James Mckendry

University of British Columbia | UBC · Food Nutrition & Health | Faculty of Land & Food Systems

The study aim was to comprehensively assess physiological function and muscle morphology in chronically-trained older individuals against untrained young and older individuals. In a cross-sectional design 15 young untrained controls (YC) (20±2.7 y, 78.9±13.3kg), 12 untrained older controls (OC) (69.8±4.1 y, 77.5±14.2kg) and 14 endurance-trained mas...

Background An impaired muscle anabolic response to exercise and protein nutrition is thought to underpin age-related muscle loss, which may be exacerbated by aspects of biological aging that may not be present in older individuals who have undertaken long-term high-level exercise training, or master athletes (MA). The aim of this study was to compa...

Skeletal muscle is the organ of locomotion, its optimal function is critical for athletic performance, and is also important for health due to its contribution to resting metabolic rate and as a site for glucose uptake and storage. Numerous endogenous and exogenous factors influence muscle mass. Much of what is currently known regarding muscle prot...

Decreased skeletal muscle contractile activity (disuse) or unloading leads to muscle mass loss, also known as muscle atrophy. The balance between muscle protein synthesis (MPS) and muscle protein breakdown (MPB) is the primary determinant of skeletal muscle mass. A reduced mechanical load on skeletal muscle is one of the main external factors leadi...

A majority of human genes produce non-protein-coding RNA (ncRNA), and some have roles in development and disease. Neither ncRNA nor human skeletal muscle is ideally studied using short-read sequencing, so we used a customised RNA pipeline and network modelling to study cell-type specific ncRNA responses during muscle growth at scale. We completed f...

A majority of human genes produce non protein-coding RNA (ncRNA) and some have important roles in development and disease. Neither ncRNA nor multinucleated adult human skeletal muscle is ideally studied using sequencing technologies, so using a customised RNA profiling pipeline and quantitative network modelling we studies cell-type specific ncRNA...

The gradual deterioration of physiological systems with ageing makes it difficult to maintain skeletal muscle mass (sarcopenia), at least partly due to the presence of ‘anabolic resistance’, resulting in muscle loss. Sarcopenia can be transiently but markedly accelerated through periods of muscle disuse‐induced (i.e., unloading) atrophy due to redu...

Low energy availability (LEA) describes a state where the energy intake is insufficient to cover the energy costs of both exercise energy expenditure and basal physiological body functions. LEA has been associated with various physiological consequences, such as reproductive dysfunction. However, the effect of LEA on skeletal muscle protein synthes...

Supplementation with Fortetropin® (FOR), a naturally occurring component from fertilized egg yolks, reduces circulating myostatin concentration. We hypothesized that FOR would mitigate muscle atrophy during immobilization. We examined the effect of FOR supplementation on muscle size and strength during 2-wk of single-leg immobilization and recovery...

Background: Ageing is associated with alterations to skeletal muscle oxidative metabolism that may be influenced by physical activity status, although the mechanisms underlying these changes have not been unraveled. Similarly, the effect of resistance exercise training (RET) on skeletal muscle mitochondrial regulation is unclear. Methods: Seven end...

Leucine is a critical amino acid stimulating myofibrillar protein synthesis (MyoPS). The consumption of higher leucine-containing drinks stimulates MyoPS, but we know less about higher leucine solid foods. Here, we examined the effect of short-term resistance exercise training (STRT) combined with supplementation of a protein and leucine-enriched b...

Skeletal muscle is essential in locomotion and plays a role in whole-body metabolism, particularly during exercise. Skeletal muscle is the largest ‘reservoir’ of amino acids, which can be released for fuel and as a precursor for gluconeogenesis. During exercise, whole-body, and more specifically skeletal muscle, protein catabolism is increased, but...

We evaluated the effects of higher-load (HL) versus (lower-load) higher-volume (HV) resistance training on skeletal muscle hypertrophy, strength, and muscle-level molecular adaptations. Trained men (n = 15, age: 23 ± 3 years; training experience: 7 ± 3 years) performed unilateral lower-body training for 6 weeks (3× weekly), where single legs were r...

Background: The stimulation of muscle protein synthesis (MPS) by dietary protein is reduced with age. We hypothesized that twice-daily milk consumption would increase daily rates of MPS in older women relative to a non-dairy milk alternative and that MPS would be enhanced by increased physical activity (PA). Methods: Twenty-two older women were...

Skeletal muscle adaptations to resistance and endurance training include increased ribosome and mitochondrial biogenesis, respectively. Such adaptations are believed to contribute to the notable increases in hypertrophy and aerobic capacity observed with each exercise mode. Data from multiple studies suggest the existence of a competition between r...

Aim We evaluated the effects of higher-load (HL) versus (lower-load) higher-volume (HV) resistance training on skeletal muscle hypertrophy, strength, and muscle-level molecular markers. Methods Trained men (n=15, age: 23±3 y; training experience: 7±3 y) performed unilateral lower body training for 6 weeks (3x weekly), where single legs were assign...

The impact of resistance exercise frequency on muscle protein synthesis rates remains unknown. The aim of this study was to compare daily myofibrillar protein synthesis rates over a 7-day period of low-frequency (LF) versus high-frequency (HF) resistance exercise training. Nine young men (21 ± 2 years) completed a 7-day period of habitual physical...

The authors would like to correct an omission in a published paper [...]

Skeletal muscle is the largest organ of the human body and plays a pivotal role in whole-body homeostasis through the maintenance of physical and metabolic health. Establishing strategies aimed at increasing the amount, and minimising loss, of muscle mass are of upmost importance. Muscle mass is primarily dictated by the meal-to-meal fluctuations i...

Background: Unavoidable periods of disuse lead to muscle atrophy and functional decline. Preventing such declines can reduce the risk of re-injury and improve recovery of normal physiological functioning. Objectives: We aimed to determine the effectiveness of high-dose leucine supplementation on muscle morphology and strength during 7 d of unila...

Skeletal muscle plays an indispensable role in metabolic health and physical function. A decrease in muscle mass and function with advancing age exacerbates the likelihood of mobility impairments, disease development, and early mortality. Therefore, the development of non-pharmacological interventions to counteract sarcopenia warrant significant at...

Skeletal muscle plays a critical role in everyday life, and its age‐associated reduction has severe health consequences. The pre‐existing presence of sarcopenia, combined with anabolic resistance, protein undernutrition, and the pro‐catabolic/anti‐anabolic milieu induced by aging and exacerbated in critical care, may accelerate the rate at which sk...

The role of dysregulated intracellular creatine metabolism in disuse atrophy is unknown. In this study, skeletal muscle biopsy samples were obtained after 7-days of unilateral leg immobilization (IMMOB) and the non-immobilized control limb (CTRL) of 15 healthy males (23.1 ± 3.5 yrs). Samples were analyzed for fibre-type cross-sectional area (CSA) a...

Purpose: Compression garments are widely used as a tool to accelerate recovery from intense exercise and have also gained traction as a performance aid, particularly during periods of limited recovery. This study tested the hypothesis that increased pressure levels applied via high-pressure compression garments would enhance "multiday" exercise pe...

Skeletal muscle plays a pivotal role in the maintenance of physical and metabolic health and, critically, mobility. Accordingly, strategies focused on increasing the quality and quantity of skeletal muscle are relevant, and resistance exercise is foundational to the process of functional hypertrophy. Much of our current understanding of skeletal mu...

Purpose: A linear dose-response relationship between resistance training (RT) volume and hypertrophy/strength has been proposed when ≤10-12 weekly sets are implemented. The present study aimed to understand the impact of low-to-high weekly RT volume on muscular adaptations in trained young males over 6-weeks of RT. Methods: RT-experienced males...

Background: Age-related muscle loss (sarcopenia) may be driven by a diminished myofibrillar protein synthesis (MyoPS) response to anabolic stimuli (i.e. exercise and nutrition). Oral phosphatidic acid (PA) ingestion has been reported to stimulate resting muscle protein synthesis in rodents, and enhance resistance training-induced muscle remodellin...

Introduction: The extent to which chronic exercise training preserves age-related decrements in physical function, muscle strength, mass and morphology is unclear. Our aim was to conduct a systematic review of the literature to determine to what extent chronically trained master athletes (strength/power and endurance) preserve levels of physical f...

Context A diminished muscle anabolic response to protein nutrition may underpin age-associated muscle loss. Objective To determine how chronological and biological ageing influence myofibrillar protein synthesis (MyoPS). Design Cross-sectional comparison. Setting Clinical Research Facility. Participants Ten older lean (OL: 71.7 ± 6 yrs; ≤25 kg⋅...

Although the signal pathways mediating muscle protein synthesis and degradation are well characterized, the transcriptional processes modulating skeletal muscle mass and adaptive growth are poorly understood. Recently, studies in mouse models of muscle wasting or acutely exercised human muscle have suggested a potential role for the transcription f...

In vitro and in vivo studies described the myokine IL-15 and its receptor IL-15Rα as anabolic/anti-atrophy agents, however the protein expression of IL-15Rα has not been measured in human skeletal muscle and data regarding IL-15 expression remain inconclusive. The purpose of the study was to determine serum and skeletal muscle IL-15 and IL-15Rα res...

Background: Manipulating rest-recovery interval between sets of resistance exercise may influence training-induced muscle remodeling. The aim of this study was to determine the acute muscle anabolic response to resistance exercise performed with short or long inter-set rest intervals. Methods: In a parallel-group designed study, 16 males complet...

Resistance exercise contractile variables can be manipulated to en- hance the muscle morphological response. Reducing the duration of rest-recovery taken between sets of resistance exercise (≤1 min) influ- ences systemic concentrations of hormones thought to be critical for muscle hypertrophy. However, local mechanisms activated through the mechani...