Sam O Shepherd

Sam O Shepherd
Liverpool John Moores University | LJMU · Research Institute for Sport and Exercise Sciences (RISES)

BSc MSc PhD

About

95
Publications
22,405
Reads
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1,892
Citations
Education
September 2008 - July 2012
University of Birmingham
Field of study
  • Exercise Metabolism
September 2007 - August 2008
University of Aberdeen
Field of study
  • Human Nutrition & Metabolism
September 2004 - July 2007
University of Birmingham
Field of study
  • Sport & Exercise Sciences

Publications

Publications (95)
Article
Full-text available
We investigated in vivo whether 20 candidate single nucleotide polymorphisms (SNPs) were associated with in vivo exercise-induced muscle damage (EIMD), and with an in vitro skeletal muscle stem cell wound healing assay. Sixty-five young, untrained Caucasian adults performed 120 maximal eccentric knee-extensions on an isokinetic dynamometer to induc...
Article
Large intramuscular triglyceride (IMTG) stores in sedentary, obese individuals have been linked to insulin resistance, yet well-trained athletes exhibit high IMTG levels whilst maintaining insulin sensitivity. Contrary to previous assumptions, it is now known that IMTG content per se does not result in insulin resistance. Rather, insulin resistance...
Article
Full-text available
Exercise referral schemes (ERS) are used to promote physical activity within primary care. Traditionally, ERS are conducted in a gym or leisure-center setting, with exercise prescriptions based on moderate-intensity continuous training (MICT). Home-based high-intensity interval training (Home-HIIT) has the potential to reduce perceived barriers to...
Article
Full-text available
Objective High intensity interval training (HIIT) is a time-efficient exercise modality to improve cardiorespiratory fitness, and has recently been popularised by social media influencers. However, little is known regarding acute physiological and perceptual responses to these online protocols compared to HIIT protocols used within research. The ai...
Article
Full-text available
Hamstring muscle injury is highly prevalent in sports involving repeated maximal sprinting. Although neuromuscular fatigue is thought to be a risk factor, the mechanisms underlying the fatigue response to repeated maximal sprints are unclear. Here, we show that repeated maximal sprints induce neuromuscular fatigue accompanied with a prolonged stren...
Article
Full-text available
Impaired postprandial glucose handling and low-grade systemic inflammation are risk factors for developing insulin resistance in individuals with overweight or obesity. Acute ingestion of anthocyanins improves postprandial glucose responses to a single carbohydrate-rich meal under strictly controlled conditions. Purpose: Examine whether acute and...
Article
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Purpose High-fat, high-calorie (HFHC) diets have been used as a model to investigate lipid-induced insulin resistance. Short-term HFHC diets reduce insulin sensitivity in young healthy males, but to date, no study has directly compared males and females to elucidate sex-specific differences in the effects of a HFHC diet on functional metabolic and...
Article
Key points: Muscle glycogen and intramuscular triglycerides (IMTG, stored in lipid droplets) are important energy substrates during prolonged exercise. Exercise-induced changes in lipid droplet (LD) morphology (i.e., LD size and number) has not yet been studied under nutritional conditions typically adopted by elite endurance athletes, that is, af...
Article
Full-text available
The methylome and transcriptome signatures following exercise that are physiologically and metabolically relevant to sporting contexts such as team sports or health prescription scenarios (e.g., high intensity interval training/HIIT) has not been investigated. To explore this, we performed two different sport/exercise relevant high-intensity runnin...
Article
Objective: To pilot a multi-component intervention to sit less and move more, with (SLAMM+) and without (SLAMM) height-adjustable workstations, in contact centre call agents. Methods: Agents were individually randomised to SLAMM or SLAMM+ in this 10-month, parallel, open-label, pilot trial. Mixed-methods assessed response, recruitment, retention...
Article
Full-text available
Despite over 50 years of research, a comprehensive understanding of how intramuscular triglyceride (IMTG) is stored in skeletal muscle and its contribution as a fuel during exercise is lacking. Immunohistochemical techniques provide information on IMTG content and lipid droplet (LD) morphology on a fibre type and subcellular-specific basis, and the...
Preprint
The methylome and transcriptome signature following exercise that is physiologically and metabolic relevant to sporting contexts such as team sports or health prescription scenarios (e.g. high intensity interval training/HIIT) has not been investigated. To explore this, we undertook two different sport/exercise relevant high-intensity sprint runnin...
Article
Full-text available
We investigated whether diurnal differences in muscle force output are associated with the post-translational state of muscle proteins. Ten physically active men (mean ± SD; age 26.7 ± 3.7 y) performed experimental sessions in the morning (08:00 h) and evening (17:00 h), which were counterbalanced in order of administration and separated by at leas...
Article
Full-text available
New findings: What is the central question of this study? What is the absolute level of pre-exercise glycogen concentration required to augment the exercise-induced signalling response regulating mitochondrial biogenesis? What is the main finding and its importance? Commencing high-intensity endurance exercise with reduced pre-exercise muscle glyc...
Article
Full-text available
Objectives: This is a protocol for a Cochrane Review (intervention). The objectives are as follows:. To assess the effects of high-intensity interval training on cardiometabolic health in healthy, sedentary adults. Copyright © 2020 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Article
Purpose: To quantify net glycogen utilisation in the vastus lateralis (VL) and gastrocnemius (G) of male (n=11) and female (n=10) recreationally active runners during three outdoor training sessions. Methods: After 2 days standardisation of carbohydrate (CHO) intakes (6 g.kg body mass per day), glycogen was assessed before and after 1) a 10-mile...
Article
Key points: We have recently shown that a high-fat high-calorie (HFHC) diet decreases whole body glucose clearance without impairing skeletal muscle insulin signalling, in healthy lean individuals. These diets are also known to increase skeletal muscle IMTG stores, but the effect on lipid metabolites leading to skeletal muscle insulin resistance h...
Article
Intramuscular triglycerides (IMTG) are a key substrate during prolonged exercise, but little is known about the rate of IMTG resynthesis in the post-exercise period. We investigated the hypothesis that the distribution of the lipid droplet (LD)-associated perilipin (PLIN) proteins is linked to IMTG storage following exercise. 14 elite male triathle...
Article
Full-text available
Background Although major improvements are achieved after cure of Cushing’s syndrome (CS), fatigue and decreased quality of life persist. This is the first study to measure aerobic exercise capacity in patients in remission of CS for >4 years in comparison with matched controls, and investigate whether the reduction in exercise capacity is related...
Article
New findings: •This symposium review provides an overview of the recent work investigating whether a virtually monitored home-based HIT (Home-HIT) intervention reduces the fear of hypoglycaemia and other common exercise barriers in people with type 1 diabetes. •Home-HIT seems to offer a strategy to reduce fear of hypoglycaemia, while simultaneousl...
Article
We investigated the repeatability of dynamic proteome profiling (DPP), which is a novel technique for measuring the relative abundance (ABD) and fractional synthesis rate (FSR) of proteins in humans. LC‐MS analysis was performed on muscle samples taken from male participants (n = 4) that consumed 4 × 50 ml doses of deuterium oxide (2H2O) per day fo...
Article
Objective: Adopt a multidisciplinary approach to evaluate a virtually supervised home-based high-intensity interval training (Home-HIT) intervention in people with type 1 diabetes. Research design and methods: Eleven individuals with type 1 diabetes (seven women; age 30 ± 3 years; VO2peak 2.5 ± 0.2 L/min; duration of diabetes 10 ± 2 years) compl...
Article
Context The mechanisms responsible for dietary fat-induced insulin resistance of skeletal muscle and its microvasculature are only partially understood. Objective To determine the impact of high-fat overfeeding on postprandial glucose fluxes, muscle insulin signaling, and muscle microvascular eNOS content and activation. Design Fifteen non-obese...
Preprint
Full-text available
Hamstring muscle injury is highly prevalent in sports involving repeated maximal sprinting. Although neuromuscular fatigue is thought to be a risk factor, the mechanisms underlying the fatigue response to repeated maximal sprints are unclear. Here, we show that repeated maximal sprints induce neuromuscular fatigue accompanied with a prolonged stren...
Article
Full-text available
Key points: Reduced carbohydrate (CHO) availability before and after exercise may augment endurance training-induced adaptations of human skeletal muscle, as mediated via modulation of cell signalling pathways. However, it is not known whether such responses are mediated by CHO restriction, energy restriction or a combination of both. In recovery...
Article
Full-text available
Key points: Obesity and sedentary behaviour are associated with capillary rarefaction and impaired muscle microvascular vasoreactivity, due to reduced nitric oxide bioavailability. Low-volume high-intensity interval training (HIT) is a time-efficient alternative to traditional moderate-intensity continuous training (MICT), but its effect on the mu...
Article
Full-text available
Purpose: To examine the validity of ultrasound (via cloud based software that measures pixilation intensity according to a scale of 0-100) to non-invasively assess muscle glycogen in human skeletal muscle. Methods: In Study 1, 14 professional male rugby league players competed in an 80-minute competitive rugby league game. In Study 2 (in a rando...
Article
Passive heat therapy (PHT) has been proposed as an alternative intervention to traditional moderate intensity continous training (MICT) in individuals who are unable or unwilling to exercise. This study aimed to make the first comparison of the effect of PHT and MICT on 1) skeletal muscle capillarisation and endothelial specific eNOS content and 2)...
Article
Full-text available
Background Call agents spend ~ 90% of their working day seated, which may negatively impact health, productivity, and wellbeing. This study aimed to explore the acceptability and feasibility of a multi-component workplace intervention targeting increased activity and decreased prolonged sitting in the contact centre setting prior to a full-scale ef...
Article
Full-text available
DNA methylation is an important epigenetic modification that can regulate gene expression following environmental encounters without changes to the genetic code. Using Infinium MethylationEPIC BeadChip Arrays (850,000 CpG sites) we analysed for the first time, DNA isolated from untrained human skeletal muscle biopsies (vastus lateralis) at baseline...
Article
AIMS To investigate whether 1) six weeks of high-intensity interval training (HIT) induces similar improvements in cardio-metabolic health markers as moderate-intensity continuous training (MICT) in people with type 1 diabetes, and 2) whether HIT abolishes acute reductions in plasma glucose observed following MICT sessions. METHODS Fourteen sedent...
Article
Objective High-fat high-calorie diets can induce whole body insulin resistance (IR) whilst increasing stores of intramuscular triglyceride (IMTG) contained within lipid droplets (LD). Perilipin (PLIN) proteins assist in IMTG storage. Synaptosomal-associated protein (SNAP23) may support LD growth and also direct IMTG-derived fatty acids (FA) to mito...
Conference Paper
Objective Obesity and inactivity lead to structural and functional muscle microvascular impairments associated with development of chronic disease. This study is the first to investigate the effect of a novel home-based high-intensity interval training (HIT) (Home-HT) intervention in obese individuals with elevated cardiovascular disease (CVD) risk...
Conference Paper
Objective Currently 40% of the UK do not meet the physical activity guidelines with a ‘lack of time’ the most commonly cited barrier to sufficient physical activity. In laboratory based training interventions, high intensity interval training (HIT) offers a time-efficient alternative to moderate intensity continuous training (MICT) but its success...
Article
Aims To compare the effect of a bout of high-intensity interval training (HIT) with a bout of moderate-intensity continuous training (MICT) on glucose concentrations over the subsequent 24h period. METHODS Fourteen people with type 1 diabetes (duration of type 1 diabetes 8.2±1.4 years), all on basal-bolus regimen, completed a randomised, counterba...
Article
Full-text available
Contact centre call agents are highly sedentary at work, which can negatively affect cardio-metabolic health. This qualitative cross-sectional study explored factors influencing call agents’ workplace physical activity (PA) and sedentary behaviour (SB), and perspectives on strategies to help agents move more and sit less at work. Semi-structured in...
Conference Paper
Full-text available
RESTRICTING CARBOHYDRATE DURING RECOVERY FROM PROLONGED EXERCISE DOES NOT EFFECT INTRAMUSCULAR TRIGLYCERIDE RESYNTHESIS. JEVONS, E.F.P.1, GEJL, K.D.2, HVID, L.G.2, FRANDSEN, U.2, JENSEN, K.2, SAHLIN, K.2, STRAUSS, J.A.1, ORTENBLAD, N.2, SHEPHERD, S.O.1 LIVERPOOL JOHN MOORES UNIVERSITY INTRODUCTION: Intramuscular triglycerides are an important sub...
Article
Full-text available
Purpose: New Zealand blackcurrant (NZBC) extract has previously been shown to increase fat oxidation during prolonged exercise, but this observation is limited to males. We examined whether NZBC intake also increases fat oxidation during prolonged exercise in females, and whether this was related to greater concentrations of circulating fatty acid...
Article
We examined the effects of whey versus collagen protein on skeletal muscle cell signalling responses associated with mitochondrial biogenesis and protein synthesis in recovery from an acute training session completed with low carbohydrate (CHO) availability. In a repeated measures design (after adhering to a 36-h exercise-dietary intervention to st...
Article
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Key points: Hormone-sensitive lipase (HSL) and adipose triglyceride lipase (ATGL) are the key enzymes involved in intramuscular triglyceride (IMTG) lipolysis. In isolated rat skeletal muscle, HSL translocates to IMTG-containing lipid droplets (LDs) following electrical stimulation, but whether HSL translocation occurs in human skeletal muscle duri...
Article
Using guidance from the reach, efficacy, adoption, implementation, and maintenance evaluation framework, we aimed to qualitatively evaluate the participant experiences of a workplace high-intensity interval training (HIIT) intervention. Twelve previously insufficiently active individuals (four males and eight females) were interviewed once as part...
Article
Full-text available
It is unknown if adult human skeletal muscle has an epigenetic memory of earlier encounters with growth. We report, for the first time in humans, genome-wide DNA methylation (850,000 CpGs) and gene expression analysis after muscle hypertrophy (loading), return of muscle mass to baseline (unloading), followed by later hypertrophy (reloading). We dis...
Article
Full-text available
We performed a systematic review and meta-analysis of proteomics literature that reports human skeletal muscle responses in the context of either pathological decline associated with obesity/T2DM and physiological adaptations to exercise training. Literature was collected from PubMed and DOAJ databases following PRISMA guidelines using the search t...
Article
Full-text available
Intramuscular triglyceride (IMTG) only accounts for a small proportion of total lipid in the human body. However, over the past two decades there has been significant interest in the area of IMTG metabolism, largely due to the contribution that IMTG makes to ATP production during moderate-intensity exercise, and the proposed role of IMTG in the dev...
Article
Background: In obesity, improved muscle insulin sensitivity following exercise training has been linked to the lowering of diacylglycerol (DAG) and ceramide concentrations. Little is known, however, about how improved insulin action with exercise training in obese individuals relates to lipid droplet (LD) adaptations in skeletal muscle. In this st...
Article
Full-text available
Neutrophils and monocytes are key components of the innate immune system that undergo age-associated declines in function. This study compared the impact of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on immune function in sedentary adults. Twenty-seven (43 ± 11 years) healthy sedentary adults were rand...