Klaus Völker

Physical activity and memory functions: An interventional study

Previous studies have suggested beneficial effects of physical activity on cognition. Here, we asked in an interventional approach if physical activity performed at different intensity levels would differentially affect episodic memory function. Additionally, we tried to identify mechanisms mediating these changes. Sixty-two healthy elderly individuals were assessed for level of physical activity, aerobic fitness, episodic memory score, neurotrophin and catecholamine levels, and received a magnetic resonance image of the brain at baseline and after a six months intervention of medium or low-intensity physical activity or control. Increase in total physical activity was positively associated with increase in memory score over the entire cohort, without significant differences between intensity groups. It was also positively associated with increases in local gray matter volume in prefrontal and cingulate cortex, and BDNF levels (trend). In conclusion, we showed that physical activity conveys the beneficial effects on memory function independently of its intensity, possibly mediated by local gray matter volume and neurotrophic factors. Our findings may carry significant implications for prevention of cognitive decline in the elderly.

Physical activity and memory functions: are neurotrophins and cerebral gray matter volume the missing link?

Epidemiological studies reveal better cognitive function in physically active individuals. Possible mediators for this effect are neurotrophins, which are up-regulated through physical exercise and induce neuronal growth and synaptogenesis in the animal model. Here we cross-sectionally assessed 75 healthy older individuals for levels of physical activity, aerobic fitness, and memory encoding, as well as neurotrophin levels and cerebral gray matter volume. We found that physical activity, but not cardiovascular fitness, was associated with better memory encoding after controlling for age, sex, education, depression, alcohol consumption, and smoking. Higher levels of physical activity were associated with higher levels of the neurotrophin granulocyte colony stimulating factor (G-CSF) and increased cerebral gray matter volume in prefrontal and cingulate cortex as assessed by magnetic resonance voxel-based morphometry. While mediating factors will need to be further elucidated, these findings indicate that even low-level physical activity exerts beneficial effects on memory functions in older individuals.

Reduced plantar sensation causes a cautious walking pattern.

The aim of this study was to investigate the influence of reduced plantar sensation on gait patterns during walking in 20 healthy subjects (25.9 +/- years, 61.6 +/- 11.5 kg, 178 +/- 9.5 cm) with no history of sensory disorders. Force plate measurements, electromyography (EMG) measurements and a three-dimensional movement analysis were performed simultaneously during barefoot walking before and after reduction of plantar sensation using an ice immersion technique. The results show that reduced plantar sensation leads to significant changes in gait patterns that are present at the ankle, knee and hip joint and indicate a more cautious ground contact and push-off with modified EMG and motion patterns.

Modified pressure distribution patterns in walking following reduction of plantar sensation

The aim of the present study was to investigate the influence of reduced plantar sensation on pressure distribution patterns during gait of 40 healthy subjects (25.3+/-3.3 yr, 70.8+/-10.6 kg and 176.5+/-7.8 cm) with no history of sensory disorders. Plantar sensation in the subjects was reduced by using an ice immersion approach, and reduced sensitivity was tested with Semmes-Weinstein monofilaments. All subjects performed six trials of barefoot walking over a pressure distribution platform under normal as well as iced conditions. Plantar cutaneous sensation was significantly reduced after the cooling procedure (p<0.0001). Pressure distribution analysis showed substantially modified plantar pressure distribution patterns during the roll-over process (ROP) under iced conditions. Analysis of peak pressures revealed significant reductions under the toes and under the heel (p<0.001). The contact time and the relative impulse for the whole foot did not change significantly between the two conditions. For the different areas, a significant load shift from the heel and toes towards the central and lateral forefoot and the lateral midfoot was observed. The results indicate the strong influence of reduced afferent information of the sole of the foot on the ROP in walking.

Characteristic Plantar Pressure Distribution Patterns During Soccer-Specific Movements

Purpose To characterize in-shoe pressure measurements during different soccer-specific maneuvers on two playing surfaces to identify the main loading areas of the foot. Methods Twenty-one experienced male soccer players participated in the study (25.5 ± 1.8 years, 78.7 ± 5.4 kg, and 182.9 ± 5.7 cm). The Pedar Mobile system was used to collect plantar pressure information inside the soccer shoe. Four soccer-specific movements were performed (normal run, cutting maneuver, sprint, and goal shot) on both a grass and a red cinder surface. Results Results showed characteristic pressure distribution patterns with specific loading areas of the foot that correspond to the evaluated movements. In addition, loading patterns with higher pressure values than those observed during normal run were found. In cutting, the medial part of the foot; in sprinting, the first and second ray; and in kicking, the lateral part of the foot are predominantly loaded. No global effect of the two surfaces on pressure parameters was found. Conclusion The results of the present investigation suggest that the high load in soccer in combination with a high repetition may have an important influence in the development of overuse injuries.

Oral magnesium supplementation reduces insulin resistance in non‐diabetic subjects – a double‐blind, placebo‐controlled, randomized trial

The incidence of insulin resistance and metabolic syndrome correlates with the availability of magnesium (Mg). We studied the effect of oral Mg supplementation on insulin sensitivity and other characteristics of the metabolic syndrome in normomagnesemic, overweight, insulin resistant, non‐diabetic subjects. Subjects were tested for eligibility using oral glucose tolerance test (OGTT) and subsequently randomized to receive either Mg–aspartate–hydrochloride (n = 27) or placebo (n = 25) for 6 months. As trial endpoints, several indices of insulin sensitivity, plasma glucose, serum insulin, blood pressure and lipid profile were determined. Mg supplementation resulted in a significant improvement of fasting plasma glucose and some insulin sensitivity indices (ISIs) compared to placebo. Blood pressure and lipid profile did not show significant changes. The results provide significant evidence that oral Mg supplementation improves insulin sensitivity even in normomagnesemic, overweight, non‐diabetic subjects emphasizing the need for an early optimization of Mg status to prevent insulin resistance and subsequently type 2 diabetes.

The effect of attentional focus on running economy

Abstract In research on motor control, the detrimental effect of an internal focus of attention on movement execution of well-learned motor skills is a frequently replicated finding. This experimental study was designed to determine whether this effect is observed with physiological variables during endurance exercise. We examined whether the focus of attention can influence running economy (oxygen consumption at a set running speed). Trained runners had to focus their attention on three different aspects while running on a treadmill. For three consecutive 10-min periods, runners concentrated on the running movement, on their breathing, and on their surroundings. Results showed an increased running economy in the external focus condition. In line with research on motor control, endurance sport also shows that an external focus of attention is better than an internal focus in terms of the physiological performance measure of oxygen consumption.

Comprehensive testing of 10 different ankle braces Evaluation of passive and rapidly induced stability in subjects with chronic ankle instability

OBJECTIVE The aim of the present investigation was to test the stability of 10 different ankle braces under passive and rapidly induced loading conditions in a population suffering from chronic ankle instability in order to provide objective information to choose or recommend an appropriate model for specific needs. In addition, the relationship between passive and rapidly induced testing of the stabilizing effect against inversion was evaluated to identify if passive support characteristics of braces are reflected under rapidly induced conditions. DESIGN An experimental in vivo study with a repeated-measures design was used. BACKGROUND Ankle braces are commonly used for treatment, rehabilitation, and prevention of ankle injuries. A variety of products exists but there is few information available to assist clinicians, physiotherapists and coaches as well as consumers in choosing a brace on a basis of objective information. Furthermore, there is a lack of studies that provide data for both passively and rapidly induced movement of the ankle joint when using different ankle braces. METHODS Twenty-four subjects with chronic ankle instability participated in the project. Passive ankle range of motion measurements were performed in a custom-built fixture and simulated inversion sprains were elicited on a tilting platform. RESULTS The tested braces restrict range of motion significantly compared to the no-brace condition for both the passively and rapidly induced inversion and marked differences between braces were revealed. A close relationship between passive and rapidly induced test results for inversion was found. CONCLUSIONS Passive as well as rapidly induced stability tests provide a basis of objective information to describe the characteristics of different ankle braces. Combined results of passive and rapidly induced inversion as well as correlation between results demonstrate that passive support characteristics of braces are reflected under rapidly induced conditions but the amount of restriction is reduced. Therefore, caution should be taken when recommending braces for applications under dynamic circumstances only on the basis of passive support characteristics. RELEVANCE A basis of information regarding the stability characteristics of different ankle braces under passive and rapidly induced conditions will help the clinician and consumer in choosing the most appropriate brace model for specific use. The results also provide more insights into factors that influence stability characteristics of ankle braces.

Exercise affects tissue lymphocyte apoptosis via redox-sensitive and Fas-dependent signaling pathways

Intensive and exhaustive exercise induces an activation of blood T-lymphocytes, which seems to be terminated by apoptotic processes in the postexercise period. Here, we report that exercise-induced T-lymphocyte apoptosis is a systemic phenomenon occurring in various lymphoid and nonlymphoid tissues. The apoptosis rate could be related to exercise intensity and type. Although in some tissues, such as the spleen and Peyers patches, an early start of apoptosis (1-3 h postexercise) could be detected, a delayed apoptosis (24 h postexercise) was observed in lung, bone marrow, and lymph nodes. Further analysis showed a similar apoptosis distribution among lymphocyte subpopulations. We tested whether components of the extrinsic or the intrinsic apoptotic pathways or both were involved in these processes. Elevated levels of lipid peroxidation-product malondialdehyde (MDA), indicating an increased production of reactive oxygen species (ROS), were found after exercise in Peyers patches, lung, and spleen, but not in lymph nodes. Application of N-acetyl-cysteine (NAC) prevented exercise-induced T-cell apoptosis completely in spleen and bone marrow, partially in lung and Peyers patches, while it was ineffective in lymph nodes. Additionally, exercise addressed the Fas-mediated apoptosis. The percentage of Fas-receptor (Fas+) and Fas-ligand positive (FasL+) lymphocytes was enhanced in Peyers patches after exercise. Moreover, FasL+ T cells were increased in the lung, while in lymph nodes Fas+ cells were increased. The critical role of Fas signaling in exercise-induced apoptosis was supported by using Fas-deficient MRL/lpr-mice. In Fas-deficient mice, exercise-induced T-lymphocyte apoptosis was prevented in spleen, lung, bone marrow, and lymph nodes, but not in Peyers patches. These data demonstrate that exercise-induced lymphocyte apoptosis is a transient systemic process with tissue-type specific apoptosis-inducing mechanisms, whose relevance for the adaptive immune competence remains to be shown.

Participation in sports and physical activity of haemophilia patients

Summary.  Modern therapy options offer haemophiliacs more and more possibilities for an active participation in sports. The purpose of the present study was to investigate the attitude of these patients towards sports, their participation in school and leisure time sports activities, and differences between juveniles and adults. We investigated 44 children and adolescents (aged from 4 to 16 years) and 27 adults (aged from 18 to 72 years) with haemophilia by means of a questionnaire. 79.6% of the juvenile patients participated always or almost always in school sports, while this percentage was significantly (P < 0.05) lower in the former school time of the adults (37%). Sports play an important or very important role in leisure time activities for 75% of the adolescent and 55.5% of the adult haemophiliacs (P < 0.05). Bleeding complications occurred in 17.6% of all patients; there was no correlation with any particular type of sports. There were only slight differences between both groups, regarding their motivation to participate in sports activities. The main reasons involved social aspects and having fun. The results show that the modern therapy of haemophilia probably leads to a more positive attitude towards sports and to a wider spectrum of practised sports. This, however, may be associated with an increasing potential of health risks, which require a high level of sports medical care.