Development of Upper-Extremity Morphological Asymmetries in Male and Female Elite Youth Tennis Players: A Longitudinal Study.

PURPOSE: This 2-year longitudinal study examined the development of upper-extremity bone mineral density (BMD), bone mineral content (BMC), and lean mass (LM) asymmetry magnitudes in male and female youth tennis players. METHODS: Dominant and nondominant upper-extremity BMD, BMC, and LM values of 49 male and 31 female players were measured yearly using dual X-ray absorptiometry. From these values, asymmetry magnitudes were calculated and expressed as a percentage. Maturity offset was estimated using anthropometric measurements. Linear mixed effect models examined the development of BMD, BMC, and LM asymmetry magnitudes according to players' maturity offset, sex, and training volume. RESULTS: Adjusted for sex and training volume, a 1-year increment in maturity offset was associated with a significant increase in BMD (1.3% [2.2%]; P < .001) and BMC (0.6% [2.4%]; P = .011) asymmetry magnitudes. Male players displayed significantly higher LM asymmetry magnitudes (Δ3.2% [8.4%]; P = .002) compared with their female counterparts. Training volume was not significantly associated with asymmetry magnitude development. CONCLUSION: In contrast to LM, male and female youth tennis players' upper-extremity bones are still responsive to mechanical loading with a significant increase in BMD and BMC asymmetry magnitudes according to maturity offset.

Morphological and functional asymmetry in elite youth tennis players compared to sex- and age-matched controls.

Besides examining upper and lower limb morphological and functional asymmetry magnitudes, this study examined the relationship between lean mass and functional asymmetry in terms of magnitude and direction in 41 youth tennis players versus 41 controls. Asymmetry magnitude was determined using anthropometric measurements (circumferences, widths), bioelectrical impedance analysis (lean mass) and a test battery (handgrip strength, seated medicine ball throw, plate tapping, single leg countermovement jump, single leg forward hop test, 6 m single leg hop test, 505 change of direction). ANOVAs compared the dominant (overall highest/best value) against the non-dominant (highest/best value of opposing limb) result. Linear regressions explored the relationship between lean mass and functional asymmetry magnitudes. Kappa coefficients examined asymmetry direction consistency between the limb displaying the highest lean mass value and the limb performing dominantly across tests. Significant asymmetry magnitudes (p < 0.05) were found for all upper and lower limb outcome measures. No significant relationship was apparent between lean mass and functional asymmetry magnitude (r-value = -0.283-0.262). Despite finding (almost) perfect consistency in asymmetry direction (k-value = 0.84-1.00) for the upper limb, poor to slight consistency (k-value = -0.03-0.15) was found for the lower limb. Therefore, lean mass and functional asymmetry should be examined independently.

Long-term effectiveness of a fundamental motor skill intervention in Belgian children: A 6-year follow-up.

The aim of this study was (1) to examine the long-term effectiveness of the "Multimove for Kids" program, a 30-week fundamental motor skill intervention (approximately 1 hour per week) for typically developing children between 3 and 8 years, and (2) to determine the influence of participation in organized sports on motor competence (MC) six years after the intervention. Of the 992 children who took part in the "Multimove" program, 399 (intervention group: N = 228, control group: N = 171) were tested again at 6-year follow-up. MC was measured with the Test of Gross Motor Development, 2nd Edition. To examine the long-term impact of "Multimove" on MC, and the effect of participation in organized sports a latent growth curve analysis was conducted. After the 30-week intervention, the intervention group outperformed the control group (ß = 5.57, P < .001). However, when the entire study period, including the 6-year follow-up, was considered, the intervention group made less progress in MC than the control group (ß = -0.41, P < .05). Looking at the engagement in organized sports, it was found that years of experience before the intervention had no significant influence on the evolution of MC over time, whereas a positive effect was observed for children's average sports participation (h/week) during the 6-year retention period (ß = 0.14, P < .001). Finally, children practicing predominantly object control-oriented sports during retention obtained slightly better MC scores at follow-up (ß = 0.01, P < .01). The "Multimove" intervention does not have a long-term effect on the development of MC. However, participation in organized sports has a positive influence on MC evolution over time.

The impact of non-residential grandchild care on physical activity and sedentary behavior in people aged 50 years and over: study protocol of the Healthy Grandparenting Project.

BACKGROUND: Finding effective ways to support people aged > 50 years to develop adequate levels of physical activity and sedentary behavior is necessary as these behaviors are positively related to the maintenance of functional independence and health-related quality of life. Given the widespread provision of grandparental child care, examining its impact on grandparents' energy-expenditure related behavior in the broader context of health is imperative. Therefore, the Healthy Grandparenting Project will aim to investigate the levels of physical activity and sedentary behavior, body composition and health-related quality of life in grandparents caring for their grandchildren and to compare these outcomes with non-caregiving grandparents and older adults without grandchildren, both momentarily and over time. An additional purpose is to identify possible predictors of potential changes over time. METHODS: A prospective cohort study will run over a period of 2 years, including three test occasions with a one-year time interval in between (T0 = baseline, T1 = 12 months, T2 = 24 months). A total of 276 participants will be recruited in Flanders through non-probability quota sampling (50-50% men-women), of which 92 caregiving grandparents, 92 non-caregiving grandparents and 92 non-grandparents. All three subsamples will be matched for age and sex. At each test occasion, anthropometric and body composition measurements will be determined. Participants' levels of physical activity and sedentary behavior will be assessed both objectively and subjectively by means of accelerometry and self-report questionnaires. Information about their grandchildren and the provided grandparental care (if applicable) as well as their health-related quality of life will also be assessed using self-report questionnaires. Mixed modelling will be used to identify differences in physical activity, sedentary behavior, body composition and health-related quality of life between the subsamples at baseline, as well as to evaluate and compare changes in energy-expenditure related behavior over time between subsamples and to identify predictors of the detected changes. DISCUSSION: The Healthy Grandparenting Project is an innovative study examining the levels of physical activity and sedentary behavior in caregiving grandparents, non-caregiving grandparents and non-grandparents. Obtained results will help in the development of campaigns to maintain/improve health in adults at a more advanced age. TRIAL REGISTRATION: clinicaltrials.gov, Identifier: NTC04307589 . Registered March 2020.

Whole-body morphological asymmetries in high-level female tennis players: A cross­sectional study.

This cross-sectional study aimed to examine the degree of whole-body morphological asymmetries in female tennis players. Data were collected in 19 high-level female tennis players (21.3 ± 3.4 years). Based on anthropometric measurements (upper arm, lower arm, wrist, upper leg and lower leg circumferences as well as elbow and knee widths) and dual x-ray absorptiometry research scans (bone mineral density (BMD), bone mineral content (BMC), lean mass (LM), fat mass (FM) as well as humerus, radio-ulnar, femur and tibia bone lengths), within-subject morphological asymmetries for both upper (dominant vs. non-dominant) and lower (contralateral vs. ipsilateral) extremities were examined. Upper arm (p = 0.015), lower arm (p < 0.001) and wrist circumferences (p < 0.001), elbow width (p = 0.049), BMD (p < 0.001), BMC (p < 0.001), LM (p = 0.001), humerus (p = 0.003) and radio-ulnar bone length (p < 0.001) were all greater in the dominant upper extremity. BMC (p < 0.001) and LM (p < 0.001) were greater in the contralateral lower extremity, whereas FM (p = 0.028) was greater in the ipsilateral lower extremity. This is the first study to report significant side-to-side differences in both upper and lower extremities in high-level female tennis players.

The effect of nudges aligned with the renewed Flemish Food Triangle on the purchase of fresh fruits: An on-campus restaurant experiment.

OBJECTIVE: This study examined the effect of nudges, inspired by the recently renewed Flemish Food Triangle, on fruit sales in a Belgian on-campus university restaurant. METHODS: In this mixed-method real-life experiment, nudges were added weekly over a period of four consecutive weeks: placement of (1) Food Triangle posters in the restaurant, (2) 'green heart' icons above the fruit stands, and (3) substitution and (4) social norm messages at the fruit stands. During baseline (no intervention) and all intervention weeks, dessert sales were registered. Short interviews were used to ask customers about their perceptions regarding the intervention. Follow-up measurements (7 and 30 weeks later) evaluated the longer-term effectiveness, while all nudges remained in place. Dessert sales were analyzed separately for both sexes, students and staff categories (based on academic degree). RESULTS: Compared to baseline, the combination of the Food Triangle and the green heart intervention materials in week 2 resulted in significant increases in fruit consumption across almost all subgroups. The other intervention materials used in the current study had rather limited effects in the short term. After 7 weeks of follow-up, significant fruit sale increases were established for all subgroups compared to baseline. At 30 weeks follow-up, the effect for staff B (Bachelor's degree) disappeared. The majority of the respondents (66.4%) had noticed at least one of the nudges, while only 3.4% indicated to have adjusted their dessert choice as a result of the nudges. CONCLUSIONS: The combination of nudges was effective in the long term and increased fruit purchase in nearly all subgroups. Short interviews show that a more active approach may be needed to increase effect sizes.

Accuracy of maturity prediction equations in individual elite male football players.

BACKGROUND: Equations predicting age at peak height velocity (APHV) are often used to assess somatic maturity and to adjust training load accordingly. However, information on the intra-individual accuracy of APHV in youth athletes is not available. AIM: The purpose of this study is to assess the accuracy of predication equations for the estimation of APHV in individual youth male football players. SUBJECTS AND METHODS: Body dimensions were measured at least every three months in 17 elite youth male football players (11.9 ± 0.8 years at baseline) from the 2008-2009 through the 2011-2012 seasons. APHV was predicted at each observation with four suggested equations. Predicted APHV was compared to the player's observed APHV using one-sample-t-tests and equivalence-tests. Longitudinal stability was assessed by comparing the linear coefficient of the deviation to zero. RESULTS: Predicted APHV was equivalent to the observed APHV in none of the players. A difference with a large effect size (Cohen's d > 0.8) was noted in 87% of the predictions. Moreover, predictions were not stable over time in 71% of the cases. CONCLUSIONS: None of the evaluated prediction equations is accurate for estimating APHV in individual players nor are predictions stable over time, which limits their utility for adjusting training programmes.

Weight loss, behavioral change, and structural neuroplasticity in children with obesity through a multidisciplinary treatment program.

This study evaluated the effect of a multidisciplinary treatment program for children with obesity (OB) on motor competence, executive functioning (EF), and brain structure. Nineteen children with OB (7-11 years), who attended a multidisciplinary treatment program consisting of diet restriction, cognitive behavioral therapy, and physical activity, were compared with an age-matched control group of 24 children with a healthy weight (HW), who did not follow any treatment. For both groups, anthropometric measurements and tests of motor competence and EF were administered twice, with 5 months between pretest and posttest. Additionally, children's brain structure was assessed by performing a magnetic resonance imaging (MRI) scan at the pretest and posttest, which included a T1 anatomical scan, diffusion MRI scan, and magnetization transfer imaging scan. Compared to HW controls, children with OB lost a considerable amount of their body mass (p ≤ .001) and significantly improved their balance skills (p ≤ .001), while no transfer effects of the program were observed for EF. Furthermore, the program resulted in a significant increase in total (p ≤ .001) and cerebellar (p ≤ .001) gray matter volume in children with OB, while no change was observed in the HW controls. Finally, only weak to moderate (nonsignificant) correlations could be observed between structural brain alterations, weight-related changes, and behavioral improvements. Altogether, this is the first longitudinal study showing behavioral and structural brain alterations in response to a multidisciplinary weight loss program for children with OB. Our findings support the need for multidimensional intervention (and prevention) measures for children with OB to deal with this multifactorial health problem.

Structural connectivity and weight loss in children with obesity: a study of the "connectobese".

BACKGROUND: Previous studies suggest that obesity (OB) is associated with disrupted brain network organization; however, it remains unclear whether these differences already exist during childhood. Moreover, it should be investigated whether deviant network organization may be susceptible to treatment. METHODS: Here, we compared the structural connectomes of children with OB with age-matched healthy weight (HW) controls (aged 7-11 years). In addition, we examined the effect of a multidisciplinary treatment program, consisting of diet restriction, cognitive behavioral therapy, and physical activity for children with OB on brain network organization. After stringent quality assessment criteria, 40 (18 OB, 22 HW) data sets of the total sample of 51 participants (25 OB, 26 HW) were included in further analyses. For all participants, anthropometric measurements were administered twice, with a 5-month interval between pre- and post tests. Pre- and post T1- and diffusion-weighted imaging scans were also acquired and analyzed using a graph-theoretical approach and network-based statistics. RESULTS: Global network analyses revealed a significantly increased normalized clustering coefficient and small-worldness in children with OB compared with HW controls. In addition, regional analyses revealed increased betweenness centrality, reduced clustering coefficient, and increased structural network strength in children with OB, mainly in the motor cortex and reward network. Importantly, children with OB lost a considerable amount of their body mass after the treatment; however, no changes were observed in the organization of their brain networks. CONCLUSION: This is the first study showing disrupted structural connectomes of children with OB, especially in the motor and reward network. These results provide new insights into the pathophysiology underlying childhood obesity. The treatment did result in a significant weight loss, which was however not associated with alterations in the brain networks. These findings call for larger samples to examine the impact of short-term and long-term weight loss (treatment) on children's brain network organization.

Upper extremity bone mineral content asymmetries in tennis players: A systematic review and meta-analysis.

The aim of this study was to examine the magnitude of upper extremity bone mineral content (BMC) asymmetries in tennis players. Furthermore, the influence of sex (male versus female versus mixed), chronological age (juniors: < 18 years; adults: 18-39 years and seniors: ≥ 40 years) and starting age (early starters: < 14 years and late starters: > 18 years) on these asymmetries were examined. Two databases were searched for scientific articles that examined upper extremity BMC in tennis players. Pooling of the individual study effect sizes was conducted using the random-effects model. Three subgroup analyses were performed based on sex, chronological age and starting age. Out of the 15 included studies 24 effect sizes were extracted resulting in a significant difference in BMC value between the dominant and nondominant upper extremity of the tennis players (Standardised Mean Difference: 0.85 [95% CI: 0.67-1.03]). The three subgroup analyses all showed medium to strong effect sizes and significant intergroup differences. To conclude, BMC was significantly higher in the dominant upper extremity compared to the nondominant upper extremity in tennis players. Nevertheless, the influence of training volume and playing experience on these asymmetries are yet to be examined.

Age and maturity related differences in motor coordination among male elite youth soccer players.

This study investigated differences in generic and soccer specific motor coordination, as well as speed and agility depending on age and maturity in elite youth soccer players (U10-U15, N = 619). Measurements included body height, body weight and sitting height to estimate age at peak height velocity (APHV); three Körperkoordinationstest für Kinder subtests (i.e. jumping sideways (JS), moving sideways (MS), balancing backwards (BB)) to assess generic motor coordination; the UGent dribbling test for soccer specific motor coordination; a 5m/30m sprint and T-test for speed and agility, respectively. Age specific z-scores of the predicted APHV identified players as earlier, on time or later maturing. (M)ANOVA analyses showed significant age by maturity interaction effects for the speed and agility test cluster, revealing maturity related differences in U14 and U15 players. Next to an overall higher performance with age for all test clusters (η2 0.080-0.468), earlier maturing players outperformed their later maturing peers in 5m/30m sprinting. The opposite was seen for JS and BB. So, players' maturity status should be taken into account to adequately value performance in talent identification. Also, the focus on characteristics that appear to be minimally biased by an earlier maturational timing (i.e. motor coordination) should be increased.

Fatness and fitness in relation to functional movement quality in overweight and obese children.

This study aimed to investigate the independent and combined associations between several fatness indicators and fitness components with functional movement quality in overweight/obese children. A total of 56 children (33 girls, aged 8-12) classified as overweight/obese according to the World Obesity Federation standard cut points, participated in this study. Participants underwent assessments of fatness [body mass index (BMI), waist circumference, and bioelectrical impedance measures], fitness [1 repetition maximum bench and leg press, and ALPHA test battery], and functional movement quality [4 tests from Functional Movement Screen TM (FMS)]. All fatness outcomes, except waist circumference, were negatively associated with total FMS score, after controlling for cardiorespiratory fitness. Cardiorespiratory fitness, lower limbs muscle strength, and speed-agility were positively associated with the total FMS score, regardless of BMI. Our results suggest that children with greater fatness indicators demonstrate lower functional movement quality independently of their fitness level, whereas children with better fitness level (i.e. cardiorespiratory fitness, lower limbs muscular strength, and speed-agility) demonstrate greater functional movement quality independently of their fatness level. However, children´s weight status seems to be more determinant than their fitness level in terms of functional movement quality, whereas being fit seems to moderately attenuate the negative influence of fatness.

The effect of a portion size intervention on French fries consumption, plate waste, satiety and compensatory caloric intake: an on-campus restaurant experiment.

BACKGROUND: One of the driving factors of dietary overconsumption throughout the last decennia is the increase of food portion sizes. Larger portions induce higher daily energy intake, so reducing portion size may reduce intake of excess calories. However, real-life studies about the effects of portion size reduction are lacking. Therefore, this study examined the effect of a French fries portion size reduction on French fries consumption, French fries plate waste, satiety and caloric intake during the subsequent afternoon among university students and employees in a Belgian on-campus restaurant setting. Moreover, this study evaluated consumers' perception about the portion size reduction. METHODS: The study took place over a two-time (i.e. baseline and intervention week) 4-day period (Tuesday-Friday) in the on-campus restaurant where ±1200 meals are served every day. French fries' portions were reduced by 20% by replacing the usual porcelain bowl served during the baseline week (±200 g) with smaller volume paper bags during the intervention week (±159 g) in a pre-post real-life experiment. French fries consumption and plate waste were measured in 2056 consumers at baseline and 2175 consumers at intervention. Additionally, interviews were conducted directly after lunch and again between 4 and 6 p.m. on the same day to assess satiety and caloric intake at pre and post in a small subsample of both French fries consumers (n = 19) and non-French fries consumers (n = 14). Post-intervention, the same subsample was interviewed about their perception of the portion size reduction (n = 28). RESULTS: Total French fries intake decreased by 9.1%, and total plate waste decreased by 66.4%. No differences were found in satiety or caloric intake between baseline and intervention week among the French fries' consumers. The majority (n = 24, 86%) of French fries consumers noticed the reduction in portion size during the intervention. Although most participants (n = 19, 68%) perceived the reduced portion size as sufficient, only a minority of participants (n = 9, 32%) indicated post-intervention that they would agree with a permanent implementation. CONCLUSIONS: Reducing portion size may lead to reduced caloric intake, without changing perceived levels of satiety.

Multidisciplinary residential treatment can improve perceptual-motor function in obese children.

AIM: This study evaluated the effects of a 10-month multidisciplinary residential treatment programme on the perceptual-motor function of obese children and compared them to children with a healthy weight. METHODS: We studied 26 obese Belgian children (10 girls and 16 boys) with a mean age of 10.1 years (±1.4 years), who followed a residential treatment programme consisting of moderate dietary restriction, psychological support and physical activity. The results were compared with 26 healthy weight children matched for age and gender. The anthropometrics and performance of both groups were assessed on two occasions, 10 months apart, based on simple and choice reaction time tasks and a tracking task using a stylus and tablet. Time by body mass index group interactions were investigated using repeated measure ANCOVAs, with age included as a covariate. RESULTS: No significant interaction effect occurred in either task. In contrast, the obese participants showed a significant improvement in tracking performance over time during the stylus and tablet tests, demonstrating mean deviation from the ideal curve. No difference in performance between baseline and follow-up was observed in the healthy weight controls. CONCLUSION: Taking part in a multidisciplinary residential treatment programme improved the perceptual-motor function of obese children.

Changes in physical fitness and sports participation among children with different levels of motor competence: a 2-year longitudinal study.

The goal of this study was to investigate differences in physical fitness and sports participation over 2 years in children with relatively high, average, and low motor competence. Physical fitness and gross motor coordination of 501 children between 6-10 years were measured at baseline and baseline+2 years. The sample compromised 2 age cohorts: 6.00-7.99 and 8.00-9.99 years. An age and sex-specific motor quotient at baseline testing was used to subdivide these children into low (MQ < P33), average (P33 ≤ MQ < P66) and high (MQ ≥ P66) motor competence groups. Measures of sports participation were obtained through a physical activity questionnaire in 278 of the same children. Repeated Measures MANCOVA and two separate ANOVAs were used to analyze differences in changes in physical fitness and measures of sports participation respectively. Children with high motor competence scored better on physical fitness tests and participated in sports more often. Since physical fitness levels between groups changed similarly over time, low motor competent children might be at risk for being less physically fit throughout their life. Furthermore, since low motor competent children participate less in sports, they have fewer opportunities of developing motor abilities and physical fitness and this may further prevent them from catching up with their peers with an average or high motor competence.

A within-subject examination of grandparents' physical activity and sedentary behavior levels in the presence or absence of grandchild care provision.

BACKGROUND: This study aimed to examine within-subject differences in levels of physical activity (PA) and sedentary behavior (SB) among Flemish grandparents aged 50 years and older during a day of providing versus not providing grandchild care. Additionally, grandparents' PA and SB levels of the specific caregiving moment within the included care day were also compared with those of the corresponding specific time frame on the matching non-care day. METHODS: Data were obtained and pooled from three assessment time points of the Healthy Grandparenting Project. Objectively measured PA and SB levels were assessed through ActiGraphs wGT3x(+) worn during waking hours for seven consecutive days and expressed relative to the total wear time of the selected days or moments (i.e., percentage of time per day or per moment). Generalized linear mixed models were used to evaluate the within-subject differences in grandparents' light intensity PA (LIPA), moderate-to-vigorous intensity PA (MVPA) and SB levels between a care and non-care day as well as between the care and non-care moment of those respective days. RESULTS: A total of 92 grandparents (64.6 ± 4.8 years, 67.4% women) were included in the analyses. During the care day and care moment, grandparents showed higher relative levels of LIPA (∆=4.0% and ∆=7.9%, respectively) and lower relative levels of SB (∆=3.7% and ∆=6.7%, respectively) as compared to their respective non-care day and non-care moment (all p < 0.001). While there was no significant difference in relative MVPA levels between a day of providing versus not providing grandchild care (∆=0.3%, p = 0.500), the grandparents showed significantly lower relative levels of MVPA during the specific care moment against the non-care moment (∆=1.3%, p = 0.029). CONCLUSIONS: The higher percentage of time of LIPA and lower percentage of time spent on SB during a care day and care moment compared to a non-care day and non-care moment, highlight the positive impact of grandchild care provision on grandparents' activity levels, potentially improving other health-related outcomes. Furthermore, grandparents seem to compensate for their lower MVPA levels during the actual care moment since no differences in MVPA levels were found at day level when compared to a day without grandchild care. TRIAL REGISTRATION: clinicaltrials.gov, Identifier: NTC04307589. Registered March 2020.

An Evaluation of the Reliability of the Pictorial Scale of Perceived Water Competence and Its Relationship With Actual Water Competence.

In its recent development, the Pictorial Scale of Perceived Water Competence (PSPWC) showed good face and construct validity. However, additional reliability and validity research is needed, including test-retest reliability and a demonstration of the relationship between PSPWEC test scores and actual water competence. Toward that aim, we administered the PSPWC to 124 children, aged 5-8 years. We repeated this test administration after one week for a subset of 55 children to determine its test-retest reliability, and the remaining 69 children also performed the fully aligned Actual Aquatic Skills Test (AAST) in an indoor swimming pool to provide data for our investigation of the relationship between PSPWC scores and actual water competence. We found good test-retest reliability, both at the global level (ICC = 0.81, n = 55) and at the level of individual skills (Weighted kappa coefficients from 0.58 to 0.90), with no significant differences between these two test scores. We also found a moderate positive relationship between PSPWC and AAST total scores (r = .64, n = 69), with no significant difference between total scores of actual and perceived water competencies. Children overestimated their competence in three specific skills: the back star, swimming on the front, and diving in deep water. While these results underline specific situations in which children's higher self-perceptions of their water competence are a risk factor for their water safety, these data confirm that the PSPWC is reliable for measuring children's perceived competencies in aquatic education and drowning prevention, and there is further support for its validity through a moderate correlation with actual water competencies.

Determinants of caregiving grandparents' physical activity and sedentary behavior: a qualitative study using focus group discussions.

BACKGROUND: Evidence on the factors influencing physical activity (PA) and sedentary behavior (SB) in middle-aged and older adults taking care of their grandchild(ren) is limited, even though this knowledge seems imperative when considering the unique relationship between grandparents and their grandchild(ren) as well as the rising popularity of intergenerational interventions targeting these energy-expenditure related behaviors. Therefore, this explorative qualitative study aimed to identify the determinants of PA and SB levels among Flemish caregiving grandparents in the presence of their grandchild(ren) aged between 0-5 years. METHODS: Six online focus group discussions were conducted via Microsoft Teams, all of which were audio- and videotaped with permission granted by the participating grandparents. In total, nine caregiving grandfathers and 28 caregiving grandmothers (overall mean age = 60.9 ± 4.1y) participated in this study. An inductive content analysis approach was used to derive subcategories, categories and themes from the verbatim transcribed data using NVivo R1. RESULTS: Caregiving grandparents' levels of PA and SB were both influenced by personal determinants (e.g., physical health, grandparental perceptions and responsibilities), interpersonal determinants (e.g., characteristics of the grandchild(ren), such as age-related physical/motor development and family interaction), and environmental determinants (e.g., weather and seasonal circumstances). PA levels of caregiving grandparents were further affected by additional personal determinants (e.g., age of the grandparent, planning and location) and interpersonal determinants (e.g., characteristics of the grandchild(ren), such as new experiences of the grandchild(ren)). Additionally, some personal determinants (e.g., perception of educational value) and interpersonal determinants (e.g., characteristics of the grandchild(ren), such as age-related cognitive development and health of the grandchild(ren)) were strictly mentioned to influence caregiving grandparents' SB. CONCLUSIONS: Acknowledging the unique relationship between grandparents and their grandchild(ren), the current study identified specific factors determining grandparents' PA and SB levels during the provision of grandchild care. Besides, it turned out of importance to take the interplay between the different determinants into account. Especially, for those grandparents with older grandchild(ren), within the studied 0-5 years age range, more attention should be paid to grandchild characteristics as part of the interpersonal determinants when setting up interventions to improve levels of PA and SB in caregiving grandparents.

Development of upper and lower extremity functional asymmetries in male and female elite youth tennis players: a longitudinal study.

BACKGROUND: This longitudinal study aimed to examine the development of both upper and lower extremity functional performances, together with asymmetry magnitudes and directionality in youth tennis players. METHODS: Dominant and non-dominant physical performance values of 90 players (53 males, 37 females) were determined yearly (with monitoring up to 3 years) using unilateral strength, power, speed and agility tests from which asymmetry magnitude percentages were calculated. Linear mixed effect models examined the development of performance values according to youth players' maturity offset, performance dominance, sex and training volume. Similarly, the development of functional asymmetry magnitudes was examined according to players' maturity offset, sex and training volume. Kappa coefficients (k) examined the consistency in directionality across test occasions. RESULTS: Regardless of sex, the dominant and non-dominant physical performance values of every test significantly (P<0.05) improved with increasing maturity offset. No sex differences were apparent except for strength and power related tests where male players performed significantly better. Functional asymmetry magnitudes (ranging from 2.0 to 15.9%) did not significantly change with increasing maturity offset (range=-0.3-0.4% per year). Training volume was not significantly associated with the performance values and asymmetry magnitudes. The dominant upper extremity (which holds the tennis racket) consistently displayed the dominant performance value (k value: 1.00) across test occasions, which was not the case at lower extremity level (k value range: -0.28-0.31). CONCLUSIONS: The functional asymmetry magnitudes did not change significantly with youth tennis players' maturity offset over a 3-year period.

International vs. national female tennis players: a comparison of upper and lower extremity functional asymmetries.

BACKGROUND: Asymmetries have been reported to negatively impact sport performance. This study examined the magnitude and direction of whole-body functional asymmetry in international versus national female tennis players. METHODS: Ten internationally and twelve nationally ranked tennis players participated. Upper extremity functional asymmetries (or side-to-side performance differences) were evaluated using handgrip strength, seated shot-put throw and plate tapping. Lower extremity functional asymmetries were determined using the single leg countermovement jump, single leg forward hop test, 6 m single leg hop test, 505 changes of direction (time and deficit), and Y-balance test (anterior, posteromedial, posterolateral). ANOVAs were used to compare the dominant (overall best or fastest result of a specific test) versus non-dominant performance values (best or fastest result of the corresponding extremity) within the internationally versus nationally ranked players. Functional asymmetry magnitudes differences (expressed as a precentage) were examined using Mann-Whitney U tests. Kappa coefficients examined the consistency as to which extremity performed dominantly across tests. RESULTS: Significant asymmetries for every upper and lower extremity test were found. The functional asymmetry magnitude was significantly (P=0.020) higher on the single leg forward hop test for the nationally (6.3%) versus internationally ranked players (2.9%). Kappa coefficients showed perfect levels of consistency regarding all upper extremity tests (k=1.00), indicating true limb dominance whereas more variance was found as to which lower extremity performed dominantly across tests (k range=-0.067-0.174). CONCLUSIONS: The included female tennis players displayed significant whole-body functional asymmetries. Poor consistency as to which lower extremity performed dominantly across tests warrants individual asymmetry monitoring.