Jörn Rittweger’s research while affiliated with University Hospital Cologne and other places

Muscle strength and hypertrophy are of high importance for almost every sport, but also for more general prevention and therapeutical approaches. While the most common way to enhance functional and structural muscle capacities is resistance training (RT), there are scenarios in which a RT routine may not be feasible or even contraindicated. Recently published works showed the potential of high-volume static stretching programs to promote muscle strength and hypertrophy, albeit with comparatively long stretching durations per bout in comparison with RT. Therefore, there is limited practical applicability of this training approach for healthy participants with access to dynamic training facilities and supervised training. However, there are potential settings in which stretch-mediated hypertrophy could be useful and should be investigated. This current opinion paper explores such potential settings, including, immobilization-induced atrophy, type 2 diabetes patients, and as a supplement to common resistance training routines to increase the accumulated volume of mechanical overload of the muscle in healthy or athletic populations. Static stretching might also be used to counteract atrophy in spaceflight because other forms of training that may induce sufficient levels of mechanical strain seem infeasible or impractical. Consequently, we explore the potential applications of static stretching routines while considering the feasibility and opportunity for their practical implementation. Consequently, this current opinion paper provides a demand for further investigations of static stretch-mediated adaptations as a potential passive alternative with a focus on therapy and prevention.

Age‐related deterioration in muscle volume, intramuscular fat content and muscle function can be modulated by physical activity. We explored whether Masters athletes, as examples of highly physically active people into old age, could prevent these age‐related muscle deteriorations. Four groups of 43 men were examined: young athletes (20–35 years, n = 10), Masters athletes (60–75 years, n = 10) and two age‐matched control groups (old: n = 11, young: n = 12). Volumes and fat fractions of 17 different hip and leg muscles were determined using magnetic resonance imaging. In the soleus muscle extra‐ and intramyocellular lipids were measured using 1H‐MR‐spectroscopy. Finally volumes of glutei, quadriceps and triceps surae muscles were cumulated and compared to peak jumping power. In both age groups the sum of glutei, quadriceps and triceps surae muscles showed larger volumes in athletes (young: 5758 ± 1139 ml, old: 5285 ± 895 ml) compared to the corresponding control groups (young: 4781 ± 833 ml, old: 4379 ± 612 ml) (p < 0.001). Fat fraction varied between 1.5% and 12.5% ¹H‐signal across muscles and groups and was greater in Masters athletes than in young athletes (p < 0.001), but lower than that in old controls (p < 0.001) and comparable with young controls. Age and exercise‐related effects on muscle fat predominantly originated from the extramyocellular lipids. Finally muscle peak power per volume was effectively halved in the combined older groups compared to the younger groups. Our findings suggest that sarcosthenia, that is, intrinsic muscle weakness, is an effective cause of age‐related power declines in addition to sarcopenia and fat accumulation. image Key points Muscle volume and muscle fat fraction from 17 hip and leg muscles of Masters athletes were compared with old controls, young athletes and young controls. Muscle volume and fat fraction were determined using magnetic resonance imaging (MRI) using a six‐point‐DIXON sequence. Muscle volume in Masters athletes was larger than that in old controls but partially smaller than that in young athletes. Muscle fat fraction of Masters athletes was lower than that in old controls but higher than that in young athletes. Muscles of old athletes and old controls produce only 50% of jumping peak power per muscle volume compared with younger subjects. The intrinsic reduction of power loss in old muscle could not be explained by the higher fat fraction in old muscle.

Prolong exposure to weightlessness leads to loss of muscle and bone mass. Therefore, astronauts on board the International Space Station (ISS) currently perform mandatory daily exercises. ISS missions usually last 6 months, and future missions will become significantly longer when going, for example, to Mars. To that purpose, an exoskeleton‐based exercise device, called ATHLETIC, was developed. The functionality and relevance of this device was evaluated in this study. Ten participants performed resistance exercises (squats) and plyometric exercises (countermovement jumps, reactive hops). Results showed that all participants were technically able to perform the intended exercises on ATHLETIC, albeit with reduced loading as compared to the reference exercises. This resulted in less mechanical performance and muscle activity. Due to the unfamiliar horizontal training axis, some participants had difficulty performing the movements correctly. Follow‐up studies are required testing, whether an adequate number of practicing sessions could enable persons to approach the performances of reference measurements, and whether further improvements of the device are needed to improve the exercise performance.

Objectives Assessing physical activity and cardiometabolic risk in masters athletes as an example of very high physical activity at old age. Methods Forty-three men were studied in full factorial design, either as sprint or jump-trained masters athletes (MA, n=10, age 60–75 years), as young sprint or jump-trained athletes (YA, n=10, age 20–35 years), older control participants (OC, n=11, age 60–75 years) or as young control participants (AC, n=12, age 20–35 years). We performed bio-electrical impedance analysis and assessed serum markers of lipids and glucose metabolism and C-reactive protein, structured training hours, and habitual activity via mobile actimetry. Results Body fat was greater in OC than in MA (23.9 [SD 4.2] % vs. 14.0 [SD 5.7] %, p<0.001), and also greater than in YA and YC (both p<0.001). Weekly training hours were comparable between MA and YA (7.9 [SD3.3] hours vs. 11.1 [SD 4.8] hours, p=0.69). Habitual walking distance was greater in MA than in OC (7,387 [SD 4,923] m/day vs. 4,110 [SD 1,772] m/day, p=0.039), and so was habitual running distance (667 [SD690] m/day vs. 132 [427] m/day, p<0.001). HOMA-index was greater in OC than in MA (2.07 [SD 1.39] vs. 0.80 [SD 0.41], p=0.0039), and so was C-reactive protein (1.35 [SD 1.74] mg/l vs. 0.58 [SD 0.27] mg/ml, p=0.018), whereas serum lipids showed only moderate or no effect (all p between 0.036 and 0.07). Conclusions Improved body composition and physical activity levels in MA are associated with lower cardiometabolic risk, which seems more pronounced for insulin sensitivity and inflammaging than for lipid metabolism.

Objectives Understanding differences between real-world walking speed (RWS) and laboratory-measured walking speed (LWS) is crucial for comprehensive mobility assessments, especially in context of prolonged immobilization. This study aimed to investigate disparities in walking speed following a 60-day bed-rest period. Methods In 11 male participants, RWS was continuously monitored using a tri-axial accelerometer worn on the waist, while LWS was assessed via a 10-m walk test at preferred speed, on three different study days after immobilization. Statistical analyses included Bland–Altman and Pearson’s correlation to evaluate agreement between RWS and LWS, alongside paired-sample t-tests and univariate linear regression models to assess significance of differences and temporal effects on gait speed. Results Results of Bland-Altman analysis showed no agreement between RWS and LWS (mean difference 0.77 m/s) and nonsignificant correlation (r=0.19, p-value=0.3). Paired-sample t-tests indicated significantly lower RWS compared to LWS for all study days (p-value <0.001). Univariate linear regression models demonstrated a significant effect of test day on RWS (p-value <0.001) but not on LWS (p-value=0.23). Conclusions These findings emphasize the importance of integrating both assessments to capture comprehensive mobility changes following prolonged periods of inactivity. Particularly significant is that RWS is constantly lower than LWS, with the former being more representative as it reflects what normally participants would do when not under observation. Lastly, understanding discrepancies between RWS and LWS would allow for more appropriate rehabilitation programs to speed up recovery while simultaneously keeping the rehabilitation safe and tailored.

Objective: Due to its high relevance in sports and rehabilitation, the exploration of interventions to further optimize flexibility becomes paramount. While stretching might be the most common way to enhance range of motion (ROM), these increases could be optimized by imposing an additional activation of the muscle, such as mechanical vibratory stimulation. While several original articles provide promising findings, contradictory results on flexibility and underlying mechanisms e.g. stiffness, reasonable effect size (ES) pooling remains scarce. With this work we systematically reviewed the available literature to explore the possibility of potentiating flexibility, stiffness and passive torque adaptations by superimposing mechanical vibration stimulation. Methods: A systematic search was conducted until December 2023 including 4 databases to identify studies comparing mechanical vibratory interventions with passive controls or the same intervention without vibration (sham) on range of motion and passive muscle stiffness in acute (immediate effects after single session) and chronic conditions (multiple sessions over a period of time). ES pooling was conducted using robust variance estimation via R to account for multiple study outcomes. Potential moderators of effects were analysed using meta regression. Results: Overall, 65 studies (acute: 1160 participants, chronic: 788 participants) were included. There was moderate certainty of evidence for acute flexibility (ES=0.71, p<0.001) and stiffness (ES=-0.89, p=0.006) effects of mechanical vibration treatments versus passive controls, without meaningful results against the sham condition (flexibility: ES=0.2, p<0.001; stiffness: ES=-0.19, p=0.076). Similarly, moderate certainty of evidence was found for chronic vibration effects on flexibility (Control: ES=0.64, p=0.043; Sham: ES=0.65, p<0.001). Lack of studies and large outcome heterogeneity prevented ES pooling for underlying mechanisms. Conclusion: Vibration improved flexibility in acute and chronic interventions compared to the stand-alone intervention, which can possibly be attributed to an accumulated mechanical stimulus through vibration. However, studies on biological mechanisms are needed to explain flexibility and stiffness effects in response to specific vibration modalities and timing.

ZUSAMMENFASSUNG Bei Langzeitaufenthalten in Mikrogravitation unterliegt die Muskulatur einer Dekonditionierung. Das Training an Bord der International Space Station ermöglicht bereits eine zügige Aufnahme der täglichen Aktivitäten nach der Landung, jedoch kommt es nach wie vor zu beobachtbarer Muskelatrophie. Daher ist eine Analyse des Muskels von physiologischer sowie von struktureller Seite vor, während und nach Raumflügen von höchster Relevanz. Eine nichtinvasive, platz- und kosteneffiziente Methode ist dabei der muskuloskelettale Ultraschall. Die Echointensität kann Aufschlüsse über die Binnenqualität des Muskels geben, jedoch sind die Ergebnisse stark untersucherabhängig. Durch Modellierung einer Funktion basierend auf Messungen des Schallwinkels und der Echointensität konnten objektivere Parameter erschlossen werden. Damit lassen sich in Zukunft Echointensitäten zwischen Muskeln vergleichen oder deren Verlauf über eine Periode der Immobilisierung verfolgen, um pathologischen Veränderungen frühzeitig und gezielt entgegenzuwirken.

Background & Objectives Arterial hypertension and age underlie the risk for diastolic dysfunction and heart failure with preserved ejection fraction. Blood pressure control and physical exercise are known to ameliorate age related cardiac adaptation. Therefore, we assessed diastolic function including left atrial (LA) strains in Masters Athletes as a model for healthy ageing. Methods At the World Masters Athletics Championships 2022 in Tampere, Finland 108 Masters Athletes partook in this field-study. Baseline data included body measures, blood pressure, age, sex and sport disciplines. Transthoracic echocardiography was performed analogous to clinical standards. Additionally, LA reservoir strain (LA-Sr) and conduit strain (LA-Scd) were assessed by speckle tracking. Results Complete data were acquired in 108 (42, 39% female) athletes with a mean age of 62±12 (35-91) years and a body-mass-index of 23,8±2,8 kg/m2. Mean systolic blood pressure was 125±16mmHg, one third (n=36) had values ≥130mmHg. 29 performed endurance, 79 resistance disciplines. LA strain was not influenced by sport discipline nor blood pressure, neither in dichotomization for clinical thresholds nor in linear correlation. Female athletes showed higher LA reservoir and conduit strain (LA-Sr: 29.1±5.3% versus 27±5.5%, p=0.046; LA-Scd: 16.6±6% versus 13.9±5.4%, p=0,018). With increasing age, body-mass-index and left-ventricular-mass-index, LA reservoir and conduit strains declined significantly, independent of blood pressure. In Masters Athletes that did not meet echocardiographic criteria of diastolic dysfunction we found significantly higher LA reservoir and conduit strains than in those with 2 criteria met (LA-Sr 29.8±5.2% versus 25.4±6.6%, p=0.007; LA-Scd -17.3±6% versus -13.4±6.5%, p=0.030). Conclusion In the specialized cohort of Masters Athletes LA reservoir and conduit strain showed the same dependency from age, body-mass-index and left-ventricular-mass-index as other parameters of diastolic function with higher values in females. Furthermore, impaired diastolic function was associated with decreased LA strain. Therefore, assessment of LA strain seems beneficial beyond classical echocardiographic measurements in determining diastolic function in the elderly. Surprisingly, long-term blood pressure control by physical exercise had no effect on LA strains.

INTRODUCTION: Accessible spaceflight may seem a distant concept. As part of a diverse European Space Agency funded Topical Team, we are working on the physiological feasibility of space missions being undertaken by people with physical disabilities. Here, the first activity of this team is presented in the form of key lessons learned from aviation to inform new work on space missions. DISCUSSION: The first lesson is agreeing on realistic expectations about impairments, their severity, and the possibility of flying independently. This is important in terms of astronaut recruitment and societal expectations. The second lesson relates to training and adjustments for people with disabilities. Flexibility is important while maintaining safety for everyone involved. The third lesson is about managing unconscious bias from the different stakeholders. We conclude by arguing that engagement with people from different backgrounds is essential for the success of the first space mission with people with physical disabilities. Miller-Smith MJ, Tucker N, Anderton R, Caplin N, Harridge SDR, Hodkinson P, Narici MV, Pollock RD, Possnig C, Rittweger J, Smith TG, Di Giulio I. Lessons for flying astronauts with disabilities drawn from experience in aviation . Aerosp Med Hum Perform. 2024; 95(9):716–719.