This study investigated the effects of treadmill exercise and swimming on spontaneous developed knee osteoarthritis in the senescence-accelerated mouse prone 8 (SAMP8). Twenty-two weeks old SAMP8 mice were randomly divided into the No-exercise group, treadmill exercise group, and swimming group (n = 6 in each group). Treadmill exercise was performed at the speed of 10-12 m/min, and swimming was performed at a water temperature of 37-38℃ for 15 min/day, 5 day a week for 6 weeks. After exercise intervention, we examined the knee joint angle, width of the knee joint, stride length, and knee joint histological changes. Comparison with No-exercise group, both exercise groups were improved the knee joint angle and stride length. In addition, increased type II collagen positive chondrocyte, reduced matrix metalloproteinase (MMP)-13 positive chondrocyte, and tumor necrosis factor (TNF)-α positive cells in the synovium were observed in both exercise groups. Notably, the swimming group significantly improved the stride length and increased the ratio of type II collagen positive chondrocyte that is important protein maintaining a chondrocyte homeostasis. This study suggested that both exercise regimens alleviate age-related OA alteration, which improved the knee joint angle and stride length. The swimming may be beneficial in maintaining homeostasis for age-related OA joint and improving age-related gait disturbance.

Brain injury often causes severe motor dysfunction. Previously, we showed that the corticospinal tract (CST) axons are rewired to form an intraspinal circuit that contributes to motor recovery after brain injury in young adult mice. Although brain injury is often suffered by elderly individuals, little is known about the ability of rewiring and functional recovery in aged rodent model. In this study, we examined CST sprouting and functional recovery in aged mice after brain injury and further investigated whether voluntary running could promote them. We found that axon sprouting was limited and motor function was not recovered in aged mice. Contrastingly, voluntary running significantly increased sprouting and enhanced motor recovery. Moreover, we performed RNA sequencing to examine exercise-induced gene expression of motor area changes in aged mice. Expressions of 91 genes increased in exercised aged mice compared to non-exercised mice, in which a set of circadian rhythm-related genes was involved. Accordingly, a day-night activity rhythm was impaired in the aged mice, whereas it was gradually recovered by exercise, similar to the patterns of younger mice. Our study reveals that voluntary running restores circadian rhythms, CST sprouting, and motor recovery after brain injury in aged mice.

Purpose: The purpose of this study is to examine the effects of predictability of step distance and differences in step distance on Anticipatory Postural Adjustments (APA) responses in healthy young subjects.

Method: Twenty healthy young subjects performed step movements at three different distances according to their height in a condition in which the step distance was taught in advance and in a condition in which the step distance was presented immediately before the step. APA time, lower limb muscle activity time, and involvement of cortical activity by Electromyography (EMG) coherence analysis were calculated and compared for each condition.

Results: Significant differences in muscle activity time were observed for the tibialis anterior and soleus muscles on the step side according to predictability, and for the tibialis anterior and gastrocnemius lateralis muscle on the step side according to step distance, but no significant differences in APA time or coherence were observed.

Conclusion: The results suggest that the predictability of step distance and differences in step distance may have little effect on the APA response in healthy young subjects.

F-waves are compound muscle action potentials generated by the retrograde activation of alpha motoneuron axons and the backfiring of anterior horn cells upon electrical stimulation. Traditionally, F-waves are recorded from the vastus lateralis muscle by electrical stimulation of the groin, but this method has several limitations. We placed stimulating electrodes at 50–80% of the proximal thigh to investigate better stimulation sites. As a result, most subjects had successful F-wave recordings with electrical stimulation at 70% and 80% of the thigh. However, some participants experienced severe pain from the electrical current. To address this issue, we tested varying the frequency of electrical stimulation while recording F-waves from the vastus lateralis muscle and found that 0.2-Hz stimulation reduced pain more than the conventional 0.5-Hz stimulation. These findings have potential clinical applications in the future, as they may help improve patient comfort and cooperation during F-wave recording procedures.

The ability to perceive the position and orientation of one's body and external objects (spatial orientation) is fundamental to action. Spatial orientation can be classified into two types: 1) egocentric spatial orientation, which estimates the direction of external objects with respect to the body parts such as the body longitudinal axis, and 2) gravity-based spatial orientation, which estimates the orientation of the body and external objects with respect to the gravitational axis. We have focused explicitly on egocentric spatial orientation and investigated its characteristics and neural basis through body tilt experiments. A series of experiments showed that the estimation of visual line orientation relative to the body axis is biased when the body is tilted and that this phenomenon is strongly related to subjective estimates of body tilt. This phenomenon indicates the human characteristic of referring to the gravitational axis when estimating the spatial relationship between one's body and an external object. In addition, a study using voxel-based morphometry and neuropsychological studies in brain-injured patients suggested that the right occipitotemporal cortex may play a vital role in this characteristic. These findings contribute to a better understanding of human spatial perception mechanisms in the gravitational field.

In the past 20 years, athletes, in particular, have used foam rollers as a form of self-care. However, there has been little evidence for foam rolling. Therefore, we investigated the acute and chronic (long-term) effects of foam rolling intervention on a range of motion (ROM) and shear elastic modulus in healthy participants and eccentrically-induced muscle damage (delayed onset muscle soreness) in an actual physical therapy setting. Our results showed that foam rolling intervention could increase the range of motion acutely and chronically. Still, there was no significant change in shear elastic modulus. However, the vibration foam roller intervention, which can be used simultaneously with vibration therapy, could decrease shear elastic modulus by stimulating the muscle belly area. In addition, foam rolling intervention could also improve muscle soreness and the range of motion loss. These results suggest that foam roller intervention could be a valuable alternative approach to stretching in clinical practice in the future.

In our daily lives, we unconsciously chose left or right arm when performing tasks such as reaching for a cup in front of us. While rehabilitation can partially restore the function of a paretic arm following a stroke, some patients tend to rely on their nonparetic arm and neglect using the paretic arm when not explicitly prompted. This lack of use hinders the recovery of the paretic arm's functionality. Therefore, it is crucial to propose interventions that encourage the unconscious use of the paretic arm, even in situations where its use is not mandatory. This study focuses on the neural mechanisms associated with arm choice and investigates neuromodulation methods that can bias arm choice. The paper summarizes the factors influencing arm choice and presents our research findings on the effects of transcranial direct current electrical stimulation targeting the posterior parietal cortex in influencing arm choice.

Paralympic athletes demonstrate remarkable neural plasticity to overcome their physical and mental impairments and achieve high performance. This paper reviews studies that have elucidated the cortical reorganization in the brain structure and function of athletes with spinal cord injury and lower limb amputation, and discusses the neural mechanisms underlying their specific adaptation. Studies have shown that athletes with spinal cord injury exhibit an expansion of the upper limb dominant area in the primary motor cortex, and an increased functional connectivity between the primary motor cortex and the superior parietal lobule, providing a neural basis for their enhanced upper limb motor function. Athletes with lower limb amputation show increased brain activity in the ipsilateral primary motor cortex during stump contraction, and a correlation with the nucleus accumbens motor network. These findings suggest that both compensatory and use-dependent plastic changes contribute to the cortical reorganization of paralympic athletes, and that their interaction induces specific reorganization.

NAD⁺ (nicotinamide adenine dinucleotide) is involved in various reactions, notably as a regulator in activating sirtuins, which play a role in aging and lifespan. It has been shown that age-associated NAD⁺ decline in tissues triggers functional deterioration perceived as “aging.” Consequently, replenishing NAD⁺ is considered a promising intervention for anti-aging. The synthesis of NAD⁺ primarily depends on a salvage pathway that has NAMPT (nicotinamide phosphoribosyl-transferase) as its rate-limiting step. Recent studies have found that NAMPT in adipose tissue not only produces intracellular NAD⁺ but also releases it into the bloodstream as eNAMPT (extracellular NAMPT), encapsulated in EVs. Further, eNAMPT boosts NAD⁺ production in the hypothalamus, recognized as the metabolic center. This elevation in eNAMPT demonstrates notable anti-aging benefits across the body and contributes to a longer lifespan. Here, we review NAD⁺ metabolism and aging control and provide an overview of eNAMPT, highlighting its potential to link exercise and healthy longevity.