@article{ZuurLundbyeJensenLeukeletal.2010,
  author    = {Zuur, Abraham T. and Lundbye-Jensen, Jesper and Leukel, Christan and Taube, Wolfgang and Grey, Michael J. and Gollhofer, Albert and Nielsen, Jens Bo and Gruber, Markus},
  title     = {Contribution of afferent feedback and descending drive to human hopping},
  issn      = {0022-3751},
  doi       = {10.1113/jphysiol.2009.182709},
  year      = {2010},
  abstract  = {During hopping an early burst can be observed in the EMG from the soleus muscle starting about 45 ms after touch-down. It may be speculated that this early EMG burst is a stretch reflex response superimposed on activity from a supra-spinal origin. We hypothesised that if a stretch reflex indeed contributes to the early EMG burst, then advancing or delaying the touch-down without the subject's knowledge should similarly advance or delay the burst. This was indeed the case when touch-down was advanced or delayed by shifting the height of a programmable platform up or down between two hops and this resulted in a correspondent shift of the early EMG burst. Our second hypothesis was that the motor cortex contributes to the first EMG burst during hopping. If so, inhibition of the motor cortex would reduce the magnitude of the burst. By applying a low-intensity magnetic stimulus it was possible to inhibit the motor cortex and this resulted in a suppression of the early EMG burst. These results suggest that sensory feedback and descending drive from the motor cortex are integrated to drive the motor neuron pool during the early EMG burst in hopping. Thus, simple reflexes work in concert with higher order structures to produce this repetitive movement.},
  language  = {en}
}
@article{GranacherGruberFoerdereretal.2010,
  author    = {Granacher, Urs and Gruber, Markus and Foerderer, Dominik and Strass, Dieter and Gollhofer, Albert},
  title     = {Effects of ankle fatigue on functional reflex activity during gait perturbations in young and elderly men},
  issn      = {0966-6362},
  doi       = {10.1016/j.gaitpost.2010.03.016},
  year      = {2010},
  abstract  = {There is growing evidence that aging and muscle fatigue result in impaired postural reflexes in humans. Therefore, the objective of this study was to examine the effects of ankle fatigue on functional reflex activity (ERA) during gait perturbations in young and elderly men. Twenty-eight young (27.0 +/- 3.1 years, n = 14) and old (67.2 +/- 3.7 years, n = 14) healthy active men participated in this study. Fatigue of the plantarflexors and dorsiflexors was induced by isokinetic contractions. Pre and post-fatigue, subjects were tested for their ability to compensate for decelerating gait perturbations while walking on a treadmill. Latency, ERA of lower extremity muscles and angular velocity of the ankle joint complex were analysed by means of surface electromyography and goniometry. After the fatigue protocol, no significant main and interaction effects were detected for the parameter latency in m. tibialis anterior (TA). For both groups, a significant pre to post-test decrease in ERA in TA (P<.001) was observed coming along with increases in antagonist coactivity (P=.013) and maximal angular velocity of the ankle joint (p=.007). However, no significant group x test interactions were found for the three parameters. Ankle fatigue has an impact on the ability to compensate for gait perturbations in young and elderly adults. However, no significant differences in all analysed parameters were detected between young and elderly subjects. These results may imply that age-related deteriorations in the postural control system do not specifically affect the ability to compensate for gait perturbations under fatigued condition.},
  language  = {en}
}
@misc{KuemmelBergmannPrieskeetal.2018,
  author    = {K{\"u}mmel, Jakob and Bergmann, Julian and Prieske, Olaf and Kramer, Andreas and Granacher, Urs and Gruber, Markus},
  title     = {Effects of conditioning hops on drop jump and sprint performance},
  series = {Postprints der Universit{\"a}t Potsdam : Humanwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Humanwissenschaftliche Reihe},
  number    = {439},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-407236},
  pages     = {8},
  year      = {2018},
  abstract  = {Background: It has previously been shown that conditioning activities consisting of repetitive hops have the potential to induce better drop jump (DJ) performance in recreationally active individuals. In the present pilot study, we investigated whether repetitive conditioning hops can also increase reactive jump and sprint performance in sprint-trained elite athletes competing at an international level. Methods: Jump and sprint performances of 5 athletes were randomly assessed under 2 conditions. The control condition (CON) comprised 8 DJs and 4 trials of 30-m sprints. The intervention condition (HOP) consisted of 10 maximal repetitive two-legged hops that were conducted 10 s prior to each single DJ and sprint trial. DJ performance was analyzed using a one-dimensional ground reaction force plate. Step length (SL), contact time (CT), and sprint time (ST) during the 30-m sprints were recorded using an opto-electronic measurement system. Results: Following the conditioning activity, DJ height and external DJ peak power were both significantly increased by 11 \% compared to the control condition. All other variables did not show any significant differences between HOP and CON. Conclusions: In the present pilot study, we were able to demonstrate large improvements in DJ performance even in sprint-trained elite athletes following a conditioning activity consisting of maximal two-legged repetitive hops. This strengthens the hypothesis that plyometric conditioning exercises can induce performance enhancements in elite athletes that are even greater than those observed in recreationally active athletes.. In addition, it appears that the transfer of these effects to other stretch-shortening cycle activities is limited, as we did not observe any changes in sprint performance following the plyometric conditioning activity.},
  language  = {en}
}
@article{KuemmelBergmannPrieskeetal.2016,
  author    = {Kuemmel, Jakob and Bergmann, Julian and Prieske, Olaf and Kramer, Andreas and Granacher, Urs and Gruber, Markus},
  title     = {Effects of conditioning hops on drop jump and sprint performance: a randomized crossover pilot study in elite athletes},
  series = {BMC sports science, medicine \& rehabilitation},
  volume    = {8},
  journal   = {BMC sports science, medicine \& rehabilitation},
  publisher = {BioMed Central},
  address   = {London},
  issn      = {2052-1847},
  doi       = {10.1186/s13102-016-0027-z},
  pages     = {8},
  year      = {2016},
  abstract  = {Background: It has previously been shown that conditioning activities consisting of repetitive hops have the potential to induce better drop jump (DJ) performance in recreationally active individuals. In the present pilot study, we investigated whether repetitive conditioning hops can also increase reactive jump and sprint performance in sprint-trained elite athletes competing at an international level. Methods: Jump and sprint performances of 5 athletes were randomly assessed under 2 conditions. The control condition (CON) comprised 8 DJs and 4 trials of 30-m sprints. The intervention condition (HOP) consisted of 10 maximal repetitive two-legged hops that were conducted 10 s prior to each single DJ and sprint trial. DJ performance was analyzed using a one-dimensional ground reaction force plate. Step length (SL), contact time (CT), and sprint time (ST) during the 30-m sprints were recorded using an opto-electronic measurement system. Results: Following the conditioning activity, DJ height and external DJ peak power were both significantly increased by 11 \% compared to the control condition. All other variables did not show any significant differences between HOP and CON. Conclusions: In the present pilot study, we were able to demonstrate large improvements in DJ performance even in sprint-trained elite athletes following a conditioning activity consisting of maximal two-legged repetitive hops. This strengthens the hypothesis that plyometric conditioning exercises can induce performance enhancements in elite athletes that are even greater than those observed in recreationally active athletes.. In addition, it appears that the transfer of these effects to other stretch-shortening cycle activities is limited, as we did not observe any changes in sprint performance following the plyometric conditioning activity.},
  language  = {en}
}
@article{FimlandHelgerudGruberetal.2010,
  author    = {Fimland, Marius S. and Helgerud, Jan and Gruber, Markus and Leivseth, Gunnar and Hoff, Jan},
  title     = {Enhanced neural drive after maximal strength training in multiple sclerosis patients},
  issn      = {1439-6319},
  doi       = {10.1007/s00421-010-1519-2},
  year      = {2010},
  abstract  = {Multiple sclerosis (MS) patients suffer from impaired muscle activation and lower limb strength. Strength training enhances muscle activation and muscle strength, but neural adaptations to strength training remain unexplored in MS patients. The hypothesis was that maximal strength training (MST) using high loads and few repetitions would improve central neural drive and thus strength capacity of MS patients. 14 MS patients staying at a national MS rehabilitation center were randomly assigned to a MST group or a control group (CG). Both groups received "today's treatment". In addition, the MST group trained 4 x 4 repetitions of unilateral dynamic leg press and plantar flexion 5 days a week for 3 weeks. Neural adaptations of the soleus muscle were assessed by surface electromyography (EMG) activity, and by superimposed H-reflexes and V-waves obtained during maximum voluntary isometric plantar flexor contractions (MVCs). H-reflexes and V-waves were normalized by the M-wave (H (SUP)/M (SUP), V/M (SUP), respectively). In the MST group, MVC increased by 20 +/- A 9\% (P < 0.05). Soleus EMG activity and V/M (SUP) ratio increased by 40 and 55\%, respectively, in the MST group compared to the CG (P a parts per thousand currency sign 0.05). The H (SUP)/M (SUP) ratio remained unchanged. No change was apparent in the CG. MST group subjects were able to complete all training sessions. No adverse effects were reported. This randomized study provides evidence that MST is effective of augmenting the magnitude of efferent motor output of spinal motor neurons in MS patients, alleviating some neuromuscular symptoms linked to the disease.},
  language  = {en}
}
@article{GruberLinnamoStrojniketal.2009,
  author    = {Gruber, Markus and Linnamo, Vesa and Strojnik, Vojko and Rantalainen, Tuomas and Avela, Janne},
  title     = {Excitability at the motoneuron pool and motor cortex is specifically modulated in lengthening compared to isometric contractions},
  issn      = {0022-3077},
  doi       = {10.1152/jn.91104.2008},
  year      = {2009},
  abstract  = {Neural control of muscle contraction seems to be unique during muscle lengthening. The present study aimed to determine the specific sites of modulatory control for lengthening compared with isometric contractions. We used stimulation of the motor cortex and corticospinal tract to observe changes at the spinal and cortical levels. Motor- evoked potentials (MEPs) and cervicomedullary MEPs (CMEPs) were evoked in biceps brachii and brachioradialis during maximal and submaximal lengthening and isometric contractions at the same elbow angle. Sizes of CMEPs and MEPs were lower in lengthening contractions for both muscles ( by similar to 28 and similar to 16\%, respectively; P < 0.01), but MEP-to-CMEP ratios increased (by similar to 21\%; P < 0.05). These results indicate reduced excitability at the spinal level but enhanced motor cortical excitability for lengthening compared with isometric muscle contractions.},
  language  = {en}
}
@article{FimlandHelgerudGruberetal.2009,
  author    = {Fimland, Marius S. and Helgerud, Jan and Gruber, Markus and Leivseth, Gunnar and Hoff, Jan},
  title     = {Functional maximal strength training induces neural transfer to single-joint tasks},
  issn      = {1439-6319},
  doi       = {10.1007/s00421-009-1096-4},
  year      = {2009},
  abstract  = {The purpose of this study was to investigate whether neural adaptations following functional multiple-joint leg press training can induce neural adaptations to the plantar flexor muscles in a single-joint contraction task. Subjects were randomised to a maximal strength training (MST) (n = 10) or a control group (n = 9). MST consisted of 24 sessions (8 weeks) of 4 x 4 repetitions of horizontal leg press using maximal intended velocity in the concentric phase with the movement ending in a plantar flexion. Neural adaptations in the soleus and gastrocnemius medialis (GM) were assessed by surface electromyographic activity and V-waves during maximum voluntary isometric contraction (MVIC), and also by H- reflexes in the soleus during rest and 20\% MVIC. One repetition maximum leg press increased by 44 +/- A 14\% (mean +/- A SD; P < 0.01). Plantar flexion MVIC increased by 20 +/- A 14\% (P < 0.01), accompanied by 13 +/- A 19\% (P < 0.05) increase in soleus, but not GM surface electromyography. Soleus V/M-SUP increased by 53 +/- A 66\% and in GM by 59 +/- A 64\% (P < 0.05). Normalised soleus H-reflexes remained unchanged by training. No changes occurred in the control group. These results suggest that leg press MST can induce neural adaptations in a single-joint plantar flexion MVIC task.},
  language  = {en}
}
@article{HortobagyiGranacherFernandezdelOlmoetal.2020,
  author    = {Hortobagyi, Tibor and Granacher, Urs and Fernandez-del-Olmo, Miguel and Howatson, Glyn and Manca, Andrea and Deriu, Franca and Taube, Wolfgang and Gruber, Markus and Marquez, Gonzalo and Lundbye-Jensen, Jesper and Colomer-Poveda, David},
  title     = {Functional relevance of resistance training-induced neuroplasticity in health and disease},
  series = {Neuroscience \& biobehavioral reviews : official journal of the International Behavioral Neuroscience Society},
  volume    = {122},
  journal   = {Neuroscience \& biobehavioral reviews : official journal of the International Behavioral Neuroscience Society},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0149-7634},
  doi       = {10.1016/j.neubiorev.2020.12.019},
  pages     = {79 -- 91},
  year      = {2020},
  abstract  = {Repetitive, monotonic, and effortful voluntary muscle contractions performed for just a few weeks, i.e., resistance training, can substantially increase maximal voluntary force in the practiced task and can also increase gross motor performance. The increase in motor performance is often accompanied by neuroplastic adaptations in the central nervous system. While historical data assigned functional relevance to such adaptations induced by resistance training, this claim has not yet been systematically and critically examined in the context of motor performance across the lifespan in health and disease. A review of muscle activation, brain and peripheral nerve stimulation, and imaging data revealed that increases in motor performance and neuroplasticity tend to be uncoupled, making a mechanistic link between neuroplasticity and motor performance inconclusive. We recommend new approaches, including causal mediation analytical and hypothesis-driven models to substantiate the functional relevance of resistance training-induced neuroplasticity in the improvements of gross motor function across the lifespan in health and disease.},
  language  = {en}
}
@article{GranacherGruberGollhofer2009,
  author    = {Granacher, Urs and Gruber, Markus and Gollhofer, Albert},
  title     = {Resistance training and neuromuscular performance in seniors},
  issn      = {0172-4622},
  doi       = {10.1055/s-0029-1224178},
  year      = {2009},
  abstract  = {Age-related processes in the neuromuscular and the somatosensory system are responsible for decreases in maximal and explosive force production capacity and deficits in postural control. Thus, the objectives of this study were to investigate the effects of resistance training on strength performance and on postural control in seniors. Forty healthy seniors (67 +/- 1 yrs) participated in this study. Subjects were randomly assigned to a resistance training (n = 20) and a control group (n = 20). Resistance training for the lower extremities lasted for 13 weeks at 80\% of the one repetition maximum. Pre and post tests included the measurement of maximal isometric leg extension force with special emphasis on the early part of the force-time-curve and the assessment of static (functional reach test) and dynamic (tandem walk test, platform perturbation) postural control. Resistance training resulted I in an enhanced strength performance with increases I in explosive force exceeding those in maximal strength. Improved performances in the functional reach and in the tandem walk test were observed. Resistance training did not have an effect: on the compensation of platform perturbations. Increases in strength performance can primarily be explained by an improved neural drive of the agonist muscles. The inconsistent effect of resistance training on postural control may be explained by heterogeneity of testing methodology or by the incapability of isolated resisiance training to improve postural control.},
  language  = {en}
}
@article{LeukelLundbyeJensenGruberetal.2009,
  author    = {Leukel, Christian and Lundbye-Jensen, Jesper and Gruber, Markus and Zuur, Abraham T. and Gollhofer, Albert and Taube, Wolfgang},
  title     = {Short-term pressure induced suppression of the short-latency response : a new methodology for investigating stretch reflexes},
  issn      = {8750-7587},
  doi       = {10.1152/japplphysiol.00301.2009},
  year      = {2009},
  abstract  = {During experiments involving ischemic nerve block, we noticed that the short-latency response (SLR) of evoked stretches in m. soleus decreased immediately following inflation of a pneumatic cuff surrounding the lower leg. The present study aimed to investigate this short-term effect of pressure application in more detail. Fifty-eight healthy subjects were divided into seven protocols. Unilateral stretches were applied to the calf muscles to elicit a SLR, and bilateral stretches to evoke a subsequent medium-latency response (MLR). Furthermore, H-reflexes and sensory nerve action potentials (SNAPs) were recorded. Additionally, stretches were applied with different velocities and amplitudes. Finally, the SLR was investigated during hopping and in two protocols that modified the ability of the muscle-tendon complex distal to the cuff to stretch. All measurements were performed with deflated and inflated cuff. Results of the protocols were as follows: 1) inflation of the cuff reduced the SLR but not the MLR; 2) the H-reflex, the M-wave, and, 3) SNAPs of n. tibialis remained unchanged with deflated and inflated cuff; 4) the SLR was dependent on the stretch velocity with deflated and also inflated cuff; 5 and 6) the reduction of the SLR by the cuff was dependent on the elastic properties of the muscle-tendon complex distal to the cuff; and 7) the cuff reduced the SLR during hopping. The present results suggest that the cuff did not affect the reflex arc per se. It is proposed that inflation restricted stretch of the muscles underlying the cuff so that most of the length change occurred in the muscle-tendon complex distal to the cuff. As a consequence, the muscle spindles lying within the muscle may be less excited, resulting in a reduced SLR. Due to its applicability in functional tasks, the introduced method can be a useful tool to study afferent feedback in motor control.},
  language  = {en}
}