Case Studies
See below for a selection of case studies and scientific publications.
Sensor insole for measuring temporal variables and vertical force during sprinting
August 10, 2017
J Sports Engineering and Technology 1–6
- Ryu Nagahara, Jean-Benoit Morin
- National Institute of Fitness and Sports in Kanoya, Kagoshima, Japan
Temporal variables and vertical ground reaction force have been used as measures characterizing sprinting. A recently developed wireless pressure sensor insole (sensor insole) could be useful for monitoring sprinting in terms of temporal variables and vertical ground reaction force during training sessions.
The purpose of this study was to examine the concurrent validity of the sensor insole for measuring temporal and vertical force variables during sprinting. One athlete performed five 50-m sprints, and the step-to-step vertical ground reaction force and plantar pressure were simultaneously measured by a long-force platform system (reference device) and the sensor insole, respectively. The temporal and vertical ground reaction force variables were calculated using signals from both devices, and a comparison was made between values obtained with both devices for 125 steps analyzed. The percentage bias, 95% limits of agreement, and Bland– Altman plots showed low agreement with the reference device for all variables except for step frequency. For the vertical ground reaction force variables, the sensor insole underestimated the values (218.9 to 248.3%) compared to the force platform.
While support time and time to maximal vertical force from the foot strike were overestimated by the sensor insole (54.668.0% and 94.2623.2%), flight time was underestimated (248.2615.0%). Moreover, t-test revealed the significant difference in all variables between the sensor insole and force platform, except for step frequency. The bias for step frequency (0.467.5%) was small. However, there was heteroscedasticity for all variables. The results from this study demonstrate that a wireless pressure sensor insole is generally not valid to measure the temporal and vertical force variables during sprinting. Thus, using the examined sensor insole for monitoring sprinting characteristics is not recommended at this time.
Postural Control as Predictor of Lower Extremity Injuries in Male Youth Soccer Players
February 1, 2019
American Journal of Men s Health 13(1), February 2019
- M. Kolodziej, S. Steinhoff, T. Jaitner
- TU Dortmund University Institute for Sports and Sports Science
Youth soccer players bear a particular high risk of injury due to a potential lack on an adequate level of physical fitness, which is considered as an intrinsic risk factor for injuries (Bahr & Krosshaug, 2005). Typically, lower extremity injuries occur in situations characterised by rapid changes of direction and single-leg landing, often with the player getting out of balance.
The ability to maintain balance has received more attention in injury prediction as increased variation in postural stability is associated with an altered neuromuscular control strategy and may lead to injuries (Murphy, Connolly, & Beynnon, 2003). However, prospective research is rare, and the relation between insufficient postural stability and injury is still unclear. Typically, force platform serve as gold-standard for the analysis of postural control. For in-field diagnosis, wearable sensor insoles provide an alternative diagnostic tool. However, less empirical evidence on sensor insoles for injury prediction is given. Furthermore, little research exists on balance measures as potential intrinsic injury risk factor in youth soccer.
The aim of this study was therefore to investigate the predictive value of the postural control measured by wearable sensor insoles in male youth soccer players.
Optimization of a foot model for the evaluation of the injury risk during cutting movements in football
June 26, 2013
Procedia Engineering 60 ( 2013 ) 325 – 330
- Stefan Lehner, Christine Dießl, Dennis Chang, Veit Senner
- Technische Universität München, Institute of Ergonomics, Department Sport Equipment and Material, Germany
Cutting movements in football (soccer) induce high loads on the anterior cruciate ligament in the knee. The injury risk is affected by the shoe-surface interaction. For the evaluation of different influencing factors of this interaction the TrakTester, a custom-made device, was used. To obtain significant results from testing ACL loading a realistic plantar pressure distribution in the shoe is required. Using the TrakTester several cutting movements were carried out using two different foot models with the resultant plantar pressure analysed with three different systems: The original foot model with Parotec insoles (24 integrated sensors; Paromed GmbH, Markt Neubeuern, Germany), the modified version of this foot model with Pedar-X insoles (99 sensors; novel GmbH, Munich, Germany) and the inflexible model was surveyed with the OpenGo science system (13 sensors, Moticon, Munich, Germany). For the inflexible model distinct angles between the lower leg and the surface were adjusted and the obtained plantar pressure distributions were analyzed.
As the first version showed high pressures in the arch region, it was modified to reduce the load in this area. A second inflexible model induced the pressure in the heel and forefoot region. For various angles similar plantar pressure distributions were obtained. Highest pressures were applied on the medial side of theheel and forefoot with minor load in the arch region. This corresponds to literature data investigating cutting movements with subjects. Tests with the inflexible foot model achieved similar and realistic patterns of the plantar pressure distribution for different angles. This is an important precondition to obtain reproducible data for ACL loading during cutting movements.
Biomechanical Adaptations and Performance Indicators in Short Trail Running
April 30, 2019
Frontiers in Physiology 10:506
Biomechanical Adaptations and Performance Indicators in Short Trail Running
- Glenn Björklund, Mikael Swarén, Dennis-Peter Born, Thomas Stöggl
- Department of Health Sciences, Swedish Winter Sports Research Centre, Mid Sweden University, Östersund, Sweden
Our aims were to measure anthropometric and oxygen uptake (˙VO2) variables in the laboratory, to measure kinetic and stride characteristics during a trail running time trial, and then analyse the data for correlations with trail running performance. Runners (13 men, 4 women: mean age: 29 ± 5 years; stature: 179.5 ± 0.8 cm; body mass: 69.1 ± 7.4 kg) performed laboratory tests to determine ˙VO2max, running economy (RE), and anthropometric characteristics. On a separate day they performed an outdoor trail running time trial (two 3.5 km laps, total climb: 486 m) while we collected kinetic and time data. Comparing lap 2 with lap 1 (19:40 ± 1:57 min vs. 21:08 ± 2:09 min, P < 0.001),runners lost most time on the uphill sections and least on technical downhills (−2.5 ± 9.1 s). Inter-individual performance varied most for the downhills (CV > 25%) and least on flat terrain (CV < 10%). Overall stride cycle and ground contact time (GCT) were shorter in downhill than uphill sections (0.64±0.03 vs. 0.84±0.09 s; 0.26±0.03 vs. 0.46 ± 0.90 s, both P < 0.001). Force impulse was greatest on uphill (248 ± 46 vs. 175 ± 24 Ns, P < 0.001) and related to GCT (r = 0.904, P < 0.001). Peak force was greater during downhill than during uphill running (1106 ± 135 vs. 959 ± 104 N, P < 0.01). Performance was related to absolute and relative ˙VO2max (P < 0.01), vertical uphill treadmill speed (P < 0.001) and fat percent (P < 0.01). Running uphill involved the greatest impulse per step due to longer GCT while downhill running generated the highest peak forces. ˙VO2max, vertical running speed and fat percent are important predictors for trail running performance.
Performance between runners varied the most on downhills through out the course, while pacing resembled are versed J pattern.
Future studies should focus on longer competition distances to verify these findings and with application of measures of 3D kinematics.
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