Much like the aerobic wave in the 1980's, the high intensity interval training craze in recent years has the potential to be more than a passing fad. If it is a fad or if it has staying-power, getting comprehensive information is vital in making informed decisions.
1. Intensity Aspect:
Hara suggests performing a HIIT workout at 80% cardio capacity for 15-20 minutes may be more realistic for the non-elite athlete. She argues how many non-athletes can perform a HIIT workout at 100% cardio capacity for 8-minutes?
2. Health Constraints:
HIIT, like any other exercise regimen, can lead to health and safety issues if you don't exercise on a regular basis. Hagikalfa recommends working out 3-5 times a week CONSISTENTLY.
According to the American College of Sports Medicine, you may have an increased risk of heart disease if you have been living a sedentary lifestyle or extended periods of physical inactivity, such as family history, cigarette smoking, hypertension, diabetes (or pre-diabetes), abnormal cholesterol levels and obesity when performing high intensity exercise. You should consult a physician prior to starting this type of training or any exercise regimen as a safety measure.
People with cardio-respiratory conditions and the obese can struggle with regular exercise. Imagine how ramping up to a high intensity interval training workout could exacerbate their problems.
Hagikalfa advises consulting your doctor is especially important considering the level of stress high intensity interval training can put your hearth and respiratory system.
ACSM suggests that you, or your personal trainer, establish a foundational fitness level (often referred to as a "base fitness level") prior to beginning high intensity interval training.
"A base fitness level is consistent aerobic training (3 to 5 times a week for 20 to 60 min per session at a somewhat hard intensity) for several weeks that produces muscular adaptations, which improve oxygen transport to the muscles. Establishing appropriate exercise form and muscle strength are important before engaging in regular high intensity interval training to reduce the risk of musculoskeletal injury, " ACSM reiterated.
Regardless of age, gender and fitness level, one of the keys to safe participation of high intensity interval training is for all people to modify the intensity of the work interval to a preferred challenging level. Safety in participation should always be primary priority, and people should focus more on finding their own optimal training intensities as opposed to keeping up with other persons.
3. Doing Too Much (DTM):
The adrenalin naturally flows when you first start, or get back to, working out. You regret that extra rep you gave the next day when you struggle to get out of bed because of muscle lactation.
Doing too much in high intensity interval training can lead to excessive muscle soreness, and in extreme cases, rhabdomyolysis (where the muscles break down muscle fibers that enter the bloodstream and poisons the kidneys) according to University of Virginia exercise physiologist and researcher Shannon Slovenski.
Furthermore, too much high intensity interval training will hinder your ability to see gains in resistance training and cardio-vascular training.
Tony Gentilcore, CSCS of Cressey Performance near Boston said, "Too many people go to the extreme, performing three or times high intensity interval training sessions a week. But even athletes do intervals once or twice a week."
Aerobic effects:
A 2009 study revealed that aerobic changes that occur with high intensity interval training are similar, and some cases higher, to aerobic changes that occur with continuous aerobic training according to Micah Zuhl and Len Kravitz PhD. The study "showed that 4 repetitions of 4-minute runs at 90%-95% of heart rate maximum (HRmax) followed by 3 minutes of active recovery at 70% HRmax performed 3 days per week for 8 weeks resulted in a 10% greater improvement in stroke volume than did long, slow distance training 3 days per week for 8 weeks."
In short, you get more bang for your buck in increasing your aerobic capacity with high intensity interval training.