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Comparison of static and dynamic methods based on knee kinematics to determine optimal saddle height in cycling

Millour Geoffrey, Duc Sebastien, Puel Frederic, Bertucci William

Acta of Bioengineering and Biomechanics

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2019

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Vol. 21, no. 4

93--99

EN

Bike-fitting methods based on knee kinematics have been proposed to determine optimal saddle height. The Holmes method recommends that knee angle be between 25° and 35° when the pedal is at bottom dead centre in static. Other authors advocate knee angle of 30–40° during maximum knee extension while pedalling. Although knee angle would be 5–10° greater at bottom dead centre during pedalling, no study has reported reference values in this condition. The purpose of this study was to compare these three methodologies on knee, hip, and ankle angles and to develop new dynamic reference range at bottom dead centre. Methods: Twenty-six cyclists volunteered for this experiment and performed a pedalling test on their personal road or mountain bike. Knee, hip, and ankle angles were assessed by two-dimensional video analysis. Results: Dynamic knee angle was 8° significantly greater than static knee angle when the pedal was at bottom dead centre. Moreover, dynamic knee angle with the pedal at bottom dead centre was 3° significantly greater than dynamic knee angle during maximum knee extension. The chosen methodology also significantly impacted hip and ankle angles under most conditions. Conclusions: The results allow us to suggest a new range of 33–43° when the pedal is at bottom dead centre during pedalling. Thus, this study defines clearly the different ranges to determine optimal saddle height in cycling according to the condition of measurement. These findings are important for researchers and bike-fitting professionals to avoid saddle height adjustment errors that can affect cyclists’ health and performance.

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Motivating Ergonomic Computer Workstation Setup: Sometimes Training Is Not Enough

Sigurdsson S. O., Artnak M., Needham M., Wirth O., Silverman K.

International Journal of Occupational Safety and Ergonomics

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2012

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Vol. 18, No. 1

27--33

EN

Musculoskeletal disorders lead to pain and suffering and result in high costs to industry. There is evidence to suggest that whereas conventional ergonomics training programs result in knowledge gains, they may not necessarily translate to changes in behavior. There were 11 participants in an ergonomics training program, and a subsample of participants received a motivational intervention in the form of incentives for correct workstation setup. Training did not yield any changes in ergonomics measures for any participant. Incentives resulted in marked and durable changes in targeted workstation measures. The data suggest that improving worker knowledge about ergonomically correct workstation setup does not necessarily lead to correct workstation setup, and that motivational interventions may be needed to achieve lasting behavior change.

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Hand Injury From Powered Wood Splitters: Machine Safety, Patterns of Use and Injury Events

Lindqvist A., Nilsson O.

International Journal of Occupational Safety and Ergonomics

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2011

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Vol. 17, No. 2

175--186

EN

Introduction. The purpose of this study was to describe factors of possible importance for the occurrence of hand injury from powered wood splitters. Patients. Patients were identified by a computerized patient registry. Information was obtained from hospital records, a written questionnaire and a structured telephone interview. Results. Very few splitters were constructed according to European standards. Twenty-one percent of patients injured with wedge splitters thought that having more than one person at the machine was one cause of the accident. Seventy-nine percent of patients injured with screw splitters stated that glove use was one cause of the accident. Conclusions. The level of safety in wood splitters that cause hand injury is often poor. Having more than one person at the machine during work may contribute to wedge splitter injury. Glove use commonly contributes to screw splitter injury. Prevention should be directed towards unsafe machines and dangerous patterns of use.