Myths and Methodologies: Standardisation in Human Physiology Research-Should We Control the Controllables?

The premise of research in human physiology is to explore a multifaceted system whilst identifying one or a few outcomes of interest. Therefore, the control of potentially confounding variables requires careful thought regarding the extent of control and complexity of standardisation. One common factor to control prior to testing is diet, as food and fluid provision may deviate from participants' habitual diets, yet a self-report and replication method can be flawed by under-reporting. Researchers may also need to consider standardisation of physical activity, whether it be through familiarisation trials, wash-out periods, or guidance on levels of physical activity to be achieved before trials. In terms of pharmacological agents, the ethical implications of standardisation require researchers to carefully consider how medications, caffeine consumption and oral contraceptive prescriptions may affect the study. For research in females, it should be considered whether standardisation between- or within-participants in regards to menstrual cycle phase is most relevant. The timing of measurements relative to various other daily events is relevant to all physiological research and so it can be important to standardise when measurements are made. This review summarises the areas of standardisation which we hope will be considered useful to anyone involved in human physiology research, including when and how one can apply standardisation to various contexts.

Myths and Methodologies: Standardisation in human physiology research-should we control the controllables?

The premise of research in human physiology is to explore a multifaceted system whilst identifying one or a few outcomes of interest. Therefore, the control of potentially confounding variables requires careful thought regarding the extent of control and complexity of standardisation. One common factor to control prior to testing is diet, as food and fluid provision may deviate from participants' habitual diets, yet a self-report and replication method can be flawed by under-reporting. Researchers may also need to consider standardisation of physical activity, whether it be through familiarisation trials, wash-out periods, or guidance on levels of physical activity to be achieved before trials. In terms of pharmacological agents, the ethical implications of standardisation require researchers to carefully consider how medications, caffeine consumption and oral contraceptive prescriptions may affect the study. For research in females, it should be considered whether standardisation between- or within-participants in regards to menstrual cycle phase is most relevant. The timing of measurements relative to various other daily events is relevant to all physiological research and so it can be important to standardise when measurements are made. This review summarises the areas of standardisation which we hope will be considered useful to anyone involved in human physiology research, including when and how one can apply standardisation to various contexts.

Exercise snacking to improve physical function in pre-frail older adult memory clinic patients: a 28-day pilot study.

BACKGROUND: Finding innovative yet feasible ways of preventing physical and cognitive decline in those at risk is a critical global challenge, with exercise being championed as a key precursor to robust health in later life. Exercise snacking, here defined as short bouts of sporadic [muscle-strengthening] exercise, is one such strategy designed to overcome typical participation barriers observed in older adults. This study examined the acceptability of exercise snacking amongst pre-frail older adults and explored the efficacy of this approach in improving physical function. METHODS: In this single group design, 21 pre-frail outpatients with mild-cognitive impairment were recruited from a UK memory clinic. To be eligible, participants were aged ≥ 65-years who scored 3-8 (inclusive) on the short physical performance battery (SPPB) and were not regularly engaging in sport or exercise. Participants completed a 28-day, twice daily, exercise snacking intervention, consisting of five muscle-strengthening exercises, with the aim being to complete as many repetitions as possible of each exercise in a minute. Acceptability of the intervention was measured quantitatively and qualitatively using a survey and topic guide informed by the Theoretical Framework of Acceptability. Pre- and post-intervention physical function was measured using the SPPB, timed up-and-go (TUG), and 60s standing balance and sit-to-stand tests. RESULTS: Eighteen participants provided follow-up data and showed 85% adherence to the exercise snacking intervention, measured as the proportion of all sessions completed out of a possible 56. Participants rated the intervention as highly acceptable (4.6/5) suggesting it supported their self-efficacy (4.3/5) was enjoyable (4.1/5) and had a low burden (2.1/5). Qualitative findings suggested the ease of use, flexibility of the programme, and perceived effectiveness was important, and particularly useful for non-exercisers. Changes in SPPB score (8(1) vs. 9(3), p < 0.01), TUG (11.32(4.02) vs. 9.18(5.25) seconds, p < 0.01) and in the 60-second sit-to-stand test (17 ± 5 vs. 23 ± 7 repetitions, p < 0.01) were seen between baseline and follow-up. CONCLUSIONS: Exercise snacking is an acceptable and potentially efficacious format of exercise for pre-frail memory clinic attendees who are at heightened risk of falling and frailty. Large scale randomised controlled trials are required to confirm whether exercise snacking is effective in the short and long term. GOV REGISTRATION: NCT05439252 (30/06/2022).

The acceptability of homebased exercise snacking and Tai-chi snacking amongst high and low function UK and Taiwanese older adults.

Introduction: Exercise "snacking" and Tai-chi 'snacking' protocols are designed to overcome typical barriers to older adults' participation in muscle strength and balance exercise, using short bouts of home-based exercise. This study aimed to investigate the acceptability of homebred exercise- and Tai-chi snacking in British and Taiwanese older adults of high and low physical function. Methods: Thirty-three British and Thirty Taiwanese older adults took part in semi-structured interviews, after trying 1-week of exercise- and Tai-chi snacking. The interview schedule and deductive framework analysis was based on the seven components of the Theoretical Framework of Acceptability (TFA). Differences between the Taiwanese and United Kingdom participants and those considered high versus low physical function were also analysed. Results: Both snacking regimes were found to be convenient and easy to implement. Participants reported that no activity had to be given up, and considered the programmes would be beneficial to their physical and mental health. Interestingly, more UK-based participants preferred the elegant and relaxing movements of Tai-chi snacking, yet participants with low physical function experienced difficulties when mastering Tai-chi movements. A few high physical function participants perceived exercise snacking to be tedious. Discussion: Overall, the snacking exercise was found to be acceptable and useful. Personal affective attitude and different cultural backgrounds may affect exercise participation. Nevertheless, it is important to consider individuals' physical function when designing exercise regime. The findings indicate that making Tai-chi snacking easier to master initially, building in progression and adding some upper body movements in the exercise snacking may further enhance acceptability.

Postprandial Metabolic Mesponses to High-fat Feeding in Healthy Adults Following Ingestion of Oolong Tea-Derived Polymerized Polyphenols: A Randomized, Double-blinded, Placebo-controlled Crossover Study.

BACKGROUND: Polymerized polyphenols (PP) found in oolong tea can inhibit pancreatic lipase activity in vitro, and pilot work indicates that this may reduce postprandial lipemia. Since tea contains caffeine and catechins, the interactions between these ingredients and PP warrant investigation. OBJECTIVES: To assess whether PP ingested alone or with caffeine and catechins lowers postprandial lipemia. METHODS: Fifty healthy adults [mean (SD) age: 26 (7) y; BMI (in kg/m2): 24.0 (2.7); female: n = 16] completed 4 oral lipid tolerance tests in a placebo-controlled randomized, crossover design. Participants ingested 40 g of fat with either 1) placebo, 2) 100 mg PP, 3) 150 mg PP, or 4) 100 mg PP plus 50 mg caffeine and 63 mg catechins (PP + CC). Blood was sampled for 3 h postprandially to assess concentrations of serum and plasma triacylglycerol and plasma markers of lipid (NEFA; glycerol; LDL and HDL cholesterol; and ApoA-I, A-II, B, C-II, C-III, and E) and glucose metabolism (glucose, insulin, and C-peptide). RESULTS: Serum and plasma triacylglycerol concentrations and lipid metabolism variables generally increased following any test drink ingestion (main effect of time, p < 0.001). Nevertheless, for the lipid metabolism responses, there were no statistically significant condition-time interactions and no statistically significant differences in incremental or total area under the curve between conditions, apart from HDL cholesterol (p = 0.021). Ingesting 100 mg PP + CC lowered peak plasma glucose, insulin, and C-peptide concentrations compared with all other conditions 30 min postingestion (p < 0.001), with persistent alterations in glucose concentrations observed for 90 min compared with placebo and 100 mg PP conditions. CONCLUSIONS: PP ingested at doses ≤150 mg does not clearly alter early-phase postprandial triacylglycerol concentrations in healthy adults, irrespective of the presence or absence of caffeine and catechins. Nevertheless, caffeine and catechins added to PP lowered postprandial glucose and insulin concentrations. This trial was registered in ClinicalTrials.gov as NCT03324191 (https://clinicaltrials.gov/ct2/show/NCT03324191).

Feasibility and Acceptability of Home-Based Exercise Snacking and Tai Chi Snacking Delivered Remotely to Self-Isolating Older Adults During COVID-19.

The purpose of this study was to examine the feasibility and acceptability of remotely delivered, home-based exercise programs on physical function and well-being in self-isolating older adults during the COVID-19 pandemic. In a four-arm randomized controlled trial, 63 participants (aged 65 years and older) were allocated to one of three home-based daily (2 × 10-min) exercise interventions (exercise snacking, tai chi snacking, and combination) or control (UK National Health Service Web pages). Functional assessments were conducted via video call at baseline and 4-week follow-up. A web-based survey assessed the acceptability of each exercise program and secondary psychological/well-being outcomes. Ecological momentary assessment data, collected in Weeks 1 and 4, explored feeling states as antecedents and consequences of exercise. All intervention groups saw increased physical function at follow-up and displayed good adherence with exercise snacking considered the most acceptable program. Multilevel models revealed reciprocal associations between feelings of energy and exercise engagement. Further studies are needed with larger, more diverse demographic samples.

Effects of neuromuscular electrical stimulation on energy expenditure and postprandial metabolism in healthy men.

It is unclear whether neuromuscular electrical stimulation (NMES) has meaningful metabolic effects when users have the opportunity to self-select the intensity to one that can be comfortably tolerated. Nine healthy men aged 28 ± 9 y (mean ± SD) with a body mass index 22.3 ± 2.3 kg/m2 completed 3 trials involving a 2-h oral glucose tolerance test whilst, in a randomised counterbalanced order, (1) sitting motionless (SIT), (2) standing motionless (STAND); and (3) sitting motionless with NMES of quadriceps and calves at a self-selected tolerable intensity. The mean (95% confidence interval [CI]) total energy expenditure was greater in the NMES trial (221 [180-262] kcal/2 h) and STAND trial (178 [164-191] kcal/2 h) than during SIT (159 [150-167] kcal/2 h) (both, p < 0.05). This was primarily driven by an increase in carbohydrate oxidation in the NMES and STAND trials compared with the SIT trial (p < 0.05). Postprandial insulin iAUC was lower in both NMES and STAND compared with SIT (16.4 [7.7-25.1], 17 [7-27] and 22.6 [10.8-34.4] nmol·120 min/L, respectively; both, p < 0.05). Compared with sitting, both NMES and STAND increased energy expenditure and whole-body carbohydrate oxidation and reduced postprandial insulin concentrations in healthy men, with more pronounced effects seen with NMES. Self-selected NMES is a potential strategy for improving metabolic health. This trial is registered at ClinicalTrials.gov (ID: NCT04389736). Novelty: NMES at a comfortable intensity enhances energy expenditure and carbohydrate oxidation, and reduces postprandial insulinemia. Thus, self-selected NMES represents a potential strategy to improve metabolic health.

Glucose control upon waking is unaffected by hourly sleep fragmentation during the night, but is impaired by morning caffeinated coffee.

Morning coffee is a common remedy following disrupted sleep, yet each factor can independently impair glucose tolerance and insulin sensitivity in healthy adults. Remarkably, the combined effects of sleep fragmentation and coffee on glucose control upon waking per se have never been investigated. In a randomised crossover design, twenty-nine adults (mean age: 21 (sd 1) years, BMI: 24·4 (sd 3·3) kg/m2) underwent three oral glucose tolerance tests (OGTT). One following a habitual night of sleep (Control; in bed, lights-off trying to sleep approximately 23.00-07.00 hours), the others following a night of sleep fragmentation (as Control but waking hourly for 5 min), with and without morning coffee approximately 1 h after waking (approximately 300 mg caffeine as black coffee 30 min prior to OGTT). Individualised peak plasma glucose and insulin concentrations were unaffected by sleep quality but were higher following coffee consumption (mean (normalised CI) for Control, Fragmented and Fragmented + Coffee, respectively; glucose: 8·20 (normalised CI 7·93, 8·47) mmol/l v. 8·23 (normalised CI 7·96, 8·50) mmol/l v. 8·96 (normalised CI 8·70, 9·22) mmol/l; insulin: 265 (normalised CI 247, 283) pmol/l; and 235 (normalised CI 218, 253) pmol/l; and 310 (normalised CI 284, 337) pmol/l). Likewise, incremental AUC for plasma glucose was higher in the Fragmented + Coffee trial compared with Fragmented. Whilst sleep fragmentation did not alter glycaemic or insulinaemic responses to morning glucose ingestion, if a strong caffeinated coffee is consumed, then a reduction in glucose tolerance can be expected.

Exercise Snacking to Improve Muscle Function in Healthy Older Adults: A Pilot Study.

Loss of muscle mass and strength are seemingly accepted as part of the ageing process, despite ultimately leading to the loss of independence. Resistance exercise is considered to be primary defence against loss of muscle function in older age, but it typically requires access to exercise equipment often in a gym environment. This pilot study aimed at examining the effect of a 28-day, unsupervised home-based exercise intervention on indices of leg strength and muscle size in healthy older adults. Twenty participants were randomly assigned to either maintain their habitual physical activity levels (Control; n=10; age, 74 (5) years; body mass, 26.3 (3.5) kg/m2) or undertake "exercise snacks" twice daily (ES; n=10; age, 70 (4) years; body mass, 25.0 (3.4) kg/m2). Both groups consumed 150 g of yogurt at their breakfast meal for the duration of the intervention. Sixty-second sit-to-stand score improved by 31% in ES, with no change in Control (p < 0.01). Large effect sizes were observed for the difference in change scores between the groups for interpolated maximum leg pressing power (6% increase in ES) and thigh muscle cross-sectional area (2% increase in ES). The present pilot data suggest that exercise snacking might be a promising strategy to improve leg muscle function and size in older adults and that further investigation into zero-cost exercise strategies that allow high frequency of training is warranted.

Habitual physical activity levels do not predict leg strength and power in healthy, active older adults.

Physical activity is considered crucial in attenuating losses in strength and power associated with ageing. However, in well-functioning, active older adults the relationship between habitual physical activity and muscle function is surprisingly unclear. Leg press velocity, force, and power, were compared between 50 older and 30 younger healthy individuals, and associations with habitual physical activity explored. An incremental power test was performed on a pneumatic leg press, with theoretical maximum velocity, force, and power calculated. Vastus lateralis muscle thickness was measured by ultrasound, and participants wore a combined accelerometer and heart rate monitor for 6-days of free-living. Older individuals produced lower absolute maximum velocity, force, and power, than younger individuals. When accounting for smaller muscle size, older individual's maximum force and power remained markedly lower. Both groups were active, however using age specific thresholds for classifying physical activity, the older individuals engaged in twice the amount of moderate-to-vigorous physical activity in comparison to the younger individuals. There were no associations between any characteristics of muscle function and physical activity. These data support that the ability to generate force and power deteriorates with age, however habitual physical activity levels do not explain inter-individual differences in muscle function in active older individuals.

The Effect of Age on Technique Variability and Outcome Variability during a Leg Press.

The aim of this study was to determine the effect of aging on power generation and joint coordination during a leg press, in order to increase understanding of how functional movements are affected during the aging process. 44 older and 24 younger adults performed eight sub-maximal power repetitions on a seated leg press dynamometer. Peak power and velocity (at 40% maximum resistance) were measured along with the coordination (coupling angle) of the lower limb joints using the vector coding technique. The younger adults produced significantly greater peak power than the older adults (mean ± SD; 762 W ± 245 vs 361 W ± 162, p < 0.01) and at higher peak velocities (mean ± SD; 1.37 m/s ± 0.05 vs 1.00 m/s ± 0.06, p < 0.01). The older adults produced less consistent values of peak power than younger adults, evidenced by a higher coefficient of variation (mean ± SD; 7.6% ± 5.2 vs 5.0% ± 3.0, p < 0.01), however, there was significantly less variability in the coupling angles displayed by the older adults compared to the younger adults (mean ± SD; 2.0° ± 1.1 vs 3.5° ± 2.7, p < 0.01 (ankle-knee); 1.7° ± 0.6 vs 4.1° ± 3.0, p < 0.01 (knee-hip)). The results of this study demonstrate that older adults display higher outcome variability but lower variability in technique (coordination). The more rigid movement strategies displayed by the older adults potentially reflects an increased risk of overuse injury due to repetitive demands on the same structures, or the reduced ability to respond to unexpected situations due to a lack of flexibility in joint control.

Exercise strategies to protect against the impact of short-term reduced physical activity on muscle function and markers of health in older men: study protocol for a randomised controlled trial.

BACKGROUND: Muscles get smaller and weaker as we age and become more vulnerable to atrophy when physical activity is reduced or removed. This research is designed to investigate the potentially protective effects of two separate exercise strategies against loss in skeletal muscle function and size, and other key indices of health, following 14 days of reduced physical activity in older men. METHODS: Three groups of 10 older men (aged 65-80 years) will undertake 2 weeks of reduced activity by decreasing daily steps from more than 3500 to less than 1500 (using pedometers to record step count). Two of the three groups will then undertake additional exercise interventions, either: 4 weeks of progressive resistance training prior to the step-reduction intervention (PT-group), or home-based 'exercise snacking' three times per day during the step-reduction intervention (ES-group). The third group undertaking only the step-reduction intervention (control) will provide a comparison against which to assess the effectiveness of the protective exercise strategies. Pre and post step-reduction assessments of muscle function, standing balance, anthropometry and muscle architecture will be taken. Pre and post step-reduction in postprandial metabolic control, resting systemic inflammation, adipose inflammation, oxidative stress, immune function, sleep quality, dietary habits, and quality of life will be measured. The stress response to exercise, and signalling protein and gene expression for muscle protein synthesis and breakdown following an acute bout of exercise will also be assessed pre and post step-reduction. Rates of muscle protein synthesis and adipose triglyceride turnover during the step-reduction intervention will be measured using stable isotope methodology. All participants will then undertake 2 weeks of supervised resistance training with the aim of regaining any deficit from baseline in muscle function and size. DISCUSSION: This study aims to identify exercise strategies that could be implemented to protect against loss of muscle power during 2 weeks of reduced activity in older men, and to improve understanding of the way in which a short-term reduction in physical activity impacts upon muscle function and health. TRIAL REGISTRATION: ClinicalTrials.gov: NCT02495727 (Initial registration: 25 June 2015).

A reduced activity model: a relevant tool for the study of ageing muscle.

Skeletal muscle mass is in a constant state of turnover, and atrophy is the result of a shift in the balance of muscle protein synthesis and breakdown resulting in net muscle protein loss. Total disuse of skeletal muscle quickly leads to muscle atrophy and loss of strength, and this has been repeatedly demonstrated in studies employing bed rest and lower limb immobilisation methodologies in young healthy participants. Fewer studies have focused on older participants (>65 years of age), but those that have provide evidence that advancing age brings increased vulnerability to rapid and marked loss of muscle size and strength during period of total muscle unloading. Increased systemic inflammation and reduced protein synthetic responses to protein feeding and muscle contraction might influence the severity of muscle protein loss during periods of total unloading compared with younger individuals. Less extreme reductions in muscle loading (e.g., 2 weeks of reducing daily ambulation to <1500 steps/day) have also been shown to result in decreases in muscle mass. This step-reduction model may be more relevant than total bed rest or limb immobilisation for examining real-world scenarios that present a physiological challenge to the maintenance of skeletal muscle mass in older individuals.