If you’re getting bored with your normal strength training routine, or if you’re not getting the results you’re looking for, think about trying HIT: High Intensity Training.
HIT is a specialized approach to strength training that was originally developed in the 1970’s by trainers and coaches who worked with professional athletes in various sports. Compared to traditional forms of strength training, evidence suggests that HIT provides better results; requires less time in the gym; and has a lower risk of injury and overuse problems.
These perks make HIT suitable for many people, including non-athletes and those simply trying to lose weight and become more fit, regardless of age or gender.
First, a General Caution
As with any form of high intensity exercise, you need to be in good basic health and free from any significant cardiovascular risk factors and muscle/joint problems that could limit your capacity to exercise safely at a high intensity level. If you have any doubts or concerns along these lines, you need to consult your doctor before trying any of these techniques. HIT is demanding—both physically and mentally.
Principles of HIT
So, how exactly does HIT differ from "traditional" strength training? There are two primary differences.
1. The Perfect Form Principle
While traditional training methods focus on total number of repetitions (8-15), sets (2-3), and weight lifted, HIT focuses on the quality of each repetition and set. By using ideal form, you can achieve better and faster improvements in strength and muscle growth with just one set of exercises for each muscle. Proper form and fewer sets virtually eliminate many of the injury risks associated with multiple sets that are performed with less than ideal form. The basic characteristics of a “perfect” HIT repetition/set include:
Slow, controlled movement. Without bouncing and without using momentum, take 2-3 full seconds to lift the weight (positive phase). Before lowering the weight, pause for half a second and "squeeze" the contracted muscle. Finish one rep by taking 4-5 full seconds to lower the weight to the starting position (negative phase). The key here is to keep the muscle under constant tension, without allowing the weight to rest on the machine or your body at the bottom of the negative phase.
Full range of motion. Each exercise should be taken through the complete range of joint movement, but don't fully straighten or “lock out” your joints.
Momentary muscle fatigue (MMF). You want to "feel the burn" in the target muscle by the end of your set—without sacrificing the perfect form described above. You will defeat the purposes of HIT by arching your back, rocking your body, or trying to use momentum to squeeze out another repetition or two. You will also limit training effectiveness by stopping at a predetermined number of repetitions per set if you could do more without sacrificing form.
You are doing it right if the target muscle is trembling, shaking, and burning during your last repetition. Pain in joints or other (non-target) muscles usually means something is wrong with your form (or with those joints or other muscles). Implementing the perfect form principle is mainly a matter of focus and concentration. You need to pay close attention to the “rules” of good form at all times during your workout (including proper breathing and body position), and to your timing. Until you can accurately estimate how many seconds you are spending on the positive and negative phases of each repetition, and the total time for each set, you may need to wear a watch with a second hand.
2. The Triple Progressive Overload Principle
Traditional weight training approaches rely on a “double progressive overload principle” that involves progressively adding weight and increasing the number of repetitions to keep overloading the muscle and produce improvements in strength and size. HIT adds a third factor to this equation: increasing the time spent with the muscle under constant tension.
Depending on your individual genetic potential, you can train your muscles to produce maximum power for up to 3-5 minutes at a time. To accomplish this, you need to keep increasing not only the amount of weight and number of repetitions you can lift, but also the total amount of time that your muscles are under continuous tension during each set and each workout session. The best way to implement the triple overload principle will vary depending on your training goals and priorities. Competitive weightlifters, bodybuilders, and endurance athletes will all need specialized approaches based on the requirements of their sports.
General HIT Guidelines
For individuals pursuing modest or general fitness goals, follow these general strategies:
Warm up. Begin each HIT session with a five-minute cardio warm-up, and a brief static stretch for each muscle group that you will work.
For each exercise in your routine, start with a weight that allows you to reach momentary muscle fatigue in 8 repetitions, using perfect form and the 6-8 second cadence described above.
For subsequent workouts, aim to increase the number of repetitions you can do, using the same 6-8 second cadence for each repetition, until you are able to do 15 repetitions with perfect form (a total of 90-120 seconds of continuous muscle tension for each set).
Once you can do this reliably, increase the weight you lift by 5-10% and repeat this process, starting with as many perfect reps as you can do and increasing the reps until you are doing 15 of them.
Each successive workout should provide at least the same and preferably more overload (i.e. more weight, more reps, or more total time under tension) than the previous workout, but only one of these factors should be changed at once.
In theory, you can achieve the benefits of HIT by performing one set of each exercise, as long as you reach momentary muscle fatigue. If you choose to add one or two more sets, perform to fatigue using the same amount of weight for each set. The number of perfect repetitions you can do will likely decline with each set.
Allowing 90 seconds to rest between sets is sufficient for beginners, but you can modify this to suit your training goals. Circuit training, for example, will add an aerobic component to your workout, while 5 minutes of rest may be ideal for power lifters using heavier weights.
Since HIT induces complete muscle fatigue, it is crucial to allow adequate time for recovery and rebuilding of muscle tissues between sessions. At a minimum, you must allow 48 hours between sessions training the same muscles. For most people, 72 or even 96 hours may produce better results.
Cool down after each workout. Take at least 5-10 minutes for a light aerobic cool down. Finish with another round of static stretches for the muscles you worked to enhance muscle recovery and reduce the risk of injury.
Although the basic concepts behind the HIT approach are pretty simple, turning them into an effective training program for you depends on many individual factors and needs which can’t be discussed in a short article like this. Everyone, from marathon runners to competitive power lifters to 58-year-old guys trying to stay in shape, can use HIT to achieve their goals. But you may need to adjust the general approach described above to suit your particular needs. If you’re interested in HIT, I highly recommend the book High Intensity Training, by John Philbin (2004, published by Human Kinetics).