Using stiffness to assess injury risk:comparison of methods for quantifying stiffness and their reliability in triathletes

Background: A review of the literature has indicated that lower body stiffness, defined as the extent to which the lower extremity joints resists deformation upon contact with the ground, may be a useful measure for assessing Achilles injury risk in triathletes. The nature of overuse injuries suggests that a variety of different movement patterns could conceivably contribute to the final injury outcome, any number and combination of which might be observed in a single individual. Measurements which incorporate both kinetics and kinematics (such as stiffness) of a movement may be better able to shed light on individuals at risk of injury, with further analysis then providing the exact mechanism of injury for the individual. Stiffness can be measured as vertical, leg or joint stiffness to model how the individual interacts with the environment upon landing. However, several issues with stiffness assessments limit the effectiveness of these measures to monitor athletes’ performance and/or injury risk. This may reflect the variety of common biomechanical stiffness calculations (dynamic, time, true leg and joint) that have been used to examine these three stiffness levels (vertical, leg and joint) across a variety of human movements (i.e. running or hopping) as well as potential issues with the reliability of these measures, especially joint stiffness. Therefore, the aims of this study were to provide a comparison of the various methods for measuring stiffness during two forms of human bouncing locomotion (running and hopping) along with the measurement reliability to determine the best methods to assess links with injury risk in triathletes. Methods: Vertical, leg and joint stiffness were estimated in 12 healthy male competitive triathletes on two occasions, 7 days apart, using both running at 5.0 ms−1 and hopping (2.2 Hz) tasks. Results: Inter-day reliability was good for vertical (ICC = 0.85) and leg (ICC = 0.98) stiffness using the time method. Joint stiffness reliability was poor when assessed individually. Reliability was improved when taken as the sum of the hip, knee and ankle (ICC = 0.86). The knee and ankle combination provided the best correlation with leg stiffness during running (Pearson’s Correlation = 0.82). Discussion: The dynamic and time methods of calculating leg stiffness had better reliability than the “true” method. The time and dynamic methods had the best correlation with the different combinations of joint stiffness, which suggests that they should be considered for biomechanical screening of triathletes. The knee and ankle combination had the best correlation with leg stiffness and is therefore proposed to provide the most information regarding lower limb mechanics during gait in triathletes

CHANGES IN LOWER EXTREMITY STIFFNESS WITH TRIATHLON SPECIFIC TRAINING

Achilles tendon injuries are problematic for triathletes ranked as the most severe injuries in club and development athletes. As an overuse injury, Achilles tendon injures were proposed to be the result of a combination of risk factors, requiring measurements which incorporated multiple risk factors. Stiffness was identified to be a measure that was influenced by many of the risk factors for Achilles injury. In a one-year prospective study, 75 triathletes were followed to determine the association between measures of lower extremity stiffness and the risk of developing an Achilles injury. Triathletes who developed a new or reoccurring injury during the surveillance period had higher leg and knee to ankle stiffness ratio compared to Uninjured athletes. The influence of transitioning from cycling to running, on lower extremity stiffness were assessed. Transitioning from cycling caused an increase in ankle stiffness (ES=0.55) but a decrease in knee stiffness (ES=-0.38). Individual responses are likely to be important when assessing injury risk

ISBS 2018 AUCKLAND CONFERENCE SPRINZ SPORT AND EXERCISE BIOMECHANICS TEACHING ARCHIVE PROGRAMME

The host of the archive is the J.E. Lindsay Carter Kinanthropometry Clinic and Archive (JELCKCA) at the Auckland University of Technology. The director of the Archive is Professor Patria Hume (AUT SPRINZ) and archive web master is Dr Anna Lorimer (Bond University and AUT SPRINZ). Initiation of this project was a result of planning and hosting the 36th Annual Conference of the International Society of Biomechanics in Sports (ISBS) in Auckland, New Zealand September 10-14, 2018. This archive is a place to share (upload) and obtain (download) electronic image files that are intended for non-profit instructional use in sport and exercise biomechanics classes and educational outreach programs (e.g. National Biomechanics Day). Archive images are indented to be stand-alone instructional slides or can be photo/images/graphics that illustrate biomechanical data, principles, theories, or application. While human sport and exercise examples are preferred, any animal biomechanical images of potential interest and instructional value are welcome. Images in the archive are organized into the following thirteen categories to facilitate user access: Active Learning Experiences, Applications in Professions, Core Concepts, Data Collection, Demonstrations, EMG/Neuromuscular, Fluids, Kinematics, Kinetics, Muscle Mechanics, Theories, Videos, and Other. Downloading and Use Expectations: Users of image-slides from this archive are expected to not alter the image to exclude the references to the original data, image, or image author(s) at the bottom of each image. These image-slides are for non-profit, educational use with universities, schools, conferences, or other service presentations. They are not intended for use in consulting for personal profit. All materials in this archive are intended for free, fair educational use, so any material (images, video, content) that has explicit for-profit copyright, trademark, or other legal limitations on educational use should NOT be uploaded. Uploading Expectations: Please upload only standard, widely supported electronic image (.jpg, .png or .gif) or short, compressed video files (.avi, .gif., .mov, .mpeg). Please strive to use a wide, horizontal layout common in MS PowerPoint slides (vertical to horizontal ratio of 1:1.9). Sources of all published data should be cited in APA format (Author, year). ALL slides should also identify the person submitting the slice on the bottom, lower left. We recommend the following format for this acknowledgement: Slide by First Initial. Slide Author Surname for educational use only. All uploads require the entry of the name and email address of the person that created the submission, along with a few suggestions describing the potential use of the image-slide. Please use a filename that is descriptive of the image-slide content (e.g., MuscleActions.jpg). All content to be uploaded will be reviewed by the Archive managers before it is made publically available

A BIOMECHANICAL COMPARISON BETWEEN STRONGMAN EVENTS AND TECHNICALLY SIMILAR TRADITIONAL WEIGHT TRAINING EXERCISES: A NARRATIVE REVIEW

A literature search was conducted to identify studies comparing biomechanical parameters of strongman events and technically similar traditional weight training exercises. While many similarities were identified, the farmers walk may result in reduced stress placed on the lumbar spine due to the more vertical trunk than when performing the deadlift under identical loading conditions, the heavy sled pull may be used to better develop anterior force production than the back squat, and the log lift may be used to better develop forceful hip extension during a triple extension movement than the clean and jerk. The identification of biomechanical similarities and differences between strongman and traditional weight training exercises may be used by strength and conditioning coaches to better prescribe exercises suited to an individual athletes’ conditioning requirements

Validation of Spatiotemporal and Kinematic Measures in Functional Exercises Using a Minimal Modeling Inertial Sensor Methodology

This study proposes a minimal modeling magnetic, angular rate and gravity (MARG) methodology for assessing spatiotemporal and kinematic measures of functional fitness exercises. Thirteen healthy persons performed repetitions of the squat, box squat, sandbag pickup, shuffle-walk, and bear crawl. Sagittal plane hip, knee, and ankle range of motion (ROM) and stride length, stride time, and stance time measures were compared for the MARG method and an optical motion capture (OMC) system. The root mean square error (RMSE), mean absolute percentage error (MAPE), and Bland–Altman plots and limits of agreement were used to assess agreement between methods. Hip and knee ROM showed good to excellent agreement with the OMC system during the squat, box squat, and sandbag pickup (RMSE: 4.4–9.8°), while ankle ROM agreement ranged from good to unacceptable (RMSE: 2.7–7.2°). Unacceptable hip and knee ROM agreement was observed for the shuffle-walk and bear crawl (RMSE: 3.3–8.6°). The stride length, stride time, and stance time showed good to excellent agreement between methods (MAPE: (3.2 ± 2.8)%–(8.2 ± 7.9)%). Although the proposed MARG-based method is a valid means of assessing spatiotemporal and kinematic measures during various exercises, further development is required to assess the joint kinematics of small ROM, high velocity movements

The biomechanical characteristics of the strongman atlas stone lift

BACKGROUND: The atlas stone lift is a popular strongman exercise where athletes are required to pick up a large, spherical, concrete stone and pass it over a bar or place it on to a ledge. The aim of this study was to use ecologically realistic training loads and set formats to (1) establish the preliminary biomechanical characteristics of athletes performing the atlas stone lift; (2) identify any biomechanical differences between male and female athletes performing the atlas stone lift; and (3) determine temporal and kinematic differences between repetitions of a set of atlas stones of incremental mass. METHODS: Kinematic measures of hip, knee and ankle joint angle, and temporal measures of phase and repetition duration were collected whilst 20 experienced strongman athletes (female: n = 8, male: n = 12) performed three sets of four stone lifts of incremental mass (up to 85% one repetition maximum) over a fixed-height bar. RESULTS: The atlas stone lift was categorised in to five phases: the recovery, initial grip, first pull, lap and second pull phase. The atlas stone lift could be biomechanically characterised by maximal hip and moderate knee flexion and ankle dorsiflexion at the beginning of the first pull; moderate hip and knee flexion and moderate ankle plantarflexion at the beginning of the lap phase; moderate hip and maximal knee flexion and ankle dorsiflexion at the beginning of the second pull phase; and maximal hip, knee extension and ankle plantarflexion at lift completion. When compared with male athletes, female athletes most notably exhibited: greater hip flexion at the beginning of the first pull, lap and second pull phase and at lift completion; and a shorter second pull phase duration. Independent of sex, first pull and lap phase hip and ankle range of motion (ROM) were generally smaller in repetition one than the final three repetitions, while phase and total repetition duration increased throughout the set. Two-way interactions between sex and repetition were identified. Male athletes displayed smaller hip ROM during the second pull phase of the first three repetitions when compared with the final repetition and smaller hip extension at lift completion during the first two repetitions when compared with the final two repetitions. Female athletes did not display these between-repetition differences. CONCLUSIONS: Some of the between-sex biomechanical differences observed were suggested to be the result of between-sex anthropometric differences. Between-repetition differences observed may be attributed to the increase in stone mass and acute fatigue. The biomechanical characteristics of the atlas stone lift shared similarities with the previously researched Romanian deadlift and front squat. Strongman athletes, coaches and strength and conditioning coaches are recommended to take advantage of these similarities to achieve greater training adaptations and thus performance in the atlas stone lift and its similar movements

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