Tom Clifford

Loughborough University | Lough · School of Sport, Exercise and Health Sciences

Purpose The primary aim of this study was to examine whether a glycine-rich collagen peptides (CP) supplement could enhance sleep quality in physically active men with self-reported sleep complaints. Methods In a randomized, crossover design, 13 athletic males (age: 24 ± 4 years; training volume; 7 ± 3 h·wk ¹ ) with sleep complaints (Athens Insomn...

Introduction: Cannabidiol (CBD) is a nonintoxicating phytocannabinoid used in clinical treatments and sold widely in consumer products. CBD products may be designed for sublingual or oral delivery, but it is unclear whether either is advantageous for CBD absorption. This study compared CBD pharmacokinetics after providing CBD oil as sublingual drop...

Background: Cannabidiol (CBD)-containing products are sold widely in consumer stores, but concerns have been raised regarding their quality, with notable discrepancies between advertised and actual CBD content. Information is limited regarding how different types of CBD products may differ in their deviation from advertised CBD concentrations. The...

Purpose This study investigated whether combining eccentric exercise and green tea supplementation synergistically increased nuclear factor erythroid 2-related factor 2 (NRF2) activity, a transcription factor responsible for coordinating endogenous antioxidant expression. Methods In a double-blinded, randomized, between-subjects design, 24 males (...

Athletes are increasingly consuming (poly)phenol supplements to modify oxidative stress and/or exercise-induced inflammation, in the hope that this will enhance exercise performance. Chokeberries are rich in (poly)phenols and may therefore influence the health and performance of athletes. The objective of this systematic review was to comprehensive...

Inorganic nitrate (NO3−) has emerged as a potential ergogenic aid over the last couple of decades. While recent systematic reviews and meta-analyses have suggested some small positive effects of NO3− supplementation on performance across a range of exercise tasks, the effect of NO3− supplementation on performance during single and repeated bouts of...

This systematic review and meta-analysis investigated the influence of dietary nitrate supplementation on resistance exercise performance according to the PRISMA guidelines. Searches were conducted on MEDLINE, PubMed, ScienceDirect, Scopus and SPORTDiscus databases up to April 2023. Inclusion criteria were adult resistance-trained males who supplem...

Introduction: Extreme endurance events may result in numerous adverse metabolic, immunologic, and physiological perturbations that may diminish athletic performance and adversely affect the overall health status of an athlete, especially in the absence of sufficient recovery. A comprehensive understanding of the post-marathon recovering metabolome,...

Purpose: To examine the effects of acute curcumin (CURC) supplementation on recovery from a soccer match in male professional players. Methods: In a randomized, placebo-controlled, crossover design, 11 players from the under-23 team of an English Premier League club (age 19 [1] y, body mass 79.4 [7.9] kg, height 180.8 [5.7] cm) consumed 500 mg o...

Background There are few community-based lifestyle interventions designed to target physical and mental health of men. We conducted a qualitative focus group study with men to explore their perceived barriers and facilitators to uptake and engagement with interventions designed to improve their physical and mental health and wellbeing. Methods A v...

Purpose We examined the effects of collagen peptides (CP) supplementation on exercise-induced gastrointestinal (GI) stress. Methods In a randomized, crossover design, 20 volunteers (16 males: $$\dot{V}$$ V ˙ O 2max , 53.4 ± 5.9 ml·kg ⁻¹ ) completed 3 trials: a non-exercise rest trial, with no supplement (REST) and then an exercise trial with CP (1...

Penile cancer is a rare but debilitating condition, which often requires aggressive treatment. Partial penectomy is considered as a treatment option when a sufficient portion of the penile shaft can be maintained to preserve functionality. This systematic review, which followed the PRIMSA guidelines, aimed to evaluate the effects of partial penecto...

This study examined sweat rate, sweat sodium concentration [Na+], and ad-libitum carbohydrate and fluid intakes in elite female soccer players during training (n = 19) and a match (n = 8); eight completed both for comparisons. Body mass (kg) was obtained before and after exercise to calculate sweat rate. The sweat [Na+] was determined from absorben...

Aging is associated with a decline in physiological function and exercise performance. These effects are mediated, at least in part, by an age-related decrease in the bioavailability of nitric oxide (NO), a ubiquitous gasotransmitter and regulator of myriad physiological processes. The decrease in NO bioavailability with aging is especially apparen...

Abbott, W, Thomas, C, and Clifford, T. Effect of playing status and fixture congestion on training load, mental fatigue, and recovery status in Premier League academy goalkeepers. J Strength Cond Res XX(X): 000-000, 2022-Soccer goalkeepers are a unique playing position and require specific programming. Despite this, there is a paucity of informatio...

Introduction Dietary inorganic nitrate is a popular nutritional supplement, which increases nitric oxide bioavailability and may improve exercise performance. Despite over a decade of research into the effects of dietary nitrate supplementation during exercise there is currently no expert consensus on how, when and for whom this compound could be r...

Beetroot is a rich source of nitrate (NO 3 -) that has been shown to reduce blood pressure (BP). Yet, no studies have examined the vascular benefits of beetroot in whole-food form and whether the effects are modified by age. This study was a four-arm, randomised, open-label, crossover design in 24 healthy adults (young n=12, age 27±4 years, old n=1...

This systematic review analyzed whether carbohydrate source (food vs. supplement) influenced performance and gastrointestinal (GI) symptoms during endurance exercise. Medline, SPORTDiscus, and citations were searched from inception to July 2021. Inclusion criteria were healthy, active males and females aged >18 years, investigating endurance perfor...

This systematic review examined the effects of whole protein and commonly consumed amino acid supplements on markers of exercise-induced inflammation and oxidative stress and was reported according to the PRISMA guidelines. MEDLINE and SPORTDiscus were searched from inception until June 2021. The inclusion criteria were randomized clinical trials i...

Background Red beetroot ( Beta vulgaris L. ) is a multifunctional functional food that reportedly exhibits potent anti-inflammatory, antioxidant, vasodilation, and cellular regulatory properties. This vegetable has gained a fair amount of scientific attention as a possible cost-effective supplement to enhance performance and expedite recovery after...

Background: Well-developed physical qualities may protect athletes from exercise-induced muscle damage and accelerate recovery following exercise. This study examined the influence of muscle strength and aerobic fitness on recovery from competitive soccer matches. Methods: Fourteen players from the English Premier League 2 (Age, 18 ± 1 yrs; heig...

Background Dietary nitrate consumption can increase concentrations of nitrate and nitrite in blood, saliva and urine. Whether the change in concentrations is influenced by age is currently unknown. Objective Measure changes in nitrate and nitrite concentrations in plasma, urine, saliva and exhaled nitric oxide (NO) concentrations following single...

Collagen peptide supplementation (COL), in conjunction with exercise, may be beneficial for the management of degenerative bone and joint disorders. This is likely due to stimulatory effects of COL and exercise on the extracellular matrix of connective tissues, improving structure and load-bearing capabilities. This systematic review aims to evalua...

Although physical activity is a health-promoting, popular global pastime, regular engagement in strenuous exercises, such as long-distance endurance running races, has been associated with a variety of detrimental physiological and immunological health effects. The resulting altered physiological state has previously been associated with fluctuatio...

Nutrition plays a key role in training for, and competing in, competitive sport, and is essential for reducing risk of injury and illness, recovering and adapting between bouts of activity, and enhancing performance. Consumption of a Mediterranean diet (MedDiet) has been demonstrated to reduce risk of various non-communicable diseases and increase...

Exercise-induced muscle damage (EIMD) is associated with oxidative stress and inflammation, muscle soreness, and reductions in muscle function. Cocoa flavanols (CF) are (poly)phenols with antioxidant and anti-inflammatory effects and thus may attenuate symptoms of EIMD. The purpose of this narrative review was to collate and evaluate the current li...

Purpose: The extra-time (ET) period of soccer is competed during fixture congested schedules with often limited recovery time between matches. The aim of this study was to assess muscle damage recovery following 90- and 120-min (i.e., incorporation of ET) of simulated soccer match-play. Methods: Twelve semi-professional soccer players completed 90...

The current investigation examined professional academy soccer players' perceived experiences of loan environments, compared to their previous academy experiences. Fifteen professional soccer players completed season-long loans at various European soccer clubs. Individual semi-structured interviews were conducted following the loans to determine th...

This systematic review and meta-analysis of randomized controlled trials examined whether dietary nitrate supplementation attenuates exercise-induced muscle damage (EIMD) and is reported according to the PRISMA guidelines. Medline and SPORTDiscus databases were searched from inception to June 2020. Inclusion criteria were studies in adult humans co...

Background Dietary inorganic nitrate (NO 3 ⁻ ) is a polyatomic ion, which is present in large quantities in green leafy vegetables and beetroot, and has attracted considerable attention in recent years as a potential health-promoting dietary compound. Numerous small, well-controlled laboratory studies have reported beneficial health effects of inor...

PurposeTo examine the prevalence of disordered eating (DE) in elite male and female soccer players and the influence of perfectionism.Methods Using a cross-sectional design, elite male (n = 137) and female (n = 70) soccer players and non-athlete controls (n = 179) completed the clinical perfectionism questionnaire (CPQ-12) and the eating attitudes...

This systematic review and meta-analysis examined the effects of creatine supplementation on recovery from exercise-induced muscle damage, and is reported according to the PRISMA guidelines. MEDLINE and SPORTDiscus were searched for articles from inception until April 2020. Inclusion criteria were adult participants (≥18 years); creatine provided b...

We conducted a systematic review of human trials examining the effects of dietary phytochemicals on Nrf2 activation. In accordance with the PRISMA guidelines, Medline, Embase and CAB abstracts were searched for articles from inception until March 2020. Studies in adult humans that measured Nrf2 activation (gene or protein expression changes) follow...

We performed a systematic review and meta-analysis to determine whether (poly)phenol supplementation augments the physiological adaptations to exercise training. Eligible studies administered a (poly)phenol supplement alongside ≥2 weeks of supervised exercise in adult humans. After screening, 22 studies were included in the analysis. Isoflavones an...

Aims This study investigated the efficacy of l-menthol mouth-rinsing on thermal sensation and perceived effort in females and males, using a fixed-rating of perceived exertion (RPE) exercise protocol in a hot environment. Methods Twenty-two participants (eleven females, eleven males) completed two trials using a fixed-RPE protocol at an exercise i...

Purpose: To investigate the cognitive, physical, and perceptual effects of sleep restriction (SR) in soccer players following a night match. Methods: In a crossover design, nine male soccer players from the English Premier League 2 (age, 21 ± 5 years; height, 1.80 ± 0.75 m; body mass, 74.2 ± 6.8 kg) recorded their sleep quality and quantity with sl...

Purpose: This study examined whether a higher protein diet following strenuous exercise can alter markers of muscle damage and inflammation in older adults. Methods: Using a double-blind, independent group design, 10 males and eight females (age 57 ± 4 years; mass 72.3 ± 5.6 kg; height 1.7 ± 6.5 m) were supplied with a higher protein (2.50 g·kg-...

Background Chronic wounds continue to be a burden to healthcare systems with ageing linked to increased prevalence of chronic wound development. Nutraceutical collagen peptides have been shown to reduce signs of skin ageing, but there therapeutic potential for cutaneous wound healing remains undefined Aims To determine the potential for nutraceuti...

Polyphenol consumption has become a popular method of trying to temper muscle damage. Cocoa flavanols (CF) have attracted attention due to their high polyphenol content and palatability. As such, this study will investigate whether an acute dose of CF can aid recovery following exercise-induced muscle damage. The study was a laboratory-based, rando...

Endurance athlete performance is greatly dependent on sufficient post-race system recovery, as endurance races have substantial physiological, immunological and metabolic effects on these athletes. To date, the effects of numerous recovery modalities have been investigated, however, very limited literature exists pertaining to metabolic recovery of...

The present study assessed changes in academy soccer players' perception of mental fatigue (MF) across a competitive season, investigating the relationship between MF and other subjective measures of wellness. Ten players completed a modified Brief Assessment of Mood (BAM+) questionnaire that included the question: "How mentally fatigued do you fee...

We conducted a systematic review and meta-analysis of randomized controlled trials examining the effect of vitamin C and/or E on exercise-induced training adaptations. Medline, Embase and SPORTDiscus databases were searched for articles from inception until June 2019. Inclusion criteria was studies in adult humans where vitamin C and/or E had to be...

Cancer-related fatigue (CRF) is a debilitating adverse effect among children with cancer and a significant barrier to physical activity (PA) participation. PA interventions are effective at reducing fatigue and improving both quality of life (QOL) and functional outcomes in children with cancer. However, 50–70% of children with cancer do not meet P...

Purpose The aim of this study was to investigate amateur runners’ knowledge and practices of the current sports nutrition guidelines for pre and post-event carbohydrate (CHO) and protein (PRO) intakes. Methods Data was collected from 100 amateur runners using an online survey. Participants provided demographic information, a dietary recall of thei...

Purpose: To investigate the effects of tart cherry juice (TCJ) on recovery from a soccer match in professional players. Methods: In a double-blind, placebo-controlled, crossover design, 10 male professional soccer players from the reserve team of an English Premier League Club (age 19 ± 1 y, height 1.8 ± 0.6 m, body mass 77.3 ± 6.4 kg) consumed...

Purpose Orthorexia nervosa (ON) is a pattern of eating characterized by a pathological fixation on restricting foods based on their perceived health. Like many eating disorders, ON is thought to be more prevalent in athletes. This was a preliminary study to explore the prevalence of ON in University students to determine whether those who compete i...

This study examined the effects of sour tart cherry juice (TC) on muscle soreness (MS) and wellbeing following a rugby union match in professional players. In a crossover design, 10 players from a senior squad in the top tier of England consumed either 2 × 30 mL servings of TC or an isocaloric cherry-flavoured control gel (CON) two days before, the...

This study examined the influence of injury, match selection and training load on mental wellbeing (MW) in a squad of professional soccer players. Using a longitudinal design, twenty-five male soccer players (age, 20 ± 1 years, height, 1.80 ± 5.79 m, body mass 76.33 ± 7.52 kg) from the under 23 squad playing in the Premier League 2 division in the...

This study examined whether consuming collagen peptides (CP) before and after strenuous exercise alters markers of muscle damage, inflammation and bone turnover. Using a double-blind, independent group’s design, 24 recreationally active males consumed either 20 g day⁻¹ of CP or a placebo control (CON) for 7 days before and 2 days after performing 1...

Exercise-induced muscle damage (EIMD) manifests as muscle soreness, inflammation, and reductions in force generating capacity that can last for several days after exercise. The ability to recover and repair damaged tissues following EIMD is impaired with age, with older adults (≥50 years old) experiencing a slower rate of recovery than their younge...

This study examined whether consuming collagen peptides (CP) before and after strenuous exercise alters markers of muscle damage, inflammation and bone turnover. Using a double-blind, independent group's design, 24 recreationally active males consumed either 20 g day −1 of CP or a placebo control (CON) for 7 days before and 2 days after performing...

This study examined whether consuming casein protein (CP) pre-sleep could accelerate acute recovery following muscle-damaging exercise. Thirty-nine active males and females performed 100 drop jumps in the morning, consumed their habitual diet during the day, and then within 30 min pre-bed consumed either ~40 g of CP (n = 19) or ~40 g of a carbohydr...

Recent research suggests a high prevalence of mental health disorders in professional soccer players, including symptoms of anxiety, depression, distress and adverse eating behaviours. Whilst a limited number of studies address this issue, the existing evidence is alarming and highlights a need for further investigations to develop a better underst...

Introduction Endurance races have been associated with a substantial amount of adverse effects which could lead to chronic disease and long-term performance impairment. However, little is known about the holistic metabolic changes occurring within the serum metabolome of athletes after the completion of a marathon. Objectives Considering this, the...

Purpose: This study examined whether consuming casein protein (CP) before sleep would enhance recovery after a night-time soccer match in professional players. Methods: In a randomized, crossover design, ten professional soccer players from the reserve squad of a team in the highest tier of English soccer consumed 40 g of CP or 40 g of carbohydr...

Purpose: The purpose of this study was to assess the utility of an inertial sensor for assessing recovery in professional soccer players. Methods: In a randomized, crossover design, 11 professional soccer players wore shorts fitted with phase change material (PCM) cooling packs or uncooled packs (control) for 3 h after a 90 minute match. Counter...

We conducted a systematic review and meta-analysis of randomized clinical trials examining the effect of inorganic nitrate or nitrite supplementation on cognitive function (CF) and cerebral blood flow (CBF). Two databases (PubMed, Embase) were searched for articles from inception until May 2017. Inclusion criteria were: randomized clinical trials;...

This study examined if subjective wellbeing in soccer players was affected by match location, match result and opposition quality before a match (PRE), 1 day after (POST-1), and 3 days after a match (POST-3). Eleven professional male soccer players from the under 23 squad playing in the Premier League 2 division completed a wellbeing questionnaire...

We report that reactive oxygen species (ROS), as measured in capillary blood taken from the finger-tip, increased after a marathon (+128% P < 0.01; ES = 1.17), indicating that this collection method might be useful for measuring ROS in field settings. However, mitochondrial DNA damage remained unchanged. Beetroot juice, taken before and after exerc...

Purpose: This study examined whether donning lower body garments fitted with cooled phase change material (PCM) would enhance recovery after a soccer match. Methods: In a randomized, crossover design, eleven elite-soccer players from the reserve squad of a team in the 2nd highest league in England wore PCM cooled to 15°C (PCMcold) or left at amb...

Purpose: T-regulatory cells (Tregs) are a sub-population of lymphocytes that act to suppress aberrant immune responses. We investigated changes in the numbers of naïve and terminally differentiated Tregs in the peripheral blood to establish their role in the immuno-suppressive response to prolonged exercise. Methods: Blood was drawn from sevente...

The aim of this study was to compare the effects of beetroot juice (BTJ) and a nitrate only drink (sodium nitrate; SN) on indices of exercise-induced muscle damage (EIMD). Thirty recreationally active males consumed either BTJ (n=10), a nitrate matched SN drink (n=10) or an isocaloric placebo (PLA; n=10) immediately, 24 and 48 h after performing 10...

Purpose: To evaluate the plasma bioavailability of betanin and nitric oxide (NOx) after consuming beetroot juice (BTJ) and whole beetroot (BF). BTJ and BF were also analysed for antioxidant capacity, polyphenol content (TPC) and betalain content. Methods: Ten healthy males consumed either 250 ml of BTJ, 300 g of BF or a placebo drink, in a rando...

Hyperaminoacidemia following ingestion of cows-milk may stimulate muscle anabolism and attenuate exercise-induced muscle damage (EIMD). However, as dairy-intolerant athletes do not obtain the reported benefits from milk-based products, A2 milk may offer a suitable alternative as it lacks the A1-protein. This study aimed to determine the effect of A...

This study examined whether beetroot juice (BTJ) would attenuate inflammation and muscle damage following a marathon. Using a double blind, independent group design, 34 runners (each having completed ca. ∼16 previous marathons) consumed either BTJ or an isocaloric placebo (PLA) for 3 days following a marathon. Maximal isometric voluntary contractio...

This study examined the effects of beetroot juice (BTJ) on recovery between two repeated-sprint tests. In an independent groups design, 20 male, team-sports players were randomized to receive either BTJ or a placebo (PLA) (2 × 250 mL) for 3 days after an initial repeated sprint test (20 × 30 m; RST1) and after a second repeated sprint test (RST2),...

This study examined the effects of beetroot juice on the repeated bout effect (RBE) to eccentric exercise. Twenty-nine recreationally active males performed two bouts of 100-drop jumps, separated by 14–21 days. Using a double-blind, independent groups design, participants consumed either a higher dose beetroot juice (H-BT; 250 ml, n = 10), a lower...

Effects of Beetroot Juice on Recovery and Performance Between Bouts of Repeated Sprint Exercise Tom Clifford1, Bram Berntzen2, Gareth W. Davison, FACSM3, Daniel J. West1, Glyn Howatson, FACSM1, Emma J. Stevenson4. 1Northumbria University, Newcastle Upon Tyne, United Kingdom. 2Maastricht University, Maastricht, Netherlands. 3University of Ulster, N...