The Intensity Level of Physical Exercise and the Bone Metabolism Response

Abstract

This study investigated the short-term effects of the intensity level of physical exercise on bone metabolism and related hormones. The responses of calciotropic hormones and bone biochemical markers were evaluated in seven male cyclists (mean age 24.4 years, range 20-39) during two 50-min cycling tests performed 15% below (-VT) and 15% above (+VT) the ventilatory threshold. In each test, venous blood samples were drawn at rest, at the 30th and 50th min of exercise, and after 15 min of recovery. For both intensity levels, no significant variation in calcium, 25-hydroxyvitamin D, 1.25-dihydroxyvitamin D, or cortisol level was observed. Intact parathyroid hormone (iPTH) level increased significantly after the last minute of the test (41%, p < 0.05) and peaked during the recovery (80%, p < 0.05) only in response to exercise performed at +VT. Serum phosphorus concentration rose during both tests, while albumin levels increased only at +VT. Concerning bone cell activity, osteocalcin, and type I-C telopeptide breakdown products transiently increased only in response to exercise performed at +VT (11% and 16.8%, respectively; p < 0.05). Bone alkaline phosphatase increased similarly for both intensity levels after 30 min (12%, p < 0.05) and 50 min (12% for -VT vs. 14% for +VT, p < 0.05). All markers of bone turnover returned to initial values during the recovery. In conclusion, a no-impact but intense and sustained exercise performed at +VT transiently stimulated bone turnover and iPTH secretion, suggesting the existence of a bone stimulation threshold. In addition to the well known effect of mechanical constraints, both the duration and intensity of exercise may induce changes in bone turnover.

Bone resorption is suppressed immediately after the third and fourth days of multiday cycling but persistently increased following overnight recovery

“…However, TEE was fairly similar within subjects between days as reflected by a low within-subject CV (6.7%), despite a marginally lower TEE on day 3 because of cyclists being fatigued and exercising at an average 9% lower intensity on day 3 compared with the other days. Previous studies have observed changes in serum bone markers following a single bout of cycling only at moderate to high intensities and not at lower intensities where exercise persisted for up to only 1 h long (Herrmann et al 2007;Maïmoun et al 2006). However, the increment between the high and low exercise intensities in those previous studies was far greater (ϳ30% difference between intensities) than the small 9% decrease in intensity on day 3 of the current study.…”

“…which is greater than the 17%-46% increase reported in previous studies (Barry et al 2011;Guillemant et al 2004;Herrmann et al 2007;Maïmoun et al 2006). This discrepancy may be due to the 3-fold longer duration of cycling in the current study.…”

“…Previous studies have evaluated the bone turnover marker response following only a single short (1 h) cycling bout (Barry et al 2011;Guillemant et al 2004;Herrmann et al 2007;Maïmoun et al 2006), and report increases in the bone resorption marker, C-terminal teleopeptide of type I collagen (␤-CTX), with no change (Barry et al 2011;Guillemant et al 2004;Herrmann et al 2007) or small relative increases in bone formation marker, bone alkaline phosphotase (bone-ALP), (Maïmoun et al 2006) compared with resting values. Thus, bone resorption is stimulated by a bout of short duration cycling, but it is unknown whether the response will be magnified by longer bouts of cycling.…”

Effect of fasting versus feeding on the bone metabolic response to running

“…Prolonged, endurance exercise increases P-CTX [15][16][17][18][19] but again, bone formation markers are largely unresponsive [15,16,18,19], suggesting that prolonged exercise might result in a transient negative remodelling balance. This acute response may be of significance to athletic populations as the net effects of changes in bone resorption and formation have been implicated in both stress fractures [20] and changes in bone mineral density (BMD) [21].…”

Low 25(OH) vitamin D concentrations in international UK track and field athletes

“…20 However, a small study on seven competitive road cyclists in the south of France identified adequate mean 25(OH)D levels of 32.4 mcg/l. 33 While there are limited data on the effects of vitamin D deficiency on performance in athletes, the potential relationship with fracture risk [34][35][36] and altered muscle function, 37,38 in addition to the additional pathological associations noted above, would suggest that the identification and subsequent treatment of vitamin D deficiency in athletes is prudent. In the UK, track and field athletes would appear to be at significant risk of deficiency given the UK latitude (51 -54°N), the indoor training environment and the proportion of dark-skinned athletes in the elite UK Athletics Track and Field team.…”