SYMMETRY AND REPRODUCIBILITY OF KINEMATIC PARAMETERS DURING VARIOUS RUNNING TECHNIQUES

The purpose of this study was to examine the reproducibility and the symmetry of a wide number of kinematic parameters while running with various running techniques. Each of twelve tested persons ran on a treadmill in combinations of three velocities (2.5, 3.0 and 3.5m/s) and three stride frequencies (preferred. +/-10% from preferred). Three cycles were recorded for each running task using a video camera (250 Hz) at each side of the body. Intraclass correlation coefficients (ICC generally> 0.80 ) for both legs were high. Only the angular velocity parameters demonstrated low reproducibility (ICC < 0.75). Significant (P 10%)

ADAPTATIONS IN TRICEPS SURAE MUSCLE-TENDON UNIT MECHANICAL PROPERTIES IN ELITE JUMPERS

The purpose of this study was to analyse the triceps surae (TS) muscle-tendon unit (MTU) mechanical properties (muscle strength, maximal tendon strain and tendon stiffness) in elite track and field jumpers (long jump, triple jump, high jump, pole vault) over several years, in order to examine potential alterations in the uniformity of adaptation within the TS MTU. The findings demonstrated a higher TS muscle strength and tendon stiffness for the take-off leg in comparison to the swing leg, irrespective of the jumping discipline. Similar symmetry indexes for muscle strength and tendon stiffness indicated to a uniform TS MTU adaptation in healthy elite track and field jumpers. Longitudinal investigation demonstrated greater fluctuations in TS MTU properties over one year in elite jumpers compared to age-matched controls, predominantly for the take-off leg, irrespective of the training period (preparation vs. competition period). Nevertheless, athletes with lower adaptive similarities between muscle and tendon adaptation may experience temporary increased demand on the tendon and potentially be at greater risk for tendon injuries

Stability-normalised walking speed:A new approach for human gait perturbation research

In gait stability research, neither self-selected walking speeds, nor the same prescribed walking speed for all participants, guarantee equivalent gait stability among participants. Furthermore, these options may differentially affect the response to different gait perturbations, which is problematic when comparing groups with different capacities. We present a method for decreasing inter-individual differences in gait stability by adjusting walking speed to equivalent margins of stability (MoS). Eighteen healthy adults walked on a split-belt treadmill for two-minute bouts at 0.4 m/s up to 1.8 m/s in 0.2 m/s intervals. The stability-normalised walking speed (MoS = 0.05 m) was calculated using the mean MoS at touchdown of the final 10 steps of each speed. Participants then walked for three minutes at this speed and were subsequently exposed to a treadmill belt acceleration perturbation. A further 12 healthy adults were exposed to the same perturbation while walking at 1.3 m/s: the average of the previous group. Large ranges in MoS were observed during the prescribed speeds (6–10 cm across speeds) and walking speed significantly (P < 0.001) affected MoS. The stability-normalised walking speeds resulted in MoS equal or very close to the desired 0.05 m and reduced between-participant variability in MoS. The second group of participants walking at 1.3 m/s had greater inter-individual variation in MoS during both unperturbed and perturbed walking compared to 12 sex, height and leg length-matched participants from the stability-normalised walking speed group. The current method decreases inter-individual differences in gait stability which may benefit gait perturbation and stability research, in particular studies on populations with different locomotor capacities. [Preprint: https://doi.org/10.1101/314757

Improving Trip- and Slip-Resisting Skills in Older People:Perturbation Dose Matters

Aging negatively affects balance recovery responses after trips and slips. We hypothesize that older people can benefit from brief treadmill-based trip and slip perturbation exposure despite reduced muscular capacities, but with neuropathology, their responsiveness to these perturbations will be decreased. Thus, to facilitate long-term benefits and their generalizability to everyday life, one needs to consider the individual threshold for perturbation dose

Effects of Corrective Training on Drop Landing Ground Reaction Force Characteristics and Lower Limb Kinematics in Older Adults With Genu Valgus:A Randomized Controlled Trial

The aim of this study was to identify the effects of a corrective exercise program on landing ground reaction force characteristics and lower limb kinematics in older adults with genu valgus. A total of 26 older male adults with genu valgus were randomized into two groups. An experimental group conducted a 14-week corrective exercise program, whereas a control group did not perform any exercise. The experimental group displayed lower peak vertical, peak anterior and posterior, and peak medial ground reaction force components during the posttest compared with the pretest. The vertical loading rate, impulses, and free moment amplitudes were not statistically different between groups. In the experimental group, the peak knee abduction during the posttest was significantly smaller and the peak hip flexion angle was significantly greater than during the pretest. The authors suggest that this corrective exercise program may be a suitable intervention to improve landing ground reaction forces and lower limb kinematics in older male adults with genu valgus

Application of Leg, Vertical, and Joint Stiffness in Running Performance: A Literature Overview

Stiffness, the resistance to deformation due to force, has been used to model the way in which the lower body responds to landing during cyclic motions such as running and jumping. Vertical, leg, and joint stiffness provide a useful model for investigating the store and release of potential elastic energy via the musculotendinous unit in the stretch-shortening cycle and may provide insight into sport performance. This review is aimed at assessing the effect of vertical, leg, and joint stiffness on running performance as such an investigation may provide greater insight into performance during this common form of locomotion. PubMed and SPORTDiscus databases were searched resulting in 92 publications on vertical, leg, and joint stiffness and running performance. Vertical stiffness increases with running velocity and stride frequency. Higher vertical stiffness differentiated elite runners from lower-performing athletes and was also associated with a lower oxygen cost. In contrast, leg stiffness remains relatively constant with increasing velocity and is not strongly related to the aerobic demand and fatigue. Hip and knee joint stiffness are reported to increase with velocity, and a lower ankle and higher knee joint stiffness are linked to a lower oxygen cost of running; however, no relationship with performance has yet been investigated. Theoretically, there is a desired “leg-spring” stiffness value at which potential elastic energy return is maximised and this is specific to the individual. It appears that higher “leg-spring” stiffness is desirable for running performance; however, more research is needed to investigate the relationship of all three lower limb joint springs as the hip joint is often neglected. There is still no clear answer how training could affect mechanical stiffness during running. Studies including muscle activation and separate analyses of local tissues (tendons) are needed to investigate mechanical stiffness as a global variable associated with sports performance

FOOTWEAR AFFECTS GEARING IN THE MUSCULO-SKELETTAL SYSTEM IN RUNNING

The purpose of this study was to evaluate the impact of barefoot running on grass versus shod running regarding the effectivness of running mechanics. Fourteen male runners performed five valid running trials at 4.0m/s ± 0.2. Running kinetics and running kinematics were recorded for one barefoot and five shod conditions. The comparison of barefoot and shod running showed different effects concerning the gear ratio at the ankle and knee joint. Running with shoes showed mechanical advantages at the ankle joint in the first, second and fifth part of the ground reaction phase but caused disadvantages at the knee joint

MUSCLE-TENDON ADAPTATION MONITORING IN ELITE ATHLETES: PRELIMINARY RESULTS FROM A LONGITUDINAL INVESTIGATION

In this study, we analysed the triceps surae (TS) muscle-tendon unit (MTU) mechanical properties (muscle strength and tendon stiffness) in elite jumping event athletes (long jump, triple jump, high jump, pole vault) and monitored the training-induced alterations in these properties over one year in nine elite jumpers, in order to detect potential changes in the uniformity of adaptation within the TS MTU. The findings indicate to a higher TS muscle strength and Achilles tendon stiffness in the take-off leg in comparison to the swing leg. The longitudinal monitoring revealed a concordant muscle and tendon adaptation in the TS MTU in both legs in the selected athletes

Effects of triceps surae muscle strength and tendon stiffness on the reactive dynamic stability and adaptability of older female adults during perturbed walking

This study aimed to examine whether the triceps surae (TS) muscle-tendon unit (MTU) mechanical properties affect gait stability and its reactive adaptation potential to repeated perturbation exposure in older adults. Thirty-four older adults each experienced eight separate unexpected perturbations during treadmill walking, while a motion capture system was used to determine the margin of stability (MoS) and base of support (BoS). Ankle plantar flexor muscle strength and Achilles tendon (AT) stiffness were analyzed using ultrasonography and dynamometry. A median split and separation boundaries classified the subjects into two groups with GroupStrong (n = 10) showing higher ankle plantar flexor muscle strength (2.26 +/- 0.17 vs. 1.47 +/- 0.20 N center dot m/kg, means +/- SD: P < 0.001) and AT stiffness (544 +/- 75 vs. 429 +/- 86 N/mm; P = 0.004) than GroupWeak in = 12). The first perturbation caused a negative Delta MoS (MoS in relation to unperturbed baseline walking) at touchdown of perturbed step (Pert(R)), indicating an unstable position. GroupStrong required four recovery steps to return to Delta MoS zero level, whereas GroupWeak was unable to return to baseline within the analyzed steps. However, after repeated perturbations, both groups increased Delta MoS at touchdown of Pert(R) with a similar magnitude. Significant correlations between Delta BoS and Delta MoS at touchdown of the first recovery step and TS MTU capacities (0.41 < r < 0.57: 0.006 < P < 0.048) were found. We conclude that older adults with TS muscle weakness have a diminished ability to control gait stability during unexpected perturbations, increasing their fall risk, but that degeneration in muscle strength and tendon stiffness may not inhibit the ability of the locomotor system to adapt the reactive motor response to repeated perturbations. NEW & NOTEWORTHY Triceps surae muscle weakness and a more compliant Achilles tendon partly limit older adults' ability to effectively enlarge the base of support and recover dynamic stability after an unexpected perturbation during walking, increasing their fail risk. However, the degeneration in muscle strength and tendon stiffness may not inhibit the ability of the locomotor system to adapt the reactive motor response to repeated perturbations