Greg Atkinson’s research while affiliated with Liverpool John Moores University and other places

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Publications (241)


Figure 1. Individual panels present the relationship between the placebo-adjusted plasma 278
Figure 3. Forest plots for systolic BP (A) and diastolic BP (B) summary effects and between-323
Inter-individual differences in the blood pressure lowering effects of dietary nitrate: A randomised double-blind placebo-controlled replicate crossover trial
  • Preprint
  • File available

December 2024

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60 Reads

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Purpose: Dietary nitrate supplementation increases nitric oxide (NO) bioavailability and reduces blood pressure (BP). Inter-individual differences in these responses are suspected but have not been investigated using robust designs, e.g., replicate crossover, and appropriate statistical models. We examined the within-individual consistency of the effects of dietary nitrate supplementation on NO biomarkers and BP, and quantified inter-individual response differences. Methods: Fifteen healthy males visited the laboratory four times. On two visits, participants consumed 140ml nitrate-rich beetroot juice (~14.0mmol nitrate) and, on the other two visits, they consumed 140ml nitrate-depleted beetroot juice (~0.03mmol nitrate). Plasma nitrate and nitrite concentrations were measured 2.5 hours post-supplementation. BP was measured pre- and 2.5 hours post-supplementation. Between-replicate correlations were quantified for the placebo-adjusted post-supplementation plasma nitrate and nitrite concentrations and pre-to-post changes in BP. Within-participant linear mixed models (LLM) and a meta-analytic approach estimated participant-by-condition treatment response variability. Results: Nitrate-rich beetroot juice supplementation elevated plasma nitrate and nitrite concentrations and reduced systolic (mean:-7mmHg, 95%CI: -3 to -11mmHg) and diastolic (mean:-6mmHg, 95%CI: -2 to -9mmHg) BP versus placebo. The LLM participant-by-condition interaction response variability was +/- 7mmHg (95%CI: 3 to 9mmHg) for systolic BP and consistent with the treatment effect heterogeneity t= +/- 7mmHg (95%CI: 5 to 12mmHg) derived from the meta-analytic approach. The between-replicate correlations were moderate-to-large for plasma nitrate, nitrite and systolic BP (r=0.55 to 0.91). Conclusions: The effects of dietary nitrate supplementation on NO biomarkers and systolic BP varied significantly from participant to participant. The causes of this inter-individual variation deserve further investigation. Trial registration: https://clinicaltrials.gov/study/NCT05514821.

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A replicate crossover trial on the inter-individual variability of sleep indices in response to acute exercise undertaken by healthy men

October 2024

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55 Reads

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1 Citation

Sleep

Study objectives Using the necessary replicate-crossover design, we investigated whether there is inter-individual variability in home-assessed sleep in response to acute exercise. Methods Eighteen healthy men (mean(SD): 26(6) years) completed two identical control (8-h laboratory rest, 08:45-16:45) and two identical exercise (7-h laboratory rest; 1-h laboratory treadmill run [62(7)% peak oxygen uptake], 15:15-16:15) trials in randomised sequences. Wrist-worn actigraphy (MotionWatch 8) measured home-based sleep (total sleep time, actual wake time, sleep latency, sleep efficiency) two nights before (nights 1-2) and three nights after (nights 3-5) the exercise/control day. Pearson’s correlation coefficients quantified the consistency of individual differences between the replicates of control-adjusted exercise responses to explore: (1) immediate (night 3 minus night 2); (2) delayed (night 5 minus night 2); and (3) overall (average post-intervention minus average pre-intervention) exercise-related effects. Within-participant linear mixed models and a random-effects between-participant meta-analysis estimated participant-by-trial response heterogeneity. Results For all comparisons and sleep outcomes, the between-replicate correlations were non-significant, ranging from trivial-to-moderate (r range = -0.44 to 0.41, P≥0.065). Participant-by-trial interactions were trivial. Individual differences SDs were small, prone to uncertainty around the estimates indicated by wide 95% confidence intervals and did not provide support for true individual response heterogeneity. Meta-analyses of the between-participant, replicate-averaged condition effect revealed that, again, heterogeneity (τ) was negligible for most sleep outcomes. Conclusion Control-adjusted sleep in response to acute exercise was inconsistent when measured on repeated occasions. Inter-individual differences in sleep in response to exercise were small compared to the natural (trial-to-trial) within-subject variability in sleep outcomes.


Are there interindividual differences in the reactive hypoglycaemia response to breakfast? A replicate crossover trial

September 2024

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60 Reads

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2 Citations

European Journal of Nutrition

Background Following consumption of a meal, circulating glucose concentrations can rise and then fall briefly below the basal/fasting concentrations. This phenomenon is known as reactive hypoglycaemia but to date no researcher has explored potential inter-individual differences in response to meal consumption. Objective We conducted a secondary analysis of existing data to examine inter-individual variability of reactive hypoglycaemia in response to breakfast consumption. Methods Using a replicate crossover design, 12 healthy, physically active men (age: 18–30 y, body mass index: 22.1 to 28.0 kg⋅m− 2) completed two identical control (continued overnight fasting) and two breakfast (444 kcal; 60% carbohydrate, 17% protein, 23% fat) conditions in randomised sequences. Blood glucose and lactate concentrations, serum insulin and non-esterified fatty acid concentrations, whole-body energy expenditure, carbohydrate and fat oxidation rates, and appetite ratings were determined before and 2 h after the interventions. Inter-individual differences were explored using Pearson’s product-moment correlations between the first and second replicates of the fasting-adjusted breakfast response. Within-participant covariate-adjusted linear mixed models and a random-effects meta-analytical approach were used to quantify participant-by-condition interactions. Results Breakfast consumption lowered 2-h blood glucose by 0.44 mmol/L (95%CI: 0.76 to 0.12 mmol/L) and serum NEFA concentrations, whilst increasing blood lactate and serum insulin concentrations (all p < 0.01). Large, positive correlations were observed between the first and second replicates of the fasting-adjusted insulin, lactate, hunger, and satisfaction responses to breakfast consumption (all r > 0.5, 90%CI ranged from 0.03 to 0.91). The participant-by-condition interaction response variability (SD) for serum insulin concentration was 11 pmol/L (95%CI: 5 to 16 pmol/L), which was consistent with the τ-statistic from the random-effects meta-analysis (11.7 pmol/L, 95%CI 7.0 to 22.2 pmol/L) whereas effects were unclear for other outcome variables (e.g., τ-statistic value for glucose: 0 mmol/L, 95%CI 0.0 to 0.5 mmol/L). Conclusions Despite observing reactive hypoglycaemia at the group level, we were unable to detect any meaningful inter-individual variability of the reactive hypoglycaemia response to breakfast. There was, however, evidence that 2-h insulin responses to breakfast display meaningful inter-individual variability, which may be explained by relative carbohydrate dose ingested and variation in insulin sensitivity of participants.





Table 1
Are there interindividual differences in the reactive hypoglycaemia response to breakfast? A replicate crossover trial

April 2024

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60 Reads

Background Following consumption of a meal, circulating glucose concentrations can rise and then fall briefly below the basal/fasting concentrations. This phenomenon is known as reactive hypoglycaemia but to date no study explored potential inter-individual differences in response to meal consumption. Objective We conducted a secondary analysis of existing data to examine inter-individual variability of reactive hypoglycaemia in response to breakfast consumption. Methods Using a replicate crossover design, 12 healthy men completed two identical control (continued overnight fasting) and two breakfast (444 kcal) conditions in randomised sequences. Blood glucose and lactate concentrations, serum insulin and non-esterified fatty acid concentrations, whole-body energy expenditure, carbohydrate and fat oxidation rates, and appetite ratings were determined before and 2 hours after the interventions. Inter-individual differences were explored using Pearson’s product-moment correlations between the first and second replicates of the control-adjusted breakfast response. Within-participant covariate-adjusted linear mixed models and a random-effects meta-analytical approach were used to quantify participant-by-condition interactions. Results Breakfast consumption lowered 2-h blood glucose 0.44 mmol/L (95%CI: 0.76 to 0.12 mmol/L) and serum NEFA concentrations, whilst increasing blood lactate and serum insulin concentrations (all p < 0.01). Large, positive correlations were observed between the first and second replicates of the control-adjusted insulin, lactate, hunger, and satisfaction responses to breakfast consumption (all r > 0.5, 90%CI ranged from 0.03 to 0.91). The participant-by-condition interaction response variability (SD) for serum insulin concentration was 11 pmol/L (95%CI: 5 to 16 pmol/L), which was consistent with the τ-statistic from the random-effects meta-analysis (11.7 pmol/L, 95%CI 7.0 to 22.2 pmol/L) whereas effects were unclear for other outcome variables (e.g., τ-statistic value for glucose: 0 mmol/L, 95%CI 0.0 to 0.5 mmol/L). Conclusions Despite observing reactive hypoglycaemia at the group level, we were unable to detect any meaningful inter-individual variability of the reactive hypoglycaemia response to breakfast. There was, however, evidence that 2-h insulin responses to breakfast display meaningful inter-individual variability, which may be explained by relative carbohydrate dose ingested and variation in insulin sensitivity of participants.


The Test–Retest Reliability of Pain Outcome Measures in People With Phantom Limb Pain

April 2024

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25 Reads

Clinical Journal of Pain

Objectives To quantify the test-retest reliability of three patient-reported outcome measures of pain for people living with phantom limb pain (PLP) and assess impact of test-retest errors on future research and clinical decisions. Methods Thirty-nine participants (30 males), mean (SD) age: 55 (16), mean (SD) years post amputation: 6.8 (8.3), reported their PLP levels on a Visual Analogue Scale (VAS) for pain intensity, the revised Short Form McGill Pain Questionnaire (SF-MPQ-2), and a pain diary, on two occasions 7-14 days apart. Mean systematic change, within-subjects SD, limits of agreement (LOA), coefficient of variation and the intraclass correlation coefficient (ICC) were quantified alongside their respective 95% confidence intervals (95%CI). Results Systematic learning effects (mean changes) were not clinically relevant across the VAS, SF-MPQ-2 and pain diary. Within-subjects SDs (95%CI) were 11.8 (9.6-15.3), 0.9 (0.7-1.2), and 8.6 (6.9-11.5), respectively. LOA (95%CI) were 32.6 (26.5-42.4), 2.5 (2-3.3), and 23.9 (19.2-31.8), respectively. ICCs (95%CI) were 0.8 (0.6-0.9), 0.8 (0.7-0.9), and 0.9 (0.8-0.9), respectively, but may have been inflated by sample heterogeneity. The test-retest errors allowed detection of clinically relevant effect sizes with feasible sample sizes in future studies, but individual errors were large. Discussion For people with PLP, a pain intensity VAS, the SF-MPQ-2, and a pain diary show an acceptable level of inter-session reliability for use in future clinical trials with feasible sample sizes. Nevertheless, the random error observed for all three of the pain outcome measures suggests they should be interpreted with caution in case studies and when monitoring individuals’ clinical status and progress.


Flow chart of included studies
Forest plot of studies using risk ratio data. CI confidence interval, REML restricted maximum likelihood
Forest plot of studies using hazard ratio data. CI confidence interval, REML restricted maximum likelihood
Risk ratio funnel plot. CI confidence interval
The Effects of Exercise-Based Injury Prevention Programmes on Injury Risk in Adult Recreational Athletes: A Systematic Review and Meta-Analysis

October 2023

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176 Reads

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5 Citations

Sports Medicine

Background Injuries are common in adult recreational athletes. Exercise-based injury prevention programmes offer the potential to reduce the risk of injury and have been a popular research topic. Yet, syntheses and meta-analyses on the effects of exercise-based injury prevention programmes for adult recreational athletes are lacking. Objectives We aimed to synthesise and quantify the pooled intervention effects of exercise-based injury prevention programmes delivered to adults who participate in recreation sports. Methods Studies were eligible for inclusion if they included adult recreational athletes (aged > 16 years), an exercise-based intervention and used a randomised controlled trial design. Exclusion criteria were studies without a control group, studies using a non-randomised design and studies including participants who were undertaking activity mandatory for their occupation. Eleven literature databases were searched from earliest record, up to 9 June, 2022. The Physiotherapy Evidence Database (PEDro) scale was used to assess the risk of bias in all included studies. Reported risk statistics were synthesised in a random-effects meta-analysis to quantify pooled treatment effects and associated 95% confidence intervals and prediction intervals. Results Sixteen studies met the criteria. Risk statistics were reported as risk ratios [RRs] (n = 12) or hazard ratios [HRs] (n = 4). Pooled estimates of RRs and HRs were 0.94 (95% confidence interval 0.80–1.09) and 0.65 (95% confidence interval 0.39–1.08), respectively. Prediction intervals were 0.80–1.09 and 0.16–2.70 for RR and HR, respectively. Heterogeneity was very low for RR studies, but high for HR studies (tau = 0.29, I2 = 81%). There was evidence of small study effects for RR studies, evidenced by funnel plot asymmetry and Egger’s test for small study bias: − 0.99 (CI − 2.08 to 0.10, p = 0.07). Conclusions Pooled point estimates were suggestive of a reduced risk of injury in intervention groups. Nevertheless, these risk estimates were insufficiently precise, too heterogeneous and potentially compromised by small study effects to arrive at any robust conclusion. More large-scale studies are required to clarify whether exercise-based injury prevention programmes are effective in adult recreational athletes.


Figure 2. Within player correlations between changes in thermal variables and log-transformed RPE load variables, error bars representing 95% confidence intervals. Statistically significant correlations, where the 95% confidence interval does not overlap zero, are indicated by black diamond markers.
Figure 3. Individual within-player regression slopes between kick-off temperature and high-speed running distance.
Outcome measure descriptive statistics.
Elite North American soccer performance in thermally challenging environments: An explorative approach to tracking outcomes

September 2023

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187 Reads

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4 Citations


Citations (79)


... To examine this, we determined concentrations of key metabolites and insulin in plasma. The smaller athletes displayed larger insulin and lactate responses at the onset of exercise compared with larger athletes, which may be explained by the greater relative dose of glucose ingested (Gonzalez et al., 2024). Another putative explanation for higher lactate responses could be that identification of lactate threshold was erroneous, and thus, exercise intensity was higher in the smaller athletes. ...

Reference:

Exogenous Glucose Oxidation During Exercise Is Positively Related to Body Size
Are there interindividual differences in the reactive hypoglycaemia response to breakfast? A replicate crossover trial

European Journal of Nutrition

... Addressing lower-limb asymmetry in this population is highly important, as all movements are performed unilaterally, which can exacerbate the increase in asymmetries. These asymmetries can predispose athletes to injuries or a reduction in performance [25,26] Although this study was focused on adolescent female players, and it may limit the generalization of the findings, this sample was chosen because it represents an important stage in the development of strength and coordination. This study indicates that during adolescence, the neuromuscular systems become more refined, leading to more coordinated movement patterns, something essential to developing sport performance [27]. ...

The Effects of Exercise-Based Injury Prevention Programmes on Injury Risk in Adult Recreational Athletes: A Systematic Review and Meta-Analysis

Sports Medicine

... In contrast, analyses of smaller regional and local sports events have received rather limited attention to date. In addition, existing studies appear to have focused on a selected number of countries, seemingly those in which sports events have already been somewhat affected by climate change in one way or another (for example, through extended heatwaves, forest fires, or the melting of snow and ice), such as the US, Canada, Australia and Austria [e.g., (14,16,(19)(20)(21)(22)(23)(24)]. Finally, the event industry as a whole lacks a unified approach among stakeholders to comprehensively understand and mitigate the adverse effects of climate change from a planning and organizational perspective and to devise strategies for adaptation (9,10,25). ...

Elite North American soccer performance in thermally challenging environments: An explorative approach to tracking outcomes

... The analysis protocol (which included data for all 15 participants) followed a four-step 168 approach consistent with previous research [30,31,33] and more recent advances [34] is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint ...

Are There Interindividual Responses of Cardiovascular Disease Risk Markers to Acute Exercise? A Replicate Crossover Trial
  • Citing Article
  • September 2023

Medicine and Science in Sports and Exercise

... High pain intensity or prolonged pain duration can negatively impact patients' muscular function (14), and the duration of neuropathic pain may affect the efficacy of pharmacological treatments (15). Baseline pain duration can also influence patient referrals (16). Despite its clinical importance, the relationship between pain duration characteristics and pain intensity in herpes zoster-related pain remains underexplored. ...

Does pain duration and other variables measured at baseline predict re-referral of low back pain patients managed on an evidence-based pathway? A cohort study
  • Citing Article
  • July 2023

Physiotherapy

... Studies supporting the 'constraint model' (i) were mostly observational in free living subjects at different levels of PA, (ii) did not take into account the effects of a negative energy balance (due to excessive exercise with at the same time insufficient energy intake) and its effect on possible hormonal determinants of EE, and (iii) had some methodological and statistical limitations (Gonzalez et al. 2023). Recently, two publications have put the 'constraint model' into perspective. ...

Perspective: Is the Response of Human Energy Expenditure to Increased Physical Activity Additive or Constrained?
  • Citing Article
  • February 2023

Advances in Nutrition

... This treatment strategy has the advantages in comparison with conventional approaches because it can be used not only for the proper glycemic control but also for effective weight loss, which is one of the main problems of this patient population. Although the presented authors identified a need for additional studies to assess the safety and effectiveness of the chosen combination, their results indicate a tremendous impact on clinical prognosis for patients with obesity and T1D [7]. ...

Glucagon-like peptide-1 secretion in people with versus without type 2 diabetes: a systematic review and meta-analysis of cross-sectional studies
  • Citing Article
  • December 2022

Metabolism

... Future research should explore alternative methods to evaluate competition and test performance against age and maturity to avoid compromising the statistical power. In addition, there is conflicting evidence regarding the efficacy of the PPAH method in correctly assigning athletes to maturity groups (32,44). Despite these potential limitations, using PPAH offers a practical, time-efficient solution to determine the maturity status repeatedly, overcoming medical restrictions on the number of Xrays and the time-consuming nature of the measurement and analysis procedures. ...

The Percentage of Mature Height as a Morphometric Index of Somatic Growth: A Formal Scrutiny of Conventional Simple Ratio Scaling Assumptions
  • Citing Article
  • September 2022

Pediatric Exercise Science

... To mitigate the occurrence of TANEC, it is crucial to identify the high-risk population and delineate specific transfusion characteristics associated with TANEC. Our study suggests that very preterm infants at 15-42 DOL or at 31-34 weeks may be more susceptible to developing TANEC, and thus could potentially benefit from preventive measures such as considering withholding feeding during transfusions 29,30 . It is also possible that the underlying cause is the high incidence of anemia during this period, which requires more blood transfusions. ...

Effects of Freshly Irradiated vs Irradiated and Stored Red Blood Cell Transfusion on Cerebral Oxygenation in Preterm Infants: A Randomized Clinical Trial

JAMA Pediatrics

... With the Findability, Accessibility, Interoperability, and Reusability principles for data sharing in mind (18), authors should share data and relevant codes when questions arise (1) as failure to uphold methodological standards leads to ethical problems (17), and it may class as misconduct (9) that should be addressed as appropriate (1,9,17). 7. Unless, for example, assessments took place in national federation settings (8,11), it remains unclear how exactly any reference chart developed from a single football academy may represent a local (i.e., national) reference as Ruf et al (14) seem to misdescribe, given the original study context itself (13), the size of the state of Germany, and the presence of many other academies across the country, which define the population of German football players (6). ...

Reference values for performance test outcomes relevant to English female soccer players
  • Citing Article
  • January 2022