Biomedical subjects

O Valdimarsson

Publications and source records attributed to O Valdimarsson.

8 recordsLinked to original sources

PubMed2006

Exercise, bone mass and bone size in prepubertal boys: one-year data from the pediatric osteoporosis prevention study.

This non-randomized prospective controlled study evaluates a daily school-based exercise intervention program of 40 min/school day for 1 year in a population-based cohort of 81 boys aged 7-9 years. Controls were 57 age-matched boys assigned to the general school curriculum of 60 min/week. Bone mineral content (BMC; g) and areal bone mineral density (aBMD; g/cm(2)) were measured with dual X-ray absorptiometry (DXA) of the total body, the third lumbar vertebra (L3) and the femoral neck (FN). Bone width for L3 and FN was calculated from the lumbar spine and hip scan. No differences between the groups were found at baseline in age, anthropometrics or bone parameters. The mean annual gain in L3 BMC was 5.9 percentage points higher (P<0.001), L3 aBMD a mean 2.1 percentage points higher (P=0.01) and L3 width a mean 2.3 percentage points higher (P=0.001) in the cases than in the controls. When all individuals were included in one cohort, the total duration of exercise including both school-based and spare-time training correlated with L3 BMC (r=0.26, P=0.003), L3 aBMD (r=0.18, P=0.04) and L3 width (r=0.24, P=0.006). The study suggests that exercise in pre-pubertal boys influences the accrual of bone mineral and bone width and that a 1-year school-based exercise program confers skeletal benefits, at least in the lumbar spine.

Anthropometry↗

PubMed2006

Daily physical education in the school curriculum in prepubertal girls during 1 year is followed by an increase in bone mineral accrual and bone width--data from the prospective controlled Malmö pediatric osteoporosis prevention study.

The aim of this study was to evaluate a general school-based 1-year exercise intervention program in a population-based cohort of girls at Tanner stage I. Fifty-three girls aged 7-9 years were included. The school curriculum-based exercise intervention program included 40 minutes/school day. Fifty healthy age-matched girls assigned to the general school curriculum of 60 minutes physical activity/week served as controls. Bone mineral content (BMC, g) and areal bone mineral density (aBMD, g/cm(2)) were measured with dual X-ray absorptiometry (DXA) of the total body (TB), lumbar spine (L2-L4 vertebrae), third lumbar vertebra (L3), femoral neck (FN), and leg. Volumetric bone mineral density (g/cm(3)) and bone width were calculated at L3 and FN. Total lean body mass and total fat mass were estimated from the TB scan. No differences at baseline were found in age, anthropometrics, or bone parameters when the groups were compared. The annual gain in BMC was 4.7 percentage points higher in the lumbar spine and 9.5 percentage points higher in L3 in cases than in controls (both P < 0.001). The annual gain in aBMD was 2.8 percentage points higher in the lumbar spine and 3.1 percentage points higher in L3 in cases than in controls (both P < 0.001). The annual gain in bone width was 2.9 percentage points higher in L3 in cases than in controls (P < 0.001). A general school-based exercise program in girls aged 7-9 years enhances the accrual of BMC and aBMD and increases bone width.

Absorptiometry, Photon↗

PubMed2005

Physical activity in the post-pubertal period is associated with maintenance of pre-pubertal high bone density-- a 5-year follow-up.

OBJECTIVE: To evaluate the association between physical activity (PA) and skeletal growth in girls during adolescence. DESIGN: A 5-year, observational, population-based study (Reykjavik, Iceland). SUBJECTS: Seventy-eight Caucasian girls, mean age 13.4+/-1.0 (mean+/-SD) years at baseline. METHODS: Bone mineral density (BMD, g/cm2) and bone width (cm) were measured in the forearm by single-photon absorptiometry at baseline and with dual-energy X-ray absorptiometry after 3 and 5 years, when lumbar spine, femoral neck (FN) and total body were also evaluated. Half of the physically active girls were compared with the other half of less active girls. RESULTS: BMD in physically active girls was higher in the forearm at both baseline (P=0.001) and after 5 years (P=0.04) in comparison with less active girls. BMD was higher for the total body (P=0.0001), spine L2-L4 (P=0.02) and FN (P=0.002) in the active girls at age 18. The accrual of forearm BMD and bone width from age 13 to 18 was no different when comparing the two groups. CONCLUSIONS: Pre-pubertal PA is associated with high BMD at age 13 and continued PA is associated with maintenance of high BMD until age 18.

Absorptiometry, Photon↗

PubMed2003

The duration of exercise as a regulator of bone turnover.

The relationship between duration of exercise and serum remodeling markers of bone turnover was evaluated by osteocalcin (OC), carboxy-terminal propeptide of type I collagen (PICP), total and bone-specific alkaline phosphatase (ALP) and carboxyterminal cross-linked telopeptide of type I collagen (ICTP) in 24 male premier league soccer players exercising 12 hours/week (range 8-18), 19 third league players exercising 8 hours/week (range 3-18) and 20 sixth league players exercising 6 hours/week (range 2-10). Twenty-seven volunteers served as controls. Forty-six former male soccer players (mean age 38 years, range 19-47), mean 15 years older than the current players, were compared with 41 matched controls. Data is presented as mean +/- SEM. Active male players had 18 +/- 4% higher OC, 37 +/- 9% higher bone ALP and 36 +/- 7% higher ICTP than controls (all P < 0.01). There were no differences in remodeling markers within the three groups of active players but each group had higher OC and ICTP than controls (both P < 0.05). Former players had no difference in bone remodeling markers compared to matched controls, but 39 +/- 4% lower OC and 69 +/- 8% lower ICTP than active players (both P < 0.001). Duration of activity was correlated with bone ALP and ICTP (both r = 0.3, P < 0.05) in individuals exercising 6 hours/week or less. No correlation was found in those exercising above this level. It seems as if the bone turnover, evaluated by serum bone remodeling markers, adapts to the current activity needed to maintain bone strength, and a duration of exercise above that level seems to confer no additional benefits.

Adolescent↗

PubMed2003

Bone turnover responses to changed physical activity.

The aim of the study was to compare bone turnover in male soccer players with controls and to follow bone turnover with changes in activity level. Serum-osteocalcin (OC), carboxy-terminal propeptide of type I collagen (PICP) and total alkaline phosphatases (tALP) were measured to assess bone formation. Bone resorption was detected by carboxyterminal cross-linked telopeptide of type I collagen (ICTP). Bone turnover of 12 male premier league soccer players (mean age 23 years, range, 17-34) exercising 12 hours/week (range, 8-15) were at the last day of the soccer season compared with 27 age- and gender-matched controls. Bone turnover was followed weekly during a 4-week resting period between two seasons, and a further 10 days following resumption of full training. Data are presented as mean +/- SEM. Both OC (22 +/- 12%) and ICTP (34 +/- 17%) were higher in the players compared with the controls at the end of the season (both P < 0.05, respectively). After 2 weeks of reduced physical activity among the athletes, the PICP levels were 21 +/- 4% (P < 0.05) lower and the ICTP levels 8 +/- 12% higher (P = 0.07) compared with baseline. OC, PICP, and tALP was then no different compared with controls and ICTP was higher than controls (P < 0.001). Ten days within the new season, there was a 23 +/- 5% increase in PICP (P < 0.001) and a 4 +/- 4% decrease in ICTP (P < 0.05) compared with the end of the resting period. In summary, male soccer players have higher bone turnover compared with age- and gender-matched controls. Changes in physical activity level were associated with changes in bone formation and resorption as evaluated by bone markers within weeks, and after 2 weeks rest, ICTP was higher in the athletes than the controls. We conclude that the higher age-related diminution in BMD, previously reported in former soccer players compared with age- and gender-matched controls, may be the result of increased bone resorption, evaluated by ICTP, compared with the controls.

Adolescent↗

PubMed1999

Lean mass and physical activity as predictors of bone mineral density in 16-20-year old women.

OBJECTIVE: The aim of the study was to quantify the inter-relationship between bone mineral density and physical activity, muscle strength, and body mass composition in a group of healthy 16-20-year-old women. DESIGN: A cross-sectional study. SETTING: Reykjavik area. SUBJECTS: Two-hundred and fifty-four Icelandic Caucasian women aged 16, 18 and 20 years, randomly selected from the registry of Reykjavik. MAIN OUTCOME MEASURES: Bone mineral content (BMC) and density (BMD) in lumbar spine, hip, distal forearm and total skeleton and lean mass and fat mass were measured with dual energy X-ray absorptiometry (DEXA) and compared with grip strength measured with a dynamometer and physical activity as assessed by a questionnaire. RESULTS: The lean mass had the strongest correlation with BMC and BMD, stronger than weight, height and fat mass, both in univariate analysis (r = 0.41-0.77; P<0.001) and in linear regression analysis. The total skeletal BMD was logarithmically higher by hours of exercise per week (P<0.001)). About 30% of variability in total skeletal BMD in this age group can be predicted by lean mass and physical exercise. CONCLUSIONS: Modifiable factors, such as exercise and adequate muscle seem to be significant predictors of the attainment of peak bone mass in women.

Absorptiometry, Photon↗

PubMed1998

Serum 25-hydroxyvitamin D levels and bone mineral density in 16-20 years-old girls: lack of association.

OBJECTIVE: Hypovitaminosis D has been shown to be associated with low bone mineral density in middle-aged and elderly women. The aim of this study was to evaluate whether such an association might exist in adolescent and young adult girls, approaching peak bone mass. DESIGN: Cross-sectional study carried out in late winter. SETTING: Reykjavik area at latitude 64 degrees N. SUBJECTS: Two-hundred and fifty-nine Icelandic Caucasian girls, aged 16, 18 and 20 years, randomly selected from the registry of Reykjavik. MAIN OUTCOME MEASURES: Bone mineral density in lumbar spine, hip, distal forearm and total skeleton was measured with dual-energy X-ray absorptiometry (DEXA) and compared with 25-hydroxyvitamin D levels [25 (OH)D] in serum, measured by radioimmunoassay. Calcium and vitamin-D intake were also assessed by a questionnaire. RESULTS: 18.5% of the girls were below 25 nmol L-1 in serum 25 (OH)D which has been recognized as the lower normal limit for adults. No significant association was found between 25 (OH)D levels and bone mineral density. CONCLUSIONS: Normal calcium and phosphate concentrations in plasma and normal bone mineral density are maintained in adolescent and young adult girls at lower 25 (OH)D levels than published 'normal' levels for middle-aged and elderly.

Absorptiometry, Photon↗

PubMed1994

Relation between calcium intake, grip strength and bone mineral density in the forearms of girls aged 13 and 15.

OBJECTIVES: To evaluate whether there is an association between calcium intake in adolescent girls and bone mineral density (BMD). Also, the relationships between BMD, various anthropometric factors and grip strength were evaluated. DESIGN: Cross-sectional comparison of BMD, calcium intake and grip strength in 13 and 15 year age groups, randomly selected. SETTING: Ten secondary elementary schools in the Reykjavik area. SUBJECTS: One hundred and ninety-seven Icelandic Caucasian girls aged 13 and 15. One hundred and seventy participated and 162 completed the study. MAIN OUTCOME MEASURES: Single photon absorptiometry was used to measure BMD and bone mineral content (BMC) in both forearms. Consumption of milk and dairy products was assessed using a food frequency questionnaire. Height and weight were measured and grip strength was determined with a hand-held dynamometer. RESULTS: Calcium intake was found to be significantly correlated to BMD in the older group after adjustment for menarcheal age and weight (r = 0.24; P < 0.05). Division into three subgroups yielded a significantly greater coefficient of correlation between calcium intake and BMD in the lowest calcium consumption group (r = 0.44; P < 0.05). No association was found in the younger age group. Significant positive correlations between grip strength and regional bone mineral density accounted for up to 16.8% of the variation in BMD (P < 0.001) and 38.4% of the variation in BMC. CONCLUSIONS: This study is consistent with the hypothesis that a threshold effect of calcium intake on BMD might exist. Above this threshold (1000-1200 mg) no further effect on BMD was seen. The results show a strong association between grip strength, a measure representative of total body strength, and BMD.

Absorptiometry, Photon↗