High-intensity functional training (HIFT) combines high-intensity cardiorespiratory and muscular-training exercises. While a newer term, this style of training has been commonly seen in boot camp-style classes and gyms for more than a decade. More recently, a growing body of research suggests that this type of training is both safe and effective for improving cardiorespiratory fitness and muscular strength and power, as well as overall health. Here’s what you and your clients need to know about HIFT, and how to incorporate it into your clients’ training programs.

Defining HIFT

First, let’s clearly define what HIFT entails before we discuss related research and how to implement it in your clients’ training programs. HIFT uses the principles of high-intensity interval training (HIIT) but adds compound functional resistance-training movements to this model. The term functional has been used in a variety of ways within the fitness industry. Here, we simply use functional to mean any exercise that uses a large group of muscles in one or more universal movement patterns—bending and lifting movements (e.g., squatting); single-leg movements (e.g., single-leg stance and lunging); pushing movements (e.g., primarily in the vertical or horizontal planes); pulling movements (e.g., primarily in the vertical or horizontal planes); and rotational (spiral) movements. This includes all the competitive lifts for both powerlifting and weightlifting, many movements from gymnastics and strongman competitions, and a variety of other exercises.

HIFT combines these exercises into a fun, fast-paced workout. Common training formats include intervals, continuous circuits, chippers (completing a specific exercise for a set number of repetitions before moving on to the next exercise) and AMRAPs (as many rounds as possible). These formats are outlined in the table below.

A Brief Rundown on HIFT Research

Multiple studies have demonstrated the safety and effectiveness of HIFT and suggest that it combines the benefits of muscular training and HIIT. Previous research indicates that HIIT can produce similar or greater results to steady-state cardio with a lower time commitment. When HIIT is combined with resistance training to create HIFT, however, research suggests that it may improve a variety of fitness parameters, including cardiorespiratory fitness, anaerobic power and muscular strength.

One study directly compared HIFT to HIIT by having female participants spend six weeks in either a group HIIT or HIFT class. The HIIT group performed six rounds of all-out rowing for 60 seconds followed by three minutes of rest. The HIFT group performed six 60-second rounds of four to six repetitions of a strength move, eight to 10 repetitions of an accessory move and a cardiorespiratory-taxing move for the remainder of the time. At the end of six weeks, the HIIT and HIFT groups had similar improvements in maximal oxygen consumption, or VO₂max, (∼7%) and anaerobic power (∼15%). However, the HIFT group also demonstrated increases in squat (39%), press (27%) and deadlift (18%) strength. The HIIT group saw no increases in strength.

Traditional muscular training does not provide a significant cardiovascular response with either acute or chronic exercise. However, when the same movements are performed in a HIFT protocol with little rest between efforts, they can serve as a powerful stimulus not only for strength and power, but also for the aerobic and anaerobic systems as well. Only one study to date has directly compared the effects of HIFT with traditional resistance training. During the intervention, both groups exercised three days a week, performing six to eight movements for two to four sets of eight to 12 repetitions. While the resistance-training group performed the exercises as straight sets, with 60 to 90 seconds of rest between sets, the HIFT group performed the exercises as a circuit, taking 10 to 60 seconds to transition between exercises. After 24 weeks, the group using the HIFT protocol had similar changes in muscular strength and endurance, while simultaneously improving aerobic endurance, agility and body composition. By contrast, the traditional muscular training group saw no changes in aerobic endurance, agility or body composition.

The combined nature of HIFT makes it an effective and time-efficient strategy for people who want to improve multiple parameters of fitness, which includes many military and law enforcement personnel. Heinrich and colleagues compared an eight-week HIFT intervention, which featured 15 exercises performed for 60 to 90 seconds as a continuous 45-minute circuit, to a combined muscular training and cardiorespiratory training program called the U.S. Army physical readiness training program. All participants were enlisted soldiers. The HIFT participants experienced significantly greater improvements in their ability to do push-ups (4.2 vs 1.3 push-ups), bench-press strength (13.2 vs. 2.7 lb), flexibility (0.6 vs. −0.5 inches), and 2-mile run time (−83.9 vs. −15.3 seconds).

Another study focused on cadets preparing for a retake of the Air Force fitness test. The group using a HIFT training protocol improved more on all tests (push-ups, crunches, 1.5-mile run and waist circumference) than the traditional cardiorespiratory-training group. It is important to note that the HIFT group spent about 70% less time exercising than the traditional cardiorespiratory-training group. 

In summary, as Wilke and Mohr noted in their review of the research on HIFT: “HIFT represents an effective method to increase muscle strength and endurance capacity. In view of the multidimensional adaptations and the relatively low time effort, it may, therefore, be of value for both active and inactive individuals.” 

Enjoyment and Retention Benefits

Two additional benefits of HIFT are enjoyment and retention. As health and exercise professionals, we know that it isn’t enough to just make a workout program that’s effective, time efficient and safe. We need to create programs that our clients want to do. Some highly motivated clients are willing to suffer through anything we throw at them, especially if they believe it will make them better. Others clients, particularly new ones, need the workouts to be at least partially enjoyable. Heinrich and colleagues compared the enjoyment of a HIFT exercise program to a combined moderate-intensity cardiorespiratory and muscular-training program and found that the HIFT program had fewer dropouts and higher ratings of exercise enjoyment. The participants in the HIFT program also reported being more likely to continue their exercise program following the conclusion of the study. Many HIFT-style gyms typically promote a greater sense of community than their traditional counterparts, which promotes adherence to exercise training.

How to Incorporate HIFT Into Your Clients’ Programs

The practice of HIFT can be the basis of its own program or it can be implemented into an already established exercise routine. Three logical uses for HIFT training are:

1. As accessory work for strength athletes
2. As cross-training for endurance athletes
3. As stand-alone training

As Accessory Work

When used as accessory work during strength programs, HIFT can be incorporated after the main movement(s), or exercises you normally perform as part of your muscular training program, to increase the stimulus on targeted muscle groups while also improving cardiorespiratory conditioning. Cardiorespiratory conditioning is commonly overlooked by strength athletes, but it does offer some specific benefits to this group. Improved cardiorespiratory conditioning improves oxygen exchange and allows for quicker recovery between sets. The increased blood flow from a HIFT or cardio session can help repair the damaged muscles quickening recovery before the next strength session.

As Cross-training

When used as cross-training for endurance athletes, HIFT can be incorporated in place of easy/recovery days. This allows the athlete to accomplish similar cardiorespiratory work with less running volume. The reduction in volume may reduce injury risk, as most running injuries come from repetitive stress. Additionally, HIFT allows the athlete to build some strength. This increased strength could reduce running form breakdowns when fatigued or on technical terrain, which increases efficiency and potentially reduces injury risk.

As Stand-alone Training

HIFT can also be used as the basis of a training program for anyone training for general physical fitness. Due to its high-intensity nature, allow for at least 48 hours between sessions when possible. More volume, additional strength, skill or aerobic workouts can be added as needed.

How to Progress

Progression can be one of the most challenging aspects of HIFT-style training. With so many different workout possibilities, it can be tempting to randomly generate workouts, throwing new and exciting things at your clients. While this constant variation can produce good results, especially for someone new to HIFT, the principle of overload still applies. To optimize progress and avoid plateaus, the difficulty of HIFT workouts can be incrementally increased by:

• Increasing the load used
• Increasing the volume
• Increasing the work:rest ratio

Here is an example of a basic beginner HIFT workout and how it can be progressed. The base workout consists of four rounds of:

• 12 jumping jacks
• 4 deadlifts (135 lb)
• 6 push presses (95 lb)
• 30-second plank
• 30-second rest

Is HIFT Safe?

Any exercise program that is not executed properly can result in injury. When adding HIFT workouts to your clients’ programs, it is important to use movements that each individual has already mastered. HIFT is a time to bring intensity to familiar movements to build cardiorespiratory and musculoskeletal capacities. It is not a time to learn new skills.

Overall, injury rates are similar, and often even lower, than those typically reported for running or other fitness activities. For example, a review of the available literature found that HIFT-related injury incidence rates programs were between 0.0 to 3.9 injuries per 1000 hours of training. This is similar to the rates seen in other forms of muscular training, such as weightlifting (2.4 to 3.3 injuries/1000 hours) and powerlifting (1.0 to 4.4 injuries/1000 hours). It is also considerably lower than injury rates of runners: 17.8 injuries/1000 hours in novice and 7.7 injuries/1000 hours in recreational runners.

Overall, HIFT is a safe and effective training option for improving both muscular strength and cardiorespiratory fitness. As you integrate HIFT into your clients’ programs, be sure to keep in mind the guidance and precautions detailed in this article, which include numerous evidence-based options.