the greatest happiness-boosting effects when training in the 7-8/10 intensity range during your workouts. During a typical HIRT workout, you attempt to fatigue your muscle to a maximum before moving on to the next muscle group (so you would be training at a 9-10/10 intensity). If you are in it purely for enjoying the feelings of euphoria following the workout, I recommend you train at a 7-8/10 intensity, add a second set for each exercise to your workout, as well as train 3 days/week.
You can read more about the optimal exercise stimulus for endorphin production, as well as my personalized “Prime-Your-Happiness” workouts in my free e-guide here.
High Intensity Resistance Training:
The “Inroad Process”
Before we get into the practical side of high intensity resistance training, we need to understand the science behind why we are doing what we are doing. If we are not fully aware of why we do what we do, it is only a matter of time before we return to our old ways of exercising.
The Inroad process is the physiological process that underlies high-intensity resistance training. It defines the process that is required for your muscles to undergo during the workout that stimulates the desired growth and strength adaptations. In simple terms, the inroad process refers to the momentary weakening of your musculature. It is the point where even though you try everything in your power to move the resistance, you are unable to do so. Important terms that we have to familiarize ourselves with in order to fully understand the “Inroad Process” are: time under load, sequential recruitment of motor units, and momentary muscular failure.
Time Under Load
The term time under load (also called time under tension or time to concentric failure) refers to the amount of time that your muscles are performing work without having been given the opportunity to rest. For traditional strength training workouts, this is quantified in the amount of repetitions that were performed. However, since we are moving at a much slower repetition speed during a HIRT workout (more about this later), this does not become a reliable measure. Additionally, due to the inevitable variations in the repetition speed, it does not become an accurate measure of performance and thereby not a good progress tracking tool. Adopting the technique of timing our muscle group’s “time under load”, starting at the point where you initially lift the load and ending at the point when you drop the load, allows us to recognise smaller gradations of performance improvement. [1]
Sequential recruiting of Motor Units
A motor unit is a functional muscle unit that is composed of the single nerve cell that innervates it (often referred to as the alpha motor neuron), as well as the muscle fibres that are connected to it. If you are planning to initiate a movement, your brain creates a signal within your brain that travels down your nervous system towards the alpha motor neuron, which innervates the muscle fibres connected to that nerve cell. This causes your innervated muscles fibres to contract and initiate movement. Once your alpha motor neuron receives the signal, it will cause a contraction of the attached muscle fibres at full force.
Your body is great at conserving energy. It attempts to use the least amount of energy as possible. As a result, your body will only recruit an amount of motor units that are required for the task at hand. This can create a challenge during our workouts, as the effect of training will be directly proportional to the amount of motor units you have fatigued (so the higher the intensity of your workout, the more motor units you will recruit, which translates into higher workout effectiveness). Therefore, your brain will recruit less motor units with easier tasks, than with more challenging tasks.
Let us translate this concept into practice. Throughout the course of the exercise, you slowly recruit required motor units that are needed to successfully accomplish the task (e.g. pulling the bar toward you during a pulldown exercise). Once those motor units have fatigued, your body will sequentially recruit more and more motor units so that you are able to continue the task. Towards the end of the set, you will have fatigued most of your available motor units until a point comes where you are unable to generate sufficient force due to the fatigue of your motor units.
Momentary Muscular Failure
Momentary muscular failure (MMF) is defined as the point in your set where you cannot lift the load actively through your joint’s full available range of motion. It is the point that let’s you know that you are getting close to finishing your set and that you are close to successfully inroading your musculature.
At this point in your set you may experience severe sensations of panic and the urge to escape the pain, as you are pushing your muscles capabilities to their maximum. The important thing to remember is that you are not causing harm to your body by pushing through this point. Try your best to stay as calm as possible and accept the temporary sensation of deep muscular discomfort. You may have difficulty with this at the start, but you will become better at this after you have performed a few workouts.
Ideally, you would want the point of MMF to occur about 120-180 seconds into your set, to allow sufficient time to sequentially recruit and fatigue your muscle’s available motor units.
Exercise Guidelines
In order to effectively inroad our muscles and get the desired effects from your HIRT training regime, you will need to properly follow certain exercise techniques. These differ from traditional strength training techniques and will be discussed in further detail below:
- Single Set Exercises
- Slow Repetition Speed
- Rest Periods
- Training Frequency
- The “Big Five” Workout
- Breathing
For further in-depth information of the exercise guidelines below, make sure to check out Dr. Doug McGouff & John Little’s book “Body by Science”. The book goes deep into the theory, science and application of high intensity resistance training.
1. Single Set exercises
When it comes to the number of sets, HIRT is taking a quite unique approach. The good news is that with you will only need to perform one single set per exercise. As stated in the book “Body by Science”, one single set, if taken to the point of momentary muscular failure, is a sufficient stimulus to trigger growth and strength adaptations. As mentioned above, a good time under load for each set lies around 120-180+ seconds to provide your muscles with enough time to sequentially recruit and fatigue the majority of your muscle’s motor units.
2. Repetition Speed
Compared to traditional strength training routines, during HIRT you need to ensure that you are moving at the slowest possible pace as you can move without “getting stuck” halfway into your repetition. The reasons for that is that this is the most effective way for recruiting and fatiguing the greatest amount of muscle fibres as possible. Additionally you want to avoid taking advantage of momentum during your exercise set.
There is no set recommended speed at which you should move, and it is normal for a repetition to last about 20-25 seconds. The variable time it takes per repetition is the reason why you should measure your time under load, as opposed to counting your repetitions.
3. Breathing
Ensure that you are breathing the entire time throughout your set. Avoid holding your breath at any point and breathe continuously. If you have difficulty doing so, practice breathing at higher frequencies when breathing becomes more challenging.
Why? There are two reasons why you should avoid holding your breath during your workout. The first reason being that holding your breath as you are exercising can significantly increase your blood pressure, which can leave you feeling dizzy and nauseate. The second reason is that you are depriving your muscles of oxygen. As a result, your muscles will not receive the nutrient required to produce energy. Your workout will end earlier and be less effective than if you breathed continuously throughout your workout.
4. Rest Periods
Try your best to keep your rest periods in between exercises to a minimum. Allow yourself to calm down following the termination of the exercise and then move on to the next exercise.
Why? A major benefit of HIRT beside physiological adaptations in the muscles (translating into greater muscle strength, muscle mass and muscle endurance) is the positive effect on the cardiovascular system. By minimizing your rest periods in between exercises, your heart rate will stay elevated, resulting in greater cardiovascular benefits as a result of training.
5. Training Frequency
As mentioned above, “HIRT workouts are typically performed 1-2x per week. Individuals that are new to HIRT may want to start out with 3x/week to gradually get used to the feelings of severe muscle exhaustion. However, once you are past this stage and realize that the short-lasting feelings of panic at the end of your set will translate into improved muscle strength, mood and heart health, 1-2x/week are sufficient.
Due to the fact that you fatigue your musculature to a deeper level, greater rest periods in between workouts are needed to fully recover and prevent muscle breakdown from occurring. Older adults are recommended to perform 2 workouts per week to combat the effects of sarcopenia (age-related muscle loss).”
6. The Big Five
Typical full-body routines consist of approximately 5-6 exercises. Try to alternate between push and pull exercises to allow temporary recovery of opposing muscle groups and plan to start with your largest muscle groups before moving on to exercises that involve smaller muscle groups. For instance, you should perform a leg press before you move on to a biceps curl. Exercises should be multi-jointed (e.g. during a leg press exercise you are engaging your hip and knee joints) and involve large muscle groups.
You can design your workout in different ways based on your needs, however a widely popular HIRT full-body workout regime is composed of “The Big Five”:
- Seated Row (back musculature, biceps)
- Chest Press (chest musculature, triceps)
- Pulldown (Torso, back, forearm flexors)
- Overhead Press (Shoulders, Triceps, Chest)
- Leg Press (All lower extremity muscle groups)