Bone mineral status of young cyclists

ˑ: 

Barbara Długołęcka
Józef  Piłsudski University of Physical Education in Warsaw, Faculty of Physical Education and Health in Biala Podlaska, Poland

Keywords: road cyclists, bone mineralisation and density, physical activity, diet.

Introduction. The majority of studies point to the fact that sports exert an extremely beneficial influence on bone tissue. Compared to adults with a sedentary lifestyle, sports people almost always display greater bone mass (sometimes even by 20-30%) [1,2]. Taking these facts into consideration, the impact of the type of loads on bone mineralisation seems to be the issue that needs further research. It is thought that not every type of physical activity affects BMD in the same manner [3].Based on the above considerations, it may be presumed that, compared to untrained population, athletes who do certain sports may constitute a group with increased osteoporosis risk.

Objective of the study is to make an attempt to answer the question: to what extent cycling is a sporting discipline promoting (or not) an increase in mineralization, in view of the existing controversy about the beneficial impact of cycling on bone tissue.

Material and methods. The study included 75 men in the period of reaching peak bone mass (21-22 years). The study group consisted of cyclists (n=30) and untrained men (n=45).  Cyclists belonged to youth cycling clubs.

Body composition, BMC (g) and BMD (g/cm2) were determined in the lumbar spine (L2-L4) with the use of Dual Energy X-ray Absorptiometry (DEXA) on the HORIZON Ci device (USA). Diet composition was assessed based on three individual questionnaire interviews regarding nutrition in the last 24 hours prior to the study. The interviews were carried out by trained interviewers on two weekdays and one day without classes (Sunday) [4]. The project was approved by the Ethics Commission of the University of Physical Education in Warsaw.

Statistical analysis was performed on the basis of one-way analysis of variance (ANOVA) and Tukey's post-hoc tests, where differences at the level of p<0.05 were regarded as significant.

Results. The groups under examination turned out to be very similar in body build and body composition. No significant differences were noted in any of the examined parameters. Average values of bone parameters did not differentiate the studied groups. However, tendencies to higher average values of these parameters in the control group were observed in comparison to the group of cyclists. There were no statistically significant differences between the studied groups in diet.

Table 1. General characteristics of the examined men (±SD )

GROUP

Age    (years)

Body Mass       ( kg)

Body Height (cm)

Fat-Free Body Mass (kg)

Muscle Mass    (kg)

Fat Tissue     (%)

Cyclists (n=30)

22.1±0.8

76.7±8.9

177.2±5.2

60.3±5.7

62.1 ± 5.7

18.2 ± 5.6

Control group(n=45)

21.7±1.3

81.8±8.5

182.2±5.7

61.1±5.9

60.4 ± 5.7

20.4 ± 4.6

Table 2. Data related to sports careers of the examined men (±SD )

 

GROUP

Age of training commencement                 (years)

Length of training experience  (years)

Weekly training loads  (hours)

Weekly training loads (days)

Cyclists                  (n=30)

16.2±1.6

5.9±4.2

9.0±2.6

4.2±0.7

Table 3.  Characteristics of bone parameters of the examined men (±SD )

 

Cyclists  (n=30)

Control group   (n=45)

BMC  (g)

77.52±7.69

80.58±11.58

BMD g/cm2

1.062±0.07

1.100±0.109

BMD compared to age (%)

92.15±7.05

95.2±9.86

Table 4. Mean intake of energy, protein, magnesium, calcium and phosphorus in the examined men (±SD )

 

GROUP

Energy    (kcal)

Protein      (g)

Magnesium  (mg)

Calcium  (mg)

Phosphorus (mg)

Ca : P

Cyclists (n=30)

2786±664

126.2±42.3

451.7±155.7

877±418

1942±519

1 : 2.2

Control group (n=45)

2964±552

131.4±36.1

425.6±163.2

821±299

2023±488

 1 :  2.5
 
Discussion. Bone mineralisation examinations in athletes are crucial for two reasons. Firstly, such tests help to determine the effects of various sports on the skeletal system, thus contributing to more effective prevention of osteoporosis through identifying sports that exert the most beneficial influence on bone tissue. Secondly, when it comes to changes that may take place in bone tissue as a result of various risk factors, they may occur already at a young age and are most often irreversible [5,6]. Not every type of physical activity connected with doing particular sports exerts a positive influence on bone mass. Activities performed in a sitting position (weight-supporting activities) such as cycling are considered to predispose to the development of bone pathology. It was observed that in the case of road cyclists the bone mineral density was almost 10% lower than in the control group. In some highly susceptible parts, the difference was as high as 18%. [7]. The above observations were not recorded in our own studies, the average values of the determined bone parameters in the group of cyclists were lower, although they were not statistically significant in relation to the examined men in the control group. In addition to physical activity, a diet (including adequate calcium intake) is also responsible for proper bone mineralisation and density. 99% of body calcium can be found in bones. Its role is to build the skeleton and to strengthen it when its mass loss occurs. Moreover, vigorous physical activity enhances this process. A number of studies point to a beneficial correlation between calcium intake and bone mineralisation [8]. However, it should be remembered that the process of calcium absorption in bone tissue is correct if the ratio of calcium to phosphorus in the body is 1:1. If there is too much phosphorus in a diet, it causes hyperthyroidism and increased calcitonin secretion. Calcitonin stimulates calcium secretion from bones, thus leading to their weakening [9]. The findings of the present study did not show any significant differences between the examined groups with regard to nutrition. The values of the parameters in the groups fell within the norms for age and physical activity. It was only in the case of phosphorus that a disturbing trend towards its excessive intake was noted. In all the groups under investigation, a considerably higher norm of phosphorus intake was observed, which resulted in a substantial increase in the ratio of calcium to phosphorus in the diets of all the examined men.

Conclusions

  1. The analysis of the results of the tests (BMC, BMD) allows us to believe that the cycling training did not negatively influence the mineral density of the bones of the examined athletes.
  2. The results obtained do not suggest that cyclists are at increased risk of osteopenia in their further sporting careers, provided that special is paid attention to diet.

Acknowledgements

The work was carried out as part of a research project carried out at the Faculty of Physical Education and Sport in Biala Podlaska, Jozef Pilsudski University of Physical Education in Warsaw - DS. 248, financed by the Ministry of Science and Higher Education.

References

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  8. Liberato S.C., Bressan, J., Hills A.P. The role of physical activity and diet on bone mineral indices in young men: a cross-sectional study. J IntSoc Sports Nutr.2013.10.pp.43.
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Corresponding author: tomasz.niznikowski@awf-bp.edu.pl

Abstract

The aim of this work was to assess bone mineral content (BMC) and bone mineral density (BMD) in men practicing road cycling at peak bone mass in comparison with men at the same age not practicing sport. Road cyclists, representatives of youth cycling clubs (n=30) aged 21-22 and men of similar age who do not practice sports (n=45) took part in the research. BMC (g) and BMD (g/cm2) in the lumbar spine (L2-L4) were determined with the use of the DEXA method.The analysis of the results showed that the mean values of the determined bone parameters did not differentiate the studied groups. However, tendencies to higher values in the control group were observed. Excessive phosphorus intake was observed in both groups. On the basis of the results obtained it can be concluded that the examined cyclists do not constitute a group of increased risk of developing osteopenia in comparison with men who do not train.