Functional electrical stimulation (FES)-assisted rowing combined with zoledronic acid, but not alone, preserves distal femur strength and stiffness in people with chronic spinal cord injury

The Effect of Electrical Stimulation Strength Training on Lower Limb Muscle Activation Characteristics During the Jump Smash Performance in Badminton Based on the EMS and EMG Sensors

This study investigates the effects of electrical stimulation (EMS) combined with strength training on lower limb muscle activation and badminton jump performance, specifically during the "jump smash" movement. A total of 25 male badminton players, with a minimum of three years of professional training experience and no history of lower limb injuries, participated in the study. Participants underwent three distinct conditions: baseline testing, strength training, and EMS combined with strength training. Each participant performed specific jump tests, including the jump smash and static squat jump, under each condition. Muscle activation was measured using electromyography (EMG) sensors to assess changes in the activation of key lower limb muscles. The EMS intervention involved targeted electrical pulses designed to stimulate both superficial and deep muscle fibers, aiming to enhance explosive strength and coordination in the lower limbs. The results revealed that the EMS + strength condition significantly improved performance in both the jump smash and static squat jump, as compared to the baseline and strength-only conditions (F = 3.39, p = 0.042; F = 3.67, p = 0.033, respectively). Additionally, increased activation of the rectus femoris (RF) was observed in the EMS + strength condition, indicating improved muscle recruitment and synchronization, likely due to the activation of fast-twitch fibers. No significant differences were found in the eccentric-concentric squat jump (F = 0.59, p = 0.561). The findings suggest that EMS, when combined with strength training, is an effective method for enhancing lower limb explosiveness and muscle activation in badminton players, offering a promising training approach for improving performance in high-intensity, explosive movements.

Effect of Adapted Ergometer Setup and Rowing Speed on Lower Extremity Loading in People with and Without Spinal Cord Injury

BACKGROUND

Functional electrical stimulation-assisted rowing (FES rowing) is a rehabilitation exercise used to prevent disuse osteoporosis, which is common in people with spinal cord injury (SCI). However, its effect on bone loss prevention varied in SCI patients, potentially due to inconsistent loading. This study investigates the effect of ergometer setup and rowing speed on lower extremity loading during rowing.

METHODS

Twenty able-bodied participants and one participant with SCI rowed on an adapted ergometer with different speeds and setups. We calculated foot reaction force and knee moment for all participants, and tibiofemoral force for the rower with SCI.

RESULTS

Able-bodied rowers generated 0.22-0.45 body weight (BW) foot reaction forces, and a higher force was associated with a fast speed, forward seat position, and large knee range of motion (RoM). The rower with SCI had the greatest foot reaction force (0.39 BW) when rowing with a small knee RoM at a rear seat position, and the highest tibiofemoral force (2.23 BW) with a large knee RoM or at a rear seat position.

CONCLUSIONS

Ergometer setup and speed both affect lower limb loading and should be further studied in more rowers with SCI. This can inform rehabilitation protocols to standardize ergometer configuration to improve bone health.

Spinal Cord Injury Associated Disease of the Skeleton, an Unresolved Problem with Need for Multimodal Interventions

Spinal cord injury is associated with skeletal unloading, sedentary behavior, decreases in skeletal muscle mass, and exercise intolerance, which results in rapid and severe bone loss. To date, monotherapy with physical interventions such as weight-bearing in standing frames, computer-controlled electrically stimulated cycling and ambulation exercise, and low-intensity vibration are unsuccessful in maintaining bone density after SCI. Strategies to maintain bone density with commonly used osteoporosis medications also fail to provide a significant clinical benefit, potentially due to a unique pathology of bone deterioration in SCI. In this review, the available data is discussed on evaluating and monitoring bone loss, fracture, and physical and pharmacological therapeutic approaches to SCI-associated disease of the skeleton. The treatment of SCI-associated disease of the skeleton, the implications for clinical management, and areas of need are considered for future investigation.

Exercise for optimizing bone health after hormone-induced increases in bone stiffness

Hormones and mechanical loading co-regulate bone throughout the lifespan. In this review, we posit that times of increased hormonal influence on bone provide opportunities for exercise to optimize bone strength and prevent fragility. Examples include endogenous secretion of growth hormones and sex steroids that modulate adolescent growth and exogenous administration of osteoanabolic drugs like teriparatide, which increase bone stiffness, or its resistance to external forces. We review evidence that after bone stiffness is increased due to hormonal stimuli, mechanoadaptive processes follow. Specifically, exercise provides the mechanical stimulus necessary to offset adaptive bone resorption or promote adaptive bone formation. The collective effects of both decreased bone resorption and increased bone formation optimize bone strength during youth and preserve it later in life. These theoretical constructs provide physiologic foundations for promoting exercise throughout life.

Pharmacologic and nonpharmacologic treatment modalities for bone loss in SCI - Proposal for combined approach

Increased risk of bone fracture due to bone mineral density (BMD) loss is a serious consequence of spinal cord injury (SCI). Traditionally, pharmaceutical approaches, such as bisphosphonates, have been prescribed to prevent bone loss. However, there is controversy in the literature regarding efficacy of these medications to mitigate the drastic bone loss following SCI. Individuals with SCI are particularly at risk of osteoporosis because of the lack of ambulation and weight bearing activities. In the past two decades, functional electric stimulation (FES) has allowed for another approach to treat bone loss. FES approaches are expanding into various modalities such as cycling and rowing exercises and show promising outcomes with minimal consequences. In addition, these non-pharmacological treatments can elevate overall physical and mental health. This article provides an overview of efficacy of different treatment options for BMD loss for SCI and advocates for a combined approach be pursued in standard of care.

The Effects of Exercise and Activity-Based Physical Therapy on Bone after Spinal Cord Injury

Spinal cord injury (SCI) produces paralysis and a unique form of neurogenic disuse osteoporosis that dramatically increases fracture risk at the distal femur and proximal tibia. This bone loss is driven by heightened bone resorption and near-absent bone formation during the acute post-SCI recovery phase and by a more traditional high-turnover osteopenia that emerges more chronically, which is likely influenced by the continual neural impairment and musculoskeletal unloading. These observations have stimulated interest in specialized exercise or activity-based physical therapy (ABPT) modalities (e.g., neuromuscular or functional electrical stimulation cycling, rowing, or resistance training, as well as other standing, walking, or partial weight-bearing interventions) that reload the paralyzed limbs and promote muscle recovery and use-dependent neuroplasticity. However, only sparse and relatively inconsistent evidence supports the ability of these physical rehabilitation regimens to influence bone metabolism or to increase bone mineral density (BMD) at the most fracture-prone sites in persons with severe SCI. This review discusses the pathophysiology and cellular/molecular mechanisms that influence bone loss after SCI, describes studies evaluating bone turnover and BMD responses to ABPTs during acute versus chronic SCI, identifies factors that may impact the bone responses to ABPT, and provides recommendations to optimize ABPTs for bone recovery.

Effect of External Mechanical Stimuli on Human Bone: a narrative review

Bone is a living composite material that has the capacity to adapt and respond to both internal and external stimuli. This capacity allows bone to adapt its structure to habitual loads and repair microdamage. Although human bone evolved to adapt to normal physiologic loading (for example from gravitational and muscle forces), these same biological pathways can potentially be activated through other types of external stimuli such as pulsed electromagnetic fields, mechanical vibration, and others. This review summarizes what is currently known about how human bone adapts to various types of external stimuli. We highlight how studies on sports-specific athletes and other exercise interventions have clarified the role of mechanical loading on bone structure. We also discuss clinical scenarios, such as spinal cord injury, where mechanical loading is drastically reduced, leading to rapid bone loss and permanent alterations to bone structure. Finally, we highlight areas of emerging research and unmet clinical need.

Heterogeneity in microstructural deterioration following spinal cord injury

BACKGROUND

Modelling and remodelling adapt bone morphology to accommodate strains commonly encountered during loading. If strains exceed a threshold threatening fracture, modelling-based bone formation increases bone volume reducing these strains. If unloading reduces strains below a threshold that inhibits resorption, increased remodelling-based bone resorption reduces bone volume restoring strains, but at the price of compromised bone volume and microstructure. As weight-bearing regions are adapted to greater strains, we hypothesized that microstructural deterioration will be more severe than at regions commonly adapted to low strains following spinal cord injury.

METHODS

We quantified distal tibial, fibula and radius volumetric bone mineral density (vBMD) using high-resolution peripheral quantitative computed tomography in 31 men, mean age 43.5 years (range 23.5-75.0), 12 with tetraplegia and 19 with paraplegia of 0.7 to 18.6 years duration, and 102 healthy age- and sex-matched controls. Differences in morphology relative to controls were expressed as standardized deviation (SD) scores (mean ± SD). Standardized between-region differences in vBMD were expressed as SDs (95% confidence intervals, CI).

RESULTS

Relative to controls, men with tetraplegia had deficits in total vBMD of -1.72 ± 1.38 SD at the distal tibia (p < 0.001) and - 0.68 ± 0.69 SD at distal fibula (p = 0.041), but not at the distal radius, despite paralysis. Deficits in men with paraplegia were -2.14 ± 1.50 SD (p < 0.001) at the distal tibia and -0.83 ± 0.98 SD (p = 0.005) at the distal fibula while distal radial total vBMD was 0.23 ± 1.02 (p = 0.371), not significantly increased, despite upper limb mobility. Comparing regions, in men with tetraplegia, distal tibial total vBMD was 1.04 SD (95%CI 0.07, 2.01) lower than at the distal fibula (p = 0.037) and 1.51 SD (95%CI 0.45, 2.57) lower than at the distal radius (p = 0.007); the latter two sites did not differ from each other. Results were similar in men with paraplegia, but total vBMD at the distal fibula was 1.06 SD (95%CI 0.35, 1.77) lower than at the distal radius (p = 0.004).

CONCLUSION

Microarchitectural deterioration following spinal cord injury is heterogeneous, perhaps partly because strain thresholds regulating the cellular activity of mechano-transduction are region specific.