TSAC Research Column – April 2022

High-Intensity Functional Training (HIFT) Improves Fitness in Recruit Firefighters. International Journal of Environmental Research and Public Health 18(24): 13400, 2021.

Chizewski, A, Box, A, Kesler, RM, and Petruzzello, SJ.

High-intensity training has become popular among many tactical athletes in recent years. One aspect of high-intensity training researchers are interested in is the use of “functional” movements. A functional movement is a movement that uses the whole body in different planes of motion and incorporates exercises that mimic everyday activities. Researchers analyzed the data from a seven-week high-intensity functional training (HIFT) program to understand how fitness may change using these movements.

Eighty-nine firefighter academy recruits were analyzed during seven weeks of HIFT at the firefighter academy. Recruits had their body mass index calculated and performed various fitness tests before and after training. Aerobic fitness as an estimated VO₂max was collected using a 1.5-mile run. Muscular fitness was assessed using the YMCA bench press and maximum push-up and sit-up repetitions in one minute each. Flexibility was assessed using a sit-and-reach test, and lower body performance was evaluated using a vertical jump test. Functional tests included those similar to the candidate physical ability test, such as a KeiserR Sled to mimic forceful entry, a self-contained breathing apparatus (SCBA) crawl through a darkened course in a sea-land shipping container, a 110 lb victim drag for 100 ft, running a charged hose 75 ft, a down-back 50 ft farmers carry including two chainsaws (15 lb), and a ladder raise.

Recruits participated in HIFT for 60 min across five days per week during the seven-week academy program. The entire training schedule can be found in the article, but it was designed to incorporate exercises that were done for time or completed as quickly as possible. Exercises were mainly performed using bodyweight (e.g., bear crawls, walking lunges, push-ups, etc.) or equipment a firefighter would use (e.g., hoses, ladders, body dummy, etc.).

After the seven-week program, almost every variable improved except the vertical jump. Notable changes with large effect sizes included the 1.5-mile run (-10.7%, d = 0.85), estimated VO₂max (11%, d = 0.88), push-ups (37.2%, d = 1.22), sit-ups (22%, d = 0.99), and the SCBA crawl (-20.4%, d = 0.87). Considering the study did not include a control group, it is unclear if HIFT is a superior training style. However, these results highlight that aerobic fitness and muscular endurance can significantly improve using HIFT. Tactical facilitators working with firefighter recruits could benefit from incorporating HIFT into their programs. If lower body power needs to be improved, HIFT may not be the best option.

Skeletal Muscle Mass and Fat Mass Relationships with Physical Fitness Test Performance in Law Enforcement Recruits before Academy. The Journal of Strength and Conditioning Research 35(5): 1287-1295, 2021.

Lockie, RG, Carlock, BN, Ruvalcaba, TJ, Dulla, JM, Orr, RM, Dawes, JJ, and Mcguire, MB.

Body composition is an integral part of physical fitness, and it may affect an individual’s ability to carry out their duties in tactical populations. A recent research article examined how law enforcement recruits’ physical fitness may be related to body composition. Data from 338 law enforcement recruits (271 male and 67 female) were analyzed from four different academies to compare their body composition to various fitness test performances.

Fat mass and muscle mass were estimated using a bioelectrical impedance analysis instrument (Omron HBF-510) the researchers identified as being reliable based on previous research. The data was used to separate the recruits into quartiles based on muscle mass and fat mass percentage while controlling for sex. Group 1 had the lowest percent of muscle mass and the highest body fat, and group 4 had the highest percent muscle mass and lowest body fat. Body composition data were correlated to grip strength, vertical jump, push-ups, sit-ups, medicine ball (two kilogram) throw, a 75-m pursuit run, and a 20-m multistage fitness (beep) test.

Muscle mass was significantly related to all fitness tests except the medicine ball toss. Fat mass significantly correlated with all fitness tests except grip strength and medicine ball toss. Compared to group 1, group 4 had significantly better vertical jump (51.1 +} 1.8 versus 58.1 +} 1.4 cm, d = 1.2), 75-m pursuit run (17.2 +} 0.2 versus 16.75 +} 0.1 sec, d = -1.0), push-ups (36.0 +} 1.9 versus 47.9 +} 1.4 repetitions, d = 2.0), sit-ups (32.2 +} 1.5 versus 39.6 +} 1.2 repetitions, d = 1.6), and the beep test (45.3 +} 2.5 versus 61.7 +} 1.9 shuttles, d = 2.1.) These results indicate that recruits with a higher percentage of skeletal muscle mass and lower body fat perform better on fitness tests that incorporate muscular endurance, lower body power, and changing of direction. Tactical facilitators working with law enforcement recruits, should aim to build as much muscle as possible before entering the academy. If body fat is high, consulting a registered dietician may help with losing fat mass, possibly leading to better fitness results while in the academy.

The Effects of Military Style Ruck Marching on Lower Extremity Loading And Muscular, Physiological and Perceived Exertion in ROTC Cadets. Ergonomics 63(5): 629-38, 2020.

Earl-Boehm, JE, Poel, DN, Zalewski, K, and Ebersole, KT.

Most tactical athletes conduct their duties while wearing some torso-borne loads. Training with these loads can help acclimate the athlete and improve their performance while wearing the load, but they may also lead to physiological stress. Fifteen United States Army Reserve Officers’ Training Corps (ROTC) cadets (age: 21 +} 3 years, height: 1.8 +} 0.1 m, weight: 71.5 +} 13.8 kg) participated in the following study to analyze physiological and perceptual factors associated with a four-mile ruck march.

Before the ruck march, cadets had their ground reaction force (GRF), split into peak impact force (PIF), and loading rate (LR) measured by walking across a force plate. Researchers measured ankle strength using a handheld dynamometer while lying in a supine position. Cadets performed maximal contractions in four planes, utilizing dorsiflexors, plantar-flexors, invertors, and evertors. Lower body power was tested using a vertical jump test on a force plate to record peak power. After the pre-test, cadets participated in a four-mile ruck march on an indoor track wearing their combat uniform, including boots, helmet (1.5 kg), vest (3.7 kg), and a rucksack (16 kg). A 60-min time limit was set to ensure the cadets used an adequate pace. After the march, GRF, ankle strength, and vertical jump power were retested along with heart rate and perceived exertion.

Post-march, PIF and LR significantly increased by 5.8% (d = 0.1) and 11.3% (d = 0.2), respectively. The authors noted that significant increases to ground reaction forces might increase the risk of bone stress injuries, based on previous literature. However, the current study had small effect sizes. Either way, maintaining healthy bone mineral density through weight-bearing activity, such as back squats, may help decrease bone stress injuries. Additionally, dorsiflexion and plantar-flexion strength decreased by 10.2% (d = 0.2) and 7.4% (d = 0.1) with no change to perceived exertion. These strength decreases have been shown to decrease GRF, but the authors mentioned that larger and more commonly trained muscles, such as the glutes and quadriceps, should be studied in the future. Tactical facilitators should know how much loaded marching their personnel are doing to avoid overuse injury when working with the military.

This article originally appeared in TSAC Report, the NSCA’s quarterly, online-only publication geared toward the training of tactical athletes, operators, and facilitators. It provides research-based articles, performance drills, and conditioning techniques for operational, tactical athletes. The TSAC Report is only available for NSCA Members. Read more articles from TSAC Report 

Skeletal Muscle Mass and Fat Mass Relationships with Physical Fitness Test Performance in Law Enforcement Recruits Before Academy