Development and maintenance of physical capabilities is an essential part of combat readiness in the military [1, 2]. Physical Readiness is loosely defined as “the ability to meet the physical demands of any combat or duty position, accomplish the mission, and continue to fight and win” [3]. This readiness requires continuous training and is therefore compromised by injury. Perhaps surprisingly, the primary cause of military casualties is daily physical training (PT), estimated at 78% of all DNBI casualties. [1, 2]. There are more than 2 million musculoskeletal injuries (MSKIs) sustained annually by soldiers, with disease and non-battle injury (DNBI) casualties constituting more than 50% of all injuries and up to 43% of DNBI casualties requiring evacuation [4, 5]. MSkIs greatly and negatively impact military populations in terms of healthcare utilization, deployability and combat readiness, and task performance [6] [4]. For example, losses from MSKIs for the U.S. Marine Corps were about $111 million and 356,000 lost duty days in 2019 [7]. Because Service Members (SMs) must be physically and cognitively prepared to conduct multifaceted operations in support of strategic objectives, and because the Department of Defense’s (DoD) non-deployable rate and annual costs associated with treating SMs continue to rise at an alarming rate, finding a far-reaching and efficient solution to prevent such injuries is a high priority [8].
By the time MSKIs emerge, the damage has been done. Instead of reacting once an SM is injured, a better strategy is to prevent the injuries before they happen. One step toward injury prevention is a focus on recovery during training. Strenuous exercise, eccentric exercise, or unaccustomed exercise can result in damage to muscle fibers and is the primary cause of delayed onset muscle soreness (DOMS) and reduction in muscle function, often referred to as exercise-induced muscle damage (EIMD). EIMD is characterized by symptoms including pain, strength loss, stiffness, swelling, and an increase in the blood circulation of intra-muscular metabolites. Some symptoms, such as myocellular proteins and metabolites, do not begin to peak until 24–72 hours post-exercise. Although soreness and loss of range of motion occur nearly immediately, they also typically peak 24–48 hours after exercise and can last up to 96 hours [9, 10]. The severity of EIMD depends on an individual’s exercise familiarity, intensity, and the duration of the activity. Inadequate recovery time and misalignment of training exercises and rest periods can cause unintended overtraining, which can lead to excessive microtears in muscles and lead to MSKIs, and, ultimately, a non-deployable SM with potential sequelae.
To date, a sound and consistent treatment for DOMS/EIMD has not been established, although many pre-and post-exercise interventions using pharmacological, therapeutic and nutritional supplements have been explored [10]. In the world of elite athletics, there has been an embrace of compression garments (CGs) as a means of improving performance and, especially, recovery [11, 12, 13, 14, 15, 16]. Compression garments are tightly-fitting elastic garments that apply substantial mechanical pressure on the surface of body zones for stabilizing, compressing, and supporting underlying tissues. CGs are feasible and scalable for all body types and are provided in a variety of styles, such as stockings (knee-length and mid-thigh length), sleeves, upper-body garments (covering upper extremities and terminating at the torso), and lower-body garments (from the waist to the malleoli). In addition, CGs do not interfere or hinder training exercises and performances, since garments have seamless comfortable integration with the wearer.
Compression garments have become increasingly popular over the past decade in human performance applications, and reportedly facilitate post-exercise recovery by reducing muscle soreness, increasing blood lactate removal, and increasing perception of recovery, but the evidence is mixed, at best [16, 17, 18, 19, 20, 21]. One review study, for example, found that CGs help in recovery in terms of subsequent performance for endurance but not sprinting or jumping [22].
Studies also differed in their approach to CGs and recovery - most studies had participants wear CGs only during the recovery period (e.g. [23]), while others had participants wear compression garments both during fatiguing exercise and during the subsequent recovery period (e.g. [24]). Results were mixed [16]. These mixed results in elite athletes may or may not translate to SMs. Service Members are tactical athletes whose training is different in kind and amount from elite sports athletes. Tactical athletes need to train for real-life movements (e.g. lifting, crawling, rucking), carrying heavy and potentially unevenly balanced loads (e.g. rucksacks, equipment) and for long term endurance (tactical athletes do not have an off-season where their bodies have the chance of full recovery) [25].In the current study we explored whether CG use, and duration of use, improves recovery and mitigates muscle soreness effectively in an elite Marine training course [26]. In order to test this, we subjected SMs to fatiguing exercise and then measured subjective and objective recovery and soreness using participant reports and grip and leg strength over a 72-hour recovery period.