IGF-I, IGFBPs, and Inflammatory Cytokine Responses During Gender-Integrated Israeli Army Basic Combat Training

Abstract

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-α), 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-α, 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-α (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.

Physical fitness, hormonal, and immunological responses during prolonged military field training

“…In the present study, no significant differences in the IL-6 concentrations were observed during the study period due to large individual variation. Chester et al (2013) and Nindl et al (2012) have also reported similar findings previously. Gomez-Merino et al (2002) and McClung et al (2013) have found, however, increases in the IL-6 concentrations during prolonged MFT.…”

“…IL-6 has been shown to remain unchanged (Chester et al 2013) or increase (Gomez-Merino et al 2003;McLung et al 2013) during MFT. No changes in IL-6 concentrations were observed during Israeli army basic training (Nindl et al 2012). However, these studies did not report the associations between IL-6 concentration and physical performance of warfighters.…”

“…Nindl et al. () studied the changes in TNF‐ α during a 4‐month basic training period and found a decrease in TNF‐ α . Increases in TNF‐ α concentration has been suggested to be due to the inflammation state in the body, caused by muscle damage (Espersen et al.…”

“…It appears that it is affected by the duration and intensity of training and subjects training age (Dufaux and Order 1989;Espersen et al 1990;Rivier et al 1994). Nindl et al (2012) studied the changes in TNF-a during a 4-month basic training period and found a decrease in TNF-a. Increases in TNF-a concentration has been suggested to be due to the inflammation state in the body, caused by muscle damage (Espersen et al 1990).…”

“…No changes in IL‐6 concentrations were observed during Israeli army basic training (Nindl et al. ). However, these studies did not report the associations between IL‐6 concentration and physical performance of warfighters.…”