Browsing by Author "Nigg, Benno Maurus"
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- ItemOpen AccessLower Extremity Muscle Activation Following a Previous Knee Injury: Implications for Post-Traumatic Knee Osteoarthritis(2018-12-05) Mohr, Maurice; Nigg, Benno Maurus; Emery, Carolyn A.; Von Tscharner, Vinzenz; Herzog, WalterIndividuals who sustain an intra-articular knee injury are at a high risk of developing post-traumatic knee osteoarthritis (PTOA) 10-20 years later. Compensatory activation patterns of knee muscles in response to the trauma may persist past the acute injury phase and result in abnormal mechanical loading and subsequent osteoarthritis of the knee. This dissertation aimed to use surface electromyography (sEMG) to explore abnormal leg muscle activation patterns and their possible involvement in PTOA development in individuals who suffered a previous knee injury 3-12 years ago. The first part of this thesis presents methodological investigations related to two sEMG-based assessments of knee muscle activation strategies. It was shown that 1) sEMG amplitude-based co-contraction indices during gait exhibit poor between-day reliability and 2) the magnitude of intermuscular coherence strongly depends on the configuration and alignment of the sEMG electrodes. Building on the methodological findings, the second part of this thesis investigated the association between a previous knee injury and leg muscle activation during walking and squatting while considering the influence of sex. Sex-specific abnormalities in quadricep and hamstring muscle activation patterns were present for the affected leg in individuals more than three years after a previous knee injury. Altered quadricep and hamstring muscle activation may result in abnormal movement and loading of the knee joint and thus be linked to mechanical risk factors for PTOA development. This dissertation could not provide evidence, however, that altered thigh muscle activation was associated with more self-reported knee pain or symptoms indicative of PTOA development. From a methodological perspective, the poor reliability of current sEMG-based markers for abnormal muscle activation may lower the sensitivity to detect associations with risk factors for PTOA. From a conceptual perspective, the development of PTOA is not solely based on joint mechanics but depends on the interplay between mechanical, biological, and structural abnormalities of the joint following a knee injury. Therefore, the pathway to PTOA is likely unique to each individual such that a consistent association between abnormal muscle activation following a knee injury and PTOA risk may not exist.
- ItemOpen AccessRunning Pattern Recognition in a Comfortable and an Uncomfortable Shoe Condition(2018-12-07) Manz, Sabina; Nigg, Benno Maurus; Edwards, William Brent; Von Tscharner, Vinzenz; Kuo, Arthur D.The diverse development of running shoes has mostly been driven by three functional factors: reducing injury risk, increasing performance, and increasing perceived comfort. The few studies that focused on comfort provide contradicting results. Comfort is a subjective impression, different for every individual, and is speculated to be one of the most important features of a running shoe, however, it is not well understood or quantifiable. As a result, comfort and its relationship to running biomechanics has not been established. The purpose of this study was to (a) distinguish movement patterns while running in a comfortable shoe condition from movement patterns while running in an uncomfortable shoe condition, (b) determine if these patterns are localized to a specific body segment, and (c) determine which classification tool (linear or spherical) yields the most conclusive results. The movement patterns while running in two different shoes were compared and classified using a support vector machine and spherical classification. The classifications were performed using accelerations and angular velocities from all five sensor locations as well as using subsets of the data. The highest classification (61.88%) was found using spherical classification and a subset of the data. Both classification tools resulted in low success rates. The running kinematics in this study were unaffected by a change in comfort. Keywords: running, pattern recognition, comfort, shoes, inertial measurement units
- ItemOpen AccessShoe Bending Stiffness and Muscle-Tendon Unit Function in Running(2021-01-08) Čigoja, Saša; Nigg, Benno Maurus; Edwards, William Brent; Stefanyshyn, Darren John; von Tscharner, Vinzenz; Boyd, Steven K.; Hoogkamer, WouterThe latest records set during long-distance running competitions have been attributed to recent footwear midsole innovations. One of these midsole innovations that has been claimed to have large effects on biomechanical, physiological, and performance variables is the use of a carbon fibre plate to increase the longitudinal bending stiffness of a shoe. Several mechanisms were proposed to be associated with performance improvements when running in footwear with carbon fibre plates. One of these mechanisms, the principle of optimising muscle function is currently not well understood. Therefore, this thesis aimed to investigate the effects of midsole bending stiffness of athletic footwear on muscle and muscle-tendon unit function in running. The first part of this thesis showed that running in stiff footwear resulted in a redistribution of positive work from proximal to distal lower limb joints. Specifically, it was found that a fatigue-induced redistribution of joint work from distal to proximal joints can be delayed when running in stiff footwear. The second part of this thesis dealt with the shortening velocities of muscle-tendon units. Estimated shank muscle-tendon unit shortening velocities were reduced when running in stiffer shoes. Experimental results using ultrasound imaging of the gastrocnemius medialis muscle revealed that the muscle shortened to a lesser extent and with lower average velocities in stiff running footwear. These findings could have implications for long-distance running performance. Positive work generation at more distal joints (i.e., ankle) may result in lower active muscle volume, which has been shown to be the main determinant of changes in the energetic cost of running. Slower shortening velocities of the gastrocnemius medialis could allow the muscle to operate on a more favourable position on its force-velocity relationship. This could allow for more economical force generation for a longer period during long-distance running. Altered muscle function could be a source of improved performance when running in stiff shoes.
- ItemOpen AccessTask-Dependent Intermuscular Motor Unit Synchronization between Medial and Lateral Vastii Muscles during Dynamic and Isometric Squats(PLoS ONE, 2015-11-03) Mohr, Maurice; Nann, Marius; von Tschamer, Vinzenz; Eskofier, Bjoern; Nigg, Benno MaurusPurpose Motor unit activity is coordinated between many synergistic muscle pairs but the functional role of this coordination for the motor output is unclear. The purpose of this study was to investigate the short-term modality of coordinated motor unit activity–the synchronized discharge of individual motor units across muscles within time intervals of 5ms–for the Vastus Medialis (VM) and Lateralis (VL). Furthermore, we studied the task-dependency of intermuscular motor unit synchronization between VM and VL during static and dynamic squatting tasks to provide insight into its functional role. Methods Sixteen healthy male and female participants completed four tasks: Bipedal squats, single-leg squats, an isometric squat, and single-leg balance. Monopolar surface electromyography (EMG) was used to record motor unit activity of VM and VL. For each task, intermuscular motor unit synchronization was determined using a coherence analysis between the raw EMG signals of VM and VL and compared to a reference coherence calculated from two desynchronized EMG signals. The time shift between VM and VL EMG signals was estimated according to the slope of the coherence phase angle spectrum. Results For all tasks, except for singe-leg balance, coherence between 15–80Hz significantly exceeded the reference. The corresponding time shift between VM and VL was estimated as 4ms. Coherence between 30–60Hz was highest for the bipedal squat, followed by the single-leg squat and the isometric squat. Conclusion There is substantial short-term motor unit synchronization between VM and VL. Intermuscular motor unit synchronization is enhanced for contractions during dynamic activities, possibly to facilitate a more accurate control of the joint torque, and reduced during single-leg tasks that require balance control and thus, a more independent muscle function. It is proposed that the central nervous system scales the degree of intermuscular motor unit synchronization according to the requirements of the movement task at hand.