Neural and musculotendinous mechanisms underpinning age-related force reductions

A personalized clinical assessment: multi-sensor approach for understanding musculoskeletal health in the frail population

BACKGROUND

Sarcopenia is a muscle disorder causing a progressive reduction of muscle mass and strength, but the mechanism of its manifestation is still partially unknown. The three main parameters to assess are: muscle strength, muscle volume or quality and low physical performance. There is not a definitive approach to assess the musculoskeletal condition of frail population and often the available tests to be performed in those clinical bedridden patients is reduced because of physical impairments. In this paper, we propose a novel instrumental multi-domain and non-invasive approach during a well-defined protocol of measurements for overcoming these limitations. A group of 28 bedridden elder people, subjected to surgery after hip fracture, was asked to perform voluntary isometric contractions at the 80% of their maximum voluntary contraction with the non-injured leg. The sensor employed before and/or during the exercise were: ultrasound to determine the muscle architecture (vastus lateralis); force acquisition with a load cell placed on the chair, giving an indication of the muscle strength; surface electromyography (EMG) for monitoring muscular electrical activity; time-domain (TD) near-infrared spectroscopy (NIRS) for evaluating muscle oxidative metabolism.

RESULTS

A personalized "report card" for each subject was created. It includes: the force diagram (both instantaneous and cumulative, expected and measured); the EMG-force diagram for a comparison between EMG derived median frequency and measured force; two graphs related to the hemodynamic parameters for muscle oxidative metabolism evaluation, i.e., oxy-, deoxy-, total-hemoglobin and tissue oxygen saturation for the whole exercise period. A table with the absolute values of the previous hemodynamic parameters during the rest and the ultrasound related parameters are also included.

CONCLUSIONS

In this work, we present the union of protocols, multi-domain sensors and parameters for the evaluation of the musculoskeletal condition. The novelties are the use of sensors of different nature, i.e., force, electrical and optical, together with a new way to visualize and combine the results, by means of a concise, exhaustive and personalized medical report card for each patient. This assessment, totally non-invasive, is focused on a bedridden population, but can be extended to the monitoring of rehabilitation progresses or of the training of athletes.

Exercise training and vascular heterogeneity in db/db mice: evidence for regional- and duration-dependent effects

Exercise training (ET) has several health benefits; however, our understanding of regional adaptations to ET is limited. We examined the functional and molecular adaptations to short- and long-term ET in elastic and muscular conduit arteries of db/db mice in relation to changes in cardiovascular risk factors. Diabetic mice and their controls were exercised at moderate intensity for 4 or 8 weeks. The vasodilatory and contractile responses of thoracic aortae and femoral arteries isolated from the same animals were examined. Blood and aortic samples were used to measure hyperglycemia, oxidative stress, inflammation, dyslipidemia, protein expression of SOD isoforms, COX, eNOS, and Akt. Short-term ET improved nitric oxide (NO) mediated vasorelaxation in the aortae and femoral arteries of db/db mice in parallel with increased SOD2 and SOD3 expression, reduced oxidative stress and triglycerides, and independent of weight loss, glycemia, or inflammation. Long-term ET reduced body weight in parallel with reduced systemic inflammation and improved insulin sensitivity along with increased SOD1, Akt, and eNOS expression and improved NO vasorelaxation. Exercise did not restore NOS- and COX-independent vasodilatation in femoral arteries, nor did it mitigate the hypercontractility in the aortae of db/db mice; rather ET transiently increased contractility in association with upregulated COX-2. Long-term ET differentially affected the aortae and femoral arteries contractile responses. ET improved NO-mediated vasodilation in both arteries likely due to collective systemic effects. ET did not mitigate all diabetes-induced vasculopathies. Optimization of the ET regimen can help develop comprehensive management of type 2 diabetes.

Ageing reduces persistent inward current contribution to motor neurone firing: Potential mechanisms and the role of exercise

Nervous system deterioration is a primary driver of age-related motor impairment. The motor neurones, which act as the interface between the central nervous system and the muscles, play a crucial role in amplifying excitatory synaptic input to produce the desired motor neuronal firing output. For this, they utilise their ability to generate persistent (long-lasting) depolarising currents that increase cell excitability, and both amplify and prolong the output activity of motor neurones for a given synaptic input. Modulation of these persistent inward currents (PICs) contributes to the motor neurones' capacities to attain the required firing frequencies and rapidly modulate them to competently complete most tasks. Thus, PICs are crucial for adequate movement generation. Impairments in intrinsic motor neurone properties can impact motor unit firing capacity, with convincing evidence indicating that the PIC contribution to motor neurone firing is reduced in older adults. Indeed, this could be an important mechanism underpinning the age-related reductions in strength and physical function. Furthermore, resistance training has emerged as a promising intervention to counteract age-associated PIC impairments, with changes in PICs being correlated with improvements in muscular strength and physical function after training. In this review, we present the current knowledge of the PIC magnitude decline during ageing and discuss whether reduced serotonergic and noradrenergic input onto the motor neurones, voltage-gated calcium channel dysfunction or inhibitory input impairments are candidates that: (i) explain age-related reductions in the PIC contribution to motor neurone firing and (ii) underpin the enhanced PIC contribution to motor neurone firing following resistance training in older adults.

Intrinsic motor neuron excitability is increased after resistance training in older adults

This study investigated the effects of high-intensity resistance training on estimates of the motor neuron persistent inward current (PIC) in older adults. Seventeen participants (68.5 ± 2.8 yr) completed a 2-wk nonexercise control period followed by 6 wk of resistance training. Surface electromyographic signals were collected with two 32-channel electrodes placed over soleus to investigate motor unit discharge rates. Paired motor unit analysis was used to calculate delta frequency (ΔF) as an estimate of PIC amplitudes during 1) triangular-shaped contractions to 20% of maximum torque capacity and 2) trapezoidal- and triangular-shaped contractions to 20% and 40% of maximum torque capacity, respectively, to understand their ability to modulate PICs as contraction intensity increases. Maximal strength and functional capacity tests were also assessed. For the 20% triangular-shaped contractions, ΔF [0.58-0.87 peaks per second (pps); P ≤ 0.015] and peak discharge rates (0.78-0.99 pps; P ≤ 0.005) increased after training, indicating increased PIC amplitude. PIC modulation also improved after training. During the control period, mean ΔF differences between 20% trapezoidal-shaped and 40% triangular-shaped contractions were 0.09-0.18 pps (P = 0.448 and 0.109, respectively), which increased to 0.44 pps (P < 0.001) after training. Also, changes in ΔF showed moderate to very large correlations (r = 0.39-0.82) with changes in peak discharge rates and broad measures of motor function. Our findings indicate that increased motor neuron excitability is a potential mechanism underpinning training-induced improvements in motor neuron discharge rate, strength, and motor function in older adults. This increased excitability is likely mediated by enhanced PIC amplitudes, which are larger at higher contraction intensities.NEW & NOTEWORTHY Resistance training elicited important alterations in soleus intrinsic motor neuronal excitability, likely mediated by enhanced persistent inward current (PIC) amplitude, in older adults. Estimates of PICs increased after the training period, accompanied by an enhanced ability to increase PIC amplitudes at higher contraction intensities. Our data also suggest that changes in PIC contribution to self-sustained discharging may contribute to increases in motor neuron discharge rates, maximal strength, and functional capacity in older adults after resistance training.

Fiber-Type Shifting in Sarcopenia of Old Age: Proteomic Profiling of the Contractile Apparatus of Skeletal Muscles

The progressive loss of skeletal muscle mass and concomitant reduction in contractile strength plays a central role in frailty syndrome. Age-related neuronal impairments are closely associated with sarcopenia in the elderly, which is characterized by severe muscular atrophy that can considerably lessen the overall quality of life at old age. Mass-spectrometry-based proteomic surveys of senescent human skeletal muscles, as well as animal models of sarcopenia, have decisively improved our understanding of the molecular and cellular consequences of muscular atrophy and associated fiber-type shifting during aging. This review outlines the mass spectrometric identification of proteome-wide changes in atrophying skeletal muscles, with a focus on contractile proteins as potential markers of changes in fiber-type distribution patterns. The observed trend of fast-to-slow transitions in individual human skeletal muscles during the aging process is most likely linked to a preferential susceptibility of fast-twitching muscle fibers to muscular atrophy. Studies with senescent animal models, including mostly aged rodent skeletal muscles, have confirmed fiber-type shifting. The proteomic analysis of fast versus slow isoforms of key contractile proteins, such as myosin heavy chains, myosin light chains, actins, troponins and tropomyosins, suggests them as suitable bioanalytical tools of fiber-type transitions during aging.

Facilitation-inhibition control of motor neuronal persistent inward currents in young and older adults

A well-coordinated facilitation-inhibition control of motor neuronal persistent inward currents (PICs) via diffuse neuromodulation and local inhibition is essential to ensure motor units discharge at required times and frequencies. Present best estimates indicate that PICs are reduced in older adults; however, it is not yet known whether PIC facilitation-inhibition control is also altered with ageing. We investigated the responses of PICs to (i) a remote handgrip contraction, which is believed to diffusely increase serotonergic input onto motor neurones, and (ii) tendon vibration of the antagonist muscle, which elicits reciprocal inhibition, in young and older adults. High-density surface electromyograms were collected from soleus and tibialis anterior of 18 young and 26 older adults during triangular-shaped plantar and dorsiflexion contractions to 20% (handgrip experiments) and 30% (vibration experiments) of maximum torque (rise-decline rate of 2%/s). A paired-motor-unit analysis was used to calculate ∆F, which is assumed to be proportional to PIC strength. ΔF increased in both soleus (0.55 peaks per second (pps), 16.0%) and tibialis anterior (0.42 pps, 11.4%) after the handgrip contraction independent of age. Although antagonist tendon vibration reduced ΔF in soleus (0.28 pps, 12.6%) independent of age, less reduction was observed in older (0.42 pps, 10.7%) than young adults (0.72 pps, 17.8%) in tibialis anterior. Our data indicate a preserved ability of older adults to amplify PICs following a remote handgrip contraction, during which increased serotonergic input onto the motor neurones is expected, in both lower leg muscles. However, PIC deactivation in response to reciprocal inhibition was impaired with ageing in tibialis anterior despite being preserved in soleus. KEY POINTS: Motor neuronal persistent inward currents (PICs) are facilitated via diffuse neuromodulation and deactivated by local inhibition to ensure motor units discharge at required times and frequencies, allowing normal motor behaviour. PIC amplitudes appear to be reduced with ageing; however, it is not known whether PIC facilitation-inhibition control is also altered. Remote handgrip contraction, which should diffusely increase serotonergic input onto motor neurones, facilitated PICs similarly in both soleus and tibialis anterior of young and older adults. Antagonist tendon vibration, which induces reciprocal inhibition, reduced PICs in soleus in both young and older adults but had less effect in tibialis anterior in older adults. Data from lower-threshold motor units during low-force contractions suggest that PIC facilitation is preserved with ageing in soleus and tibialis anterior. However, the effect of reciprocal inhibition on the contribution of PICs to motor neurone discharge seems reduced in tibialis anterior but preserved in soleus.

Effect of Physical Activity/Exercise on Oxidative Stress and Inflammation in Muscle and Vascular Aging

Functional status is considered the main determinant of healthy aging. Impairment in skeletal muscle and the cardiovascular system, two interrelated systems, results in compromised functional status in aging. Increased oxidative stress and inflammation in older subjects constitute the background for skeletal muscle and cardiovascular system alterations. Aged skeletal muscle mass and strength impairment is related to anabolic resistance, mitochondrial dysfunction, increased oxidative stress and inflammation as well as a reduced antioxidant response and myokine profile. Arterial stiffness and endothelial function stand out as the main cardiovascular alterations related to aging, where increased systemic and vascular oxidative stress and inflammation play a key role. Physical activity and exercise training arise as modifiable determinants of functional outcomes in older persons. Exercise enhances antioxidant response, decreases age-related oxidative stress and pro-inflammatory signals, and promotes the activation of anabolic and mitochondrial biogenesis pathways in skeletal muscle. Additionally, exercise improves endothelial function and arterial stiffness by reducing inflammatory and oxidative damage signaling in vascular tissue together with an increase in antioxidant enzymes and nitric oxide availability, globally promoting functional performance and healthy aging. This review focuses on the role of oxidative stress and inflammation in aged musculoskeletal and vascular systems and how physical activity/exercise influences functional status in the elderly.

DO MOTONEURON DISCHARGE RATES SLOW WITH AGING? A SYSTEMATIC REVIEW AND META-ANALYSIS

Nervous system maladaptation is linked to the loss of maximal strength and motor control with aging. Motor unit discharge rates are a critical determinant of force production; thus, lower discharge rates could be a mechanism underpinning maximal strength and motor control losses during aging. This meta-analysis summarized the findings of studies comparing motor unit discharge rates between young and older adults, and examined the effects of the selected muscle and contraction intensity on the magnitude of discharge rates difference between these two groups. Estimates from 29 studies, across a range of muscles and contraction intensities, were combined in a multilevel meta-analysis, to investigate whether discharge rates differed between young and older adults. Motor unit discharge rates were higher in younger than older adults, with a pooled standardized mean difference (SMD) of 0.66 (95%CI= 0.29-1.04). Contraction intensity had a significant effect on the pooled SMD, with a 1% increase in intensity associated with a 0.009 (95%CI= 0.003-0.015) change in the pooled SMD. These findings suggest that reductions in motor unit discharge rates, especially at higher contraction intensities, may be an important mechanism underpinning age-related losses in maximal force production.

A neuromuscular perspective of sarcopenia pathogenesis: deciphering the signaling pathways involved

The escalation of life expectancy is accompanied by an increase in the prevalence of age-related conditions, such as sarcopenia. Sarcopenia, a muscle condition defined by low muscle strength, muscle quality or quantity, and physical performance, has a high prevalence among the elderly and is associated to increased mortality. The neuromuscular system has been emerging as a key contributor to sarcopenia pathogenesis. Indeed, the age-related degeneration of the neuromuscular junction (NMJ) function and structure may contribute to the loss of muscle strength and ultimately to the loss of muscle mass that characterize sarcopenia. The present mini-review discusses important signaling pathways involved in the function and maintenance of the NMJ, giving emphasis to the ones that might contribute to sarcopenia pathogenesis. Some conceivable biomarkers, such as C-terminal agrin fragment (CAF) and brain-derived neurotrophic factor (BDNF), and therapeutic targets, namely acetylcholine and calcitonin gene-related peptide (CGRP), can be retrieved, making way to future studies to validate their clinical use.

Intrinsic motoneuron excitability is reduced in soleus and tibialis anterior of older adults

Age-related deterioration within both motoneuron and monoaminergic systems should theoretically reduce neuromodulation by weakening motoneuronal persistent inward current (PIC) amplitude. However, this assumption remains untested. Surface electromyographic signals were collected using two 32-channel electrode matrices placed on soleus and tibialis anterior of 25 older adults (70 ± 4 years) and 17 young adults (29 ± 5 years) to investigate motor unit discharge behaviors. Participants performed triangular-shaped plantar and dorsiflexion contractions to 20% of maximum torque at a rise-decline rate of 2%/s of each participant's maximal torque. Pairwise and composite paired-motor unit analyses were adopted to calculate delta frequency (ΔF), which has been used to differentiate between the effects of synaptic excitation and intrinsic motoneuronal properties and is assumed to be proportional to PIC amplitude. Soleus and tibialis anterior motor units in older adults had lower ΔFs calculated with either the pairwise [-0.99 and -1.46 pps; -35.4 and -33.5%, respectively] or composite (-1.18 and -2.28 pps; -32.1 and -45.2%, respectively) methods. Their motor units also had lower peak discharge rates (-2.14 and -2.03 pps; -19.7 and -13.9%, respectively) and recruitment thresholds (-1.50 and -2.06% of maximum, respectively) than young adults. These results demonstrate reduced intrinsic motoneuron excitability during low-force contractions in older adults, likely mediated by decreases in the amplitude of persistent inward currents. Our findings might be explained by deterioration in the motoneuron or monoaminergic systems and could contribute to the decline in motor function during aging; these assumptions should be explicitly tested in future investigations.

Utilisation of Post-Activation Performance Enhancement in Elderly Adults

With age, many physiological changes occur in the human body, leading to a decline in biological functions, and those related to the locomotor system are some of the most visible. Hence, there is a particular need to provide simple and safe exercises for the comprehensive development of physical fitness among elderly adults. The latest recommendations for the elderly suggest that the main goal of training should be to increase muscle power. The post-activation performance enhancement effect underpinning complex training might be an approach that will allow for the development of both muscle strength and velocity of movement, which will result in an increase in muscle power and improve the ability to perform daily activities and decrease injury risk. This article briefly introduces a complex training model adapted to the elderly with its potential benefits and proposes a direction for further studies.

Dose-Response Effect of Dietary Nitrate on Muscle Contractility and Blood Pressure in Older Subjects: A Pilot Study

We have recently demonstrated that dietary nitrate, a source of nitric oxide (NO) via the nitrate → nitrite → NO enterosalivary pathway, can improve muscle contractility in healthy older men and women. Nitrate ingestion has also been shown to reduce blood pressure in some, but not all, studies of older individuals. However, the optimal dose for eliciting these beneficial effects is unknown. A pilot randomized, double-blind, placebo-controlled crossover study was therefore performed to determine the effects of ingesting 3.3 mL/kg of concentrated beetroot juice containing 0, 200, or 400 µmol/kg of nitrate in 9 healthy older subjects (mean age 70 ± 1 years). Maximal knee extensor power (Pmax) and speed (Vmax) were measured ~2.5 hours after nitrate ingestion using isokinetic dynamometry. Blood pressure was monitored periodically throughout each study. Pmax (in W/kg) was higher (p < .05) after the lower dose (3.9 ± 0.4) compared to the placebo (3.7 ± 0.4) or higher dose (3.7 ± 0.4). Vmax (in rad/s) also tended to be higher (p = .08) after the lower dose (11.9 ± 0.7) compared to the placebo (10.8 ± 0.8) or higher dose (11.2 ± 0.8). Eight out of 9 subjects achieved a higher Pmax and Vmax after the lower versus the higher dose. These dose-related changes in muscle contractility generally paralleled changes in breath NO levels. No significant changes were found in systolic, diastolic, or mean arterial blood pressure. A lower dose of nitrate increases muscle speed and power in healthy older individuals, but these improvements are lost at a higher dose. Blood pressure, on the other hand, is not reduced even with a higher dose.

Is power training effective to produce muscle hypertrophy in older adults? A systematic review and meta-analysis

Power training has been suggested to be effective in improving strength, power, and functional capacity in older adults. However, there is still a lack of systematic investigations reporting its effectiveness for muscle hypertrophy. Thus, this study investigated the effect of power training on muscle hypertrophy and compared its magnitude with traditional moderate-velocity resistance training in older adults. A systematic search was conducted to identify clinical trials investigating the effect of power training on muscle hypertrophy (power training vs. control) and/or comparing the effect of power training versus moderate-velocity resistance training for a meta-analytical approach. Ten studies comparing power training to control conditions and 9 studies comparing power training to moderate-velocity resistance training were selected. Three studies were classified as high quality and 2 were preregistered. The meta-analysis showed that power training was superior for muscle hypertrophy compared with control condition (n = 8 studies; standardised mean difference (SMD) = 0.31; 95% confidence interval (CI) = 0.04, 0.58; p = 0.029), and resulted in similar hypertrophy compared with moderate-velocity resistance training (n = 7 studies; SMD = 0.07; 95% CI = –0.18, 0.32; p = 0.50). No significant heterogeneity was observed (p = 0.46 and 0.54, and I2 = 0% and 0%, respectively). Our data suggest that power training is effective for muscle hypertrophy in older adults, with similar effectiveness as moderate-velocity resistance training. (PROSPERO registration no.: CRD42019128951.)

Novelty It is known that power training might be superior to moderate-velocity resistance training for function improvements in older adults, but there was no meta-analysis investigating its effect on muscle hypertrophy. Power training is effective to induce muscle hypertrophy in older adults to a similar extent as moderate-velocity resistance training.

Neuromuscular determinants of explosive torque: Differences among strength-trained and untrained young and older men

This study compared the differences in neural and muscular mechanisms related to explosive torque in chronically strength-trained young and older men (>5 years). Fifty-four participants were allocated into four groups according to age and strength training level: older untrained (n = 14; 65.6 ± 2.9 years), older trained (n = 12; 63.6 ± 3.8 years), young untrained (n = 14; 26.2 ± 3.7 years), and young trained (n = 14; 26.7 ± 3.4 years). Knee extension isometric voluntary explosive torque (absolute and normalized as a percentage of maximal voluntary torque) was assessed at the beginning of the contraction (ie, 50, 100, and 150 ms-T50, T100, and T150, respectively), and surface electromyogram (sEMG) amplitude (normalized as a percentage of sEMG recorded during maximal voluntary isometric contraction) at 0-50, 50-100, and 100-150 time windows. Supramaximal electrically evoked T50 was assessed with octet trains delivered to the femoral nerve (8 pulses at 300 Hz). Voluntary T50, T100, and T150 were higher for trained than untrained in absolute (P < 0.001) and normalized (P < 0.030) terms, accompanied by higher sEMG at 0-50, 50-100, and 100-150 ms (P < 0.001), and voluntary T50/octet T50 ratio for trained. Greater octet T50 was observed for the young trained (P < 0.001) but not for the older trained (P = 0.273) compared to their untrained counterparts. Age effect was observed for voluntary T50, T100, and T150 (P < 0.050), but normalization removed these differences (P > 0.417). Chronically strength-trained young and older men presented a greater explosive torque than their untrained pairs. In young trained, the greater explosive performance was attributed to enhanced muscular and neural mechanisms, while in older trained to neural mechanisms only.

Effects of a Multimodal Exercise Program Plus Neural Gliding on Postural Control, Pain, and Flexibility of Institutionalized Older Adults: A Randomized, Parallel, and Double-Blind Study

BACKGROUND AND PURPOSE

The effect of adding neural mobilization to a multimodal program of exercises has not been investigated, despite its potential positive effects. The aim of this study was to compare the acute effects of a multimodal exercise program and neural gliding against a multimodal exercise program only, on pain intensity, gait speed, Timed Up and Go (TUG) test, lower limb flexibility, and static balance of institutionalized older adults.

METHODS

Older adults who were institutionalized (n = 26) were randomized to receive a multimodal exercise program plus neural gliding or a multimodal exercise program only. Both interventions were delivered twice a week for 8 weeks. Participants were assessed for pain, gait velocity, balance, flexibility, and TUG at baseline and postintervention.

RESULTS

A significant main effect of time for pain intensity (F1,24 = 8.95, P = .006), balance (F1,24 = 10.29, P = .004), and gait velocity (F1,24 = 5.51, P = .028) was observed, indicating a positive impact of both interventions. No other significant effects were found (TUG and flexibility; P > .05).

DISCUSSION

A 45-minute multimodal exercise program, twice a week for 8 weeks, has a positive impact on pain intensity, balance, and gait velocity, but neural gliding has no additional benefit. It is unclear whether dose and type of neural mobilization may have had an impact on results. Considering the structural and physiological changes that tend to occur with age, future studies could explore the effects of neural tensioning or of higher doses of neural mobilization.

CONCLUSIONS

This study suggests that adding neural gliding to a multimodal exercise program has no additional benefit.

Effects of resistance training concentric velocity on older adults' functional capacity: A systematic review and meta-analysis of randomised trials

Reduced levels of functional capacity in older adults are related to lower quality of life, frailty, and sarcopenia, and can increase risk of falling, fractures and hospitalisation. Resistance training is an effective method to attenuate age-related functional declines. Based on the findings that muscle power and explosive strength are strongly associated with functional performance in older adults, it has been suggested that fast-intended-velocity resistance training may elicit greater improvements in functional capacity when compared to moderate-velocity resistance training. However, currently, there is no high-quality systematic review and meta-analysis supporting this assertion. The present study compared the magnitude of functional capacity improvements following resistance training performed with fast-intentional velocity versus moderate velocity. Pubmed, Scopus, and Web of Science databases were searched from inception to January 2019. The following eligibility criteria for selecting studies was adopted: Participants aged ≥60 years; resistance training based intervention for lower limbs performed solely with slow to moderate concentric velocity (≥2 s for each concentric phase) or solely with the intention of maximising velocity (i.e., as fast as possible); and at least one functional test for lower limbs, with pre- and post-intervention measurements. When studies employed multiple functional tests, a single (pooled) standardised mean difference was calculated and presented as combined functional capacity. In addition, functional tests were grouped accordingly to their specificity for the sub-groups meta-analyses. Fifteen studies were selected (high quality, n = 3; and pre-registered, n = 2). The results presented heterogeneity and small-studies publication bias, leading to a biased advantage for fast-intended-velocity resistance training (95%CI = 0.18, 0.65; I² = 45%). Short physical performance battery indicated an advantage for fast-intended-velocity resistance training (95%CI = 0.10, 0.94; I² = 0%). There was no difference for timed up and go (95%CI = -0.07, 0.94; I² = 48%), 30-s chair stand (95%CI = -0.24, 1.39; I² = 71%), 5-times chair stand (95%CI = -1.63, 1.27; I² = 57%) stair climb (95%CI = -1.89, 2.81; I² = 0%), short walk (95%CI = -0.99, 0.96; I² = 21%) and long walk (95%CI = -0.59, 1.00; I² = 0%). These results suggest that there is inconclusive evidence to support the superiority of fast-intended-velocity resistance training to improve functional capacity when compared to moderate-velocity resistance training. These results may have been influenced by the lack of high-quality and pre-registered studies, high heterogeneity, and small-studies publication bias. PROSPERO REGISTRATION NUMBER: CRD42019122251.