Dennis E. Scofield

Physiological Employment Standards III: physiological challenges and consequences encountered during international military deployments

Modern international military deployments in austere environments (i.e., Iraq and Afghanistan) place considerable physiological demands on soldiers. Significant physiological challenges exist: maintenance of physical fitness and body composition, rigors of external load carriage, environmental extremes (heat, cold, and altitude), medical illnesses, musculoskeletal injuries, traumatic brain injuries, post-traumatic stress disorder, and environmental exposure hazards (i.e., burn pits, vehicle exhaust, etc.). To date there is very little published research and no comprehensive reviews on the physiological effects of deployments. The purpose of this paper is to overview what is currently known from the literature related mainly to current military conflicts with regard to the challenges and consequences from deployments. Summary findings include: (1) aerobic capacity declines while muscle strength, power and muscular endurance appear to be maintained, (2) load carriage continues to tax the physical capacities of the Soldier, (3) musculoskeletal injuries comprise the highest proportion of all injury categories, (4) environmental insults occur from both terrestrial extremes and pollutant exposure, and (5) post-deployment concerns linger for traumatic brain injury and post-traumatic stress disorder. A full understanding of these responses will assist in identifying the most effective risk mitigation strategies to ensure deployment readiness and to assist in establishment of military employment standards.

Recovery of Endocrine and Inflammatory Mediators Following an Extended Energy Deficit

CONTEXT Due to current operational requirements, elite soldiers deploy quickly after completing arduous training courses. Therefore, it is imperative that endocrine and inflammatory mediators have fully recovered. OBJECTIVE Our objective was to determine whether a short-term (2-6 wk) recovery period was sufficient to restore endocrine and inflammatory homeostasis after sustained energy deficit. DESIGN Before and immediately after the course, serum concentrations of inflammatory and endocrine markers were taken along with anthropometric measures prior to and immediately after the Army Ranger course. In addition, nine soldiers were assessed between 2 and 6 weeks after the course. SETTING This research occurred in a field setting during an intensive 8-week military training course characterized by high-energy expenditure, energy restriction, and sleep deprivation (U.S. Army Ranger School). PARTICIPANTS Twenty-three male soldiers (23.0 ± 2.8 y; 177.6 ± 7.9 cm; 81.0 ± 9.6 kg, 16.8 ± 3.9% body fat) participated in this study. INTERVENTIONS There were no interventions used in this research. OUTCOME MEASURES AND RESULTS Significant changes occurred in circulating total testosterone (-70%), brain-derived neurotrophic factor (-33%), total IGF-1 (-38.7%), free IGF-1 (-41%), IGF binding protein (IGFBP-6; -23.4%), sex-hormone binding globulin (+46%), thyroid stimulating hormone (+85%), IGFBP-1 (+534.4%), IGFBP-2 (+98.3%), IGFBP-3 (+14.7%), IL-4 (+135%), IL-6 (+217%), and IL-8 (+101%). Significant changes in body mass (-8%), bicep (-14%), forearm (-5%), thigh (-7%), and calf (-2%) circumferences, sum of skinfolds (-52%), and percentage body fat (-54%). All anthropometric, inflammatory, and hormonal values, except T3, were restored to baseline levels within 2-6 weeks after the course. CONCLUSIONS Endocrine markers and anthropometric measures were degraded, and inflammatory mediators increased after an extended energy deficit. A short-term recovery of 2-6 weeks was sufficient to restore these mediators.

Effects of acute caloric restriction compared to caloric balance on the temporal response of the IGF-I system.

OBJECTIVE Insulin-like growth factor-I (IGF-I) is a key regulator of metabolism during altered energy states. The IGF-I system components respond to prolonged caloric restriction but it is not clear if this system responds similarly to acute caloric restriction. The purpose of this study was to characterize the IGF-I system response to acute caloric restriction with a secondary purpose of determining if two isocaloric diets with different ratios of carbohydrate to fat alter the IGF-I system under conditions of caloric balance. MATERIALS/METHODS A double-blind, placebo-controlled crossover design was used in which 27 subjects underwent three, 48-h experimental treatments: 1) caloric restriction 2) carbohydrate and 3) carbohydrate/fat. Blood was sampled periodically (6 time points total) for IGF-I (total and free), IGFBPs1-4, insulin and glucose. ANOVAs were used with significance set at P<0.05. RESULTS Total IGF-I decreased 7% during CR (P=0.051) and remained stable during CHO and CHO/F. Free IGF-I decreased 43% during CR (P<0.05) and remained stable during CHO and CHO/F. IGFBP-1 increased by 445% during CR (P<0.05) compared to CHO and CHO/F with no changes for IGFBP-2, IGFBP-3 and IGFBP-4. There was no change in glucose or insulin during CR over the course of the study. Insulin and glucose increased (P<0.05) after a meal in both the CHO and CHO/F groups with no difference between these two groups. CONCLUSION Our findings indicate that free IGF-I decreases and IGFBP-1 increases during caloric restriction, but they are not altered with diets differing in carbohydrate and fat content. Changes in free IGF-I and IGFBP-1 are sensitive to caloric restriction, and their measurement may be valuable in monitoring the physiological response to refeeding in those consuming suboptimal calories.

IGF-I, IGFBPs, and inflammatory cytokine responses during gender-integrated Israeli Army basic combat training.

Abstract Nindl, BC, Scofield, DE, Strohbach, CA, Centi, AJ, Evans, RK, Yanovich, R, Moran, DS. IGF-I, IGFBPs, and inflammatory cytokine responses during gender-integrated Israeli Army basic combat training. J Strength Cond Res 26(7): S73–S81, 2012—Insulin-like growth factor 1 (IGF-I) is a robust metabolic and anabolic biomarker that has been demonstrated to be reflective of military training–induced body composition changes and influenced by initial aerobic fitness level. Greater mechanistic insight into the IGF-I response to physical training can potentially be gleaned by also examining other regulatory factors that influence IGF-I biological activity (i.e., insulin-like growth factor–binding proteins [IGFBPs] and inflammatory cytokine responses). The purpose of this study was to assess the influence of sex and initial fitness level on the IGF-I and inflammatory cytokine response to gender-integrated Israeli Defense Forces (IDF) basic combat training (BCT). Recruits (29 men, 19.1 ± 1.3 years; 93 women, 18.8 ± 0.6 years) were recruited from a 4-month gender-integrated BCT of the IDF. Blood was drawn and assayed for total IGF-I, free IGF-I, IGFBPs 1-6, tumor necrosis factor alpha (TNF-&agr;), interleukin 6, and interleukin 1 beta. Body composition was determined via a 4-site skinfold (biceps, triceps, suprailiac, and subscapular) equation. Physical performance was assessed via a maximum volume of oxygen consumption (V[Combining Dot Above]O2max) test using a treadmill protocol. All measures were obtained pre- and posttraining. A 2-way (sex × time) analysis of variance was used to test for statistical differences (p ⩽ 0.05). Additionally, subjects were further partitioned (men and women separately) by tertiles of initial V[Combining Dot Above]O2max to assess the influence of initial fitness level on the IGF-I system and inflammatory cytokine responses to physical training. Pearson product moment correlational analysis was also used to examine relationships between percent changes in blood measures and physical performance and body composition changes. All data are presented as mean ± SE. Time effects were observed only for total IGF-I, IGFBP-2, TNF-&agr;, V[Combining Dot Above]O2max, fat-free mass, and fat mass. The only significant (p ⩽ 0.05) correlations observed for percent changes were in men between total IGF-I and V[Combining Dot Above]O2max (r = 0.49) and body mass (r = −0.42) During gender-integrated Israeli Army BCT, men and women generally respond in a similar fashion with regard to blood measures (IGF-I system and inflammatory cytokines) and V[Combining Dot Above]O2max. Initial fitness level only influenced the IGF-I response to training in women. Although the training-induced changes in total IGF-I (increase), IGFBP-2 (decrease), and TNF-&agr; (decrease) are all indicative of an enhanced circulating anabolic milieu, only total IGF-I for the men was correlated with body composition and fitness improvements.

Bioavailable IGF-I Is Associated with Fat-Free Mass Gains after Physical Training in Women

UNLABELLED The contributions of systemic versus local insulin-like growth factor-I (IGF-I) action for mediating fat-free mass (FFM) accretion have yet to be fully clarified, but circulating IGF-I is the preferred measure in clinical practice, and its merits as a biomarker have been demonstrated for a number of physiological outcomes. PURPOSE To test the hypothesis that bioavailable IGF-I would have a stronger association with physical activity-induced FFM accretion than total IGF-I and would serve as a prognostic indicator of FFM accretion. METHODS Seventy-seven young healthy women (21 ± 5 yr, 62.7 ± 8.5 kg, 27.0% ± 6.0% body fat) participated in 8 wk of Army basic training involving intense physical activity. Total and bioavailable IGF-I; IGF binding proteins (IGFBP) 1, 2, 3, 4, 5, and 6; and body composition parameters were measured before and after the training. RESULTS There were significant (P≤0.05) increases in FFM (6%) and decreases in fat mass (-13%). Total IGF-I and IGFBP-4 to -6 increased, whereas IGFBP-1 and IGFBP-2 decreased. Bioavailable IGF-I (24%) explained three times the amount of variance in relative FFM changes than did total IGF-I (8%). Receiver operator characteristic curve analysis revealed that women with lower baseline bioavailable IGF-I were twice as likely to experience FFM gains >7%. Women gaining >7% FFM had greater increases in total IGF-I, maintained bioavailable IGF-I concentrations and experienced greater decreases in IGFBP-2 and increases in IGFBP-6 than those women gaining <7% FFM. CONCLUSIONS Circulating bioavailable IGF-I has a moderate association with physical activity-induced increases in FFM accretion in young, healthy women, and this association is greater than observed for total IGF-I.

Risk Factors for Soft Tissue Knee Injuries in Active Duty U.S. Army Soldiers, 2000–2005

BACKGROUND There is a scarcity of analytic research on active duty Army (ADA) knee injuries (KI), such as soft tissue knee injuries (STKI), which are the predominant ADA KI pattern. PURPOSE To quantify the independent adjusted association of significant ADA STKI risk factors, 2000-2005. MATERIALS/METHODS Using the Total Army Injury and Health Outcomes Database, we (1) captured absolute STKI numbers and rates (N = 83,323) and (2) developed regression models to determine significant STKI risk factors. Models included STKI overall and subcategories: meniscus, patella, anterior/posterior cruciate ligament, and medial/lateral cruciate ligament. RESULTS Eight risk factors significantly increased STKI. They are: (1) prior KI (within 2 years) (odds ratio [OR] 9.83, 95% confidence interval [CI] 9.67-10.00); (2) increasing length of service (OR 1.83, 95% CI 1.76-1.90); (3) increasing age (OR 1.57, 95% CI 1.50-1.65); (4) prior deployment (OR 1.39, 95% CI 1.36-1.41); (5) prior ankle injury (OR 1.16, 95% CI 1.14-1.19); (6) Infantry occupation (OR 1.12, 95% CI 1.04-1.21); (7) marital status (OR 1.10, 95% CI 1.08-1.12); (8) and prior hip injury (OR 1.08, 95% CI 1.03-1.12). MAJOR CONCLUSION Soldiers with a prior KI have nearly a 10-fold increased relative risk of developing a subsequent STKI.

IGF-I measurement across blood, interstitial fluid, and muscle biocompartments following explosive, high-power exercise

Insulin-like growth factor-I (IGF-I) resides across different biocompartments [blood, interstitial fluid (ISF), and muscle]. Whether circulating IGF-I responses to exercise reflect local events remains uncertain. We measured the IGF-I response to plyometric exercise across blood, ISF, and muscle biopsy from the vastus lateralis. Twenty volunteers (8 men, 12 women, 22 ± 1 yr) performed 10 sets of 10 plyometric jump repetitions at a 40% 1-repetition maximum. Blood, ISF, and muscle samples were taken pre- and postexercise. Circulating IGF-I increased postexercise: total IGF-I (preexercise = 546 ± 42, midexercise = 585 ± 43, postexercise = 597 ± 45, +30 = 557 ± 42, +60 = 536 ± 40, +120 = 567 ± 42 ng/ml; midexercise, postexercise, and +120 greater than preexercise, P < 0.05); Free IGF-I (preexercise = 0.83 ± 0.09, midexercise = 0.78 ± 0.10, postexercise = 0.79 ± 0.11, +30 = 0.93 ± 0.10, +60 = 0.88 ± 0.10, + 120 = 0.91 ± 0.11 ng/ml; +30 greater than all other preceding time points, P < 0.05). No exercise-induced changes were observed for ISF IGF-I (preexercise = 2.35 ± 0.29, postexercise = 2.46 ± 0.35 ng/ml). No changes were observed for skeletal muscle IGF-I protein, although IGF-I mRNA content increased ∼40% postexercise. The increase in circulating total and free IGF-I was not correlated with increases in ISF IGF-I or muscle IGF-I protein content. Our data indicate that exercise-induced increases in circulating IGF-I are not reflective of local IGF-I signaling.

The Tactical Athlete: A Product of 21st Century Strength and Conditioning

ABSTRACT OCCUPATIONS IN LAW ENFORCEMENT, THE MILITARY, OR RESCUE SERVICES REQUIRE PERSONNEL TO DEVELOP GENERAL PHYSICAL PREPAREDNESS IN ADDITION TO TECHNICAL AND TACTICAL SKILLS THAT ARE CRUCIAL IN ENVIRONMENTS INVOLVING CIVIL PROTECTION, GRAVE PHYSICAL DANGER, OR RESCUE SITUATIONS. THE TERM TACTICAL ATHLETE IS COMMONLY USED BY THOSE IN THE TACTICAL STRENGTH AND CONDITIONING COMMUNITY TO IDENTIFY PERSONNEL IN TACTICAL PROFESSIONALS WHO REQUIRE UNIQUE PHYSICAL TRAINING STRATEGIES AIMED AT IMPROVING OCCUPATIONAL PERFORMANCE. THE PURPOSE OF THIS ARTICLE IS TO PROMOTE AWARENESS AND PROVIDE RATIONALE FOR USE OF THE TERM TACTICAL ATHLETE.

Epidemiology of Ankle Sprains and the Risk of Separation From Service in US Army Soldiers

STUDY DESIGN Retrospective cohort study. OBJECTIVES To report the incidence rate of ankle sprains in active-duty soldiers and to examine if soldiers who sustain ankle sprain injuries are more likely to leave the Army than those who do not sustain an ankle sprain. BACKGROUND Ankle sprains are one of the most common musculoskeletal injuries in physically active people and have been identified as the most common foot or ankle injury in active-duty Army personnel, with a rate of 103 sprains per 1000 soldiers per year. METHODS Data were analyzed on the entire active-duty US Army population from 2000 to 2006 (n = 1 014 042). A semi-parametric Cox proportional hazard model was built. RESULTS The overall incidence rate for ankle sprains was 45.14 per 1000 person-years. After controlling for length of service prior to the study period, soldiers who sustained a single ankle sprain were 27% less likely (relative risk ratio = 0.73; 95% confidence interval: 0.73, 0.75) to leave the service than soldiers who had no documented history of an ankle sprain. However, this trend toward increased service time no longer held true for those who sustained a recurrent sprain (risk ratio = 1.07; 95% confidence interval: 0.99, 1.15). CONCLUSION It appears that individuals who sustain an incident ankle sprain have longer time in service in the Army than those who do not sustain this injury. However, this trend toward longer service time no longer held true for soldiers who sustained a recurrent. LEVEL OF EVIDENCE Prognosis, level 2b.

A novel, noninvasive transdermal fluid sampling methodology: IGF-I measurement following exercise

This study tested the hypothesis that transdermal fluid (TDF) provides a more sensitive and accurate measure of exercise-induced increases in insulin-like growth factor-I (IGF-I) than serum, and that these increases are detectable proximal, but not distal, to the exercising muscle. A novel, noninvasive methodology was used to collect TDF, followed by sampling of total IGF-I (tIGF-I) and free IGF-I (fIGF-I) in TDF and serum following an acute bout of exercise. Experiment 1: eight men (23 ± 3 yrs, 79 ± 7 kg) underwent two conditions (resting and 60 min of cycling exercise at 60% Vo(2)(peak)) in which serum and forearm TDF were collected for comparison. There were no significant changes in tIGF-I or fIGF-I in TDF obtained from the forearm or from serum following exercise (P > 0.05); however, the proportion of fIGF-I to tIGF-I in TDF was approximately fourfold greater than that of serum (P ≤ 0.05). These data suggest that changes in TDF IGF-I are not evident when TDF is sampled distal from the working tissue. To determine whether exercise-induced increases in local IGF-I could be detected when TDF was sampled directly over the active muscle group, we performed a second experiment. Experiment 2: fourteen subjects (22 ± 4 yr, 68 ± 11 kg) underwent an acute plyometric exercise condition consisting of 10 sets of 10 plyometric jumps with 2-min rest between sets. We observed a significant increase in TDF tIGF-I following exercise (P ≤ 0.05) but no change in serum tIGF-I (P > 0.05). Overall, these data suggest that TDF may provide a noninvasive means of monitoring acute exercise-induced changes in local IGF-I when sampled in proximity to exercising muscles. Moreover, our finding that the proportion of free to tIGF-I was greater in TDF than in serum suggests that changes in local IGF-I may be captured more readily using this system.