Responses of bone turnover markers to repeated endurance running in humans under conditions of energy balance or energy restriction

Abstract

Distance running in humans has been associated with both positive and negative effects on the balance of bone remodelling. There is evidence to suggest that the negative effects may be linked to a failure to balance energy expenditure with an adequate energy intake. Energy restriction is known to reduce the synthesis and serum concentration of insulin-like growth factor 1 (IGF-1), which plays an important role in bone formation. The purpose of the present study was to compare the effects of repeated periods of prolonged treadmill running, under conditions of either energy balance or energy restriction, on markers of bone turnover and serum IGF-1 concentration in trained distance runners. Eight male distance runners [mean age 25.1 (SD 5.9) years, maximal oxygen uptake 61.8 (SD 4.9) ml x kg(-1) x min(-1)] undertook an exercise and diet regime on two separate occasions, 2 weeks apart. On each occasion they performed an intensive, 60 min treadmill run on 3 consecutive days. On one occasion their energy intake was restricted to approximately 50% of their estimated energy requirement (RES), whereas on the other occasion they remained in energy balance (BAL). The N-terminal pro-peptide of type 1 collagen (P1NP), osteocalcin and IGF-1 were measured in serum collected between 0800 and 0900 hours, when fasted and rested, on the day before and the day after each regime. The cross-linked N-telopeptides of type 1 collagen and deoxypyridinoline were measured from 24 h urine collections made on the day before and the final day of each regime and adjusted for creatinine excretion. The results showed that the serum concentration of both P1NP and IGF-1 declined by 15% (P = 0.008) and 17% (P = 0.007) respectively in response to RES, but did not change in response to BAL (P > 0.05). A strong relationship was observed between the magnitude of the reduction in the serum concentration of P1NP and IGF-1 after RES (r = 0.97; P < 0.001). There were no changes in the other bone markers in response to either regime. The results suggested that in trained distance runners, repeated periods of prolonged running do not affect the balance of bone turnover unless energy balance is simultaneously altered. These findings support the link between a negative energy balance, a reduced synthesis or serum level of IGF-1 and reduced collagen synthesis. They may also help to explain the bone remodelling imbalance that has been observed in some male and female distance runners.

Participation in road cycling vs running is associated with lower bone mineral density in men

“…First, exercise per se may induce hormone synthesis and/or secretion [36,37]. Second, exercise may create an energy deficit, which, in turn, alters hormone secretion [13][14][15][16]. It has been suggested that bone loss associated with endurance exercise results from hormonally mediated suppression of bone turnover and acceleration of bone resorption.…”

“…Low body weight and weight loss have been associated with reduced bone mineral density (BMD) [13,14] due to reduced mechanical loading on the skeleton and hormonal changes associated with inadequate energy intake [15,16]. However, because runners and cyclists both have relatively low body weight compared with sedentary men [11], the discrepant BMD has been attributed to lack of ground reaction forces (GRF) on the skeleton during cycling [9,11,12].…”

Re: Bone: An Acute Buffer of Plasma Sodium During Exhaustive Exercise?

“…The authors, Hew-Butler, Stuempfle and Hoffman have presented an interesting hypothesis which contradicts current thinking on explanations for low bone density frequently observed in competitive endurance athletes. At present, the current theory for bone loss in endurance athletes is based on an uncoupling of bone turnover due to an energy deficit, whereby there is a reduction in collagen synthesis which coincides with reductions in circulating oestradiol, triiodothyronine (T3) and insulin-like growth factor (IGF) 1 [2,3]. Energy conservation is thought to be the primary reason for hypo-oestrogenism and reduced bone density in athletes who are either intentionally or unintentionally energy deficient, and there is strong evidence to support this.…”

“…This evidence has accumulated over the last 3 decades, from the initial observations of low bone density in amenorrheic female runners, to observations also in male endurance runners [4][5]. The research progressed to uncover associations of low body weight, body fat, high volume training, energy deficient diets, with low bone density, and to well-controlled studies where energy deficit has been experimentally induced and a reduction in bone formation markers reported [2,3].…”

Metabolismo ósseo de vacas jovens Nelore em pastos de Brachiaria brizantha suplementadas ou não durante a seca com fósforo/cálcio e concentrado

“…A restrição de energia foi relacionada à redução da síntese e da concentração sérica de IGF-I, bem como à diminuição da síntese de colágeno em seres humanos (Zanker & Swaine, 2000). Em ratas, a restrição da energia dietética provocou elevação na reabsorção óssea e redução da massa corporal e da densidade do osso.…”