The effects of improved strength on obstacle negotiation in community-living older adults

Poor mobility has been associated with age-related deterioration in muscle strength. While previous work has examined the effects of improved strength on level walking, we have quantified the effects of a resistance-training program on obstructed gait tasks using biomechanical-dependent measures. Forty-five community-dwelling participants aged 62 years or older were randomised to either a control (n=16) or experimental group (n=29). The experimental subjects exercised for 24 weeks on a progressive resistance-training program designed to improve lower body strength. Dynamic strength was assessed at weeks 0 and 24 as well as specific laboratory gait kinetics and kinematics during stepping over an obstacle and negotiation of a raised surface set at 10, 20 and 30% of each subject's leg length.

Growth of highly versus moderately trained competitive female artistic gymnasts

Purpose: To investigate whether growth was adversely affected in 137 young competitive female artistic gymnasts involved in different training volumes.

Methods: This was a 2-yr prospective cohort study in which height, sitting height, leg length, weight, skinfolds, and pubertal status were measured in competitive advanced (20–27 h·wk-1) and intermediate (7.5–22 h·wk-1) training level female gymnasts every 6–12 months. Biological parameters of the adolescent growth curve were estimated using the Preece–Baines growth model. Growth rates were estimated for both groups from the mixed-longitudinal data.

Results: Estimated ages at peak height velocity (PHV) (13–13.5 yr) and mean PHV (6.2–6.4 cm·yr-1) for the advanced- and intermediate-level gymnasts suggest that these gymnasts were later maturing and experienced a blunting of the growth spurt relative to reference values for U.S. youth. Comparison of growth velocities by pubertal status revealed that height velocity was lower in the advanced- versus the intermediate-level peripubertal gymnasts, which was due to a significant reduction in sitting height velocity (2.3 vs 3.1 cm·yr-1, P. < 0.05). No marked acceleration in height or sitting height velocity was detected in the advanced-level gymnasts from pre- to peripuberty. Inspection of individual growth rates revealed that over 35% of the pre- and peripubertal gymnasts experienced growth faltering (height velocity less than 4.5 cm·yr-1) during follow-up.

Conclusion: Advanced–and intermediate–training level competitive female gymnasts tend to exhibit an adolescent growth spurt that is similar in timing and tempo to short, normal, slowly maturing girls, but the high frequency of growth faltering suggests that training may alter the tempo of growth and maturation in some, but not all, female gymnasts.

Clinical features of patellar tendinopathy and their implications for rehabilitation

This study investigated the clinical features of patellar tendinopathy (PT), with focus on individuals with unilateral and bilateral PT. A cross-sectional study design was employed to compare individuals with unilateral (n = 14) or bilateral (n = 13) PT and those without PT (control, n = 31). Features assessed included thigh strength (normalized peak knee extensor torque) and flexibility (sit-and-reach and active knee extension), calf endurance (heel-rise test), ankle flexibility (dorsiflexion), alignment measures (arch height and leg length difference), and functional measures (hop for distance and 6 m hop test). Groups were matched for age and height; however, unilateral and bilateral PT had greater mass with a higher body mass index (BMI) than control. Also, bilateral PT performed more sport hours per week than both unilateral PT and control. Unilateral PT had less thigh strength than control and bilateral PT, whereas bilateral PT had more thigh flexibility than control and unilateral PT. Both unilateral and bilateral PT had altered alignment measures compared to control. Features that predicted symptoms in PT were lower thigh flexibility and strength, whereas those that predicted function were higher thigh strength and lower ankle flexibility.  These findings indicate that unilateral and bilateral PT represent distinct entities, and that thigh strength appears particularly important in PT as it predicted both symptoms and function in PT.

Is growth inhibited in non-elite competitive female gymnasts?

PURPOSE
We asked: 1) is statural growth inhibited in non-elite competitive female gymnasts?; and 2) if growth is reduced, is the effect similar for legs and spine?

METHODS
Height(Ht), sitting height(StHt) and leg length(LL) were measured in gymnasts and controls at baseline and every 12 mths for 2 yrs. Pubertal status was assessed by Tanner stage. Gymnasts were from USGF levels 4–10 and trained 7.5 to 22.5 hrs/wk. Age-adjusted Z-scores were determined for gymnasts on the anthropometric measures and based on linear regression analyses of data for 45 controls.

RESULTS
At baseline, pre-(N=40), peri-(N=16) and post-pubertal(N=11) gymnasts were shorter than controls(-0.9 to -1.3 SD, p < 0.01). In pre- and peri-pubertal gymnasts, this was due to a reduction in StHt (-0.8 to -1.3 SD) and LL (-0.8 to -1.1 SD)(p < 0.01). In post-pubertal gymnasts, StHt (-0.8 SD) was reduced (p < 0.05). No differences were observed in z-score deficits between pubertal groups, nor were there any differences in StHt and LL deficits. During 12 mths follow-up in 39 gymnasts, deficits in Ht z-scores were reduced further in pre-pubertal gymnasts (-0.2 SD, p < 0.001) due to a greater increase in the deficit in LL (-0.3 SD, p < 0.001). While the magnitude of z-score deficits for peri-pubertal gymnasts remained unchanged, Ht z-scores improved in post-pubertal gymnasts(+0.2SD, p < 0.05) due primarily to an increase in StHt (+0.4 SD, p < 0.01). Similar results were found in 16 gymnasts followed for 2 yrs.

CONCLUSION
Although small size may relate to self-selection for gymnastics, some non-elite female gymnasts may experience attenuated growth during early puberty due mainly to reduced leg growth. The increased growth observed in post-pubertal gymnasts is consistent with catch-up growth associated with delayed maturation.

Muscle determinants of bone mass, geometry and strength in prepubertal girls

Purpose: The aim of this study was to compare the relative contribution of peak muscle force (isokinetic peak torque) with surrogate estimates of muscle force, including leg lean tissue mass (LTM) and vertical jump height (VJH), on bone mass, geometry and strength in healthy prepubertal girls (n = 103).

Methods: Total leg and FN BMC and leg LTM were measured by DXA; the hip strength analysis program was used to assess FN diameter, cross-sectional area (CSA) and section modulus (Z). Isokinetic peak torque of the knee extensors and flexors (60°·s-1) were used as direct measures of peak muscle force. VJH was measured as an estimate of neuromuscular function. Total leg length or femoral length was used as a surrogate measure of moment arm length.

Results: All estimates of muscle function, except VJH, were positively associated with leg BMC (r = 0.72 - 0.90) and FN BMC, geometry and strength (r = 0.35-0.65) (all, P < 0.001). Multiple linear regression analyses revealed that leg LTM and isokinetic peak torque were independently and equally predictive of leg BMC and FN BMC, bone geometry and strength, explaining 8 to 28% of the variance in each of the bone traits after accounting for moment arm length. When isokinetic peak torque was corrected for both leg LTM and moment arm length, it remained an independent predictor of BMC, CSA and Z, but only accounted for an additional 2 to 5% of the variance.

Conclusion: These data suggest that DXA-derived leg LTM can be used as a reasonable surrogate for isokinetic peak muscle forces when assessing bone strength in relation to muscular function in healthy pre-pubertal girls.

A machine-driven process for human limb length estimation using inertial sensors

The computer based human motion tracking systems are widely used in medicine and sports. The accurate determination of limb lengths is crucial for not only constructing the limb motion trajectories which are used for evaluation process of human kinematics, but also individually recognising human beings. Yet, as the common practice, the limb lengths are measured manually which is inconvenient, time-consuming and requires professional knowledge. In this paper, the estimation process of limb lengths is automated with a novel algorithm calculating curvature using the measurements from inertial sensors. The proposed algorithm was validated with computer simulations and experiments conducted with four healthy subjects. The experiment results show the significantly low root mean squared error percentages such as upper arm - 5.16%, upper limbs - 5.09%, upper leg - 2.56% and lower extremities - 6.64% compared to measured lengths.

Effects of approach velocity and foot-target characteristics on the visual regulation of step length

Two questions emerge from the literature concerning the perceptual-motor processes underlying the visual regulation of step length. The first concerns the effects of velocity on the onset of visual control (VCO), when visual regulation of step length begins during goal-directed locomotion. The second concerns the effects of different obstacles such as a target or raised surface on step length regulation. In two separate experiments, participants (Experiment 1 & 2: n=12, 6 female, 6 male) walked, jogged, or sprinted towards an obstacle along a 10 m walkway, consisting of two marker-strips with alternating black and white 0.50 m markings. Each experiment consisted of three targeting or obstacle tasks with the requirement to both negotiate and continue moving (run-through) through the target. Five trials were conducted for each task and approach speed, with trials block randomised between the six participants of each gender. One 50 Hz video camera panned and filmed each trial from an elevated position, adjacent to the walkway. Video footage was digitized to deduce the gait characteristics. Results for the targeting tasks indicate a linear relationship between approach velocity and accuracy of final foot placement (r=0.89). When foot placement was highly constrained by the obstacle step length shortened during the entire approach. VCO was found to occur at an earlier tau-margin for lower approach velocities for both experiments, indicating that the optical variable ‘tau' is affected by approach velocity. A three-phase kinematic profile was found for all tasks, except for the take-off board condition when sprinting. Further research is needed to determine whether this velocity affect on VCO is due to ‘whole-body' approach velocity or whether it is a function of the differences between gait modes.

The effects of target length on the visual control of step length for hard and soft impacts

Adjustments to gait were examined when positioning the foot within a narrow target at the end of an approach for two impact conditions, hard and soft. Participants (6 M, 6 F) ran toward a target of three lengths along a 10-m walkway consisting of two marker strips with alternating black and white 0.5-m markings. Five trials were conducted for each target length and impact task, with trials block randomized between the 6 participants of each gender. A 50-Hz digital video camera panned and filmed each trial from an elevated position adjacent to the walkway. Video footage was digitized to deduce the gait characteristics. A linear speed/accuracy tradeoff between target length and approach time was found for both impact tasks (hard, r = 0.99, p < 0.01; soft, r = 0.96, p < 0.05). For the hard-impact task, visual control time increased linearly (r = 0.99, p < 0.05) when whole-body approach velocity decreased. Visual control time was unaffected by whole-body approach velocity in the soft-impact task. A constant tau-margin of 1.08 describes the onset of visual control when approaching a target while running, with the control of braking during visual control described by a tau-dot of –0.85. Further research is needed to examine the control of braking in different targeting tasks.

Concerning the length of time slots for efficient gang scheduling

Applying gang scheduling can alleviate the blockade problem caused by exclusively used space-sharing strategies for parallel processing. However, the original form of gang scheduling is not practical as there are several fundamental problems associated with it. Recently many researchers have developed new strategies to alleviate some of these problems. Unfortunately, one important problem has not been so far seriously addressed, that is, how to set the length of time slots to obtain a good performance of gang scheduling. In this paper we present a strategy to deal with this important issue for efficient gang scheduling.

The long and the short of flagellar length control

Discusses key issues concerning the length control of flagellates. How the cell maintains the consistency of length; Final flagellar length achieved when the rate of flagellar assembly slows down to a point where it exactly balances the rate of flagellar disassembly; Implications on phycology.

Bond length dependence on quantum states as shown by spectroscopy

Undergraduate students often have the misconception that molecules have fixed, unchanging bond lengths. This article discusses how linear-molecule rotational band spacings in infrared spectroscopy can be used as a qualitative, visual demonstration of the elongation of average bond lengths on vibrational excitation. The method does not depend on a detailed mathematical analysis of the spectra. In UV–vis spectroscopy, the rotational band spacings give rise to distinctive linear-molecule rotational contours, which easily show whether the average bond length has increased or decreased. The method is based on a spreadsheet simulation of the vibration–rotation or rovibronic (electronic–vibration–rotation) spectrum and is applied to hydrogen chloride IR, iodine UV–vis, and nitrogen UV–vis spectra in this article.

Are unilateral and bilateral patellar tendinopathy distinguished by differences in anthropometry, body composition, or muscle strength in elite female basketball players?

Background: Overuse injury to the patellar tendon (patellar tendinopathy) is a major reason for interrupted training and competition for elite athletes. In both sexes, the prevalence of unilateral and bilateral tendinopathy has been shown to differ. It has been proposed that bilateral pathology may have a different aetiology from unilateral pathology. Investigation of risk factors that may be unique to unilateral and bilateral patellar tendinopathy in female athletes may reveal insights into the aetiology of this condition.
Objectives: To examine whether anthropometry, body composition, or muscle strength distinguished elite female basketball players with unilateral or bilateral patellar tendinopathy.
Methods: Body composition, anthropometry, and muscle strength were compared in elite female basketball players with unilateral (n = 8), bilateral (n = 7), or no (n = 24) patellar tendinopathy. Body composition was analysed using a dual energy x ray absorptiometer. Anthropometric measures were assessed using standard techniques. Knee extensor strength was measured at 180°/s using an isokinetic dynamometer. z scores were calculated for the unilateral and bilateral groups (using the no tendinopathy group as controls). z scores were tested against zero.
Results: The tibia length to stature ratio was approximately 1.3 (1.3) SDs above zero in both the affected and non-affected legs in the unilateral group (p<0.05). The waist to hip ratio was 0.66 (0.78) SD above zero in the unilateral group (p<0.05). In the unilateral group, leg lean to total lean ratio was 0.42 (0.55) SD above zero (p<0.07), the trunk lean to total lean ratio was 0.63 (0.68) SD below zero (p<0.05), and leg fat relative to total fat was 0.47 (0.65) SD below zero (p<0.09). In the unilateral group, the leg with pathology was 0.78 (1.03) SD weaker during eccentric contractions (p<0.07).
Conclusions: Unilateral patellar tendinopathy has identifiable risk factors whereas bilateral patellar tendinopathy may not. This suggests that the aetiology of these conditions may be different. However, interpretation must respect the limitation of small subject numbers.

Concerning the length of time slots for efficient gang scheduling

Applying gang scheduling can alleviate the blockade problem caused by exclusively used space-sharing strategies for parallel processing. However, the original form of gang scheduling is not practical as there are several fundamental problems associated with it. Recently many researchers have developed new strategies to alleviate some of these problems. Unfortunately, one important problem has not been so far seriously addressed, that is, how to set the length of time slot to obtain a good performance of gang scheduling. With gang scheduling time is divided into time slots of equal length, the number of time slots introduced in the system forms a scheduling round and each new job is first allocated to a particular time slot and then starts to run in the following scheduling round. Ideally, the length of time slot should be set long to avoid frequent context switches and so to reduce the scheduling overhead. The number of time slots in a scheduling round should also be limited to avoid a large number of jobs competing for limited resources (CPU time and memory). Long time slots and the limited number of time slots in each scheduling round may cause jobs to wait for a long time before it can be executed after arrival, which can significantly affect the performance of jobs, especially short jobs which are normally expected to finish quickly. However, the performance of a short job can also suffer if the length of time slot is not long enough to let the short job complete in a single time slot. In this paper we present a strategy to deal with this important issue for efficient gang scheduling.

Choosing response scale labels and length: guidance for researchers and clients

There has been much debate over the optimal format for scales, particularly in regard to two key issues - the labelling of points and the overall length of response scales. This paper reviews the evidence regarding the advantages of different scale types and lengths, and provides guidance as to what scale types suit different research objectives. Using a direct comparison of 400 responses on 5-point and 11 -point scales to the same question, by the same people, we examine some of the important differences previously found and then illustrate the impact they have on data quality and useability. Our conclusion, based on past research and our own analysis, is that longer, balanced and unlabelled scales offer the maximum flexibility and reliability in the majority of cases.