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Hall EC, Larruskain J, Gil SM, Lekue JA, Baumert P, Rienzi E, Moreno S, Tannure M, Murtagh CF, Ade JD, Squires P, Orme P, Anderson L, Whitworth-Turner CM, Morton JP, Drust B, William AG, Erskine RM. Playing Position is Associated with Injury Incidence Rate in Male Academy Soccer Players. J Athl Train 2022; 57:696-703. [PMID: 35142844 DOI: 10.4085/1062-6050-0346.21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
CONTEXT It is unclear whether playing position influences injury in male academy soccer players (ASP). OBJECTIVE To determine if playing position is associated with injury in ASP. DESIGN Descriptive Epidemiology Study. SETTING English, Spanish, Uruguayan and Brazilian soccer academies. PARTICIPANTS 369 ASP from Under 14 (U14) to U23 age groups, classified as 'post-peak height velocity' using maturity offset, and grouped as goalkeepers (GK), lateral defenders (LD), central defenders (CD), lateral midfielders (LM), central midfielders (CM) and forwards (FWD). Additional analysis compared central (CENT) with lateral/forward (LAT/FWD) positions. MAIN OUTCOME MEASURES Injuries were recorded prospectively over one season. Injury prevalence proportion (IPP), days missed and injury incidence rate (IIR, injuries per 1000 training/match hours, n=116) were analysed according to playing position. RESULTS No association with playing position was observed for any injury type/location regarding IPP (P≥0.089) or days missed (P≥0.235). The IIR was higher in CD than LD for general (9.30 vs. 4.18 injuries/1000h, P=0.009), soft-tissue (5.14 vs. 1.95 injuries/1000h, P=0.026) and ligament/tendon injuries (2.69 vs. 0.56 injuries/1000h, P=0.040). Regarding CENT vs. LAT/FWD, there were no associations with IPP (P≥0.051) or days missed (P≥0.083), but general IIR was greater in CENT than LAT/FWD (8.67 vs. 6.12 injuries/1000h, P=0.047). CONCLUSIONS ASP playing position was not associated with IPP or days missed but the higher general, soft-tissue and ligament/tendon IIR in CD suggests this position warrants specific attention regarding injury prevention strategies. These novel findings highlight the importance of including training/match exposure when investigating the influence of playing position on injury in ASP.
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Bennett S, Tiollier E, Brocherie F, Owens DJ, Morton JP, Louis J. Three weeks of a home-based "sleep low-train low" intervention improves functional threshold power in trained cyclists: A feasibility study. PLoS One 2021; 16:e0260959. [PMID: 34855913 PMCID: PMC8639084 DOI: 10.1371/journal.pone.0260959] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 11/21/2021] [Indexed: 11/24/2022] Open
Abstract
Background “Sleep Low-Train Low” is a training-nutrition strategy intended to purposefully reduce muscle glycogen availability around specific exercise sessions, potentially amplifying the training stimulus via augmented cell signalling. The aim of this study was to assess the feasibility of a 3-week home-based “sleep low-train low” programme and its effects on cycling performance in trained athletes. Methods Fifty-five trained athletes (Functional Threshold Power [FTP]: 258 ± 52W) completed a home-based cycling training program consisting of evening high-intensity training (6 × 5 min at 105% FTP), followed by low-intensity training (1 hr at 75% FTP) the next morning, three times weekly for three consecutive weeks. Participant’s daily carbohydrate (CHO) intake (6 g·kg-1·d-1) was matched but timed differently to manipulate CHO availability around exercise: no CHO consumption post- HIT until post-LIT sessions [Sleep Low (SL), n = 28] or CHO consumption evenly distributed throughout the day [Control (CON), n = 27]. Sessions were monitored remotely via power data uploaded to an online training platform, with performance tests conducted pre-, post-intervention. Results LIT exercise intensity reduced by 3% across week 1, 3 and 2% in week 2 (P < 0.01) with elevated RPE in SL vs. CON (P < 0.01). SL enhanced FTP by +5.5% vs. +1.2% in CON (P < 0.01). Comparable increases in 5-min peak power output (PPO) were observed between groups (P < 0.01) with +2.3% and +2.7% in SL and CON, respectively (P = 0.77). SL 1-min PPO was unchanged (+0.8%) whilst CON improved by +3.9% (P = 0.0144). Conclusion Despite reduced relative training intensity, our data demonstrate short-term “sleep low-train low” intervention improves FTP compared with typically “normal” CHO availability during exercise. Importantly, training was completed unsupervised at home (during the COVID-19 pandemic), thus demonstrating the feasibility of completing a “sleep low-train low” protocol under non-laboratory conditions.
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Hall ECR, Baumert P, Larruskain J, Gil SM, Lekue JA, Rienzi E, Moreno S, Tannure M, Murtagh CF, Ade JD, Squires P, Orme P, Anderson L, Brownlee TE, Whitworth-Turner CM, Morton JP, Drust B, Williams AG, Erskine RM. The genetic association with injury risk in male academy soccer players depends on maturity status. Scand J Med Sci Sports 2021; 32:338-350. [PMID: 34633711 DOI: 10.1111/sms.14077] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 10/04/2021] [Accepted: 10/08/2021] [Indexed: 11/29/2022]
Abstract
It is currently unknown if injury risk is associated with genetic variation in academy soccer players (ASP). We investigated whether nine candidate single nucleotide polymorphisms were associated (individually and in combination) with injury in ASP at different stages of maturation. Saliva samples and one season's injury records were collected from 402 Caucasian male ASP from England, Spain, Uruguay, and Brazil, whose maturity status was defined as pre- or post-peak height velocity (PHV). Pre-PHV COL5A1 rs12722 CC homozygotes had relatively higher prevalence of any musculoskeletal soft tissue (22.4% vs. 3.0%, p = 0.018) and ligament (18.8% vs. 11.8%, p = 0.029) injury than T-allele carriers, while VEGFA rs2010963 CC homozygotes had greater risk of ligament/tendon injury than G-allele carriers. Post-PHV IL6 rs1800795 CC homozygotes had a relatively higher prevalence of any (67.6% vs. 40.6%, p = 0.003) and muscle (38.2% vs. 19.2%, p = 0.013) injuries than G-allele carriers. Relatively more post-PHV EMILIN1 rs2289360 CC homozygotes suffered any injury than CT and TT genotypes (56.4% vs. 40.3% and 32.8%, p = 0.007), while the "protective" EMILIN1 TT genotype was more frequent in post- than pre-PHV ASP (22.3 vs. 10.0%, p = 0.008). Regardless of maturity status, T-alleles of ACTN3 rs1815739 and EMILIN1 rs2289360 were associated with greater absence following ankle injury, while the MMP3 rs679620 T-allele and MYLK rs28497577 GT genotype were associated with greater absence following knee injury. The combination of injury-associated genotypes was greater in injured vs. non-injured ASP. This study is the first to demonstrate that a genetic association exists with injury prevalence in ASP, which differs according to maturity status.
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Westerterp KR, Yamada Y, Sagayama H, Ainslie PN, Andersen LF, Anderson LJ, Arab L, Baddou I, Bedu-Addo K, Blaak EE, Blanc S, Bonomi AG, Bouten CVC, Bovet P, Buchowski MS, Butte NF, Camps SGJA, Close GL, Cooper JA, Das SK, Cooper R, Dugas LR, Ekelund U, Entringer S, Forrester T, Fudge BW, Goris AH, Gurven M, Hambly C, El Hamdouchi A, Hoos MB, Hu S, Joonas N, Joosen AM, Katzmarzyk P, Kempen KP, Kimura M, Kraus WE, Kushner RF, Lambert EV, Leonard WR, Lessan N, Martin CK, Medin AC, Meijer EP, Morehen JC, Morton JP, Neuhouser ML, Nicklas TA, Ojiambo RM, Pietiläinen KH, Pitsiladis YP, Plange-Rhule J, Plasqui G, Prentice RL, Rabinovich RA, Racette SB, Raichlen DA, Ravussin E, Reynolds RM, Roberts SB, Schuit AJ, Sjödin AM, Stice E, Urlacher SS, Valenti G, Van Etten LM, Van Mil EA, Wells JCK, Wilson G, Wood BM, Yanovski J, Yoshida T, Zhang X, Murphy-Alford AJ, Loechl CU, Luke AH, Pontzer H, Rood J, Schoeller DA, Wong WW, Speakman JR. Physical activity and fat-free mass during growth and in later life. Am J Clin Nutr 2021; 114:1583-1589. [PMID: 34477824 PMCID: PMC8574623 DOI: 10.1093/ajcn/nqab260] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 07/14/2021] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Physical activity may be a way to increase and maintain fat-free mass (FFM) in later life, similar to the prevention of fractures by increasing peak bone mass. OBJECTIVES A study is presented of the association between FFM and physical activity in relation to age. METHODS In a cross-sectional study, FFM was analyzed in relation to physical activity in a large participant group as compiled in the International Atomic Energy Agency Doubly Labeled Water database. The database included 2000 participants, age 3-96 y, with measurements of total energy expenditure (TEE) and resting energy expenditure (REE) to allow calculation of physical activity level (PAL = TEE/REE), and calculation of FFM from isotope dilution. RESULTS PAL was a main determinant of body composition at all ages. Models with age, fat mass (FM), and PAL explained 76% and 85% of the variation in FFM in females and males < 18 y old, and 32% and 47% of the variation in FFM in females and males ≥ 18 y old, respectively. In participants < 18 y old, mean FM-adjusted FFM was 1.7 kg (95% CI: 0.1, 3.2 kg) and 3.4 kg (95% CI: 1.0, 5.6 kg) higher in a very active participant with PAL = 2.0 than in a sedentary participant with PAL = 1.5, for females and males, respectively. At age 18 y, height and FM-adjusted FFM was 3.6 kg (95% CI: 2.8, 4.4 kg) and 4.4 kg (95% CI: 3.2, 5.7 kg) higher, and at age 80 y 0.7 kg (95% CI: -0.2, 1.7 kg) and 1.0 kg (95% CI: -0.1, 2.1 kg) higher, in a participant with PAL = 2.0 than in a participant with PAL = 1.5, for females and males, respectively. CONCLUSIONS If these associations are causal, they suggest physical activity is a major determinant of body composition as reflected in peak FFM, and that a physically active lifestyle can only partly protect against loss of FFM in aging adults.
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Pontzer H, Yamada Y, Sagayama H, Ainslie PN, Andersen LF, Anderson LJ, Arab L, Baddou I, Bedu-Addo K, Blaak EE, Blanc S, Bonomi AG, Bouten CVC, Bovet P, Buchowski MS, Butte NF, Camps SG, Close GL, Cooper JA, Cooper R, Das SK, Dugas LR, Ekelund U, Entringer S, Forrester T, Fudge BW, Goris AH, Gurven M, Hambly C, El Hamdouchi A, Hoos MB, Hu S, Joonas N, Joosen AM, Katzmarzyk P, Kempen KP, Kimura M, Kraus WE, Kushner RF, Lambert EV, Leonard WR, Lessan N, Martin C, Medin AC, Meijer EP, Morehen JC, Morton JP, Neuhouser ML, Nicklas TA, Ojiambo RM, Pietiläinen KH, Pitsiladis YP, Plange-Rhule J, Plasqui G, Prentice RL, Rabinovich RA, Racette SB, Raichlen DA, Ravussin E, Reynolds RM, Roberts SB, Schuit AJ, Sjödin AM, Stice E, Urlacher SS, Valenti G, Van Etten LM, Van Mil EA, Wells JCK, Wilson G, Wood BM, Yanovski J, Yoshida T, Zhang X, Murphy-Alford AJ, Loechl C, Luke AH, Rood J, Schoeller DA, Westerterp KR, Wong WW, Speakman JR. Daily energy expenditure through the human life course. Science 2021; 373:808-812. [PMID: 34385400 DOI: 10.1126/science.abe5017] [Citation(s) in RCA: 188] [Impact Index Per Article: 62.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 06/21/2021] [Indexed: 12/12/2022]
Abstract
Total daily energy expenditure ("total expenditure") reflects daily energy needs and is a critical variable in human health and physiology, but its trajectory over the life course is poorly studied. We analyzed a large, diverse database of total expenditure measured by the doubly labeled water method for males and females aged 8 days to 95 years. Total expenditure increased with fat-free mass in a power-law manner, with four distinct life stages. Fat-free mass-adjusted expenditure accelerates rapidly in neonates to ~50% above adult values at ~1 year; declines slowly to adult levels by ~20 years; remains stable in adulthood (20 to 60 years), even during pregnancy; then declines in older adults. These changes shed light on human development and aging and should help shape nutrition and health strategies across the life span.
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Pugh JN, Phelan MM, Caamaño-Gutiérrez E, Sparks SA, Morton JP, Close GL, Owens DJ. Four Weeks of Probiotic Supplementation Alters the Metabolic Perturbations Induced by Marathon Running: Insight from Metabolomics. Metabolites 2021; 11:metabo11080535. [PMID: 34436476 PMCID: PMC8400326 DOI: 10.3390/metabo11080535] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 08/09/2021] [Accepted: 08/10/2021] [Indexed: 12/24/2022] Open
Abstract
Few data are available that describe how probiotics influence systemic metabolism during endurance exercise. Metabolomic profiling of endurance athletes will elucidate mechanisms by which probiotics may confer benefits to the athlete. In this study, twenty-four runners (20 male, 4 female) were block randomised into two groups using a double-blind matched-pairs design according to their most recent Marathon performance. Runners were assigned to 28-days of supplementation with a multi-strain probiotic (PRO) or a placebo (PLB). Following 28-days of supplementation, runners performed a competitive track Marathon race. Venous blood samples and muscle biopsies (vastus lateralis) were collected on the morning of the race and immediately post-race. Samples were subsequently analysed by untargeted 1H-NMR metabolomics. Principal component analysis (PCA) identified a greater difference in the post-Marathon serum metabolome in the PLB group vs. PRO. Univariate tests identified 17 non-overlapped metabolites in PLB, whereas only seven were identified in PRO. By building a PLS-DA model of two components, we revealed combinations of metabolites able to discriminate between PLB and PRO post-Marathon. PCA of muscle biopsies demonstrated no discernible difference post-Marathon between treatment groups. In conclusion, 28-days of probiotic supplementation alters the metabolic perturbations induced by a Marathon. Such findings may be related to maintaining the integrity of the gut during endurance exercise.
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Ellis DG, Speakman J, Hambley C, Morton JP, Close GL, Lewindon D, Donovan TF. Energy Expenditure of a Male and Female Tennis Player during ATP/WTA and Grand Slam Events Measured by Doubly Labelled Water. Med Sci Sports Exerc 2021; 53:2628-2634. [PMID: 34310496 DOI: 10.1249/mss.0000000000002745] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
ABSTRACT Understanding the total energy expenditure (TEE) for competition and training in sport are vital to ensure suitable nutritional strategies. This study assessed TEE of a world class male and female tennis player during competition at the highest level. Participants: Career high ranking, Female: Women's Tennis Association (WTA) top 10; Male: Association of Tennis Professionals (ATP) top 15. Methods: Doubly labelled water assessed TEE during a 17-day period analysed by day 1-7 (P1) and 7-17 (P2) which included a WTA/ATP tournament and culminated at the Wimbledon Championships. Daily training and match loads were assessed using a 10-point Borg scale multiplied by time. Match data were provided by video analysis and player tracking technology. Results: The TEE during P1 for the female player was 3383 kcal⋅day-1 (63.5 kcal⋅kg-1) FFM with 362 points played over 241 min in three matches covering a distance of 2569 m, with an additional 875 min training. During P2, TEE was 3824 kcal⋅day-1 (71.7 kcal⋅kg-1) FFM with 706 points played over 519 min during five matches, covering a distance of 7357 m with an additional 795 min training. The TEE during P1 for the male player was 3712 kcal⋅day-1 (56.3 kcal⋅kg-1) FFM with 133 points played over 88 mins during one match covering 1125 m, with an additional 795 mins training. During P2, TEE was 5520 kcal⋅day-1 (83.7 kcal⋅kg-1) FFM with 891 points played over 734 min during five matches, covering 10043 m, with an additional 350 min training. Conclusion: This novel data positions elite tennis, played at the highest level, as a highly energetic demanding sport, highlighting that nutritional strategies should ensure sufficient energy availability during competition schedules.
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Moore DR, Sygo J, Morton JP. Fuelling the female athlete: Carbohydrate and protein recommendations. Eur J Sport Sci 2021; 22:684-696. [PMID: 34015236 DOI: 10.1080/17461391.2021.1922508] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Optimal carbohydrate and protein intakes are vital for modulating training adaptation, recovery, and exercise performance. However, the research base underpinning contemporary sport nutrition guidelines has largely been conducted in male populations with a lack of consensus on whether the menstrual phase and associated changes in sex hormones allow broad application of these principles to female athletes. The present review will summarise our current understanding of carbohydrate and protein requirements in female athletes across the menstrual cycle and provide a critical analysis on how they compare to male athletes. On the basis of current evidence, we consider it premature to conclude that female athletes require sex specific guidelines in relation to CHO or protein requirements provided energy needs are met. However, there is a need for further research using sport-specific competition and training related exercise protocols that rigorously control for prior exercise, CHO/energy intake, contraceptive use and phase of menstrual cycle. Our overarching recommendation is to use current recommendations as a basis for adopting an individualised approach that takes into account athlete specific training and competition goals whilst also considering personal symptoms associated with the menstrual cycle.
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Parker LJ, Elliott-Sale KJ, Hannon MP, Morton JP, Close GL. An audit of hormonal contraceptive use in Women’s Super League soccer players; implications on symptomology. SCI MED FOOTBALL 2021; 6:153-158. [DOI: 10.1080/24733938.2021.1921248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Scott SN, Fontana FY, Cocks M, Morton JP, Jeukendrup A, Dragulin R, Wojtaszewski JFP, Jensen J, Castol R, Riddell MC, Stettler C. Post-exercise recovery for the endurance athlete with type 1 diabetes: a consensus statement. Lancet Diabetes Endocrinol 2021; 9:304-317. [PMID: 33864810 DOI: 10.1016/s2213-8587(21)00054-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 02/19/2021] [Accepted: 02/19/2021] [Indexed: 02/07/2023]
Abstract
There has been substantial progress in the knowledge of exercise and type 1 diabetes, with the development of guidelines for optimal glucose management. In addition, an increasing number of people living with type 1 diabetes are pushing their physical limits to compete at the highest level of sport. However, the post-exercise recovery routine, particularly with a focus on sporting performance, has received little attention within the scientific literature, with most of the focus being placed on insulin or nutritional adaptations to manage glycaemia before and during the exercise bout. The post-exercise recovery period presents an opportunity for maximising training adaption and recovery, and the clinical management of glycaemia through the rest of the day and overnight. The absence of clear guidance for the post-exercise period means that people with type 1 diabetes should either develop their own recovery strategies on the basis of individual trial and error, or adhere to guidelines that have been developed for people without diabetes. This Review provides an up-to-date consensus on post-exercise recovery and glucose management for individuals living with type 1 diabetes. We aim to: (1) outline the principles and time course of post-exercise recovery, highlighting the implications and challenges for endurance athletes living with type 1 diabetes; (2) provide an overview of potential strategies for post-exercise recovery that could be used by athletes with type 1 diabetes to optimise recovery and adaptation, alongside improved glycaemic monitoring and management; and (3) highlight the potential for technology to ease the burden of managing glycaemia in the post-exercise recovery period.
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Langan-Evans C, Germaine M, Artukovic M, Oxborough DL, Areta JL, Close GL, Morton JP. The Psychological and Physiological Consequences of Low Energy Availability in a Male Combat Sport Athlete. Med Sci Sports Exerc 2021; 53:673-683. [PMID: 33105389 DOI: 10.1249/mss.0000000000002519] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
PURPOSE This study aimed to evaluate the effects of low energy availability (EA) on health and performance indices associated with the Male Athlete Triad and Relative Energy Deficiency in Sport (RED-S) models. METHODS Over an 8-wk period, a male combat sport athlete adhered to a phased body mass (BM) loss plan consisting of 7-wk energy intake (EI) equating to resting metabolic rate (RMR) (1700 kcal·d-1) (phase 1), 5 d of reduced EI (1200-300 kcal·d-1) before weigh-in (phase 2), and 1 wk of ad libitum EI postcompetition (phase 3). EA fluctuated day by day because of variations in exercise energy expenditure. Regular assessments of body composition, RMR, cardiac function, cardiorespiratory capacity, strength and power, psychological state and blood clinical chemistry for endocrine, bone turnover, hydration, electrolyte, renal, liver, and lipid profiles were performed. RESULTS BM was reduced over the 8-wk period by 13.5% (72.5 to 62.7 kg). No consequences of Male Athlete Triad or RED-S were evident during phase 1, where mean daily EA equated to 20 kcal·kg·fat free mass (FFM)-1·d-1 (range, 7 to 31 kcal·kg FFM-1·d-1) and BM and fat mass (FM) losses were 6.5 and 4.4 kg, respectively. However, consequences did present in phase 2 when mean daily EA was consistently <10 kcal·kg FFM-1·d-1, as evidenced by alterations to endocrine hormones (e.g., testosterone <5 nmol.L-1) and reduced RMR (-257 kcal·d-1). CONCLUSION Data demonstrate that 7 wk of daily fluctuations in EA equating to a mean value of 20 kcal·kg FFM-1·d-1 permits reductions of BM and FM without perturbations to physiological systems associated with the Male Athlete Triad and RED-S. By contrast, a subsequent period of five consecutive days of EA <10 kcal·kg FFM-1·d-1 induced consequences of Male Athlete Triad and RED-S.
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Fell JM, Hearris MA, Ellis DG, Moran JEP, Jevons EFP, Owens DJ, Strauss JA, Cocks M, Louis JB, Shepherd SO, Morton JP. Carbohydrate improves exercise capacity but does not affect subcellular lipid droplet morphology, AMPK and p53 signalling in human skeletal muscle. J Physiol 2021; 599:2823-2849. [PMID: 33772787 DOI: 10.1113/jp281127] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 03/22/2021] [Indexed: 11/08/2022] Open
Abstract
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) have not yet been studied under nutritional conditions typically adopted by elite endurance athletes, that is, after carbohydrate (CHO) loading and CHO feeding during exercise. We report for the first time that exercise reduces IMTG content in both central and peripheral regions of type I and IIa fibres, reflective of decreased LD number in both fibre types whereas reductions in LD size were exclusive to type I fibres. Additionally, CHO feeding does not alter subcellular IMTG utilisation, LD morphology or muscle glycogen utilisation in type I or IIa/II fibres. In the absence of alterations to muscle fuel selection, CHO feeding does not attenuate cell signalling pathways with regulatory roles in mitochondrial biogenesis. ABSTRACT We examined the effects of carbohydrate (CHO) feeding on lipid droplet (LD) morphology, muscle glycogen utilisation and exercise-induced skeletal muscle cell signalling. After a 36 h CHO loading protocol and pre-exercise meal (12 and 2 g kg-1 , respectively), eight trained males ingested 0, 45 or 90 g CHO h-1 during 180 min cycling at lactate threshold followed by an exercise capacity test (150% lactate threshold). Muscle biopsies were obtained pre- and post-completion of submaximal exercise. Exercise decreased (P < 0.01) glycogen concentration to comparable levels (∼700 to 250 mmol kg-1 DW), though utilisation was greater in type I (∼40%) versus type II fibres (∼10%) (P < 0.01). LD content decreased in type I (∼50%) and type IIa fibres (∼30%) (P < 0.01), with greater utilisation in type I fibres (P < 0.01). CHO feeding did not affect glycogen or IMTG utilisation in type I or II fibres (all P > 0.05). Exercise decreased LD number within central and peripheral regions of both type I and IIa fibres, though reduced LD size was exclusive to type I fibres. Exercise induced (all P < 0.05) comparable AMPKThr172 (∼4-fold), p53Ser15 (∼2-fold) and CaMKIIThr268 phosphorylation (∼2-fold) with no effects of CHO feeding (all P > 0.05). CHO increased exercise capacity where 90 g h-1 (233 ± 133 s) > 45 g h-1 (156 ± 66 s; P = 0.06) > 0 g h-1 (108 ± 54 s; P = 0.03). In conditions of high pre-exercise CHO availability, we conclude CHO feeding does not influence exercise-induced changes in LD morphology, glycogen utilisation or cell signalling pathways with regulatory roles in mitochondrial biogenesis.
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Kasper AM, Langan-Evans C, Hudson JF, Brownlee TE, Harper LD, Naughton RJ, Morton JP, Close GL. Come Back Skinfolds, All Is Forgiven: A Narrative Review of the Efficacy of Common Body Composition Methods in Applied Sports Practice. Nutrients 2021; 13:nu13041075. [PMID: 33806245 PMCID: PMC8065383 DOI: 10.3390/nu13041075] [Citation(s) in RCA: 59] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 03/17/2021] [Accepted: 03/21/2021] [Indexed: 01/11/2023] Open
Abstract
Whilst the assessment of body composition is routine practice in sport, there remains considerable debate on the best tools available, with the chosen technique often based upon convenience rather than understanding the method and its limitations. The aim of this manuscript was threefold: (1) provide an overview of the common methodologies used within sport to measure body composition, specifically hydro-densitometry, air displacement plethysmography, bioelectrical impedance analysis and spectroscopy, ultra-sound, three-dimensional scanning, dual-energy X-ray absorptiometry (DXA) and skinfold thickness; (2) compare the efficacy of what are widely believed to be the most accurate (DXA) and practical (skinfold thickness) assessment tools and (3) provide a framework to help select the most appropriate assessment in applied sports practice including insights from the authors' experiences working in elite sport. Traditionally, skinfold thickness has been the most popular method of body composition but the use of DXA has increased in recent years, with a wide held belief that it is the criterion standard. When bone mineral content needs to be assessed, and/or when it is necessary to take limb-specific estimations of fat and fat-free mass, then DXA appears to be the preferred method, although it is crucial to be aware of the logistical constraints required to produce reliable data, including controlling food intake, prior exercise and hydration status. However, given the need for simplicity and after considering the evidence across all assessment methods, skinfolds appear to be the least affected by day-to-day variability, leading to the conclusion 'come back skinfolds, all is forgiven'.
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Hannon MP, Coleman NM, Parker LJF, McKeown J, Unnithan VB, Close GL, Drust B, Morton JP. Seasonal training and match load and micro-cycle periodization in male Premier League academy soccer players. J Sports Sci 2021; 39:1838-1849. [PMID: 33759688 DOI: 10.1080/02640414.2021.1899610] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
We quantified on pitch external loading of English Premier League (EPL) academy soccer players (n=76; U12-U18 age groups) over an entire competitive season. Mean accumulative weekly duration and total distance, respectively, was similar in the U12 (329±29 min; 19.9±2.2 km), U13 (323±29 min; 20.0±2.0 km) and U14 (339±25 min; 21.7±2.0 km; P>0.05 for all comparisons) age-groups, though all teams were less than U15 (421±15 min; 26.2±2.1 km), U16 (427±20 min; 25.9±2.5 km) and U18 (398±30 min; 26.1±2.6 km) players (P<0.05 for all comparisons). Mean weekly high-speed running and sprint distance was not different between U12 (220±95 m and 6±9 m respectively), U13 (331±212 m and 6±27 m) and U14 (448±193 m and 21±29 m) age-groups (P>0.05 for all pairwise comparisons) though all squads were less than U15 (657±242 m and 49±98 m), U16 (749±152 m and 95±55 m) and U18 (979±254 m and 123±56 m) age-groups (P<0.05 for all pairwise comparisons). Data demonstrate that absolute weekly training volume in EPL academy soccer players increases throughout the academy pathway. Furthermore, although U16-U18 players are capable of achieving similar training and match volumes as previously reported in adult EPL players, they do not yet achieve the absolute intensities of adult EPL players.
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Speakman JR, Yamada Y, Sagayama H, Berman ESF, Ainslie PN, Andersen LF, Anderson LJ, Arab L, Baddou I, Bedu-Addo K, Blaak EE, Blanc S, Bonomi AG, Bouten CVC, Bovet P, Buchowski MS, Butte NF, Camps SGJA, Close GL, Cooper JA, Creasy SA, Das SK, Cooper R, Dugas LR, Ebbeling CB, Ekelund U, Entringer S, Forrester T, Fudge BW, Goris AH, Gurven M, Hambly C, El Hamdouchi A, Hoos MB, Hu S, Joonas N, Joosen AM, Katzmarzyk P, Kempen KP, Kimura M, Kraus WE, Kushner RF, Lambert EV, Leonard WR, Lessan N, Ludwig DS, Martin CK, Medin AC, Meijer EP, Morehen JC, Morton JP, Neuhouser ML, Nicklas TA, Ojiambo RM, Pietiläinen KH, Pitsiladis YP, Plange-Rhule J, Plasqui G, Prentice RL, Rabinovich RA, Racette SB, Raichlen DA, Ravussin E, Reynolds RM, Roberts SB, Schuit AJ, Sjödin AM, Stice E, Urlacher SS, Valenti G, Van Etten LM, Van Mil EA, Wells JCK, Wilson G, Wood BM, Yanovski J, Yoshida T, Zhang X, Murphy-Alford AJ, Loechl CU, Melanson EL, Luke AH, Pontzer H, Rood J, Schoeller DA, Westerterp KR, Wong WW. A standard calculation methodology for human doubly labeled water studies. CELL REPORTS MEDICINE 2021; 2:100203. [PMID: 33665639 PMCID: PMC7897799 DOI: 10.1016/j.xcrm.2021.100203] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 09/16/2020] [Accepted: 01/20/2021] [Indexed: 11/25/2022]
Abstract
The doubly labeled water (DLW) method measures total energy expenditure (TEE) in free-living subjects. Several equations are used to convert isotopic data into TEE. Using the International Atomic Energy Agency (IAEA) DLW database (5,756 measurements of adults and children), we show considerable variability is introduced by different equations. The estimated rCO2 is sensitive to the dilution space ratio (DSR) of the two isotopes. Based on performance in validation studies, we propose a new equation based on a new estimate of the mean DSR. The DSR is lower at low body masses (<10 kg). Using data for 1,021 babies and infants, we show that the DSR varies non-linearly with body mass between 0 and 10 kg. Using this relationship to predict DSR from weight provides an equation for rCO2 over this size range that agrees well with indirect calorimetry (average difference 0.64%; SD = 12.2%). We propose adoption of these equations in future studies.
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Hannon MP, Parker LJF, Carney DJ, McKeown J, Speakman JR, Hambly C, Drust B, Unnithan VB, Close GL, Morton JP. Energy Requirements of Male Academy Soccer Players from the English Premier League. Med Sci Sports Exerc 2021; 53:200-210. [PMID: 32701871 DOI: 10.1249/mss.0000000000002443] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE This study aimed to inform the energy requirements of highly trained adolescent soccer players. Total energy expenditure (TEE) was quantified in academy soccer players from the English Premier League (EPL). METHODS Twenty-four male adolescent soccer players from an EPL academy (under (U) 12/13 (U12/13), n = 8; U15, n = 8; U18, n = 8) were assessed for baseline maturity (maturity offset), body composition (dual-energy x-ray absorptiometry), and resting metabolic rate (indirect calorimetry). Subsequently, TEE, energy intake (EI) and physical loading patterns were assessed over a 14-d in-season period using doubly labeled water, the remote food photographic method, and global positioning system technology, respectively. RESULTS U18 players presented with greater resting metabolic rate (2236 ± 93 kcal·d) and TEE (3586 ± 487 kcal·d; range, 2542-5172 kcal·d) than did both U15 (2023 ± 162 and 3029 ± 262 kcal·d, respectively; TEE range, 2738-3726 kcal·d) and U12/13 players (1892 ± 211 and 2859 ± 265 kcal·d, respectively; TEE range, 2275-3903 kcal·d; all, P < 0.01), although no difference in TEE was apparent between the U12/13 and U15 age groups. Fat-free mass was significantly different between all comparisons in a hierarchal manner (U18: 57.2 ± 6.1 kg > U15: 42.9 ± 5.8 kg > U12/13: 31.1 ± 3.5 kg; all, P < 0.01). Within age groups, no differences were apparent between EI and TEE (U12/13: -29 ± 277 kcal·d, P = 0.78; U15: -134 ± 327 kcal·d, P = 0.28; U18: -243 ± 724 kcal·d, P = 0.37), whereas U18 players (3180 ± 279 kcal·d) reported higher EI than did both U15 (2821 ± 338 kcal·d; P = 0.05) and U12/13 players (2659 ± 187 kcal·d; P < 0.01). CONCLUSIONS The TEE of male academy soccer players progressively increase as players progress through the academy age groups. In some individuals (evident in all age groups), TEE was greater than that previously observed in adult EPL soccer players.
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Hannon MP, Close GL, Morton JP. Energy and Macronutrient Considerations for Young Athletes. Strength Cond J 2020. [DOI: 10.1519/ssc.0000000000000570] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Collins J, Maughan RJ, Gleeson M, Bilsborough J, Jeukendrup A, Morton JP, Phillips SM, Armstrong LE, Burke LM, Close GL, Duffield R, Larson-Meyer E, Louis J, Medina D, Meyer F, Rollo I, Sundgot-Borgen JK, Wall B, Boullosa B, Dupont G, Lizarraga A, Res P, Bizzini M, Castagna C, Cowie CM, D'Hooghe M, Geyer H, Meyer T, Papadimitiou N, Vouillamoz M, McCall A. Infographic. UEFA expert group 2020 statement on nutrition in elite football. Br J Sports Med 2020; 55:453-455. [PMID: 33097526 DOI: 10.1136/bjsports-2020-103410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/15/2020] [Indexed: 11/04/2022]
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Collins J, Maughan RJ, Gleeson M, Bilsborough J, Jeukendrup A, Morton JP, Phillips SM, Armstrong L, Burke LM, Close GL, Duffield R, Larson-Meyer E, Louis J, Medina D, Meyer F, Rollo I, Sundgot-Borgen J, Wall BT, Boullosa B, Dupont G, Lizarraga A, Res P, Bizzini M, Castagna C, Cowie CM, D'Hooghe M, Geyer H, Meyer T, Papadimitriou N, Vouillamoz M, McCall A. UEFA expert group statement on nutrition in elite football. Current evidence to inform practical recommendations and guide future research. Br J Sports Med 2020; 55:416. [PMID: 33097528 DOI: 10.1136/bjsports-2019-101961] [Citation(s) in RCA: 94] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/18/2020] [Indexed: 01/09/2023]
Abstract
Football is a global game which is constantly evolving, showing substantial increases in physical and technical demands. Nutrition plays a valuable integrated role in optimising performance of elite players during training and match-play, and maintaining their overall health throughout the season. An evidence-based approach to nutrition emphasising, a 'food first' philosophy (ie, food over supplements), is fundamental to ensure effective player support. This requires relevant scientific evidence to be applied according to the constraints of what is practical and feasible in the football setting. The science underpinning sports nutrition is evolving fast, and practitioners must be alert to new developments. In response to these developments, the Union of European Football Associations (UEFA) has gathered experts in applied sports nutrition research as well as practitioners working with elite football clubs and national associations/federations to issue an expert statement on a range of topics relevant to elite football nutrition: (1) match day nutrition, (2) training day nutrition, (3) body composition, (4) stressful environments and travel, (5) cultural diversity and dietary considerations, (6) dietary supplements, (7) rehabilitation, (8) referees and (9) junior high-level players. The expert group provide a narrative synthesis of the scientific background relating to these topics based on their knowledge and experience of the scientific research literature, as well as practical experience of applying knowledge within an elite sports setting. Our intention is to provide readers with content to help drive their own practical recommendations. In addition, to provide guidance to applied researchers where to focus future efforts.
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Hearris MA, Owens DJ, Strauss JA, Shepherd SO, Sharples AP, Morton JP, Louis JB. Graded reductions in pre‐exercise glycogen concentration do not augment exercise‐induced nuclear AMPK and PGC‐1α protein content in human muscle. Exp Physiol 2020; 105:1882-1894. [DOI: 10.1113/ep088866] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 08/21/2020] [Indexed: 02/03/2023]
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Areta JL, Iraki J, Owens DJ, Joanisse S, Philp A, Morton JP, Hallén J. Achieving energy balance with a high‐fat meal does not enhance skeletal muscle adaptation and impairs glycaemic response in a sleep‐low training model. Exp Physiol 2020; 105:1778-1791. [DOI: 10.1113/ep088795] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 08/17/2020] [Indexed: 11/08/2022]
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Kirk C, Clark DR, Langan-Evans C, Morton JP. The physical demands of mixed martial arts: A narrative review using the ARMSS model to provide a hierarchy of evidence. J Sports Sci 2020; 38:2819-2841. [PMID: 32783581 DOI: 10.1080/02640414.2020.1802093] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The physical demands of mixed martial arts (MMA) training and competition is not yet well quantified. The Applied Research Model for the Sport Sciences (ARMSS) provides a framework through which to conduct sport science, determining pertinent questions to test research findings in real-world settings. The aim of this review was to evaluate MMA research within the context of ARMSS to critically analyse our understanding of the physical requirements of MMA training and competition. Research databases were searched, with 70 peer-reviewed articles being discussed in relation to the specific stage of the ARMSS in which their results best fit. MMA research was found to be mostly foundational and descriptive in nature and has generally not developed along systematic lines. The internal and external loads and responses to training and competition have not been adequately identified. Therefore, it is not currently possible to state which variables are key predictors of success, or how coaches can optimally manipulate these variables. We propose that MMA research be refocused to be conducted within ARMSS. Specifically, stage 2 studies describing the physical, physiological and technical demands of MMA training and competition, and stage 3 studies determining the physiological predictors of performance should be initially prioritised.
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Morehen JC, Clarke J, Batsford J, Barrow S, Brown AD, Stewart CE, Morton JP, Close GL. Montmorency tart cherry juice does not reduce markers of muscle soreness, function and inflammation following professional male rugby League match-play. Eur J Sport Sci 2020; 21:1003-1012. [PMID: 32672095 DOI: 10.1080/17461391.2020.1797181] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Rugby League (RL) match-play causes muscle damage, inflammation and symptoms of fatigue. To facilitate recovery, nutritional interventions are often employed, including Montmorency cherry juice (MC). We assessed the effects of MC on recovery following RL match-play in eleven male professional RL players who played in two matches (7-days apart) with MC or placebo (PLB) supplemented for 5-days pre-match, matchday and 2-days post-match. Blood was collected 48h pre-match, half-time, within 30-mins of full-time and 48h post-match to assess Interleukin concentrations (IL-6, -8 -10). Self-reported sleep, fatigue, mood, stress, and muscle-soreness were assessed 24h pre and 24 and 48h post-matches with muscle function assessed 48h pre and 48h post-match. No differences in distance covered (6334 ± 1944 Vs 6596 ± 1776m) and total collisions (28 ± 11 Vs 29 ± 13) were observed between both matches. There was a small albeit significant increase in IL-6, -8 and -10 concentrations pre to post-match in both PLB (IL-6: 0.83 ± 0.92 Vs 2.91 ± 1.40, IL-8: 2.16 ± 1.22 Vs 3.91 ± 1.61 and IL-10: 2.51 ± 2.14 Vs 0.61 ± 0.50 pg.mL-1) and MC groups (IL-6: 0.53 ± 0.53 Vs 2.24 ± 1.73, IL-8: 1.85 ± 0.96 Vs 3.46 ± 1.12 and IL-10: 0.48 ± 0.50 Vs 2.54 ± 2.10 pg.mL-1), although there were no significant differences between groups (P<0.05). Likewise, there was a small but significant increase in muscle soreness (P=0.01) and reduction in CMJ (P=0.003) with no significant differences between groups. No significant changes in sleep, fatigue or mood (P>0.05) were observed pre to post-match or between groups. These data suggest MC does not affect the modest changes observed in cytokine responses and markers of recovery from RL match-play.Keywords: Team Sport, Nutrition, Performance, Recovery.
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Routledge HE, Graham S, Di Michele R, Burgess D, Erskine RM, Close GL, Morton JP. Training Load and Carbohydrate Periodization Practices of Elite Male Australian Football Players: Evidence of Fueling for the Work Required. Int J Sport Nutr Exerc Metab 2020; 30:280-286. [PMID: 32470922 DOI: 10.1123/ijsnem.2019-0311] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 03/30/2020] [Accepted: 03/30/2020] [Indexed: 11/18/2022]
Abstract
The authors aimed to quantify (a) the periodization of physical loading and daily carbohydrate (CHO) intake across an in-season weekly microcycle of Australian Football and (b) the quantity and source of CHO consumed during game play and training. Physical loading (via global positioning system technology) and daily CHO intake (via a combination of 24-hr recall, food diaries, and remote food photographic method) were assessed in 42 professional male players during two weekly microcycles comprising a home and away fixture. The players also reported the source and quantity of CHO consumed during all games (n = 22 games) and on the training session completed 4 days before each game (n = 22 sessions). The total distance was greater (p < .05) on game day (GD; 13 km) versus all training days. The total distance differed between training days, where GD-2 (8 km) was higher than GD-1, GD-3, and GD-4 (3.5, 0, and 7 km, respectively). The daily CHO intake was also different between training days, with reported intakes of 1.8, 1.4, 2.5, and 4.5 g/kg body mass on GD-4, GD-3, GD-2, and GD-1, respectively. The CHO intake was greater (p < .05) during games (59 ± 19 g) compared with training (1 ± 1 g), where in the former, 75% of the CHO consumed was from fluids as opposed to gels. Although the data suggest that Australian Football players practice elements of CHO periodization, the low absolute CHO intakes likely represent considerable underreporting in this population. Even when accounting for potential underreporting, the data also suggest Australian Football players underconsume CHO in relation to the physical demands of training and competition.
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Routledge HE, Bradley WJ, Shepherd SO, Cocks M, Erskine RM, Close GL, Morton JP. Ultrasound Does Not Detect Acute Changes in Glycogen in Vastus Lateralis of Man. Med Sci Sports Exerc 2020; 51:2286-2293. [PMID: 31169793 DOI: 10.1249/mss.0000000000002052] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE To examine the validity of ultrasound (via cloud-based software that measures pixilation intensity according to a scale of 0-100) to noninvasively assess muscle glycogen in human skeletal muscle. METHODS In study 1, 14 professional male rugby league players competed in an 80-min competitive rugby league game. In study 2 (in a randomized repeated measures design), 16 recreationally active males completed an exhaustive cycling protocol to deplete muscle glycogen followed by 36 h of HIGH or LOW carbohydrate intake (8 g·kg vs 3 g·kg body mass). In both studies, muscle biopsies and ultrasound scans were obtained from the vastus lateralis (at 50% of the muscle length) before and after match play in study 1 and at 36 h after glycogen depletion in study 2. RESULTS Despite match play reducing (P < 0.01) muscle glycogen concentration (pregame: 443 ± 65; postgame: 271 ± 94 mmol·kg dw, respectively) in study 1, there were no significant changes (P = 0.4) in ultrasound scores (pregame: 47 ± 6, postgame: 49 ± 7). In study 2, muscle glycogen concentration was significantly different (P < 0.01) between HIGH (531 ±129 mmol·kg dw) and LOW (252 ± 64 mmol·kg dw) yet there was no difference (P = 0.9) in corresponding ultrasound scores (HIGH: 56 ± 7, LOW: 54 ± 6). In both studies, no significant correlations (P > 0.05) were present between changes in muscle glycogen concentration and changes in ultrasound scores. CONCLUSIONS Data demonstrate that ultrasound (as based on measures of pixilation intensity) is not valid to measure muscle glycogen status within the physiological range (i.e., 200-500 mmol·kg dw) that is applicable to exercise-induced muscle glycogen utilization and postexercise muscle glycogen resynthesis.
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