title: Focusing on Increasing Velocity during Heavy Resistance Knee Flexion Exercise Boosts Hamstring Muscle Activity in Chronic Stroke Patients.
abstract: Background. Muscle strength is markedly reduced in stroke patients, which has negative implications for functional capacity and work ability. Different types of feedback during strength training exercises may alter neuromuscular activity and functional gains. Objective. To compare levels of muscle activity during conditions of blindfolding and intended high contraction speed with a normal condition of high-intensity knee flexions. Methods. Eighteen patients performed unilateral machine knee flexions with a 10-repetition maximum load. Surface electromyography (EMG) was recorded from the quadrics and hamstring muscles and normalized to maximal EMG (nEMG) of the nonparetic limb. Results. For the paretic leg, the speed condition showed higher values of muscle activity compared with the normal and blindfolded conditions for both biceps femoris and semitendinosus. Likewise, the speed condition showed higher co-contraction values compared with the normal and blindfolded conditions for the vastus lateralis. No differences were observed between exercise conditions for the nonparetic leg. Conclusion. Chronic stroke patients are capable of performing heavy resistance training with intended high speed of contraction. Focusing on speed during the concentric phase elicited higher levels of muscle activity of the hamstrings compared to normal and blindfolded conditions, which may have implications for regaining fast muscle strength in stroke survivors.
authors.affiliation: National Research Centre for the Working Environment, Lersø Parkalle 105, 2100 Copenhagen, Denmark; Physical Activity and Human Performance Group, SMI, Department of Health Science and Technology, Aalborg University, 9220 Aalborg, Denmark.
authors.forename: Jonas
authors.identifier: 0000-0001-8430-0139
authors.initials: J
authors.lastname: Vinstrup
authors.affiliation: National Research Centre for the Working Environment, Lersø Parkalle 105, 2100 Copenhagen, Denmark; Research Unit in Sports and Health, Department of Physical Education and Sports, University of Valencia, 46010 Valencia, Spain.
authors.forename: Joaquin
authors.identifier: 0000-0002-8670-8346
authors.initials: J
authors.lastname: Calatayud
authors.affiliation: National Research Centre for the Working Environment, Lersø Parkalle 105, 2100 Copenhagen, Denmark.
authors.forename: Markus D
authors.initials: MD
authors.lastname: Jakobsen
authors.affiliation: National Research Centre for the Working Environment, Lersø Parkalle 105, 2100 Copenhagen, Denmark.
authors.forename: Emil
authors.identifier: 0000-0001-7408-222X
authors.initials: E
authors.lastname: Sundstrup
authors.affiliation: National Research Centre for the Working Environment, Lersø Parkalle 105, 2100 Copenhagen, Denmark; Physical Activity and Human Performance Group, SMI, Department of Health Science and Technology, Aalborg University, 9220 Aalborg, Denmark.
authors.forename: Lars L
authors.identifier: 0000-0003-2777-8085
authors.initials: LL
authors.lastname: Andersen