Strength training | EPFL Graph Search

Strength training or resistance training involves the performance of physical exercises that are designed to improve strength and endurance. It is often associated with the lifting of weights. It can also incorporate a variety of training techniques such as bodyweight exercises, isometrics, and plyometrics. Training works by progressively increasing the force output of the muscles and uses a variety of exercises and types of . Strength training is primarily an anaerobic activity, although circuit training also is a form of aerobic exercise. Strength training can increase muscle, tendon, and ligament strength as well as bone density, metabolism, and the lactate threshold; improve joint and cardiac function; and reduce the risk of injury in athletes and the elderly. For many sports and physical activities, strength training is central or is used as part of their training regimen. Principles and training methods The basic principles of strength training involve repeated

Targeting mitochondrial bioenergetics and NAD+ metabolism during sarcopenia and regeneration of skeletal muscle

Tanja Sonntag

The progressive decline of muscle mass and function called sarcopenia is a multi-factorial process associated to frailty, disability, and low quality of life in the elderly. The co-factor nicotinamide adenine dinucleotide (NAD+) becomes a limiting factor in the course of aging and other pathological conditions. It has emerged as a major regulator of cellular metabolism, which is modulated by dietary precursors of the vitamin B3 family. So far, no direct link between sarcopenia and alterations in NAD+ metabolism has been reported. In this thesis, I have taken a multi-disciplinary approach combining molecular profiling in humans and dietary and genetic manipulations in rodents to characterize the skeletal muscle NAD+ metabolism in the context of muscle plasticity and aging. We have performed a multi-center study to characterize the molecular signature of human sarcopenia compared to age-matched controls. Sarcopenic participants of three cohorts in Singapore, the United Kingdom and Jamaica presented a prominent transcriptional signature of mitochondrial dysfunction, which translated into functional bioenergetic deficiency with lower mitochondrial protein expression and activity. Furthermore, we established a concurrent decrease in NAD+ content of sarcopenic muscle, which correlated to lower muscle strength and function in these patients. Supplementation with the dietary NAD+ precursor nicotinamide riboside (NR) was shown to improve pathological muscle conditions and revert age-related mitochondrial dysfunction and stem cell senescence in mice. To test whether boosting NAD+ through NR can be beneficial in the context of sarcopenia, we investigated the acute response to NR supplementation in young adult and old sarcopenic rats. Acute NR treatment efficiently increased NAD+ levels and normalized specific age-related gene expression signatures in old rats, in particular related to fibrosis. Interestingly, our transcriptional profiling also revealed that the molecular response to NR is partially blunted in aging and suggests that aged muscle could be in a state of partial NAD+ resistance. To investigate the role of endogenous NR as NAD+ precursor in the muscle, we studied mice deficient for NR kinases 1 and 2 (NRK1/2 dKO), the rate-limiting enzymes for NR salvage. NRK1/2 dKO mice develop normally, but exhibit elevated salvage of the NAD+ precursor nicotinamide (NAM) to maintain tissue NAD+. Thus, our results demonstrate for the first time that an endogenous NRK-dependent flux actively converts NR into NAD+ in healthy skeletal muscle. Moreover, we demonstrated that NRKs are required for muscle regeneration, as dKO mice failed to efficiently regenerate the NAD+ pool during the active phases of myofiber remodeling, which coincided with a transient delay of myofiber maturation. Conversely, dietary NR improved the activation of muscle stem cells and accelerated recovery of NAD+ levels in regenerating myofibers of wild-type mice. Altogether, this work demonstrates that both in humans and preclinical models, sarcopenia is tightly linked to mitochondrial bioenergetics and NAD+ metabolism. Dietary manipulation of NAD+ levels is a promising therapeutic strategy for the management of age-related muscle dysfunction for which we uncovered important mechanistic insights linking metabolic fluxes through the NAD+ pathway to physiological adaptations.

EPFL2019

Behavioural compass: animal behaviour recognition using magnetometers

Kamiar Aminian, Pritish Chakravarty, Maiki Maalberg

Animal-borne data loggers today often house several sensors recording simultaneously at high frequency. This offers opportunities to gain fine-scale insights into behaviour from individual-sensor as well as integrated multi-sensor data. In the context of behaviour recognition, even though accelerometers have been used extensively, magnetometers have recently been shown to detect specific behaviours that accelerometers miss. The prevalent constraint of limited training data necessitates the importance of identifying behaviours with high robustness to data from new individuals, and may require fusing data from both these sensors. However, no study yet has developed an end-to-end approach to recognise common animal behaviours such as foraging, locomotion, and resting from magnetometer data in a common classification framework capable of accommodating and comparing data from both sensors. We address this by first leveraging magnetometers’ similarity to accelerometers to develop biomechanical descriptors of movement: we use the static component given by sensor tilt with respect to Earth’s local magnetic field to estimate posture, and the dynamic component given by change in sensor tilt with time to characterise movement intensity and periodicity. We use these descriptors within an existing hybrid scheme that combines biomechanics and machine learning to recognise behaviour. We showcase the utility of our method on triaxial magnetometer data collected on ten wild Kalahari meerkats (Suricata suricatta), with annotated video recordings of each individual serving as groundtruth. Finally, we compare our results with accelerometer-based behaviour recognition. The overall recognition accuracy of > 94% obtained with magnetometer data was found to be comparable to that achieved using accelerometer data. Interestingly, higher robustness to inter-individual variability in dynamic behaviour was achieved with the magnetometer, while the accelerometer was better at estimating posture. Magnetometers were found to accurately identify common behaviours, and were particularly robust to dynamic behaviour recognition. The use of biomechanical considerations to summarise magnetometer data makes the hybrid scheme capable of accommodating data from either or both sensors within the same framework according to each sensor’s strengths. This provides future studies with a method to assess the added benefit of using magnetometers for behaviour recognition.

2019

Use-Dependent Plasticity in Human Primary Motor Hand Area: Synergistic Interplay Between Training and Immobilization

Estelle Emeline Raffin

Training and immobilization are powerful drivers of use-dependent plasticity in human primary motor hand area (M1HAND). In young right-handed volunteers, corticomotor representations of the left first dorsal interosseus and abductor digiti minimi muscles were mapped with neuronavigated transcranial magnetic stimulation (TMS) to elucidate how finger-specific training and immobilization interact within M1HAND. A first group of volunteers trained to track a moving target on a smartphone with the left index or little finger for one week. Linear sulcus shape-informed TMS mapping revealed that the tracking skill acquired with the trained finger was transferred to the nontrained finger of the same hand. The cortical representations of the trained and nontrained finger muscle converged in proportion with skill transfer. In a second group, the index or little finger were immobilized for one week. Immobilization alone attenuated the corticomotor representation and pre-existing tracking skill of the immobilized finger. In a third group, the detrimental effects of finger immobilization were blocked by concurrent training of the nonimmobilized finger. Conversely, immobilization of the nontrained fingers accelerated learning in the adjacent trained finger during the first 2 days of training. Together, the results provide novel insight into use-dependent cortical plasticity, revealing synergistic rather than competitive interaction patterns within M1HAND

2018