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Harrison KD, Dakin CJ, Beethe AZ, Louder T. Effects of Stroboscopic Vision on Depth Jump Motor Control: A Biomechanical Analysis. Bioengineering (Basel) 2024; 11:290. [PMID: 38534564 DOI: 10.3390/bioengineering11030290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 03/07/2024] [Accepted: 03/13/2024] [Indexed: 03/28/2024] Open
Abstract
Researchers commonly use the 'free-fall' paradigm to investigate motor control during landing impacts, particularly in drop landings and depth jumps (DJ). While recent studies have focused on the impact of vision on landing motor control, previous research fully removed continuous visual input, limiting ecological validity. The aim of this investigation was to evaluate the effects of stroboscopic vision on depth jump (DJ) motor control. Ground reaction forces (GRF) and lower-extremity surface electromyography (EMG) were collected for 20 young adults (11 male; 9 female) performing six depth jumps (0.51 m drop height) in each of two visual conditions (full vision vs. 3 Hz stroboscopic vision). Muscle activation magnitude was estimated from EMG signals using root-mean-square amplitudes (RMS) over specific time intervals (150 ms pre-impact; 30-60 ms, 60-85 ms, and 85-120 ms post-impact). The main effects of and interactions between vision and trial number were assessed using two-way within-subjects repeated measures analyses of variance. Peak GRF was 6.4% greater, on average, for DJs performed with stroboscopic vision compared to full vision (p = 0.042). Tibialis anterior RMS EMG during the 60-85 ms post-impact time interval was 14.1% lower for DJs performed with stroboscopic vision (p = 0.020). Vastus lateralis RMS EMG during the 85-120 ms post-impact time interval was 11.8% lower for DJs performed with stroboscopic vision (p = 0.017). Stroboscopic vision altered DJ landing mechanics and lower-extremity muscle activation. The observed increase in peak GRF and reduction in RMS EMG of the tibialis anterior and vastus lateralis post-landing may signify a higher magnitude of lower-extremity musculotendinous stiffness developed pre-landing. The results indicate measurable sensorimotor disruption for DJs performed with stroboscopic vision, warranting further research and supporting the potential use of stroboscopic vision as a sensorimotor training aid in exercise and rehabilitation. Stroboscopic vision could induce beneficial adaptations in multisensory integration, applicable to restoring sensorimotor function after injury and preventing injuries in populations experiencing landing impacts at night (e.g., military personnel).
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Affiliation(s)
- Kenneth D Harrison
- School of Kinesiology, Auburn University, Auburn, AL 36849, USA
- Department of Kinesiology and Health Science, Utah State University, Logan, UT 84322, USA
| | - Christopher J Dakin
- Department of Kinesiology and Health Science, Utah State University, Logan, UT 84322, USA
| | - Anne Z Beethe
- PEAK Performance, Colby College Athletics, Waterville, ME 04901, USA
| | - Talin Louder
- Department of Kinesiology and Health Science, Utah State University, Logan, UT 84322, USA
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Sara LK, Gaudette LW, Souza Júnior JRD, Tenforde AS, Wasserman L, Johnson CD. Cues to land softly and quietly result in acute reductions in ground reaction force loading rates in runners. Gait Posture 2024; 109:220-225. [PMID: 38364508 PMCID: PMC10939780 DOI: 10.1016/j.gaitpost.2024.02.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 01/26/2024] [Accepted: 02/08/2024] [Indexed: 02/18/2024]
Abstract
BACKGROUND A common gait retraining goal for runners is reducing vertical ground reaction force (GRF) loading rates (LRs), which have been associated with injury. Many gait retraining programs prioritize an internal focus of attention, despite evidence supporting an external focus of attention when a specific outcome is desired (e.g., LR reduction). RESEARCH QUESTION Does an external focus of attention (using cues for quiet, soft landings) result in comparable reductions in LRs to those achieved using a common internal focus (forefoot striking while barefoot)? METHODS This observational study included 37 injured runners (18 male; mean age 36 (14) years) at the OMITTED Running Center. Runners wore inertial measurement units over the distal-medial tibia while running on an instrumented treadmill at a self-selected speed. Data were collected for three conditions: 1) Shod-Control (wearing shoes, without cues); 2) Shod-Quiet (wearing shoes, cues for quiet, soft landings); and 3) Barefoot-FFS (barefoot, cues for forefoot strike (FFS)). Within-subject variables were compared across conditions: vertical instantaneous loading rate (LR, primary outcome); vertical stiffness during initial loading; peak vertical GRF; peak vertical tibial acceleration (TA); and cadence. RESULTS Vertical LR, stiffness, and TA were lower in the Shod-Quiet compared to Shod-Control p < 0.001). Peak vertical GRF and cadence were not different between Shod-Quiet and Shod-Control. Reductions in stiffness and LR were similar between Shod-Quiet and Barefoot-FFS, and GRF in Barefoot-FFS remained similar to both shod conditions. However, runners demonstrated additional reductions in TA and increased cadence when transitioning from Shod-Quiet to the Barefoot-FFS condition (p < 0.05). SIGNIFICANCE These results suggests that a focus on quiet, soft landings may be an effective gait retraining method for future research.
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Affiliation(s)
- Lauren K Sara
- Spaulding National Running Center, Spaulding Rehabilitation Hospital, Cambridge, MA 02138, USA; Department of Physical Medicine and Rehabilitation, Harvard Medical School, Cambridge, MA 02138, USA; Department of Rheumatology, Boston University, Boston, MA 02215, USA.
| | - Logan W Gaudette
- Spaulding National Running Center, Spaulding Rehabilitation Hospital, Cambridge, MA 02138, USA
| | - José Roberto de Souza Júnior
- Spaulding National Running Center, Spaulding Rehabilitation Hospital, Cambridge, MA 02138, USA; Department of Physical Medicine and Rehabilitation, Harvard Medical School, Cambridge, MA 02138, USA; Graduate Program of Sciences and Technologies in Health, University of Brasília, Brasília, Federal District 72220-275, Brazil
| | - Adam S Tenforde
- Spaulding National Running Center, Spaulding Rehabilitation Hospital, Cambridge, MA 02138, USA; Department of Physical Medicine and Rehabilitation, Harvard Medical School, Cambridge, MA 02138, USA
| | - Lindsay Wasserman
- Spaulding National Running Center, Spaulding Rehabilitation Hospital, Cambridge, MA 02138, USA
| | - Caleb D Johnson
- Spaulding National Running Center, Spaulding Rehabilitation Hospital, Cambridge, MA 02138, USA; Department of Physical Medicine and Rehabilitation, Harvard Medical School, Cambridge, MA 02138, USA; United States Army Research Institute of Environmental Medicine, Natick, MA 01760, USA
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Yang Z, Cui C, Zhou Z, Zheng Z, Yan S, Liu H, Qu F, Zhang K. Effect of midsole hardness and surface type cushioning on landing impact in heel-strike runners. J Biomech 2024; 165:111996. [PMID: 38377740 DOI: 10.1016/j.jbiomech.2024.111996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 01/29/2024] [Accepted: 02/13/2024] [Indexed: 02/22/2024]
Abstract
High loading impact associated with heel strikes causes running injuries. This study aimed to investigate how loading impact is affected by midsole hardness and running surface type. Twelve young rear-foot runners ran at a fixed speed along an 18 m runway wearing shoes with different midsole hardness (Asker C-45, C-50, C-55, C-60, from soft to hard) and on two different surfaces (rubber and concrete). We quantified vertical average loading rate (VALR) and vertical impact peak force (VIPF). We conducted midsole × surface repeated-measures ANOVA on loading impact measures, and one-sample t-tests to compare VALR with a threshold value (80 BW·s-1). Midsole hardness and surface type mainly affected VALR. Although no significant effect of these variables was observed for VIPF magnitude, there were effects on time to VIPF and steps with VIPF. Several combinations of midsole and surface hardness reduced VALR below 80 BW·s-1: Asker C-45 with both surfaces, and Asker C-50 with a rubber surface. The combination of softer midsole and surface effectively reduced loading rates as shown by increased time to VIPF and reduced VALR. Combining softer midsole and surface results in the greatest cushioning, which demonstrates the benefit of considering both factors in reducing running injuries.
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Affiliation(s)
- Zihan Yang
- Fashion Accessory Art and Engineering College, Beijing Institute of Fashion Technology, Beijing, China; School of Biomedical Engineering, Capital Medical University, Beijing, China; Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, China; Biomechanics Laboratory, Beijing Sport University, Beijing, China
| | - Chuyi Cui
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA
| | - Zhipeng Zhou
- College of Sports and Health, Shandong Sport University, Jinan, Shandong, China
| | - Zhiyi Zheng
- Anta (China) Co., Ltd. Anta Sports Science Laboratory, Xiamen, Fujian, China
| | - Songhua Yan
- School of Biomedical Engineering, Capital Medical University, Beijing, China; Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, China
| | - Hui Liu
- Biomechanics Laboratory, Beijing Sport University, Beijing, China
| | - Feng Qu
- Biomechanics Laboratory, Beijing Sport University, Beijing, China
| | - Kuan Zhang
- School of Biomedical Engineering, Capital Medical University, Beijing, China; Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, China.
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McCain EM, Dalman MJ, Berno ME, Libera TL, Lewek MD, Sawicki GS, Saul KR. The influence of induced gait asymmetry on joint reaction forces. J Biomech 2023; 153:111581. [PMID: 37141689 PMCID: PMC10424665 DOI: 10.1016/j.jbiomech.2023.111581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 02/24/2023] [Accepted: 04/04/2023] [Indexed: 05/06/2023]
Abstract
Chronic injury- or disease-induced joint impairments result in asymmetric gait deviations that may precipitate changes in joint loading associated with pain and osteoarthritis. Understanding the impact of gait deviations on joint reaction forces (JRFs) is challenging because of concurrent neurological and/or anatomical changes and because measuring JRFs requires medically invasive instrumented implants. Instead, we investigated the impact of joint motion limitations and induced asymmetry on JRFs by simulating data recorded as 8 unimpaired participants walked with bracing to unilaterally and bilaterally restrict ankle, knee, and simultaneous ankle + knee motion. Personalized models, calculated kinematics, and ground reaction forces (GRFs) were input into a computed muscle control tool to determine lower limb JRFs and simulated muscle activations guided by electromyography-driven timing constraints. Unilateral knee restriction increased GRF peak and loading rate ipsilaterally but peak values decreased contralaterally when compared to walking without joint restriction. GRF peak and loading rate increased with bilateral restriction compared to the contralateral limb of unilaterally restricted conditions. Despite changes in GRFs, JRFs were relatively unchanged due to reduced muscle forces during loading response. Thus, while joint restriction results in increased limb loading, reductions in muscle forces counteract changes in limb loading such that JRFs were relatively unchanged.
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Affiliation(s)
| | | | | | - Theresa L Libera
- North Carolina State University, Raleigh, NC, USA; University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
| | - Michael D Lewek
- University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
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Johnson CD, Davis IS. What differentiates rearfoot strike runners with low and high vertical load rates? Gait Posture 2022; 96:149-153. [PMID: 35660239 DOI: 10.1016/j.gaitpost.2022.05.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 04/19/2022] [Accepted: 05/17/2022] [Indexed: 02/02/2023]
Abstract
BACKGROUND Runners with a rearfoot strike pattern typically show high vertical ground reaction force loading rates (LRs), that are associated with injuries, compared with forefoot strikers. However, some runners with a rearfoot strike pattern run in a way that reduces LRs. Our purpose was to identify differences in running mechanics between rearfoot strike runners with high and low vertical LRs. METHODS 42 healthy runners, 21 with high (≥ 80.5 BW/s) and 21 with low (≤ 46.3 BW/s) LRs, were included in the current study. Lower extremity kinematic and kinetic data were then collected while participants ran along a 30 m runway. Running mechanics were calculated, including sagittal plane knee stiffness during early stance, the components of knee stiffness (Δ knee flexion and flexion moment), sagittal joint angles at initial contact, as well as cadence. The two LR groups were compared for differences in outcome variables using independent t-tests or Mann Whitney U tests. FINDINGS Knee stiffness was significantly lower in the low LR group (p < 0.01, d = 0.87), due to higher knee flexion excursion (p < 0.01, d = 1.38). At initial contact, the low LR group showed lower hip and knee flexion, but greater ankle and foot dorsiflexion (p = 0.01-0.04, d = 0.64-0.93). No differences were found in cadence. INTERPRETATION These results provide potential targets, related to gait kinematics and kinetics, for gait retraining aimed at reducing LRs in rearfoot strike runners.
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Affiliation(s)
- Caleb D Johnson
- Spaulding National Running Center, Department of Physical Medicine and Rehabilitation, Harvard Medical School, 1575 Cambridge St., Cambridge, MA 02139, USA.
| | - Irene S Davis
- Spaulding National Running Center, Department of Physical Medicine and Rehabilitation, Harvard Medical School, 1575 Cambridge St., Cambridge, MA 02139, USA
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Application of Leg, Vertical, and Joint Stiffness in Running Performance: A Literature Overview. Appl Bionics Biomech 2021; 2021:9914278. [PMID: 34721664 PMCID: PMC8553457 DOI: 10.1155/2021/9914278] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 09/08/2021] [Accepted: 09/17/2021] [Indexed: 12/01/2022] Open
Abstract
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.
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Borgia B, Radzak KN, Freedman Silvernail J. Similarities in joint stiffness across footwear conditions in younger and masters-aged runners. FOOTWEAR SCIENCE 2021. [DOI: 10.1080/19424280.2021.1906331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Brianne Borgia
- Departments of Kinesiology and Nutrition Sciences, University of Nevada, Las Vegas, Las Vegas, NV, USA
| | - Kara N. Radzak
- Departments of Kinesiology and Nutrition Sciences, University of Nevada, Las Vegas, Las Vegas, NV, USA
| | - Julia Freedman Silvernail
- Departments of Kinesiology and Nutrition Sciences, University of Nevada, Las Vegas, Las Vegas, NV, USA
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Cheung VCK, Cheung BMF, Zhang JH, Chan ZYS, Ha SCW, Chen CY, Cheung RTH. Plasticity of muscle synergies through fractionation and merging during development and training of human runners. Nat Commun 2020; 11:4356. [PMID: 32868777 PMCID: PMC7459346 DOI: 10.1038/s41467-020-18210-4] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 08/06/2020] [Indexed: 12/22/2022] Open
Abstract
Complex motor commands for human locomotion are generated through the combination of motor modules representable as muscle synergies. Recent data have argued that muscle synergies are inborn or determined early in life, but development of the neuro-musculoskeletal system and acquisition of new skills may demand fine-tuning or reshaping of the early synergies. We seek to understand how locomotor synergies change during development and training by studying the synergies for running in preschoolers and diverse adults from sedentary subjects to elite marathoners, totaling 63 subjects assessed over 100 sessions. During development, synergies are fractionated into units with fewer muscles. As adults train to run, specific synergies coalesce to become merged synergies. Presences of specific synergy-merging patterns correlate with enhanced or reduced running efficiency. Fractionation and merging of muscle synergies may be a mechanism for modifying early motor modules (Nature) to accommodate the changing limb biomechanics and influences from sensorimotor training (Nurture).
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Affiliation(s)
- Vincent C K Cheung
- School of Biomedical Sciences, and The Gerald Choa Neuroscience Centre, The Chinese University of Hong Kong, Hong Kong, China.
- Joint Laboratory of Bioresources and Molecular Research of Common Diseases, The Chinese University of Hong Kong and Kunming Institute of Zoology of The Chinese Academy of Sciences, Hong Kong, China.
| | - Ben M F Cheung
- School of Biomedical Sciences, and The Gerald Choa Neuroscience Centre, The Chinese University of Hong Kong, Hong Kong, China
| | - Janet H Zhang
- Gait & Motion Analysis Laboratory, Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hong Kong, China
- Department of Integrative Physiology, University of Colorado, Boulder, CO, USA
| | - Zoe Y S Chan
- Gait & Motion Analysis Laboratory, Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hong Kong, China
- Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
| | - Sophia C W Ha
- School of Biomedical Sciences, and The Gerald Choa Neuroscience Centre, The Chinese University of Hong Kong, Hong Kong, China
| | - Chao-Ying Chen
- Gait & Motion Analysis Laboratory, Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hong Kong, China
| | - Roy T H Cheung
- Gait & Motion Analysis Laboratory, Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hong Kong, China.
- School of Health Sciences, Western Sydney University, Sydney, NSW, Australia.
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Vermeulen E, Grobbelaar SS, Botha A. Conceptualising a systems thinking perspective in sport studies. THEORETICAL ISSUES IN ERGONOMICS SCIENCE 2020. [DOI: 10.1080/1463922x.2020.1788662] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Euodia Vermeulen
- Department Industrial Engineering, Stellenbosch University, South Africa
| | - Sara S. Grobbelaar
- Department Industrial Engineering, Stellenbosch University, South Africa
- DST-NRF Centre of Excellence in Scientometrics and Science, Technology and Innovation Policy (SciSTIP), Stellenbosch University, South Africa
| | - Adele Botha
- Department Industrial Engineering, Stellenbosch University, South Africa
- Next Generation Enterprises and Institutions, CSIR, South Africa
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Garofolini A, Oppici L, Taylor S. A real-time feedback method to reduce loading rate during running: Effect of combining direct and indirect feedback. J Sports Sci 2020; 38:2446-2453. [PMID: 32627694 DOI: 10.1080/02640414.2020.1788288] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Impact loading plays a key role in the pathophysiology of running-related injuries. Providing real-time feedback may be an effective strategy to reduce impact loading; however, it is currently unclear what an effective training method to help runners achieve a habitual low loading rate is. We subjected 20 healthy non-runners to a structured sequence of direct and indirect biofeedback designed to facilitate broader exploration of neuro-mechanical workspace for potential movement solutions (indirect feedback on cadence and foot-strike angle) and to refine and converge upon an optimal sub-set of that space to match the task goal (direct feedback on loading rate). While indirect biofeedback on foot-strike angle yielded a lower impact load than providing direct biofeedback on loading rate, compared to indirect biofeedback on foot-strike angle, providing direct feedback on loading rate statistically increased (+58%, p = 0.007) the range of goal-relevant solutions participants used to lower their impact loading. Results showed that structured feedback was effective in increasing the range of input parameters that match the task goal, hence expanding the size of goal-relevant solutions, which may benefit running performance under changing environmental constraints.
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Affiliation(s)
| | - Luca Oppici
- Psychology of Learning and Instruction, Department of Psychology, School of Science, Technische Universität Dresden , Dresden, Germany.,Centre for Tactile Internet with Human-in-the-Loop (Ceti), Technische Universität Dresden , Dresden, Germany
| | - Simon Taylor
- Institute for Health and Sport (IHES), Victoria University , Melbourne, Australia
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Vernillo G, Martinez A, Baggaley M, Khassetarash A, Giandolini M, Horvais N, Edwards WB, Millet GY. Biomechanics of graded running: Part I - Stride parameters, external forces, muscle activations. Scand J Med Sci Sports 2020; 30:1632-1641. [PMID: 32396672 DOI: 10.1111/sms.13708] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 02/07/2020] [Accepted: 05/04/2020] [Indexed: 11/30/2022]
Abstract
Biomechanical alterations with graded running have only been partially quantified, and the potential interactions with running speed remain unclear. We measured spatiotemporal parameters, ground reaction forces, and leg muscle activations (EMG) in nineteen adults (10F/9M) running on an instrumented treadmills at 2.50, 3.33, and 4.17 m·s-1 and 0, ±5°, and ±10°. Step frequency illustrated a significant speed × grade interaction (P < .001) and was highest (+3%) at the steepest grade (+10°) and fastest speed (4.17 m·s-1 ) when compared to level running (LR) at the same speed. Significant interaction was also observed for ground reaction forces (all P ≤ .047). Peak ground reaction forces in the normal direction increased with running speed during downhill running (DR) only (+9% at -10° and 4.17 m·s-1 ). Impulse in the normal direction decreased at fastest speed and steepest DR (-9%) and uphill running (UR) (-17%) grades. Average normal loading rate increased and decreased at fastest speed and steepest DR (+52%) and UR (-28%) grades, respectively. Negative parallel impulse increased and decreased at fastest speed and steepest DR (+166%) and UR (-90%), respectively. Positive parallel impulse decreased and increased at fastest speed and steepest DR (-75%) and UR (+111%), respectively. EMG showed comparable u-shaped curves across the grades investigated, although only a change in vastus lateralis and tibilias anterior activity was detectable at the steepest grades and fastest speed. Overall, running grade and speed significantly influences spatiotemporal parameters, ground reaction forces, and muscle activations.
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Affiliation(s)
- Gianluca Vernillo
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada.,Department of Biomedical Sciences for Health, Università degli Studi di Milano, Milan, Italy
| | - Aaron Martinez
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada
| | - Michael Baggaley
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada
| | - Arash Khassetarash
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada
| | | | - Nicolas Horvais
- Innovation and Sport Science Lab, Salomon SAS, Annecy, France
| | - William Brent Edwards
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada
| | - Guillaume Y Millet
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada.,UJM-Saint-Etienne, Inter-University Laboratory of Human Movement Biology, Université de Lyon, Saint-Etienne, France
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