Overnight responses of the circulating IGF-I system after acute, heavy-resistance exercise

Abstract

This study evaluated the individual components of the insulin-like growth factor I (IGF-I) system [i.e., total and free IGF-I, insulin-like growth factor binding protein (IGFBP)-2 and -3, and the acid-labile subunit (ALS)] in 10 young, healthy men (age: 22 +/- 1 yr, height: 177 +/- 2 cm, weight: 79 +/- 3 kg, body fat: 11 +/- 1%) overnight for 13 h after two conditions: a resting control (Con) and an acute, heavy-resistance exercise protocol (Ex). The Ex was a high-volume, multiset exercise protocol that alternated between 10- and 5-repetition maximum sets with 90-s rest periods between sets. The Ex was performed from 1500 to 1700; blood was obtained immediately postexercise and sampled throughout the night (every 10 min for the first hour and every hour thereafter) until 0600 the next morning. For the first hour, significant differences (P < or = 0.05) were only observed for IGFBP-3 (Ex: 3,801 > Con: 3,531 ng/ml). For the overnight responses, no differences were observed for total or free IGF-I or IGFBP-3, whereas IGFBP-2 increased (Ex: 561 > Con: 500 ng/ml) and ALS decreased (Ex: 35 < Con: 39 microg/ml) after exercise. The results from this study suggest that the impact that resistance exercise exerts on the circulating IGF-I system is not in the alteration of the amount of IGF-I but rather of the manner in which IGF-I is partitioned among its family of binding proteins. Thus acute, heavy-resistance exercise can lead to alterations in the IGF-I system that can be detected in the systemic circulation.

The Effect of Endurance-Type Exercise Training on Growth Mediators and Inflammatory Cytokines in Pre-Pubertal and Early Pubertal Males

“…Acute exercise leads to a brief increase in IGF-I, but, if the exercise is sufficiently intense, is followed by a reduction (17,18). There are no studies that have examined the duration of the exercise-associated reduction in circulating IGF-I, but recent observations from Nindl et al (19) indicate that IGF-I returns to baseline levels at least overnight after a heavy bout of exercise. Results are shown as mean Ϯ SE.…”

Hormonal responses following eccentric exercise in humans

“…Another study showed that circulating levels of IGFBP-3 were only increased for the first hour after a mechanical overloading exercise and further suggested that the acute effect of a resistance exercise bout is not the changes in circulating IGF-1 levels but rather the manner in which this anabolic factor is partitioned among its binding proteins. 40 Moreover, a potentiation of IGF activity by IGFBP-3 has been demonstrated in many in vitro systems, leading to the concept that cell association and processing of IGFBP-3 to a form of reduced affinity to IGF-1 is involved in the enhancement of the availability of IGF-1 to its receptor(s), 41,42 while, further, GH induces IGFBP-3 local accumulation in cells. 43 Hence, we could speculate that GH and IGFBP-3 responses and their negative correlations found in this study may indicate a GH-induced tissue accumulation of circulating IGFBP-3 as a mechanism of potentiating the regenerative and anabolic effects of IGF-1 following muscle damage.…”

Efeitos do treinamento de força sobre os níveis de IGF1 e de força muscular nas fases neurogência e miogênica de idosas

“…11,35 O trabalho de Nindl et al 17 ressalta que o treinamento de força pode alterar o padrão temporal de liberação do GH durante a noite, e que o exercício resistido pode ocasionar alteração no sistema do IGF-1 e sua detecção na circulação. Este tipo de treinamento apresenta maior correlação positiva com aumentos séricos do IGF-1, dando sustentação aos resultados obtidos no estudo vigente.…”

“…Portanto, além da liberação do IGF-1 pelo fígado, induzida pelo aumento de GH, vários tecidos o produzem e ainda são estimulados a utilizá-lo como efeitos agudos do exercício. 17,29,30,36 Entretanto, a investigação de Aizawa, Hayashi e Mesak 37 contrapõe tal informação, pois embora os autores tenham revelado uma correlação positiva do dehydroepiandrosterone sulfate (DHEAS) com o pico de torque muscular, nenhum resultado significativo foi encontrado com o IGF1.…”

“…16 Dentre as diversas modalidades, o treinamento de força é o que apresenta maior correlação positiva, com aumentos séricos de IGF1. 17 Portanto, a estimulação do IGF1 contribuirá de forma significativa para a hipertrofia e para o aumento do conteúdo de miofibrilas esqueléticas. 18 O presente estudo teve por objetivo avaliar os efeitos do treinamento de força sobre os níveis basais de IGF1 e de força muscular nas fases neurogência e miogênica de idosas sedentárias.…”