Determining influence of landing technique in ground reaction forces

This paper provides and example of problem-based learning to assess effects from landing strategies during drop jumps on ground reaction forces calculated from a wearable accelerometer. Problem Title: Determining influence of landing technique on ground reaction forces Course Level: Undergraduate Introductory. Learning Outcomes: Determine the effects of landing technique on ground reaction forces Calculate ground reaction force from body worn accelerometer data Discuss the relationship between force and time when the change in momentum is controlled Analyse and apply the data obtained to design a training progra

CHANGES IN BODY POSITION ON THE BIKE DURING SPRINT CYCLING: APPLICATIONS TO BIKE FITTING

This study compared hip flexion angles during sprint cycling with those during sub maximal cycling performed using a range of handlebar positions (changing height and reach). Eleven competitive cyclists were assessed in two sessions. The first session involved determining handlebar positions that resulted in a range of pre-determined hip flexion angle (70-110°) during sub maximal cycling. In the second session, cyclists performed 2 x 6-s sprints at the handlebar positions determined during the first session. Xsens motion tracking system was used to measure hip flexion angles during sprints completed with the handlebar positions determined during the first session. Differences between predetermined hip flexion angles and the angles measured during the sprint ranged fro

On-line schedulability tests for adaptive reservations in fixed priority scheduling

Adaptive reservation is a real-time scheduling technique in which each application is associated a fraction of the computational resource (a reservation) that can be dynamically adapted to the varying requirements of the application by using appropriate feedback control algorithms. An adaptive reservation is typically implemented by using an aperiodic server (e.g. sporadic server) algorithm with fixed period and variable budget. When the feedback law demands an increase of the reservation budget, the system must run a schedulability test to check if there is enough spare bandwidth to accommodate such increase. The schedulability test must be very fast, as it may be performed at each budget update, i.e. potentially at each instance of a task; yet, it must be as efficient as possible, to maximize resource usage. In this paper, we tackle the problem of performing an efficient on-line schedulability test for adaptive resource reservations in fixed priority schedulers. In the literature, a number of algorithms have been proposed for on-line admission control in fixed priority systems. We describe four of these tests, with increasing complexity and performance. In addition, we propose a novel on-line test, called Spare-Pot al- gorithm, which has been specifically designed for the problem at hand, and which shows a good cost/performance ratio compared to the other tests

Float like a butterfly : comparison between off and on-ice torso kinematics during the butterfly stance in ice hockey goalkeepers

In ice hockey, the butterfly style/stance is a technique distinguished by the goalkeepers (goalie) dropping to their knees to block attempts to score. Although this goalie style has been around for many years, comparisons between on and off-ice attire has not been undertaken. Therefore, this preliminary study compared differences in torso acceleration and energy expenditure by way of the Metabolic Equivalent of Task (MET) during off-ice and on-ice butterfly stances/saves. Seven participants each performed 8 on-ice butterfly saves/stances whilst wearing full hockey attire followed by 8 off-ice butterfly stances without wearing full hockey attire whilst torso acceleration was collected. The off-ice movement significantly increased vertical torso acceleration (p 0.90) with increased MET, compared to on-ice motion. Despite no significant difference in anteroposterior and mediolateral torso kinematics, vector magnitudes were significantly greater (p 0.90) when the stance was performed off-ice. The increased vertical acceleration observed when goalies performed the movement off-ice could be due to a failure to maintain adequate posture without the support of the external load. The results of this study may help inform off-ice training interventions for ice hockey goalkeeping. © 2022 by the authors

EXTERNAL WORK BILATERAL SYMMETRY DURING INCREMENTAL CYCLING EXERCISE

The aim of the present study was to compare the bilateral external work and torque at four stages of an incremental maximal cycling. Eleven cyclists were evaluated on a cycle ergometer. Four stages of the incremental cycling workload were defined as 60, 75, 90 and 100% of maximal oxygen uptake (VO2Max). Pedal forces and kinematics variables were measured through each stage. Crank torque and external work were computed (both sides). Crank work and torque increased throughout the incremental test. There were no differences between legs in relation to work and torque at the crank. The high variability of force symmetry between subjects, and between days may indicate the difference of our results compared to previous studies

Pedal force effectiveness in cycling: A review of constraints and training effects

Pedal force effectiveness in cycling is usually measured by the ratio of force perpendicular to the crank (effective force) and total force applied to the pedal (resultant force). Most studies measuring pedal forces have been restricted to one leg but a few studies have reported bilateral asymmetry in pedal forces. Pedal force effectiveness is increased at higher power output and reduced at higher pedaling cadences. Changes in saddle position resulted in unclear effects in pedal force effectiveness, while lowering the upper body reduced pedal force effectiveness. Cycling experience and fatigue had unclear effects on pedal force effectiveness. Augmented feedback of pedal forces can improve pedal force effectiveness within a training session and after multiple sessions for cyclists and non-cyclists. No differences in pedal force effectiveness were evident between summarized and instantaneous feedback. Conversely, economy/efficiency seems to be reduced when cyclists are instructed to improve pedal force effectiveness during acute intervention studies involving one session. Decoupled crank systems effectively improved pedal force effectiveness with conflicting effects on economy/efficiency and performance

VARIABILITY IN VERTICAL JUMP HEIGHT AND LOWER LIMB KINEMATICS BETWEEN DAYS

The purpose of this study was to determine the variability of lower limb range of motion (ROM) during vertical jumps using inertial-based systems. Ten participants attended three laboratorial session to familiarise with the countermovement jump (session 1) and to perform three maximum countermovement jumps (session 2 and 3). Motion from the lower limbs and pelvis were tracked using an inertial-based system and sagittal plane ROM computed for the hip, knee and ankle joints. ROM was compared between sessions using t-test, typical error and effect sizes. Moderate effect sizes were observed with differences in angular data varying from12° for similar heights of the jump (p = 0.27 and d = 0.21). Moderate differences in sagittal plane ROM for the lower limbs were observed for vertical countermovement jumps which limits the use of joint ROM between sessions from inertial-based system

Validity of neural networks to determine body position on the bicycle

Peer ReviewedPostprint (author's final draft

Criterion validity of neural networks to assess lower limb motion during cycling

The use of marker-less methods to automatically obtain kinematics of movement is expanding but validity to high-velocity tasks such as cycling with the presence of the bicycle on the field of view is needed when standard video footage is obtained. The purpose of this study was to assess if pre-trained neural networks are valid for calculations of lower limb joint kinematics during cycling. Motion of twenty-six cyclists pedalling on a cycle trainer was captured by a video camera capturing frames from the sagittal plane whilst reflective markers were attached to their lower limb. The marker-tracking method was compared to two established deep learning-based approaches (Microsoft Research Asia-MSRA and OpenPose) to estimate hip, knee and ankle joint angles. Poor to moderate agreement was found for both methods, with OpenPose differing from the criterion by 4–8° for the hip and knee joints. Larger errors were observed for the ankle joint (15–22°) but no significant differences between methods throughout the crank cycle when assessed using Statistical Parametric Mapping were observed for any of the joints. OpenPose presented stronger agreement with marker-tracking (criterion) than the MSRA for the hip and knee joints but resulted in poor agreement for the ankle joint.Peer ReviewedPostprint (author's final draft

ASSESSMENT OF A MARKLESS MOTION TRACKING METHOD TO DETERMINE BODY POSITION ON THE BIKE

This study compared body position on the bicycle using manual and automatically determined body segments during stationary cycling. High speed video (120 fps) was obtained from 14 cyclists using their own bikes on a stationary cycle trainer in a single session. Torso, hip, knee and ankle angles were measured in two positions of the crank (3 o’clock and 6 o’clock-dynamically) to determine body position on the bike. Significant differences (3-12°, d=0.38-1.92) were observed for all joints between the manual and automated method for both crank positions (except for the ankle at the 6 o’clock). Overall, the automated method overestimated torso and knee flexions and underestimated hip flexion and ankle dorsiflexion. The implications of these changes in terms of bike setup are to be determined in future research but it is unlikely that errors from the automated method will result in large changes in joint forces