Bone health and risk of stress fracture in female endurance athletes

One in two women over the age of 50 will be diagnosed with an osteoporotic fracture during their life time (Van Staa et al. 2001). Osteoporosis is a condition in which the bone mineral density (BMD) is lost causing the bone to become weak and liable to fracture. It is well established that participation in weight bearing exercise (gymnastics and running) may be beneficial to BMD, due to the high mechanical loading (Drinkwater 1994; Kannus et al. 1994a; Marcus et al. 1992; Snow 1996).The high prevalence of amenorrhoea (1-44%) (Bennell et al. 1997b) in female athletes may result in poor bone health, leading to increased risk of premature osteoporosis or stress fracture injury, disabling an athlete s present and future career (Nattiv 2000; Nattiv et al. 1997). Oestrogen deficiency in amenorrhoeic athletes may compromise the beneficial effects of exercise, leading to lower BMD (Bass 2003; Saxon and Turner 2006), but it is unknown whether this is accompanied by structural differences such as changes to section modulus (Z). There is evidence that athletes display seasonal gains and losses in BMD with changes in training (McClanahan et al. 2002; Snow et al. 2001; Winters and Snow 2000), however, in amenorrhoeic athletes, it is possible that any seasonal losses may not be recovered thus contributing to lower BMD. Studies have reported incidence rates of stress fracture to range between 8.7 -21.1 % in athletes with female endurance athletes at the greatest risk possibly due to the aforementioned high prevalence of menstrual dysfunction and a demand for thinness (Bennell et al. 1996a; Kelsey et al. 2007; Nattiv et al. 2000). However prospective monitoring of stress fracture in female endurance athletes, the gold standard for measuring incidence, is limited with conflicting evidence of incidence and risk factors of stress fracture, possibly due to varying methodology and with no standard definition of stress fracture (Snyder et al. 2006). There is also limited robust evidence to determine whether psychological traits are associated with stress fracture history. There is solid evidence to suggest that the reoccurrence rate of stress fracture in athletes is high over the first 12-months following an initial stress fracture; this could be caused by retraining when the bone is at its weakest. Studies of other musculoskeletal injuries have shown bone loss following injury up to 12-months, however there is no research to suggest how much bone may be lost following a stress fracture injury. It is important therefore, to monitor, using robust methodology, the incidence and subsequent consequences for bone loss associated with stress fracture in athletes in order to provide support for potential intervention and treatment. The main aims of this thesis are two-fold to: 1) determine prospectively the predictors of bone health and stress fracture in female endurance athletes, and 2) determine whether bone geometry and density change following a stress fracture. The specific objectives of the thesis were five-fold to: 1) determine the correlates of stress fracture history, 2) compare bone density and geometry according to menstrual function, 3) determine the incidence rates of stress fracture and identifiable risk factors, 4) quantify the seasonal variation in parameters of bone health and 5) determine the magnitude and timescale of bone loss and subsequent regain. Seventy United Kingdom based female endurance athletes (runners and triathletes) aged 18-45 years were prospectively monitored for 12-months. At each assessment (baseline, 6-month and 12-months) questionnaires were used to assess menstrual, nutritional, eating psychopathology, exercise cognition, and injury histories. BMD, bone mineral content (BMC), hip geometric parameters, and body composition were assessed using dual x-ray absorptiometry (DXA), and anthropometric measures were taken. Training and stress fracture injury were prospectively monitored. Retrospective data determined 19 (27%) of the athletes had a history of clinically diagnosed stress fracture. Athletes with a history of stress fracture had a significantly higher prevalence of current (47% vs 27%, p=0.008) and past (79% vs 53%, p=0.035) menstrual dysfunction and higher global scores on the eating disorders examination questionnaire (EDE-Q) (p=0.049) and the compulsive exercise test (CET) (p=0.016) compared to non-stress fracture athletes. Bone parameters by DXA, training duration, age, age at menarche and anthropometric measurements did not differ between groups. This study found a high prevalence of past stress fracture, and identified eating and exercise behaviour to be related to stress fracture risk independent of menstrual dysfunction. To compare bone geometry and density according to menstrual function the athletes were classified as either a/oligomenorrhoeic athletes (10 periods/year) (EA) and compared to 88 eumenorrhoeic sedentary controls (EC). 30 athletes were AA and 40 EA. EC were significantly older, heavier and shorter than EA and AA who did not differ significantly. Femoral neck BMD was significantly higher in EA than AA and EC (mean (SE) EA: 1.117 (0.015), AA: 1.036 (0.020) and EC: 0.999 (0.014) g/cm2 respectively; p<0.001). Section modulus (Z) was significantly higher in EA than EC (EA: 657 (20), AA: 639 (20), EC: 592 (10) cm3 p=0.004), although AA did not differ significantly from EA and EC. Lumbar spine BMD was significantly lower in AA than EC (1.141 (0.019), AA: 1.105 (0.026) EC: 1.188 (0.014) g/cm2, p=0.007). All differences persisted after adjustment for height, age, and body mass. Eumenorrhoeic athletes had significantly higher femoral neck BMD and Z than controls, consistent with previous research. Femoral neck Z and hence strength in bending was relatively maintained in athletes with menstrual dysfunction despite their lower BMD at this site, indicating possible structural adaptation. Incidence of stress fracture was determined prospectively. Following withdrawal of 9 participants, 61 female athletes were monitored prospectively for the 12-month period. Among the 61 athletes, two sustained a stress fracture, both diagnosed by MRI, giving an annual incidence rate of 3.3%. The stress fracture cases were: both 800m runners aged 19 and 22 years, training on average 14.2 hours/week, eumenorrhoeic, and with no history of amenorrhoea. BMD, energy intake and EDE-Q and CET scores were similar to the mean values in the non-stress fracture group. Thus the incidence of stress fracture in this sample of female endurance athletes is lower than previously reported, possibly due to the increased awareness of stress fracture diagnosis, risk factors and athlete management. Seasonal bone changes were determined in 61 female athletes. The greatest variation was observed in the endurance runners (n=52). The endurance runners were classified according to menstrual function (28 were EA and 24 AA). There were no significant differences at baseline or seasonal variation in height, weight, and body fat percentage. In EA, trochanter BMD increased over the summer (0.885 (0.019) to 0.947 (0.177) g/cm2, p=0.002) with no significant change over the winter (0.880 (0.018) to 0.885 (0.018) g/cm2 p=0.153). In AA femoral neck BMD decreased over the winter (1.065 (0.021) to 1.052 (0.020), g/cm2, p= 0.030) with no significant change over the summer (1.050 (0.020) to 1.052 (0.020), g/cm2, p=0.770). Minimal neck width increased in the group as a whole over the winter (28.4(0.3) to 28.7(0.3), mm p=0.039) with no significant change over the summer 28.8(0.3) 28.7(0.3), mm p=0.333). There were no significant seasonal variations in other bone parameters, and seasonal changes did not differ significantly between groups. EA increased trochanter BMD over the summer, and this was maintained over the winter. Conversely, AA lost femoral neck BMD over the winter and this was not recovered over the summer, although the increase in width of the femoral neck may have partly compensated BMD loss to maintain strength in bending. The final prospective analysis was conducted in a separate sample of female athletes who were diagnosed with a stress fracture injury. The aim of this analysis was to determine the magnitude and time scale of bone loss following a stress fracture injury and subsequent regain following retaining. A group of 4 stress fracture cases and 3 controls were followed for a period of 6-8 months following a stress fracture injury. BMD and BMC (lumbar spine, femoral neck, and trochanter) and estimations of geometric properties CSA, Z and buckling ratio) were assessed using DXA. The mean difference of bone loss and bone regain was determined by BMD, BMC and geometric parameters from baseline to 6-8 weeks and 6-8 weeks to 6-8 months respectively. No significant bone loss was found in either cases or controls from baseline to 6-8 weeks at any of the bone parameters. A significant difference at the femoral neck was found in the injured leg of the stress fracture cases from 6-8weeks to 6-8months (mean (SE) 1.042(0.102) to 1.070(0.102) g/cm2, p=0.004) with no significant change in the contra-lateral case leg 1.036 (0.102) to 1.054(0.109) g/cm2). No significant bone regain was found in the control subjects (health or injured legs ). Thus athletes do not seem to lose significant BMD during the recovery phase of training when partial weight bearing is required. Subsequent bone regain above the initial baseline value does seem to occur in the injured leg within 8 months following the stress fracture once training is resumed. In conclusion the work within this thesis has not only reinforced previous stress fracture findings, showing that a history of stress fracture is increased in athletes with a history of amenorrhoea, but has identified novel results indicating a lower incidence of stress fracture in female endurance athletes than previously reported. Exercise cog

Bone health and risk of stress fracture in female endurance athletes

Conversely, AA lost femoral neck BMD over the winter and this was not recovered over the summer, although the increase in width of the femoral neck may have partly compensated BMD loss to maintain strength in bending. The final prospective analysis was conducted in a separate sample of female athletes who were diagnosed with a stress fracture injury. The aim of this analysis was to determine the magnitude and time scale of bone loss following a stress fracture injury and subsequent regain following retaining. A group of 4 stress fracture cases and 3 controls were followed for a period of 6-8 months following a stress fracture injury. BMD and BMC (lumbar spine, femoral neck, and trochanter) and estimations of geometric properties CSA, Z and buckling ratio) were assessed using DXA. The mean difference of bone loss and bone regain was determined by BMD, BMC and geometric parameters from baseline to 6-8 weeks and 6-8 weeks to 6-8 months respectively. No significant bone loss was found in either cases or controls from baseline to 6-8 weeks at any of the bone parameters. A significant difference at the femoral neck was found in the injured leg of the stress fracture cases from 6-8weeks to 6-8months (mean (SE) 1.042(0.102) to 1.070(0.102) g/cm2, p=0.004) with no significant change in the contra-lateral case leg 1.036 (0.102) to 1.054(0.109) g/cm2). No significant bone regain was found in the control subjects (health or injured legs ). Thus athletes do not seem to lose significant BMD during the recovery phase of training when partial weight bearing is required. Subsequent bone regain above the initial baseline value does seem to occur in the injured leg within 8 months following the stress fracture once training is resumed. In conclusion the work within this thesis has not only reinforced previous stress fracture findings, showing that a history of stress fracture is increased in athletes with a history of amenorrhoea, but has identified novel results indicating a lower incidence of stress fracture in female endurance athletes than previously reported. Exercise cognitions have been identified as risk factors for stress fracture history independent of menstrual dysfunction. Furthermore and potentially the most novel finding of this research is the importance for the examination of bone geometric properties in amenorrhoeic athletes. Findings suggest that possible structural adaptations counteract the effects of low BMD and annual losses of BMD during seasonal training in amenorrhoeic endurance athletes. In light of these findings this thesis highlights scope for further longitudinal research in the area of structural adaptation to bone in amenorrhoeic athletes. Keywords: Stress fracture, bone mineral density, bone geometry, endurance athletes, menstrual dysfunction, eating and exercise cognitions.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

KINEMATIC ANALYSIS OF THE SKELETON START

The purpose of this study was to describe the kinematics of the skeleton start and to compare one-foot versus two-foot starting techniques. The first two steps of the start of six national team skeleton athletes were videotaped during competition and analyzed. There were similarities between the kinematics of skeleton starts and sprint starts; however, the results showed that despite similar 50 meter start times there were differences between the one-foot and two-foot groups in knee angles off the block, trunk angle, toe height during recovery, support and flight times, and step length. These results suggest that the one-foot and two-foot starts are unique yet both effective techniques

Kinematic analysis of the skeleton start

The purpose of this study was to describe the kinematics of the skeleton start and to compare one-foot versus two-foot starting techniques. The first two steps of the start of six national team skeleton athletes were videotaped during competition and analyzed. There were similarities between the kinematics of skeleton starts and sprint starts; however, the results showed that despite similar 50 meter start times there were differences between the one-foot and two-foot groups in knee angles off the block, trunk angle, toe height during recovery, support and flight times, and step length. These results suggest that the one-foot and two-foot starts are unique yet both effective techniques

College physical activity is related to mid-life activity levels in women

It has been suggested, but not clearly established, that physical activity (PA) during the college years is a determinant of long-term PA patterns. The purpose of this study was to examine the relationship between PA during the college years and current PA in college-educated women. Fifty-five college-educated women, aged 39.3 ± 6.5 y, were recruited for this study and were, on average, 14.9 ± 7.4 y post-college. Participant\u27s history of PA during college years and the present time was determined from the Lifetime Physical Activity Questionnaire. A brief demographic questionnaire that addressed current PA patterns was also administered. Results showed a significant correlation between leisure activity (LA) during college years and current LA (r = 0.424, p = 0.001). There was no difference between median college LA and current LA (22.4 and 27.9 MET hours per week, respectively, p = 0.129). However, total college PA reported was significantly lower than total current PA (34.7 and 70.7 MET hours per week, respectively, p = 0.001), with this difference due to an increase in household activities during mid-life. Marital status, the presence of children under the age of 18 in the home, and employment status had no significant impact on LA for this sample. These data suggest that leisure-time PA patterns practiced during college years may carry over to mid- life

Risk factors for stress fracture in female endurance athletes : a cross-sectional study

Objective To identify psychological and physiological correlates of stress fracture in female endurance athletes. Design A cross-sectional design was used with a history of stress fractures and potential risk factors assessed at one visit. Methods Female-endurance athletes (58 runners and 12 triathletes) aged 26.0±7.4 years completed questionnaires on stress fracture history, menstrual history, athletic training, eating psychopathology and exercise cognitions. Bone mineral density, body fat content and lower leg lean tissue mass (LLLTM) were assessed using dual-x-ray absorptiometry. Variables were compared between athletes with a history of stress fracture (SF) and those without (controls; C) using χ², analysis of variance and Mann-Whitney U tests. Results Nineteen (27%) athletes had previously been clinically diagnosed with SFs. The prevalence of current a/oligomenorrhoea and past amenorrhoea was higher in SF than C (p=0.008 and p=0.035, respectively). SF recorded higher global scores on the eating disorder examination questionnaire (p=0.049) and compulsive exercise test (p=0.006) and had higher LLLTM (p=0.029) compared to C. These findings persisted with weight and height as covariates. In multivariate logistic regression, compulsive exercise, amenorrhoea and LLLTM were significant independent predictors of SF history (p=0.006, 0.009 and 0.035, respectively). Conclusions Eating psychopathology was associated with increased risk of SF in endurance athletes, but this may be mediated by menstrual dysfunction and compulsive exercise. Compulsive exercise, as well as amenorrhoea, is independently related to SF risk

Sex differences in circumstances and consequences of outdoor and indoor falls in older adults in the MOBILIZE Boston cohort study

Background: Despite extensive research on risk factors associated with falling in older adults, and current fall prevention interventions focusing on modifiable risk factors, there is a lack of detailed accounts of sex differences in risk factors, circumstances and consequences of falls in the literature. We examined the circumstances, consequences and resulting injuries of indoor and outdoor falls according to sex in a population study of older adults. Methods: Men and women 65 years and older (N = 743) were followed for fall events from the Maintenance of Balance, Independent Living, Intellect, and Zest in the Elderly (MOBILIZE) Boston prospective cohort study. Baseline measurements were collected by comprehensive clinical assessments, home visits and questionnaires. During the follow-up (median = 2.9 years), participants recorded daily fall occurrences on a monthly calendar, and fall circumstances were determined by a telephone interview. Falls were categorized by activity and place of falling. Circumstance-specific annualized fall rates were calculated and compared between men and women using negative binomial regression models. Results: Women had lower rates of outdoor falls overall (Crude Rate Ratio (RR): 0.72, 95% Confidence Interval (CI): 0.56-0.92), in locations of recreation (RR: 0.34, 95% CI: 0.17-0.70), during vigorous activity (RR: 0.38, 95% CI: 0.18-0.81) and on snowy or icy surfaces (RR: 0.55, 95% CI: 0.36-0.86) compared to men. Women and men did not differ significantly in their rates of falls outdoors on sidewalks, streets, and curbs, and during walking. Compared to men, women had greater fall rates in the kitchen (RR: 1.88, 95% CI: 1.04-3.40) and while performing household activities (RR: 3.68, 95% CI: 1.50-8.98). The injurious outdoor fall rates were equivalent in both sexes. Women’s overall rate of injurious indoor falls was nearly twice that of men’s (RR: 1.98, 95% CI: 1.44-2.72), especially in the kitchen (RR: 6.83, 95% CI: 2.05-22.79), their own home (RR: 1.84, 95% CI: 1.30-2.59) and another residential home (RR: 4.65, 95% CI: 1.05-20.66) or other buildings (RR: 2.29, 95% CI: 1.18-4.44). Conclusions: Significant sex differences exist in the circumstances and injury potential when older adults fall indoors and outdoors, highlighting a need for focused prevention strategies for men and women

Risk factors for stress fracture in female endurance athletes: a cross-sectional study

Objective: To identify psychological and physiological correlates of stress fracture in female endurance athletes. Design: A cross-sectional design was used with a history of stress fractures and potential risk factors assessed at one visit. Methods: Female-endurance athletes (58 runners and 12 triathletes) aged 26.0±7.4 years completed questionnaires on stress fracture history, menstrual history, athletic training, eating psychopathology and exercise cognitions. Bone mineral density, body fat content and lower leg lean tissue mass (LLLTM) were assessed using dual-x-ray absorptiometry. Variables were compared between athletes with a history of stress fracture (SF) and those without (controls; C) using χ², analysis of variance and Mann-Whitney U tests. Results: Nineteen (27%) athletes had previously been clinically diagnosed with SFs. The prevalence of current a/oligomenorrhoea and past amenorrhoea was higher in SF than C (p=0.008 and p=0.035, respectively). SF recorded higher global scores on the eating disorder examination questionnaire (p=0.049) and compulsive exercise test (p=0.006) and had higher LLLTM (p=0.029) compared to C. These findings persisted with weight and height as covariates. In multivariate logistic regression, compulsive exercise, amenorrhoea and LLLTM were significant independent predictors of SF history (p=0.006, 0.009 and 0.035, respectively). Conclusions: Eating psychopathology was associated with increased risk of SF in endurance athletes, but this may be mediated by menstrual dysfunction and compulsive exercise. Compulsive exercise, as well as amenorrhoea, is independently related to SF risk