Markus Gruber

Universität Konstanz | Uni-Konstanz · Department of Sports Science

The removal of skeletal muscle tension (unloading or disuse) is followed by many changes in the neuromuscular system, including muscle atrophy and loss of isometric maximal strength (measured by maximal force, Fmax). Explosive strength, i.e. the ability to develop the highest force in the shortest possible time, to maximise rate of force developmen...

A bstract Humans use multiple sensory systems to estimate body orientation in space. A predominant concept for the underlying multisensory integration (MSI) is the linear summation of weighted inputs from individual sensory systems. The sensory contributions change depending on context and environmental conditions. These changes are typically attri...

Recently, AI‐driven skeleton reconstruction tools that use multistage computer vision pipelines were designed to estimate 3D kinematics from 2D video sequences. In the present study, we validated a novel markerless, smartphone video‐based artificial intelligence (AI) motion capture system for hip, knee, and ankle angles during countermovement jumps...

Background Despite the global increase in older employees, workplace physical activity interventions (WPAIs) for this target group have not yet been sufficiently developed. The major drawback of existing WPAIs is low adherence due to lack of time or limited motivation. A novel approach could be to integrate tailored neuromotor and strength exercise...

This study aimed to pilot-test a markerless motion analysis approach (i.e., SMARTGAIT) for estimating knee and hip joint kinematics in the sagittal and frontal plane during overground walking. One person (age 24 years) walked four times over an 8-meter distance. Joint kinematics were measured using SMARTGAIT (single RGB smartphone camera) and Vicon...

Introduction: Clinical gait analysis plays a central role in the rehabilitation of stroke patients. However, practical and technical challenges limit their use in clinical settings. This study aimed to validate SMARTGAIT, a deep learning-based gait analysis system that addresses these limitations. Methods: Eight stroke patients took part in the stu...

Golf is a sport that consists of complex movement skills that need to be executed with utmost precision. Consequently, motor skill learning plays a crucial role in golf, and large numbers of studies address various methods of motor learning. In the present review, we give a systematic overview of randomized controlled trials (RCTs) on motor learnin...

Background Despite the increasing number of research studies examining the effects of age on the control of posture, the number of annual fall-related injuries and deaths continues to increase. A better understanding of how old age affects the neural mechanisms of postural control and how countermeasures such as balance training could improve the n...

Background: The global increase in older employees requires target-group-specific approaches for health promotion. Traditional occupational health interventions (OHI) are rarely taken up due to a lack of time or motivation. LiFE (Lifestyle-integrated Functional Exercise) integrates neuromotor and strength exercises into everyday life. This study ai...

Handball players are at a high risk of suffering a sport-related injury. Recent studies in various adult populations (e.g., US Army soldiers/warrior athletes, and military members) showed that poor scores in the upper quarter Y-balance test (YBT-UQ) are related to an increased risk of injury. Yet, it is unclear whether this also applies to adolesce...

Das sensomotorische System bildet die physiologische Grundlage der Haltungs- und Bewegungskontrolle. In dem vorliegenden Kapitel wird der Aufbau des sensomotorischen Systems erläutert, indem die einzelnen Bestandteile voneinander abgegrenzt und definiert werden. Anschließend wird deren Funktionalität zunächst allgemein dargestellt und anschließend...

Das Motoneuron und die von ihm innervierten Muskelfasern bilden die kleinste funktionelle Einheit des neuromuskulären Systems. In dem vorliegenden Kapitel werden die physiologischen und funktionellen Eigenschaften motorischer Einheiten beschrieben und vertiefend diskutiert. Insbesondere wird auf die Plastizität der motorischen Einheit und deren Bes...

Spaceflight and its associated stressors, such as microgravity, radiation exposure, confinement, circadian derailment and disruptive workloads represent an unprecedented type of exposome that is entirely novel from an evolutionary stand point. Within this perspective, we aimed to review the effects of prolonged spaceflight on immune-neuroendocrine...

Handball is an Olympic contact sport with high physical, tactical, and technical demands by the players. Out of the different techniques, throwing is the most important one to be able to score. The objective of the study was to investigate the relationships between core muscle strength endurance (Bourban test: ventral, dorsal and lateral chain) and...

This study evaluated the reliability and sensitivity of a set of different common strength and power tests in a healthy adult population in a span of 9 weeks. Seventeen subjects (24.2 ± 2.2 years, 1.75 ± 0.10 m, 68.6 ± 14.2 kg, seven women) participated in the study. We tested countermovement jumps, reactive hops, and the maximal voluntary contract...

The purpose of the present study was to assess the validity and reliability of the jump height measured by the Polar Vantage V2 sports watch in comparison to a gold-standard force plate measurement. Fifteen healthy adults, seven female, age 20–42 years participated in the study and performed six sets of three CMJs, on two consecutive days. The part...

This paper presents the NEX4EX project Novel Exercise Hardware for Exploration, which aims to design, build and validate a full-body countermeasure platform that enables high intensive resistive and plyometric exercise as well as postural control training, and strength training. The NEX4EX exerciser herewith addresses neuromuscular and musculoskele...

Background High prevalence rates have been reported for physical inactivity, mobility limitations, and falls in older adults. Home-based exercise might be an adequate means to increase physical activity by improving health- (i.e., muscle strength) and skill-related components of physical fitness (i.e., balance), particularly in times of restricted...

The impact of endurance training on spinal neural circuitries remains largely unknown. Some studies have reported higher H-reflexes in endurance trained athletes and therefore, adaptations within the Ia afferent pathways after long term endurance training have been suggested. In the present study we tested the hypothesis that cyclists (n = 12) demo...

Purpose Spaceflight impairs physical capacity. Here we assessed the protective effect of artificial gravity (AG) on aerobic exercise capacity and muscle function during bed rest, a spaceflight analogue. Methods 24 participants (33 ± 9 years, 175 ± 9 cm, 74 ± 10 kg, 8 women) were randomly allocated to one of three groups: continuous AG (cAG), inter...

Noisy galvanic vestibular stimulation (nGVS) at imperceptible levels has been shown to reduce body sway. This reduction was commonly attributed to the mechanism of stochastic resonance (SR). However, it has never been explicitly tested whether nGVS-induced effects on body sway consistently follow a SR-like bell-shaped performance curve with maximal...

Background: High prevalence rates have been reported for physical inactivity, mobility limitations, and falls in older adults. Home-based exercise might be an adequate means to increase physical activity by improving health- (i.e., muscle strength) and skill-related components of physical fitness (i.e., balance), particularly in times of restricte...

Das sensomotorische System bildet die physiologische Grundlage der Haltungs- und Bewegungskontrolle. In dem vorliegenden Kapitel wird der Aufbau des sensomotorischen Systems erläutert, indem die einzelnen Bestandteile voneinander abgegrenzt und definiert werden. Anschließend wird deren Funktionalität zunächst allgemein dargestellt und anschließend...

Noisy galvanic vestibular stimulation (nGVS) at imperceptible levels has been shown to reduce body sway. This improvement was commonly attributed to the mechanism of stochastic resonance (SR). However, it has never been explicitly tested whether nGVS-induced effects on body sway consistently follow a SR-like bell-shaped performance curve with optim...

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 nervou...

Notwithstanding the apparent demands regarding fine motor skills that are required to perform in action video games, the motor nervous system of players has not been studied systematically. In the present study, we hypothesized to find differences in sensorimotor performance and corticospinal characteristics between action video game players (Playe...

Background: The deconditioning of astronauts in space during long-term missions due to the absence of gravitational forces is a well-known problem and constitutes an obstacle for longer missions, such as a mission to Mars. If the absence of gravitational forces is the cause of the decline in physical performance, one potential countermeasure is art...

Purpose Long stays in space require countermeasures for the degrading effects of weightlessness on the human body, and artificial gravity (AG) has been proposed as an integrated countermeasure. The aim of this study was to assess the cardiorespiratory and neuromuscular demand of AG elicited via daily centrifugation during 60 days of bed rest. Meth...

Microgravity during long-term space flights induces degeneration of articular cartilage. Artificial gravity through centrifugation combined with exercise has been suggested as a potential countermeasure for musculoskeletal degeneration. The purpose of this study was to investigate the effect of different types of impact loading under normal and art...

Humans are accustomed to Earth’s constant gravitational acceleration of 1g. Here we assessed if complex movements such as jumps can be adapted to different acceleration levels in a non-constant force field elicited through centrifugation. Kinematics, kinetics and muscle activity of 14 male subjects (age 27±5years, body mass 77±6kg, height 181±7cm)...

Key points The spinal cord is an important contributor to motor learning It remains unclear whether short‐term spinal cord adaptations are general or task‐specific Immediately after task acquisition, neural adaptations were not specific to the trained task (i.e. were general) Twenty‐four hours after acquisition, neural adaptations appeared to be ta...

Studies investigating balance control often use external perturbations to probe the system. These perturbations can be administered as randomized, pseudo-randomized, or predictable sequences. As predictability of a given perturbation can affect balance performance, the way those perturbations are constructed may affect the results of the experiment...

Previous research demonstrated that six sessions of cycling sprint-interval training (SIT) within a duration of only 2 weeks can increase endurance performance considerably. Primarily muscular mechanisms have been under investigation explaining such performance improvements. However, it has been shown in other exercise tasks that training-induced c...

It has been proposed that one reason physical effort is perceived as costly is because of the self-control demands that are necessary to persist in a physically demanding task. The application of control has been conceptualized as a value-based decision, that hinges on an optimization of the costs of control and available reward. Here, we drew on l...

Background: Training programs for fall prevention often fail to induce large general effects. To improve the efficacy of fall prevention programs, it is crucial to determine which type of training is most effective in inducing generalizable effects, i.e., improvements in untrained situations. Two likely candidates are balance and resistance traini...

It has been proposed that one reason physical effort is perceived as costly is because of the self-control demands that are necessary to persist in a physically demanding task. The application of control has been conceptualized as a value-based decision, that hinges on an optimization of the costs of control and available reward. Here, we drew on l...

Mixed Martial Arts (MMA) is a full-contact sport whose popularity and professionalism is rapidly growing. However, the specific physiological demands of this sport have been only scarcely studied so far, and especially the amount or type of neuromuscular fatigue induced by an MMA bout remains completely unknown. We estimated neuromuscular fatigue o...

Humans develop posture and balance control during childhood. Interestingly, adults can also learn to master new complex balance tasks, but the underlying neural mechanisms are not fully understood yet. Here, we combined broad scale brain connectivity fMRI at rest and spinal excitability measurements during movement. Six weeks of slackline training...

Several studies indicate that acute exercise induces DNA damage, whereas regular exercise increases DNA repair kinetics. Although the molecular mechanisms are not completely understood, the induction of endogenous reactive oxygen species (ROS) during acute exhaustive exercise due to metabolic processes might be responsible for the observed DNA dama...

Statistical analysis of real in-game situations plays an increasing role in talent identification and player recruitment across team sports. Recently, visual exploration frequency (VEF) in football has been discussed as being one of the important performance-determining parameters. However, until now, VEF has been studied almost exclusively in labo...

Purpose High-intensity interval training (HIT) has been shown to be an effective endurance training method. However, most HIT research has been conducted on running and cycling. The aim of this study was to assess the suitability of intermittent exercises such as jumps as a type of HIT. Methods Respiratory gases, heart rate and ground reaction for...

Pronounced muscle and bone losses indicate that the musculoskeletal system suffers substantially from prolonged microgravity. A likely reason for these detrimental adaptations in the lower extremity is the lack of impact loading and the difficulty to apply large loading forces on the human body in microgravity. The human body is well adapted to amb...

Physical inactivity causes a deconditioning of the human body. Concerns due to chronic bed-rest include deficits in posture and gait control, predisposing individuals to an increased fall and injury risk. This study assessed the efficiency of a high-load jump exercise (JUMP) as a countermeasure to prevent detrimental effects on gait, posture contro...

Slackline training is a challenging and motivating type of balance training, with potential usefulness for fall prevention and balance rehabilitation. However, short-term slackline training seems to elicit mostly task-specific performance improvements, reducing its potential for general fall prevention programs. It was tested whether a longer durat...

Background: It has been shown that balance training induces task-specific performance improvements with very limited transfer to untrained tasks. Thus, regarding fall prevention, one strategy is to practice as many tasks as possible to be prepared for a multitude of situations with increased fall risk. However, it is not clear whether the learning...

Objectives: We wanted to verify if the "learning to learn" effect observed in the learning of visuomotor tasks is also present when learning a balance task, i.e., whether the learning rate of a balance task is improved by prior practice of similar balance tasks. Design: Single centre, parallel group, controlled training study. Methods: 32 youn...

Objective: Inactivity results in a marked loss of muscle function, especially in movements requiring high power, force, and rate of force development. The aim of the present study was to evaluate if jump training can prevent these deteriorating effects of physical inactivity. Methods: Performance and muscle activity during several types of jumps wa...

Purpose Active recovery is often used by athletes after strenuous exercise or competition but its underlying mechanisms are not well understood. We hypothesized that active recovery speeds-up recovery processes within the muscle and the central nervous system (CNS). Methods We assessed muscular and CNS recovery by measuring the voluntary activatio...

Transcranial direct current stimulation (tDCS) has the capacity to enhance force output during a short‐lasting maximal voluntary contraction (MVC) as well as during a long‐lasting submaximal voluntary contraction until task failure. However, its effect on an intermittent maximal effort is not known. We hypothesized that anodal tDCS applied during o...

Aims: Different modalities of strength training cause performance enhancements, which are specific for the trained task. However, the involved mechanisms are still largely unknown. It has been demonstrated that strength training could induce neuroplasticity, which might underlie the performance improvements during the first training sessions. Thus...

Physical inactivity leads to a deconditioning of the skeletal, neuromuscular and cardiovascular system. It can lead to impaired quality of life, loss of autonomy, falls and fractures. Regular exercise would be a logical remedy, but the generally recommended high-volume endurance and strength training programs require a lot of time and equipment. In...

Post-activation potentiation can improve athletic performance, but the underlying mechanisms are poorly understood. This study investigated the effect of conditioning hops on triceps surae muscle force and tendon strain and its contribution to potentiated stretch-shortening cycle (SSC) performance. Thirty-two subjects participated in two experiment...

Purpose Space agencies are looking for effective and efficient countermeasures for the degrading effects of weightlessness on the human body. The aim of this study was to assess the effects of a novel jump exercise countermeasure during bed rest on vitals, body mass, body composition, and jump performance. Methods 23 male participants (29±6 years,...

Stretching can decrease a muscle's maximal force, whereas short but intense muscle contractions can increase it. We hypothesized that when combined, postactivation potentiation induced by reactive jumps would counteract stretch-induced decrements in drop jump (DJ) performance. Moreover, we measured changes in muscle twitch forces and ankle joint st...

Introduction It has been shown that a set of maximal reactive hops can induce post-activation potentiation in the triceps surae muscle and enhance drop jump (DJ) performance (Bergmann et al., 2013). The underlying mechanisms are not yet clear. In the present study we hypothesized that hops could modulate muscle-tendon interaction, facilitating high...

Background: The effects that microgravity induces to the human body are well known. Unfortunately, how to completely counter them is not yet clear. One method among others is very effective to mimic and simulate these effects to study them on Earth – the bed-rest study. To date, the best countermeasure known to preserve the physiological functions...

Background It has become common practice to incorporate balance tasks into the training program for athletes who want to improve performance and prevent injuries, in rehabilitation programs, and in fall prevention programs for the elderly. However, it is still unclear whether incorporating balance tasks into a training program increases performance...

Despite the potential of repetitive transcranial magnetic stimulation (rTMS) to improve performances in patients suffering from motor neuronal afflictions, its effect on motor performance enhancement in healthy subjects during a specific sport task is still unknown. We hypothesized that after an intermittent theta burst (iTBS) treatment, performanc...

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-trai...

Neurologische Erkrankungen bringen häufig gravierende Einschränkungen der körperlichen Leistungsfähigkeit mit sich. Diese vermindern die Lebensqualität der betroffenen Patienten drastisch. Daher ist die Verbesserung der motorischen Leistungsfähigkeit durch Training ein zentrales Ziel rehabilitativer Maßnahmen bei neurologischen Patienten. Erkenntni...

Despite much research on balance training, it is still unclear whether balance training leads to highly task-specific adaptations or rather non-specific adaptations. Hence, in this study we examined whether balance training increased performance only in the balance task that was trained or also in non-trained tasks. Forty healthy participants (28m...