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Epixylic bryophytes are important components of forest vegetation but are currently endangered by increment of wood harvest and intensive forest management. In this paper we present a study about the relationship between forest management, deadwood abundance, deadwood attributes and species richness of epixylic bryophytes on 30 plots comprising three forest types (managed coniferous, managed deciduous and unmanaged deciduous forests) in three regions in Germany. Additionally we analyzed the relations between deadwood attributes (wood species, decay, deadwood type, size) and bryophytes on deadwood items (n = 799) and calculated species interaction networks of wood species and bryophytes. Overall, species richness of epixylic bryophytes was positively related to deadwood abundance and diversity. The mean deadwood abundance was lowest in unmanaged forests (9.7 m(3) ha(-1)) compared with 15.0 m(3) ha(-1) in managed deciduous and 25.1 m(3) ha(-1) in managed coniferous forests. Accordingly, epixylic bryophyte species richness per plot increased from 7 species per 400 m(2) in unmanaged, 10 in managed deciduous and 16 in managed coniferous forests. The interaction network provided evidence of importance of tree-species diversity for bryophyte diversity and the relevance of particular wood species for rare bryophytes.
Generally, the results demonstrate a considerable lack of deadwood in all forest types, even in unmanaged forests. Species richness of epixylic bryophytes was strongly limited by available substrates within the observed deadwood abundance ranging up to only 60 m(3) ha(-1). Altogether, this suggests a high demand to increase both abundance and diversity of deadwood in forests.
Introduction: Gait speed is one of the most commonly and frequently used parameters to evaluate gait development. It is characterized by high variability when comparing different steps in children. The objective of this study was to determine intra-individual gait speed variability in children.
Methods: Gait speed measurements (6-10 trials across a 3 m walkway) were performed and analyzed in 8263 children, aged 1-15 years. The coefficient of variation (CV) served as a measure for intra-individual gait speed variability measured in 6.6 +/- 1.0 trials per child. Multiple linear regression analysis was conducted to evaluate the influence of age and body height on changes in variability. Additionally, a subgroup analysis for height within the group of 6-year-old children was applied.
Results: A successive reduction in gait speed variability (CV) was observed for age groups (age: 1-15 years) and body height groups (height: 0.70-1.90 m). The CV in the oldest subjects was only one third of the CV (CV 6.25 +/- 3.52%) in the youngest subjects (CV 16.58 +/- 10.01%). Up to the age of 8 years (or 1.40 m height) there was a significant reduction in CV over time, compared to a leveling off for the older (taller) children.
Discussion: The straightforward approach measuring gait speed variability in repeated trials might serve as a fundamental indicator for gait development in children. Walking velocity seems to increase to age 8. Enhanced gait speed consistency of repeated trials develops up to age 15.
The aim of this study was to acquire static and dynamic foot geometry and loading in childhood, and to establish data for age groups of a population of 1-13 year old infants and children.
A total of 10,382 children were recruited and 7788 children (48% males and 52% females) were finally included into the data analysis. For static foot geometry foot length and foot width were quantified in a standing position. Dynamic foot geometry and loading were assessed during walking on a walkway with self selected speed (Novel Emed X, 100 Hz, 4 sensors/cm(2)). Contact area (CA), peak pressure (PP), force time integral (FTI) and the arch index were calculated for the total, fore-, mid- and hindfoot.
Results show that most static and dynamic foot characteristics change continuously during growth and maturation. Static foot length and width increased with age from 13.1 +/- 0.8 cm (length) and 5.7 +/- 0.4 cm (width) in the youngest to 24.4 +/- 1.5 cm (length) and 8.9 +/- 0.6 cm (width) in the oldest. A mean walking velocity of 0.94 +/- 0.25 m/s was observed. Arch-index ranged from 0.32 +/- 0.04 [a.u.] in the one-year old to 0.21 +/- 0.13 [a.u.] in the 5-year olds and remains constant afterwards.
This study provides data for static and dynamic foot characteristics in children based on a cohort of 7788 subjects. Static and dynamic foot measures change differently during growth and maturation. Dynamic foot measurements provide additional information about the children's foot compared to static measures.
Background: Isokinetic measurements are widely used to assess strength capacity in a clinical or research context. Nevertheless, the validity of isokinetic measures for identifying strength deficits and the evaluation of therapeutic process regarding different pathologies is yet to be established. Therefore, the purpose of this review is to evaluate the validity of isokinetic measures in a specific case: that of muscular capacity in low back pain (LBP).
Methods: A literature search (PubMed; ISI Web of Knowledge; The Cochrane Library) covering the last 10 years was performed. Relevant papers regarding isokinetic trunk strength measures in healthy and patients with low back pain (PLBP) were searched. Peak torque values [Nm] and peak torque normalized to body weight [Nm/kg BW] were extracted for healthy and PLBP. Ranked mean values across studies were calculated for the concentric peak torque at 60 degrees/s as well as the flexion/extension (F/E) ratio.
Results: 34 publications (31 flexion/extension; 3 rotation) were suitable for reporting detailed isokinetic strength measures in healthy or LBP (untrained adults, adolescents, athletes). Adolescents and athletes were different compared to normal adults in terms of absolute trunk strength values and the F/E ratio. Furthermore, isokinetic measures evaluating therapeutic process and isokinetic rehabilitation training were infrequent in literature (8 studies).
Conclusion: Isokinetic measurements are valid for measuring trunk flexion/extension strength and F/E ratio in athletes, adolescents and (untrained) adults with/without LBP. The validity of trunk rotation is questionable due to a very small number of publications whereas no reliable source regarding lateral flexion could be traced. Therefore, isokinetic dynamometry may be utilized for identifying trunk strength deficits in healthy adults and PLBP.
Mueller, J, Mueller, S, Stoll, J, Baur, H, and Mayer, F. Trunk extensor and flexor strength capacity in healthy young elite athletes aged 11-15 years. J Strength Cond Res 28(5): 1328-1334, 2014-Differences in trunk strength capacity because of gender and sports are well documented in adults. In contrast, data concerning young athletes are sparse. The purpose of this study was to assess the maximum trunk strength of adolescent athletes and to investigate differences between genders and age groups. A total of 520 young athletes were recruited. Finally, 377 (n = 233/144 M/F; 13 +/- 1 years; 1.62 +/- 0.11 m height; 51 +/- 12 kg mass; training: 4.5 +/- 2.6 years; training sessions/week: 4.3 +/- 3.0; various sports) young athletes were included in the final data analysis. Furthermore, 5 age groups were differentiated (age groups: 11, 12, 13, 14, and 15 years; n = 90, 150, 42, 43, and 52, respectively). Maximum strength of trunk flexors (Flex) and extensors (Ext) was assessed in all subjects during isokinetic concentric measurements (60 degrees center dot s(-1); 5 repetitions; range of motion: 55 degrees). Maximum strength was characterized by absolute peak torque (Flex(abs), Ext(abs); N center dot m), peak torque normalized to body weight (Flex(norm), Ext(norm); N center dot m center dot kg(-1) BW), and Flex(abs)/Ext(abs) ratio (RKquot). Descriptive data analysis (mean +/- SD) was completed, followed by analysis of variance (alpha = 0.05; post hoc test [Tukey-Kramer]). Mean maximum strength for all athletes was 97 +/- 34 N center dot m in Flex(abs) and 140 +/- 50 N center dot m in Ext(abs) (Flex(norm) = 1.9 +/- 0.3 N center dot m center dot kg(-1) BW, Ext(norm) = 2.8 +/- 0.6 N center dot m center dot kg(-1) BW). Males showed statistically significant higher absolute and normalized values compared with females (p < 0.001). Flex(abs) and Ext(abs) rose with increasing age almost 2-fold for males and females (Flex(abs), Ext(abs): p < 0.001). Flex(norm) and Ext(norm) increased with age for males (p < 0.001), however, not for females (Flex(norm): p = 0.26; Ext(norm): p = 0.20). RKquot (mean +/- SD: 0.71 +/- 0.16) did not reveal any differences regarding age (p = 0.87) or gender (p = 0.43). In adolescent athletes, maximum trunk strength must be discussed in a gender- and age-specific context. The Flex(abs)/Ext(abs) ratio revealed extensor dominance, which seems to be independent of age and gender. The values assessed may serve as a basis to evaluate and discuss trunk strength in athletes.