Bone formation is increased to a greater extent than bone resorption during a cycling stage race

The Bone Metabolic Response to Exercise and Nutrition

Bone (re)modeling markers can help determine how the bone responds to different types, intensities, and durations of exercise. They also might help predict those at risk of bone injury. We synthesized evidence on the acute and chronic bone metabolic responses to exercise, along with how nutritional factors can moderate this response. Recommendations to optimize future research efforts are made.

Longitudinal Assessment of Bone Mineral Density and Body Composition in Competitive Cyclists

Baker, BS and Reiser II, RF. A longitudinal assessment of bone mineral density and body composition in competitive cyclists. J Strength Cond Res 31(11): 2969-2976, 2017-Competitive cycling has been associated with low bone mineral density (BMD); however, BMD is a multifaceted issue. The purpose of this study was to investigate how age (18-49 years), sex, USA Cycling Category (elite-4), and racing type (road and multiple bikes), influenced body composition across a season in competitive cyclists. February marked the preseason, where 42 participants (22 males, 20 females) completed a health history and cycling questionnaire, 4-day dietary log and a dual-energy X-ray absorptiometry scan, and repeated the measures 180 ± 11 days later. Preseason BMD and Z-Scores were within healthy ranges and similar between sexes, age groups, competition levels and racing-type groups (p ≥ 0.053). Age was significantly correlated with whole group BMD (r = 0.309; p = 0.047). Postseason analysis revealed very encouraging findings as no significant changes in BMD or Z-Score were observed in any group (p ≥ 0.067). A significant main effect for time was found in all groups as lean mass (LM) decreased and fat mass increased across the season (p ≤ 0.001). Additional analysis showed a significant time × group interaction as cat. 1 riders decreased body mass and body mass index, whereas cat. 4 riders responded in the opposite direction (p ≤ 0.037). Postseason correlations highlighted significant positive relationships between BMD and age, LM, and Kcal ingested (r ≥ 0.309; p ≤ 0.047). The only significant negative correlate of BMD was percent body fat (r = -0.359; p = 0.020). Armed with this information, cyclists and coaches should aim to prioritize balance between body mass and caloric intake while meeting the demands of training to minimize risk of cycling related low bone mass.

Bone metabolism markers and vitamin D in adolescent cyclists

This study aimed to describe bone metabolic activity in adolescent competitive cyclists compared to age-matched controls. The main result is that younger subjects present a higher bone turnover than the older ones. Moreover, cyclists under the age of 17 have higher scores on all markers than age-matched controls.

PURPOSE

The purpose of this study was to describe bone metabolic activity in adolescent competitive cyclists compared to age-matched controls.

METHODS

Twenty-two male adolescent cyclists between 14 and 20 years (y) and 20 age-matched controls participated in this study. Serum osteocalcin (OC), aminoterminal propeptide of type I procollagen (PINP), and β-isomerized C-telopeptides (β-CTX) were analyzed by electrochemiluminescence immunoassay (ECLIA); plasma 25 hydroxyvitamin D [25(OH)D] was analyzed by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Analysis of variance revealed no significant differences in bone metabolism markers and vitamin D between cyclists and controls. Cyclists over 17 y had a significantly lower concentration in bone formation and resorption biochemical markers compared to cyclists under 17 y (all P < 0.05). Moreover, controls over 17 y presented lower concentration for PINP (P < 0.05) compared to their peers under 17 y. Comparisons between cyclists and controls under 17 y revealed higher concentrations of OC and PINP (P < 0.05) in cyclists. Group interaction by age was found for OC, PINP, and β-CTX (P < 0.01). Cyclists over 17 y had higher concentrations of [25(OH)D] (P < 0.05) than age-matched controls.

CONCLUSIONS

The present results support the idea that cycling during adolescence may be associated to a decrease in bone turnover that may affect bone health later in life.

Response of Bone Turnover Markers and Cytokines to High-Intensity Low-Impact Exercise

INTRODUCTION

Low-impact, high-intensity interval exercise (HIE) was used to investigate the postexercise response in bone turnover markers and cytokines.

METHODS

Twenty-three recreationally active males (21.8 ± 2.4 yr) performed one HIE bout on a cycle ergometer at 90% maximum workload. The total duration of the exercise was 12 min and included six 1-min high-intensity exercise intervals separated by 1-min rest intervals. Blood samples were collected before exercise, 5 min, 1 h, and 24 h after exercise and were analyzed for serum levels of anti- and pro-inflammatory cytokines (interleukin 10 [IL-10], interleukin 6 [IL-6], interleukin 1-alpha [IL-1α], interleukin 1-beta [IL-1β], and tumor necrosis factor alpha [TNF-α]) and markers of bone formation (bone alkaline phosphatase [BAP], osteoprotegerin [OPG]) and resorption (amino-terminal cross-linking propeptide [NTX], receptor activator of NF-κB ligand [RANKL]).

RESULTS

There was a significant (P < 0.05) time effect for all bone turnover markers. Post hoc analysis showed that BAP, OPG, and RANKL significantly increased from baseline to 5 min after exercise (10.9%, 13.5%, and 34.2%, P < 0.05). At 1 h after exercise, only BAP was significantly higher than baseline (9.5%, P = 0.010) and remained higher than baseline at 24 h (10.9%, P = 0.001). NTX was significantly lower than baseline 24 h after exercise (-14.6%, P = 0.046). Significant (P < 0.05) time effects were also observed for IL-1α, IL-1β, IL-6, and TNF-α, with all four significantly increasing 5 min after exercise and returning to baseline levels 1 h after exercise. The postexercise changes in bone formation markers correlated positively with the anti-inflammatory cytokine (IL-10) and negatively with the pro-inflammatory cytokines while NTX correlated positively with a pro-inflammatory cytokine, TNF-α (P < 0.05).

CONCLUSIONS

These results suggest that HIE stimulates a response in bone turnover markers and cytokines and that a correlation exists between immune and skeletal responses to this form of exercise. This type of exercise may benefit individuals for whom high-impact exercise might be contraindicated.

Bone and energy metabolism parameters in professional cyclists during the Giro d'Italia 3-weeks stage race

Cycling is a not weight-bearing activity and is known to induce bone resorption. Stage races are really strenuous endurance performances affecting the energy homeostasis. The recently highlighted link, in the co-regulation of bone and energy metabolism, demonstrates a central role for the equilibrium between carboxylated and undercarboxylated forms of osteocalcin. Aim of this study was to understand the acute physiological responses to a cycling stage race in terms of bone turnover and energy metabolism and the possible co-regulative mechanisms underlying their relationship. We studied nine professional cyclists engaged in 2011 Giro d'Italia stage race. Pre-analytical and analytical phases tightly followed academic and anti-doping authority's recommendations. Bone and energy metabolism markers (bone alkaline phosphatase, tartrate-resistant acid phosphatase 5b, total and undercarboxylated osteocalcin, leptin and adiponectin) and related hormones (cortisol and testosterone) were measured, by Sandwich Enzyme Immunoassays, at days -1 (pre-race), 12 and 22 during the race. The power output and the energy expenditure (mean and accumulated) were derived and correlated with the biochemical indexes. During the race, bone metabolism showed that an unbalance in behalf of resorption, which is enhanced, occurred along with a relative increase in the concentration of the undercarboxylated form of osteocalcin that was indirectly related to the enhanced energy expenditure, through adipokines modifications, with leptin decrease (high energy consumption) and adiponectin increase (optimization of energy expenditure). The exertion due to heavy effort induced a decrease of cortisol, while testosterone levels resulted unchanged. In conclusion, during a 3-weeks stage race, bone metabolism is pushed towards resorption. A possible relationship between the bone and the energy metabolisms is suggested by the relative correlations among absolute and relative concentrations trends of undercarboxylated OC, adipokines concentrations, BMI, fat mass (%), power output and the derived energy expenditure.