Individual differences in the responses to endurance and resistance training

Exerkine response to acute exercise: Still much to discover

•Exerkines mediate, at least partly, the salutary effects of exercise. •However, the actual responsiveness and time-course profile of most of these molecules remains unknown. •Future research should explore potential factors explaining inter-individual variability in exerkine responses.

HRV-guided training vs traditional HIIT training in cardiac rehabilitation: a randomized controlled trial

High-intensity interval training is the gold standard for cardiac rehabilitation although current revascularization therapy focuses on the recovery of autonomic nervous system balance through heart rate variability (HRV). The main objective was to analyze the effect of HRV-guided training versus high-intensity interval training on cardiorespiratory fitness, heart rate variability, quality of life, and training volume at high intensity, as well as exercise adherence, safety, and feasibility in ischemic patients. This is an 8-week cluster randomized controlled trial with an HRV-based training group (HRV-G) and a traditional HIIT group (HIIT-G). Maximal oxygen consumption, heart rate, and blood pressure were measured during the Bruce protocol treadmill test. HRV was measured with the HRV4Training application, and quality of life with the MacNew QLMI. The repeated measures ANCOVA was used with the age and the baseline scores as covariables. Forty-six patients (mean age 55 ± 11.03 years) were randomized and assigned either to HRV-G (n = 23) or HIIT-G (n = 23). Both groups improved maximal oxygen consumption and METS (P > .05). However, the resting systolic blood pressure was lower in HRV-G (4.3 ± 1.2 mmHg, P = .05). In HRV-G, the resting diastolic, maximal diastolic, and systolic blood pressure decreased (5.4 ± 5.96 mmHg, P = .007; 11.4 ± 12.46 mmHg, P = .005; and 5 ± 5.98 mmHg, P = .013, respectively) whereas the recovery heart rate increased significantly (-21.5 ± 23.16 beats/min, P = .003). The LnrMSSDcv ([LnrMSSDSD/LnrMSSDMEAN] × 100) was lower in HRV-G (1.23 ± 0.91 mmHg, P = .03) while the training volume at high intensity was higher in HIIT-G (31.4 ± 29.2 min, P = .024). HRV-guided training presents a better cardioprotective effect than HIIT-G at a lower high-intensity training volume.

Short-term swimming up-regulates pro-inflammatory mediators and cytokines in gilthead seabream (Sparus aurata)

Aerobic swimming exercise in fish has been shown to improve robustness of some species. However, the optimal conditions to be applied and the mechanisms underlying remain unknown. We investigated the effects of 6 h of induced swimming on the immune response of gilthead seabream (Sparus aurata), by analysing markers related to immune status in plasma, skin mucus, gills, heart and head-kidney. Forty fish were individually exercised in swim tunnels by applying different water currents: steady low (SL, 0.8 body lengths (BL) s-1), steady high (SH, 2.3 BL s-1), oscillating low (OL, 0.2/0.8 BL s-1) and oscillating high (OH, 0.8/2.3 BL s-1) velocities, including a non-exercised group with minimal water flow (MF, <0.1 BL s-1). Swimming conditions did not trigger a stress response or anaerobic metabolism, suggested by similar levels of cortisol, lactate, and glucose in plasma among groups. Blood haemoglobin and innate immune parameters in plasma and skin mucus also remained unaltered. However, decreased blood haematocrit was observed in fish swimming on the OL condition. Interestingly, gene expression analysis revealed that the OL condition led to the up-regulation of pro-inflammatory mediators (nfκb1 and mapk3) and cytokines (tnfα, il1β and il6) in gills. A similar response occurred in heart, with an up-regulation of nfκb1, tnfα, il6 and cox2 in the OL condition. Gene expression of these cytokines was unaltered in the head-kidney. The inflammatory response in gills and heart of gilthead seabream triggered by the OL condition highlights the importance of establishing suitable rearing conditions to improve welfare of cultured fish.

Many Pieces to the Puzzle: A New Holistic Workload Approach to Designing Practice in Sports

Representative learning design (RLD) in sport is a well-established concept in both theory and practice. The goal of RLD is to faithfully replicate competition environments in training settings to benefit improvement in athletic performance. There is currently little research that considers how representative an activity needs to be to facilitate learning transfer, and how that level of representativeness might fluctuate between activities or sessions, and across competitive cycles. Similarly, there is no existing research that specifically considers the elevated workload (in cognitive and physical load) of highly representative training, and the potential impacts of chronic overuse of these highly demanding activities. This paper addresses these limitations, making a case for the application of RLD that considers the level of representativeness (fidelity) and the demands placed on athletes (load) from both a cognitive and physical perspective. This paper also suggests several categorisations of training activities that are based on their relative representativeness, level of imposed demands, and the intended outcomes of the activity with reference to the perception-action cycle. The two core concepts of fidelity and load are combined for a new approach to representative training that allows practitioners to balance the benefits of representative training with the risks of imposing excessive load on athletes.

Effects of a 6-wk Sprint Interval Training Protocol at Different Altitudes on Circulating Extracellular Vesicles

PURPOSE

This study aimed to investigate the modulation of circulating exosome-like extracellular vesicles (ELVs) after 6 wk of sprint interval training (SIT) at sea level and at 2000, 3000, and 4000 m.

METHODS

Thirty trained endurance male athletes (18-35 yr) participated in a 6-wk SIT program (30-s all-out sprint, 4-min 30-s recovery; 4-9 repetitions, 2 sessions per week) at sea level ( n = 8), 2000 m (fraction of inspired oxygen (F io2 ) 0.167, n = 8), 3000 m (F io2 0.145, n = 7), or 4000 m (F io2 0.13, n = 7). Venous blood samples were taken before and after the training period. Plasma ELVs were isolated by size exclusion chromatography, counted by nanoparticle tracking analysis, and characterized according to international standards. Candidate ELV microRNAs (miRNAs) were quantified by real-time polymerase chain reaction.

RESULTS

When the three hypoxic groups were analyzed separately, only very minor differences could be detected in the levels of circulating particles, ELV markers, or miRNA. However, the levels of circulating particles increased (+262%) after training when the three hypoxic groups were pooled, and tended to increase at sea level (+65%), with no difference between these two groups. A trend to an increase was observed for the two ELV markers, TSG101 (+65%) and HSP60 (+441%), at sea level, but not in hypoxia. Training also seemed to decrease the abundance of miR-23a-3p and to increase the abundance of miR-21-5p in hypoxia but not at sea level.

CONCLUSIONS

A 6-wk SIT program tended to increase the basal levels of circulating ELVs when performed at sea level but not in hypoxia. In contrast, ELV miRNA cargo seemed to be modulated in hypoxic conditions only. Further research should explore the potential differences in the origin of ELVs between normoxic and local and systemic hypoxic conditions.

Sex differences in cardiovascular risk factor responses to resistance and endurance training in younger subjects

This study compared differences in cardiovascular (CV) risk factor responses between males and females following endurance (END) and resistance (RES) training. We present the frequency of responders to each training modality and the magnitude of response. Using a randomized crossover design, 68 healthy adults [age: female (F): 24.5 ± 4.6; male (M): 27.3 ± 6.6] completed 3 mo of RES and END, with 3 mo washout. Peak oxygen consumption (V̇o_2peak), strength, body composition, blood pressure, glucose, insulin, and lipids were measured. V̇o_2peak (L/min) significantly increased in both sexes following END, but not RES. The magnitude of change was larger in males (F: +0.20 L/min; M: +0.32 L/min), although this did not achieve statistical significance (P = 0.051). Strength significantly increased in both sexes following RES (P < 0.01), with a larger increase in males (Leg press: F: +39 kg; M: +63 kg; P < 0.05). Lean mass significantly increased in both sexes (P < 0.01) following RES and fat mass decreased in females following END (P = 0.019). The change in C-reactive protein following END was significantly different between sexes (F: -0.4 mg/L; M: +0.5 mg/L; P = 0.035). There were no differences between sexes in the proportion of individuals who responded positively to any variable following RES or END; differences between sexes were due to the magnitude of change. Males had a larger increase in V̇o_2peak following END and strength following RES. There were no sex differences in other CV risk factors. This suggests differences in physiological responses to strength and V̇o_2peak may not translate to changes in CV risk in healthy subjects.NEW & NOTEWORTHY This study investigated sex differences in cardiovascular risk factors in response to different exercise training modalities. Males had a larger improvement in peak oxygen consumption following endurance training and strength following resistance training compared with females. These changes in peak oxygen consumption and strength did not translate to changes in other cardiovascular risk factors. Despite the greater magnitude of change in males, there were no sex differences in the proportion of individuals who responded to training.

Unsupervised cluster analysis reveals distinct subgroups in healthy population with different exercise responses of cardiorespiratory fitness

Background

Considerable attention has been paid to interindividual differences in the cardiorespiratory fitness (CRF) response to exercise. However, the complex multifactorial nature of CRF response variability poses a significant challenge to our understanding of this issue. We aimed to explore whether unsupervised clustering can take advantage of large amounts of clinical data and identify latent subgroups with different CRF exercise responses within a healthy population.

Methods

252 healthy participants (99 men, 153 women; 36.8 ± 13.4 yr) completed moderate endurance training on 3 days/week for 4 months, with exercise intensity prescribed based on anaerobic threshold (AT). Detailed clinical measures, including resting vital signs, ECG, cardiorespiratory parameters, echocardiography, heart rate variability, spirometry and laboratory data, were obtained before and after the exercise intervention. Baseline phenotypic variables that were significantly correlated with CRF exercise response were identified and subjected to selection steps, leaving 10 minimally redundant variables, including age, BMI, maximal oxygen uptake (VO_2max), maximal heart rate, VO₂ at AT as a percentage of VO_2max, minute ventilation at AT, interventricular septal thickness of end-systole, E velocity, root mean square of heart rate variability, and hematocrit. Agglomerative hierarchical clustering was performed on these variables to detect latent subgroups that may be associated with different CRF exercise responses.

Results

Unsupervised clustering revealed two mutually exclusive groups with distinct baseline phenotypes and CRF exercise responses. The two groups differed markedly in baseline characteristics, initial fitness, echocardiographic measurements, laboratory values, and heart rate variability parameters. A significant improvement in CRF following the 16-week endurance training, expressed by the absolute change in VO_2max, was observed only in one of the two groups (3.42 ± 0.4 vs 0.58 ± 0.65 ml⋅kg^-1∙min^-1, P = 0.002). Assuming a minimal clinically important difference of 3.5 ml⋅kg^-1∙min^-1 in VO_2max, the proportion of population response was 56.1% and 13.9% for group 1 and group 2, respectively (P<0.001). Although group 1 exhibited no significant improvement in CRF at group level, a significant decrease in diastolic blood pressure (70.4 ± 7.8 vs 68.7 ± 7.2 mm Hg, P = 0.027) was observed.

Conclusions

Unsupervised learning based on dense phenotypic characteristics identified meaningful subgroups within a healthy population with different CRF responses following standardized aerobic training. Our model could serve as a useful tool for clinicians to develop personalized exercise prescriptions and optimize training effects.

Endurance versus resistance training in treatment of cardiovascular risk factors: A randomized cross-over trial

Background

Individual variability in traditional cardiovascular risk factor responses to different exercise modalities has not been directly addressed in humans using a randomized cross-over design.

Methods

Body weight and body mass index, resting blood pressure, blood glucose, insulin and lipids were assessed in 68 healthy untrained adults (26±6 years) who underwent three-months of exercise training targeted at improving cardiopulmonary fitness (endurance) and skeletal muscle function (resistance), separated by three-months washout.

Results

There were significant increases in weight and body mass index following resistance (+0.8 kg, P<0.01; and +0.26 kg/m2, P<0.01, respectively), but not endurance (+0.1 kg, P = 0.75; and +0.03 kg/m2, P = 0.70, respectively). Although no significant group changes resulted from training in other cardiovascular risk factors, the positive response rate for all variables ranged from 27–49% for resistance and 42–58% for endurance. Between 39–59% of individuals who did not respond to resistance nonetheless responded to endurance, and 28–54% who did not respond to endurance responded to resistance.

Conclusion

Whilst, on average, 12 weeks of resistance or endurance did not change most cardiovascular risk factors, many subjects showed robust positive responses. Exercise modality had an impact on the proportion of subjects who responded to training, and non-response to one mode of training did not imply non-response to the alternate mode. Although the effect of exercise on a single risk factor may be modest, the effect on overall cardiovascular risk profile can be dramatic.

Study registration

The study was registered at the Australian New Zealand Clinical Trials Registry, which was published prior to recruitment and randomization (ACTRN12616001095459).

HRV-Guided Training for Elders after Stroke: A Protocol for a Cluster-Randomized Controlled Trial

There are many consequences associated with having a stroke, all of which are important factors affecting long-term rehabilitation outcomes; these become important health issues for those of advanced age and require dedicated health strategies. High-intensity interval training (HIIT) is an effective training protocol used in cardiac rehabilitation programs; however, owing to the inter-individual variability in physiological responses to training associated with cardiovascular diseases, the exercise regimen given to each patient should be closely controlled and individualized to ensure the safety and efficiency of the exercise program. Heart rate variability (HRV) is currently being used for this purpose, as it is closely linked to parasympathetic nervous system activation, with high HRV scores associated with good cardiovascular adaptation. The objective of this protocol is to determine the effect of HIIT compared to HRV-guided training in terms of cardiorespiratory fitness, heart rate variability, functional parameters, body composition, quality of life, inflammatory markers, and cognitive function in patients who have had a stroke, as well as to assess the feasibility of patients undertaking an 8-week cardiac rehabilitation program, evaluating its safety and their adherence. The proposed protocol involved cluster-randomized controlled design in which the post-stroke patients are assigned either to an HRV-based training group (HRV-G) or a HIIT-based training group (HIIT-G). HIIT-G will train according to a predefined training program, whereas HRV-G will train depending on the patients' daily HRV. The outcomes considered are peak oxygen uptake (VO_2peak), endothelial and work parameters, heart rate variability, functional parameters, relative weight and body fat distribution, quality of life, inflammatory markers and cognitive function, as well as exercise adherence, feasibility, and safety. It is expected that this HRV-guided training protocol will improve functional performance in patients following a stroke and be safer, more feasible, and generate improved adherence relative to HIIT, providing an improved strategy for to optimize cardiac rehabilitation interventions.

Comparison of the Effects of Aerobic versus Resistance Exercise on the Autonomic Nervous System in Middle-Aged Women: A Randomized Controlled Study

This study was conducted to investigate the changes in the autonomic nervous system in middle-aged women induced by aerobic and resistance exercise. A randomized controlled design was adopted; 22 premenopausal middle-aged women were divided into the resistance training and aerobic exercise groups (n = 11 each). Each group followed a specific 60 min exercise program three times a week for 12 weeks. The participants’ heart rate variability (HRV) was measured to analyze the low(LF)- and high-frequency (HF) activity, and the LF/HF ratio was calculated to examine the autonomic nervous system’s activities. A repeated-measures analysis of variance was used to analyze the effects of resistance and aerobic exercise. LF activity significantly increased in both the resistance training (p < 0.001) and aerobic exercise (p < 0.5) groups, indicating a significant variation according to time effect. HF activity was significantly increased only in resistance training (p < 0.001) with a significant variation in time (p < 0.001) and an interaction effect (p < 0.01). The LF/HF ratio did not vary significantly in either group. The findings in this study suggest that both aerobic exercise and resistance training were effective for sympathetic nerve activities in middle-aged women and that the effects on the sympathetic and parasympathetic activities were greater for resistance training.

Left Ventricular Adaptation to Exercise Training via Magnetic Resonance Imaging: Studies of Twin Responses to Understand Exercise THerapy

PURPOSE

Changes in left ventricular mass (LVM) and end-diastolic volume (EDV) in response to exercise training are important determinants of functional capacity in health and disease, but the impact of different exercise modalities remains unclear.

METHODS

Using a randomized crossover design we studied the impact of resistance (RES) and endurance (END) training using cardiac magnetic resonance imaging in previously untrained monozygotic (MZ) and dizygotic (DZ) twin pairs (n = 72; 22 MZ pairs, 14 DZ same-sex pairs; 26.1 ± 5.4 yr). Twins, as pairs, undertook 3 months of RES and 3 months of END training (order randomized), separated by a 3-month washout.

RESULTS

Group results revealed that END increased LVM (P < 0.001) and EDV (P = 0.007), whereas RES did not (P > 0.05). A higher proportion of individuals responded to END than RES for LVM (72% vs 38%, P < 0.001) and EDV (67% vs 40%, P = 0.003). Baseline cross-sectional intraclass correlations were higher for MZ than DZ twin pairs for all variables (e.g., LVM heritability = 0.42), but no significant correlations were apparent between pairs for change in any variable in response to either RES or END (P > 0.05).

CONCLUSIONS

Our findings indicate that cardiac adaptation in response to exercise is modality-specific and that low responders to one mode of exercise can be high responders to an alternative. Heritability estimates based on cross-sectional data, which suggested a genetic contribution to LVM, do not accord with estimates based on training effects, which indicated limited genetic impact on adaptation in this 3-month study of exercise training. This study has implications for understanding the physiological and health impacts of typically used exercise modalities on cardiac adaptation in previously untrained individuals.

Hierarchical framework to improve individualised exercise prescription in adults: a critical review

Physical activity (PA) guidelines for the general population are designed to mitigate the rise of chronic and debilitating diseases brought by inactivity and sedentariness. Although essential, they are insufficient as rates of cardiovascular, pulmonary, renal, metabolic and other devastating and life-long diseases remain on the rise. This systemic failure supports the need for an improved exercise prescription approach that targets the individual. Significant interindividual variability of cardiorespiratory fitness (CRF) responses to exercise are partly explained by biological and methodological factors, and the modulation of exercise volume and intensity seem to be key in improving prescription guidelines. The use of physiological thresholds, such as lactate, ventilation, as well as critical power, have demonstrated excellent results to improve CRF in those struggling to respond to the current homogenous prescription of exercise. However, assessing physiological thresholds requires laboratory resources and expertise and is incompatible for a general population approach. A case must be made that balances the effectiveness of an exercise programme to improve CRF and accessibility of resources. A population-wide approach of exercise prescription guidelines should include free and accessible self-assessed threshold tools, such as rate of perceived exertion, where the homeostatic perturbation induced by exercise reflects physiological thresholds. The present critical review outlines factors for individuals exercise prescription and proposes a new theoretical hierarchal framework to help shape PA guidelines based on accessibility and effectiveness as part of a personalised exercise prescription that targets the individual.

Implementation of multiple statistical methods to estimate variability and individual response to training

HIGHLIGHTS

What are the findings? We implemented five statistical methods in a single study to estimate the magnitude of within-subject variability and quantify responses to exercise training at the individual level.The various proposed methods used to estimate individual responses to training provide different types of information and rely on different assumptions that are difficult to test.Within-subject variability is often large in magnitude, and as such, should be systematically evaluated and carefully considered in future studies to successfully estimate individual responses to training. How might it impact on clinical practice in the future? Within-subject variability in response to exercise training is a key factor that must be considered in order to obtain a reproducible measurement of individual response to exercise training. This is akin to ensuring data is reproducible for each subject.Our findings provide guidelines for future exercise training studies to ensure results are reproducible within participants and to minimize wasting precious research resources.By implementing five suggested methods to estimate individual response to training, we highlight their feasibility, strengths, weaknesses, and costs, for researchers to make the best decision on how to accurately measure individual responses to exercise training.

Regular exercise and patterns of response across multiple cardiometabolic traits: the HERITAGE family study

OBJECTIVES

We investigated whether high responsiveness or low responsiveness to exercise training aggregates in the same individuals across seven cardiometabolic traits.

METHODS

A total of 564 adults (29.2% black, 53.7% female) from the HERITAGE family study completed a 20-week endurance training programme (at 55%-75% of participants' maximal oxygen uptake (VO₂max)) with VO₂max, per cent body fat, visceral adipose tissue, fasting levels of insulin, high-density lipoprotein cholesterol, small low-density lipoprotein particles and inflammatory marker GlycA measured before and after training. For each exercise response trait, we created ethnicity-specific, sex-specific and generation-specific quintiles. High responses were defined as those within the 20th percentile representing the favourable end of the response trait distribution, low responses were defined as the 20th percentile from the least favourable end, and the remaining were labelled as average responses.

RESULTS

Only one individual had universally high or low responses for all seven cardiometabolic traits. Almost half (49%) of the cohort had at least one high response and one low response across the seven traits. About 24% had at least one high response but no low responses, 24% had one or more low responses but no high responses, and 2.5% had average responses across all traits.

CONCLUSIONS

Interindividual variation in exercise responses was evident in all the traits we investigated, and responsiveness did not aggregate consistently in the same individuals. While adherence to an exercise prescription is known to produce health benefits, targeted risk factors may not improve.

High-Intensity Functional Training Guided by Individualized Heart Rate Variability Results in Similar Health and Fitness Improvements as Predetermined Training with Less Effort

Heart rate variability (HRV) may be useful for prescribing high-intensity functional training (HIFT) exercise programs. This study aimed to compare effects of HRV-guided and predetermined HIFT on cardiovascular function, body composition, and performance.

METHODS

Recreationally-active adults (n = 55) were randomly assigned to predetermined HIFT (n = 29, age = 24.1 ± 4.1 years) or HRV-guided HIFT (n = 26, age = 23.7 ± 4.5) groups. Both groups completed 11 weeks of daily HRV recordings, 6 weeks of HIFT (5 d·week-1), and pre- and post-test body composition and fitness assessments. Meaningful changes in resting HRV were used to modulate (i.e., reduce) HRV-guided participants' exercise intensity. Linear mixed models were used with Bonferroni post hoc adjustment for analysis.

RESULTS

All participants significantly improved resting heart rate, lean mass, fat mass, strength, and work capacity. However, no significant between-groups differences were observed for cardiovascular function, body composition, or fitness changes. The HRV-guided group spent significantly fewer training days at high intensity (mean difference = -13.56 ± 0.83 days; p < 0.001).

CONCLUSION

HRV-guided HIFT produced similar improvements in cardiovascular function, body composition, and fitness as predetermined HIFT, despite fewer days at high intensity. HRV shows promise for prescribing individualized exercise intensity during HIFT.

A Systematic Review Examining the Approaches Used to Estimate Interindividual Differences in Trainability and Classify Individual Responses to Exercise Training

Background: Many reports describe statistical approaches for estimating interindividual differences in trainability and classifying individuals as "responders" or "non-responders." The extent to which studies in the exercise training literature have adopted these statistical approaches remains unclear. Objectives: This systematic review primarily sought to determine the extent to which studies in the exercise training literature have adopted sound statistical approaches for examining individual responses to exercise training. We also (1) investigated the existence of interindividual differences in trainability, and (2) tested the hypothesis that less conservative thresholds inflate response rates compared with thresholds that consider error and a smallest worthwhile change (SWC)/minimum clinically important difference (MCID). Methods: We searched six databases: AMED, CINAHL, EMBASE, Medline, PubMed, and SportDiscus. Our search spanned the aerobic, resistance, and clinical or rehabilitation training literature. Studies were included if they used human participants, employed standardized and supervised exercise training, and either: (1) stated that their exercise training intervention resulted in heterogenous responses, (2) statistically estimated interindividual differences in trainability, and/or (3) classified individual responses. We calculated effect sizes (ES_IR) to examine the presence of interindividual differences in trainability. We also compared response rates (n = 614) across classification approaches that considered neither, one of, or both errors and an SWC or MCID. We then sorted response rates from studies that also reported mean changes and response thresholds (n = 435 response rates) into four quartiles to confirm our ancillary hypothesis that larger mean changes produce larger response rates. Results: Our search revealed 3,404 studies, and 149 were included in our systematic review. Few studies (n = 9) statistically estimated interindividual differences in trainability. The results from these few studies present a mixture of evidence for the presence of interindividual differences in trainability because several ES_IR values lay above, below, or crossed zero. Zero-based thresholds and larger mean changes significantly (both p < 0.01) inflated response rates. Conclusion: Our findings provide evidence demonstrating why future studies should statistically estimate interindividual differences in trainability and consider error and an SWC or MCID when classifying individual responses to exercise training. Systematic Review Registration: [website], identifier [registration number].

Do exercise-associated genes explain phenotypic variance in the three components of fitness? a systematic review & meta-analysis

The aim of this systematic review and meta-analysis was to identify a list of common, candidate genes associated with the three components of fitness, specifically cardiovascular fitness, muscular strength, and anaerobic power, and how these genes are associated with exercise response phenotype variability, in previously untrained participants. A total of 3,969 potentially relevant papers were identified and processed for inclusion. After eligibility and study selection assessment, 24 studies were selected for meta-analysis, comprising a total of 3,012 participants (male n = 1,512; females n = 1,239; not stated n = 261; age 28 ± 9 years). Meta-Essentials spreadsheet 1.4 (Microsoft Excel) was used in creating the forest plots and meta-analysis. IBM SPSS statistics V24 was implemented for the statistical analyses and the alpha was set at p ≤ 0.05. 13 candidate genes and their associated alleles were identified, which were associated with the phenotypes of interest. Analysis of training group data showed significant differential phenotypic responses. Subgroup analysis showed; 44%, 72% and 10% of the response variance in aerobic, strength and power phenotypes, respectively, were explained by genetic influences. This analysis established that genetic variability explained a significant proportion of the adaptation differences across the three components of fitness in the participants post-training. The results also showed the importance of analysing and reporting specific gene alleles. Information obtained from these findings has the potential to inform and influence future exercise-related genes and training studies.

Heart Rate Variability-Guided Training for Enhancing Cardiac-Vagal Modulation, Aerobic Fitness, and Endurance Performance: A Methodological Systematic Review with Meta-Analysis

PURPOSE

This systematic review with meta-analysis was conducted to establish whether heart rate variability (HRV)-guided training enhances cardiac-vagal modulation, aerobic fitness, or endurance performance to a greater extent than predefined training while accounting for methodological factors.

METHODS

We searched Web of Science Core Collection, Pubmed, and Embase databases up to October 2020. A random-effects model of standardized mean difference (SMD) was estimated for each outcome measure. Chi-square and the I2 index were used to evaluate the degree of homogeneity.

RESULTS

Accounting for methodological factors, HRV-guided training was superior for enhancing vagal-related HRV indices (SMD+ = 0.50 (95% confidence interval (CI) = 0.09, 0.91)), but not resting HR (SMD+ = 0.04 (95% CI = -0.34, 0.43)). Consistently small but non-significant (p > 0.05) SMDs in favor of HRV-guided training were observed for enhancing maximal aerobic capacity (SMD+ = 0.20 (95% CI = -0.07, 0.47)), aerobic capacity at second ventilatory threshold (SMD+ = 0.26 (95% CI = -0.05, 0.57)), and endurance performance (SMD+ = 0.20 (95% CI = -0.09, 0.48)), versus predefined training. No heterogeneity was found for any of the analyzed aerobic fitness and endurance performance outcomes.

CONCLUSION

Best methodological practices pertaining to HRV index selection, recording position, and approaches for establishing baseline reference values and daily changes (i.e., fixed or rolling HRV averages) require further study. HRV-guided training may be more effective than predefined training for maintaining and improving vagal-mediated HRV, with less likelihood of negative responses. However, if HRV-guided training is superior to predefined training for producing group-level improvements in fitness and performance, current data suggest it is only by a small margin.

Exercise-Intensity Adherence During Aerobic Training and Cardiovascular Response During Resistance Training in Cancer Survivors

ABSTRACT

Quevedo-Jerez, K, Gil-Rey, E, Maldonado-Martín, S, and Herrero-Román, F. Exercise-intensity adherence during aerobic training and cardiovascular response during resistance training in cancer survivors. J Strength Cond Res 35(8): 2338-2345, 2021-Combined aerobic-resistance training has shown the best benefits has proved beneficial for cancer survivors (CS). To understand the adherence to the aerobic training program (in terms of the intensity and duration of the sessions) and the cardiovascular response to the resistance training program, heart rate (HR) of 48 CS was monitored in each training session with an HR monitor for a 2-year period. During aerobic training, CS had to maintain the intensity in zone 2 (Z2) (between the ventilatory threshold and respiratory compensation point). The time spent below Z2 (Z1), in Z2, and above Z2 (Z3) was assessed in both aerobic and resistance training. The exercise-intensity distribution (aerobic vs. resistance training) was as follows: Z1 6.6 ± 12.8% vs. 34.3 ± 29.9% (p < 0.001); Z2 66.6 ± 29.3% vs. 54.5 ± 27.6% (p < 0.05); and Z3 26.9 ± 29.9% vs. 11.2 ± 20.6% (p < 0.001). The most deconditioned CS (<4.5 metabolic equivalents [METs]) presented the poorest adherence in Z2 and spent the most time in Z3. A significant positive moderate-high correlation was found for the percentage of time in Z3 between resistance and aerobic exercise (r = 0.75, p < 0.001). In conclusion, the individualization of exercise intensity resulted in good adherence to the prescribed intensity. Less fit CS needed more supervision in their training sessions. Resistance training allowed the CS to train in moderate-vigorous intensities of cardiovascular response. Resistance training should have more scope in exercise prescriptions, particularly in deconditioned CS and in the first steps of exercise programs.

Indicators of response to exercise training: a systematic review and meta-analysis

BACKGROUND

Means-based analysis of maximal rate of oxygen consumption (VO2max) has traditionally been used as the exercise response indicator to assess the efficacy of endurance (END), high intensity interval (HIIT) and resistance exercise training (RET) for improving cardiorespiratory fitness and whole-body health. However, considerable heterogeneity exists in the interindividual variability response to the same or different training modalities.

OBJECTIVES

We performed a systematic review and meta-analysis to investigate exercise response rates in the context of VO2max: (1) in each training modality (END, HIIT and RET) versus controls, (2) in END versus either HIIT or RET and (3) exercise response rates as measured by VO2max versus other indicators of positive exercise response in each exercise modality.

METHODS

Three databases (EMBASE, MEDLINE, CENTRAL) and additional sources were searched. Both individual response rate and population average data were incorporated through continuous data, respectively. Of 3268 identified manuscripts, a total of 29 studies were suitable for qualitative synthesis and a further 22 for quantitative. Stratification based on intervention duration (less than 12 weeks; more than or equal to 12 weeks) was undertaken.

RESULTS

A total of 62 data points were procured. Both END and HIIT training exhibited differential improvements in VO2max based on intervention duration. VO2max did not adequately differentiate between END and HIIT, irrespective of intervention length. Although none of the other exercise response indicators achieved statistical significance, LT and HRrest demonstrated common trajectories in pooled and separate analyses between modalities. RET data were highly limited. Heterogeneity was ubiquitous across all analyses.

CONCLUSIONS

The potential for LT and HRrest as indicators of exercise response requires further elucidation, in addition to the exploration of interventional and intrinsic sources of heterogeneity.

Biological and methodological factors affecting V ̇ O 2 max response variability to endurance training and the influence of exercise intensity prescription

NEW FINDINGS

What is the topic of this review? Biological and methodological factors associated with the variable changes in cardiorespiratory fitness in response to endurance training. What advances does it highlight? Several biological and methodological factors exist that each contribute, to a given extent, to response variability. Notably, prescribing exercise intensity relative to physiological thresholds reportedly increases cardiorespiratory fitness response rates compared to when prescribed relative to maximum physiological values. As threshold-based approaches elicit more homogeneous acute physiological responses among individuals, when repeated over time, these uniform responses may manifest as more homogeneous chronic adaptations thereby reducing response variability.

ABSTRACT

Changes in cardiorespiratory fitness (CRF) in response to endurance training (ET) exhibit large variations, possibly due to a multitude of biological and methodological factors. It is acknowledged that ∼20% of individuals may not achieve meaningful increases in CRF in response to ET. Genetics, the most potent biological contributor, has been shown to explain ∼50% of response variability, whilst age, sex and baseline CRF appear to explain a smaller proportion. Methodological factors represent the characteristics of the ET itself, including the type, volume and intensity of exercise, as well as the method used to prescribe and control exercise intensity. Notably, methodological factors are modifiable and, upon manipulation, alter response rates to ET, eliciting increases in CRF regardless of an individual's biological predisposition. Particularly, prescribing exercise intensity relative to a physiological threshold (e.g., ventilatory threshold) is shown to increase CRF response rates compared to when intensity is anchored relative to a maximum physiological value (e.g., maximum heart rate). It is, however, uncertain whether the increased response rates are primarily attributable to reduced response variability, greater mean changes in CRF or both. Future research is warranted to elucidate whether more homogeneous chronic adaptations manifest over time among individuals, as a result of exposure to more homogeneous exercise stimuli elicited by threshold-based practices.

Intra-individual differences in the effect of endurance versus resistance training on vascular function: A cross-over study

We used a within‐subject, cross‐over design study to compare the impact of 4‐weeks' resistance (RT) versus endurance (END) training on vascular function. We subsequently explored the association of intra‐individual effects of RT versus END on vascular function with a single nucleotide polymorphism (SNP) of the NOS3 gene. Thirty‐five healthy males (21 ± 2 years old) were genotyped for the NOS3 rs2070744 SNP and completed both training modalities. Participants completed 12 sessions over a 4‐week period, either RT (leg‐extension) or END (cycling) training in a randomized, balanced cross‐over design with a 3‐week washout period. Participants performed peak oxygen uptake (peak VO₂) and leg‐extension single‐repetition maximum (1‐RM) testing, and vascular function assessment using flow‐mediated dilation (FMD) on 3 separated days pre/post‐training. Peak VO₂ increased after END (p < 0.001), while 1‐RM increased after RT (p < 0.001). FMD improved after 4‐weeks’ training (time effect: p = 0.006), with no difference between exercise modalities (interaction effect: p = 0.92). No relation was found between individual changes (delta, pre‐post) in FMD to both types of training (R² = 0.06, p = 0.14). Intra‐individual changes in FMD following END and RT were associated with the NOS3 SNP, with TT homozygotes significantly favoring only END (p = 0.016) and TC/CC tending to favor RT only (p = 0.056). Although both training modes improved vascular function, significant intra‐individual variation in the adaptation of FMD was found. The association with NOS3 genotype suggests a genetic predisposition to FMD adapting to a specific mode of chronic exercise. This study therefore provides novel evidence for personalized exercise training to optimize vascular health.

Does Characterizing Global Running Pattern Help to Prescribe Individualized Strength Training in Recreational Runners?

This study aimed to determine if concurrent endurance and strength training that matches the global running pattern would be more effective in increasing running economy (RE) than non-matched training. The global running pattern of 37 recreational runners was determined using the Volodalen^® method as being aerial (AER) or terrestrial (TER). Strength training consisted of endurance running training and either plyometric (PLY) or dynamic weight training (DWT). Runners were randomly assigned to a matched (n = 18; DWT for TER, PLY for AER) or non-matched (n = 19; DWT for AER, PLY for TER) 8 weeks concurrent training program. RE, maximal oxygen uptake V̇O₂max) and peak treadmill speed at V̇O₂max (PTS) were measured before and after the training intervention. None of the tested performance related variables depicted a significant group effect or interaction effect between training and grouping (p ≥ 0.436). However, a significant increase in RE, V̇O₂max, and PTS (p ≤ 0.003) was found after the training intervention. No difference in number of responders between matched and non-matched groups was observed for any of the performance related variables (p ≥ 0.248). In recreational runners, prescribing PLT or DWT according to the global running pattern of individuals, in addition to endurance training, did not lead to greater improvements in RE.

Monitoring Training and Recovery during a Period of Increased Intensity or Volume in Recreational Endurance Athletes

The purpose of the study was to examine the effects of progressively increased training intensity or volume on the nocturnal heart rate (HR) and heart rate variability (HRV), countermovement jump, perceived recovery, and heart rate-running speed index (HR-RS index). Another aim was to analyze how observed patterns during the training period in these monitoring variables were associated with the changes in endurance performance. Thirty recreationally trained participants performed a 10-week control period of regular training and a 10-week training period of either increased training intensity (INT, n = 13) or volume (VOL, n = 17). Changes in endurance performance were assessed by an incremental treadmill test. Both groups improved their maximal speed on the treadmill (INT 3.4 ± 3.2%, p < 0.001; VOL 2.1 ± 1.8%, p = 0.006). In the monitoring variables, only between-group difference (p = 0.013) was found in nocturnal HR, which decreased in INT (p = 0.016). In addition, perceived recovery decreased in VOL (p = 0.021) and tended to decrease in INT (p = 0.056). When all participants were divided into low-responders and responders in maximal running performance, the increase in the HR-RS index at the end of the training period was greater in responders (p = 0.005). In conclusion, current training periods of increased intensity or volume improved endurance performance to a similar extent. Countermovement jump and HRV remained unaffected, despite a slight decrease in perceived recovery. Long-term monitoring of the HR-RS index may help to predict positive adaptations, while interpretation of other recovery-related markers may need a more individualized approach.

Studies of Twin Responses to Understand Exercise Therapy (STRUETH): Body Composition

PURPOSE

We studied individual variability in exercise responses in twins. We hypothesized that 1) endurance (END) training would reduce fat mass whereas resistance (RES) training would increase lean mass, 2) individuals who did not respond to one modality would respond to the other, and 3) cross-sectional heritability estimates would be higher than estimates based on training responses.

METHODS

DXA was undertaken in 84 same-sex untrained twins (30 monozygotic [MZ], 12 dizygotic [DZ]). Participants underwent 3 months of END and RES training, separated by 3 months washout. Twins trained in pairs.

RESULTS

RES (P < 0.001) and END (P = 0.002) increased lean mass, with a greater change in RES (P < 0.001). Similarly, RES (P = 0.04) and END (P = 0.006) decreased fat mass. Eighty-four percent of subjects responded positively to RES for lean mass and 58% to END (P < 0.001). For fat mass, RES and END induced 56% and 66% responder rates, respectively (P = 0.28). Cross-sectional intraclass correlations, used to assess the similarity in twin responses, were higher for MZ than DZ pairs for all variables. Following training, only MZ pairs were significantly correlated (P < 0.001) for change in lean mass to RES.

CONCLUSION

To our knowledge, this study is the first to report individual responsiveness in body composition to both RES and END in the same subjects. Although RES and END induced favorable changes in fat mass, RES was superior for lean mass. The frequency of lean mass responders to RES exceeded that for END, whereas response rates for fat mass were similar. Cross-sectional heritability estimates were higher than training response estimates, and shared environment had the largest influence on changes in body composition. This study suggests that exercise professionals should consider modality and environmental factors when optimizing exercise interventions.

Effects of Sprint Interval Training at Different Altitudes on Cycling Performance at Sea-Level

BACKGROUND

Benefits of sprint interval training performed in hypoxia (SIH) compared to normoxia (SIN) have been assessed by studies mostly conducted around 3000 m of simulated altitude. The present study aims to determine whether SIH at an altitude as high as 4000 m can elicit greater adaptations than the same training at 2000 m, 3000 m or sea-level.

METHODS

Thirty well-trained endurance male athletes (18-35 years old) participated in a six-week repeated sprint interval training program (30 s all-out sprint, 4 min 30 s recovery; 4-9 repetitions, 2 sessions/week) at sea-level (SL, n = 8), 2000 m (FiO2 16.7%, n = 8), 3000 m (FiO2 14.5%, n = 7) or 4000 m (FiO2 13.0%, n = 7). Aerobic and anaerobic exercise components were evaluated by an incremental exercise test, a 600 kJ time trial and a Wingate test before and after the training program.

RESULTS

After training, peak power output (PPO) during the incremental exercise test increased (~6%) without differences between groups. The lactate threshold assessed by Dmax increased at 2000 m (+14 ± 12 W) and 4000 m (+12 ± 11 W) but did not change at SL and 3000 m. Mean power during the Wingate test increased at SL, 2000 m and 4000 m, although peak power increased only at 4000 m (+38 ± 38 W).

CONCLUSIONS

The present study indicates that SIH using 30 s sprints is as efficient as SIN for improving aerobic and anaerobic qualities. Additional benefits such as lactate-related adaptations were found only in SIH and Wingate peak power only increased at 4000 m. This finding is of particular interest for disciplines requiring high power output, such as in very explosive sports.

Inter-Individual Different Responses to Continuous and Interval Training in Recreational Middle-Aged Women Runners

A crucial subject in sports is identifying the inter-individual variation in response to training, which would allow creating individualized pre-training schedules, improving runner’s performance. We aimed to analyze heterogeneity in individual responses to two half-marathon training programs differing in running volume and intensity in middle-aged recreational women. 20 women (40 ± 7 years, 61 ± 7 kg, 167 ± 6 cm, and VO₂max = 48 ± 6 mL⋅kg^–1⋅min^–1) underwent either moderate-intensity continuous (MICT) or high-intensity interval (HIIT) 12-week training. They were evaluated before and after training with maximal incremental tests in the laboratory (VO₂max) and in the field (time to exhaustion, TTE; short interval series and long run). All the women participated in the same half-marathon and their finishing times were compared with their previous times. Although the improvements in the mean finishing times were not significant, MICT elicited a greater reduction (3 min 50 s, P = 0.298), with more women (70%) improving on their previous times, than HIIT (reduction of 2 min 34 s, P = 0.197, 50% responders). Laboratory tests showed more differences in the HIIT group (P = 0.008), while both groups presented homogeneous significant (P < 0.05) increases in TTE. Both in the short interval series and in the long run, HIIT induced better individual improvements, with a greater percentage of responders compared to MICT (100% vs 50% in the short series and 78% vs 38% in the long run). In conclusion, variability in inter-individual responses was observed after both MICT and HIIT, with some participants showing improvements (responders) while others did not (non-responders) in different performance parameters, reinforcing the idea that individualized training prescription is needed to optimize performance.

Women and men with coronary heart disease respond similarly to different aerobic exercise training modalities: a pooled analysis of prospective randomized trials

We aimed to compare cardiopulmonary exercise test (CPET) parameters, cardiac adaptations, and proportion of responders after different aerobic training programs amongst women and men with coronary heart disease (CHD). Patients with CHD were evaluated with a CPET and echocardiography before and after 3 months of aerobic exercise training. Peak oxygen uptake exercise training response was assessed according to the median peak oxygen uptake change for post- versus pretraining in the whole cohort (stratification non/low responders (NLR) vs. high-responders) and normalized for lean body mass (LBM). Eighty-three CHD patients were included (19 women, 64 men; 27 patients with interval, 19 with continuous, and 37 with combination exercises). Peak oxygen uptake, peak workload normalized for LBM, pulmonary variables (i.e., ventilation and oxygen uptake efficiency slope), and O₂ pulse were significantly lower in women versus men. These parameters improved similarly with training in both sexes (p < 0.05). There were no differences in the proportion of NLR among women and men with CHD (7/19 (37%) vs. 35/64 (55%), p = 0.1719). Left ventricular ejection fraction and mean peak early diastolic mitral annulus velocity improved similarly with training in both sexes (p < 0.05). Women and men with CHD have a similar exercise training response regarding key CPET and echocardiographic parameters. The proportion of responders is similar. ClinicalTrials.gov: NCT03414996, NCT02048696, NCT03443193. Novelty: Cardiopulmonary adaptations to exercise training are similar among CHD men and women. Proportion of peak oxygen uptake for non/low/high responders is similar in CHD men and women. Left ventricular systolic and diastolic function improved similarly after exercise training in CHD men and women.

HRV-Guided Training for Professional Endurance Athletes: A Protocol for a Cluster-Randomized Controlled Trial

Physiological training responses depend on sympathetic (SNS) and parasympathetic nervous system (PNS) balance. This activity can be measured using heart rate variability (HRV). Such a measurement method can favor individualized training planning to improve athletes’ performance. Recently, HRV-guided training has been implemented both on professional and amateur sportsmen and sportswomen with varied results. There is a dearth of studies involving professional endurance athletes following a defined HRV-guided training protocol. The objectives of the proposed protocol are: (i) to determine changes in the performance of high-level athletes after following an HRV-guided or a traditional training period and (ii) to determine differences in the athletes’ performance after following both training protocols. This will be a 12-week cluster-randomized controlled protocol in which professional athletes will be assigned to an HRV-based training group (HRV-G) or a traditional-based training group (TRAD-G). TRAD-G will train according to a predefined training program. HRV-G training will depend on the athletes’ daily HRV. The maximal oxygen uptake (VO_2max) attained in an incremental treadmill test will be considered as the primary outcome. It is expected that this HRV-guided training protocol will improve functional performance in the high-level athletes, achieving better results than a traditional training method, and thus providing a good strategy for coaches of high-level athletes.

An appraisal of the SDIR as an estimate of true individual differences in training responsiveness in parallel-arm exercise randomized controlled trials

Calculating the standard deviation of individual responses (SD_IR) is recommended for estimating the magnitude of individual differences in training responsiveness in parallel‐arm exercise randomized controlled trials (RCTs). The purpose of this review article is to discuss potential limitations of parallel‐arm exercise RCTs that may confound/complicate the interpretation of the SD_IR. To provide context for this discussion, we define the sources of variation that contribute to variability in the observed responses to exercise training and review the assumptions that underlie the interpretation of SD_IR as a reflection of true individual differences in training responsiveness. This review also contains two novel analyses: (1) we demonstrate differences in variability in changes in diet and physical activity habits across an intervention period in both exercise and control groups, and (2) we examined participant dropout data from six RCTs and found that significantly (P < 0.001) more participants in control groups (12.8%) dropped out due to dissatisfaction with group assignment compared to exercise groups (3.4%). These novel analyses raise the possibility that the magnitude of within‐subject variability may not be equal between exercise and control groups. Overall, this review highlights that potential limitations of parallel‐arm exercise RCTs can violate the underlying assumptions of the SD_IR and suggests that these limitations should be considered when interpreting the SD_IR as an estimate of true individual differences in training responsiveness.

Sprint Interval Running and Continuous Running Produce Training Specific Adaptations, Despite a Similar Improvement of Aerobic Endurance Capacity-A Randomized Trial of Healthy Adults

The purpose of the present study was to investigate training-specific adaptations to eight weeks of moderate intensity continuous training (CT) and sprint interval training (SIT). Young healthy subjects (n = 25; 9 males and 16 females) performed either continuous training (30-60 min, 70-80% peak heart rate) or sprint interval training (5-10 near maximal 30 s sprints, 3 min recovery) three times per week for eight weeks. Maximal oxygen consumption, 20 m shuttle run test and 5·60 m sprint test were performed before and after the intervention. Furthermore, heart rate, oxygen pulse, respiratory exchange ratio, lactate and running economy were assessed at five submaximal intensities, before and after the training interventions. Maximal oxygen uptake increased after CT (before: 47.9 ± 1.5; after: 49.7 ± 1.5 mL·kg^-1·min^-1, p < 0.05) and SIT (before: 50.5 ± 1.6; after: 53.3 ± 1.5 mL·kg^-1·min^-1, p < 0.01), with no statistically significant differences between groups. Both groups increased 20 m shuttle run performance and 60 m sprint performance, but SIT performed better than CT at the 4th and 5th 60 m sprint after the intervention (p < 0.05). At submaximal intensities, CT, but not SIT, reduced heart rate (p < 0.05), whereas lactate decreased in both groups. In conclusion, both groups demonstrated similar improvements of several performance measures including VO_2max, but sprint performance was better after SIT, and CT caused training-specific adaptations at submaximal intensities.

Do Non-Responders to Exercise Exist-and If So, What Should We Do About Them?

It is well established that exercise is an important component in the maintenance of good health, and yet recent studies have demonstrated that a sub-section of individuals experience no significant improvements following an exercise training intervention. Such individuals are commonly termed “non-responders”. However, recently a number of researchers have taken a skeptical view as to whether exercise non-response either exists, or is clinically relevant. Here, we explore the research underpinning exercise response, to determine whether non-response to exercise actually exists. We discuss the impact of measurement error and assessment type on the identification of “non-responders”, and whether such non-response is global- or modality-specific. Additionally, we discuss whether, if non-response to an exercise intervention is meaningful and relevant, certain additional interventions—in the form of increasing exercise intensity, volume, or duration—could be made in order to enhance training adaptations. Consequently, based on our interpretations of the available evidence, we suggest that it is unlikely that global non-responders to exercise exist. Furthermore, we suggest this realization effectively counters the perception that some individuals will not positively respond to exercise, and that in turn, this insight serves to encourage health professionals to create more nuanced, efficacious, and individually-focused exercise prescriptions designed to circumvent and overcome apparent non-responsiveness. Adopting a more individually-adaptive approach to exercise prescription could, subsequently, prove a powerful tool in promoting population health.

Benefits of Adhering to the Canadian Physical Activity Guidelines for Adults with Multiple Sclerosis Beyond Aerobic Fitness and Strength

Background

The Canadian Physical Activity Guidelines for Adults with Multiple Sclerosis (PAGs) were released in 2013 but have yet to be validated. We aimed to test the effectiveness of the PAGs in improving fitness, mobility, fatigue symptoms, and quality of life (QOL) in a large cohort of adults with multiple sclerosis (MS).

Methods

As part of an ongoing randomized controlled trial examining implementation of the PAGs, participants were randomized to either a direct referral group (physician referral to an exercise program following the PAGs; n = 42) or a control group (provided a print copy of the PAGs; n = 37). Physical activity behavior was assessed through weekly physical activity logs. Fitness, mobility, fatigue symptoms, and QOL were assessed at baseline and after 16 weeks. Participants were categorized as either PAG adherers (n = 30) or nonadherers (n = 49) to the PAGs based on achieving the weekly exercise recommendations at least 75% of the time.

Results

Adherence to the PAGs was twice as high in the referral group compared with the control group. Adherers experienced significantly greater improvements in peak oxygen consumption (29%), strength (7%-18%), mobility (16%), fatigue symptoms (-36%), and QOL (17%-22%) compared with nonadherers (P < .05).

Conclusions

Following the PAGs for at least 12 of 16 weeks results in improvements in fitness, mobility, fatigue symptoms, and QOL, confirming their effectiveness for improving health in people with MS.

Artificial Neural Network Correlation and Biostatistics Evaluation of Physiological and Molecular Parameters in Healthy Young Individuals Performing Regular Exercise

Studies support that regular physical activity (PA) decelerates senescence-related decline of physiological and molecular parameters in the elderly. We have addressed the other end of this spectrum: healthy and young, inactive individuals participated in a 6-month long personal trainer-guided lifestyle program. We have measured physiological and molecular parameters (differentiating high- and low responders) and their correlation with PA (sedentary status). Cluster analysis helped to distinguish individuals with high- or low PA and differentiate high- and low-responders of each parameter. The assessed cardiovascular parameters (heart rate, blood pressure, 6-min walking distance, relative VO₂max), body composition parameters (body fat and muscle mass percentage) metabolic parameters (glucose, insulin, HDL, LDL), immune parameters (cortisol, CRP, lymphocyte counts, hTREC) all showed improvement. Artificial neural network analysis (ANN) showed correlation efficiencies of physiological and molecular parameters using a concept-free approach. ANN analysis appointed PA as the mastermind of molecular level changes. Besides sedentary status, insulin and hTREC showed significant segregation. Biostatistics evaluation also supported the schism of participants for their sedentary status, insulin concentration and hTREC copy number. In the future ANN and biostatistics, may predict individual responses to regular exercise. Our program reveals that high responder individuals of certain parameters may be low responders of others. Our data show that moderate regular PA is essential to counteract senescence in young and healthy individuals, despite individual differences in responsiveness. Such PA may not seem important in the everyday life of young and healthy adults, but shall become the base for healthy aging.

Exercise Response Efficiency: A Novel Way to Enhance Population Health?

The rates of obesity and its related comorbidities have increased substantially over the last 30 years, with approximately 35% of all US adults now classified as obese. Whilst the causes of obesity are both complex and multifactorial, one contributor is a reduction in leisure time physical activity, with no concurrent reduction in energy intake. Physical activity interventions have been demonstrated to promote fat loss, yet more than 50% of US adults undertake no leisure time physical activity at all, with a lack of time and enjoyment often cited as the main drivers of rising inactivity levels. Furthermore, recent evidence has demonstrated that a sub-group of individuals may experience no improvement in a given fitness or health-related measure following a specific training programme, suggesting that there may be optimal exercise types for different groups of individuals. In this paper, we introduce the concept of exercise response efficiency, whereby individuals are matched to the training type from which they are most likely to derive the greatest improvements for the least time commitment. We propose that a more precise targeting of exercise interventions is likely to drive more rapid improvements in health, thereby promoting exercise adherence and enjoyment, whilst simultaneously reducing obesity and mortality risks. Such an innovation would, we suggest, confer important public health benefits.

Time Course Changes in Confirmed 'True' VO 2 max After Individualized and Standardized Training

This study sought to examine time course changes in maximal oxygen consumption (VO ₂ max) confirmed with verification testing following 12 weeks of standardized vs. individualized exercise training. Participants (N=39) were randomly allocated to differing exercise intensity prescription groups: ventilatory threshold (individualized) or % heart rate reserve (standardized). At baseline, 4, 8, and 12 weeks, participants completed maximal exercise testing with a verification protocol to confirm ‘true VO ₂ max.’ VO ₂ max in the standardized group changed from 24.3±4.6 ml·kg ⁻¹ ·min ⁻¹ at baseline to 24.7±4.6, 25.9±4.7, and 26.0±4.2 ml·kg ⁻¹ ·min ⁻¹ at week 4, 8, and 12, respectively, with a significant difference (p<0.05) in VO ₂ max at week 8 and 12 compared to baseline. The individualized group had increases in VO ₂ max from _{online 2} 9.5±7.5 ml·kg ⁻¹ ·min ⁻¹ at baseline to 30.6±8.4, 31.4±8.4, and 32.8±8.6 ml·kg ⁻¹ ·min ⁻¹ at week 4, 8, and 12, respectively. In the individualized group, there were significant differences (p<0.05) in VO ₂ max from baseline to week 8 and 12 and a significant increase in VO ₂ max from week 8 to 1 _{online 2} . Although not statistically significant, our preliminary data demonstrates a more rapid and potent improvement in VO ₂ max when exercise intensity is individualized. This is the first investigation to employ use of the verification procedure to confirm ‘true VO ₂ max’ changes following exercise training using ventilatory thresholds.

Repeatability of exercise-induced changes in mRNA expression and technical considerations for qPCR analysis in human skeletal muscle

NEW FINDINGS

What is the central question of this study? Are individual changes in exercise-induced mRNA expression repeatable (i.e. representative of the true response to exercise rather than random error)? What is the main finding and its importance? Exercise-induced changes in mRNA expression are not repeatable even under identical experimental conditions, thereby challenging the use of mRNA expression as a biomarker of adaptive potential and/or individual responsiveness to exercise.

ABSTRACT

It remains unknown if (1) the observed change in mRNA expression reflects an individual's true response to exercise or random (technical and/or biological) error, and (2) the individual responsiveness to exercise is protocol-specific. We examined the repeatability of skeletal muscle PGC-1α, PDK4, NRF-1, VEGF-A, HSP72 and p53 mRNA expression following two identical endurance exercise (END) bouts (END-1, END-2; 30 min of cycling at 65% of peak work rate (WR_peak ), n = 11) and inter-individual variability in PGC-1α and PDK4 mRNA expression following END and sprint interval training (SIT; 8 × 20 s cycling intervals at ∼170% WR_peak , n = 10) in active young males. The repeatability of key gene analysis steps (RNA extraction, reverse transcription, qPCR) and within-sample fibre-type distribution (n = 8) was also determined to examine potential sources of technical error in our analyses. Despite highly repeatable exercise bout characteristics (work rate, heart rate, blood lactate; ICC > 0.71; CV < 10%; r > 0.85, P < 0.01), gene analysis steps (ICC > 0.73; CV < 24%; r > 0.75, P < 0.01), and similar group-level changes in mRNA expression, individual changes in PGC-1α, PDK4, VEGF-A and p53 mRNA expression were not repeatable (ICC < 0.22; CV > 20%; r < 0.21). Fibre-type distribution in two portions of the same muscle biopsy was highly variable and not significantly related (ICC = 0.39; CV = 26%; r = 0.37, P = 0.37). Since individual changes in mRNA expression following identical exercise bouts were not repeatable, inferences regarding individual responsiveness to END or SIT were not made. Substantial random error exists in changes in mRNA expression following acute exercise, thereby challenging the use of mRNA expression for analysing individual responsiveness to exercise.

Variability in Individual Response to Aerobic Exercise Interventions Among Older Adults

Although a plethora of evidence supports the benefits of exercise among older adults, a majority of studies have emphasized group differences, while giving little, if any, attention to individual differences. Given the lack of data on variability in response, the present review examined how nonresponse to aerobic exercise has been defined in older adult populations and characteristics associated with nonresponse among older adults. The results of this review suggest that interindividual variability in response of maximal oxygen consumption to aerobic exercise interventions is prevalent among older adults (1.4-63.4%); age, sex, race, and body mass index may not be critical determinants of nonresponse; whereas health status, baseline fitness, and exercise dose appear important. Future intervention studies should evaluate and report the variability in individual response of older adults to exercise; investigators should develop programs that allow for modification of components to assist older adults in achieving optimal benefit from exercise programs.

Does Early Recruitment Predict Greater Physical Performance in Academy Soccer Players?

The purpose of this longitudinal study was to investigate whether recruitment status influences neuromuscular and endurance performances in academy soccer players over a 2-year training period (from Under-16 to Under-18). Thirty-seven male soccer players from an elite academy were selected and divided in two cohorts according to their recruitment status: Early Recruitment group (ER; n = 16), training and competing for the academy since Under-14 and Under-15 age groups, and; Late Recruitment group (LR; n = 21) included in the academy training process at Under-16. Squat (SJ) and countermovement jump with (CMJwA) and without arms swing (CMJ), 10-m sprint time, and Vam-Eval test (MAV) were performed in three successive occasions always pre-season (Under-16, Under-17 and Under-18 age groups, T1, T2, and T3 respectively). A two-way (recruitment status × time) analysis of variance with repeated measurements was performed as well as the magnitude of difference using both effect size and magnitude-based inferences. There was no difference between ER and LR for MAV, 10 m-sprint, and SJ from T1 to T3. However, LR players presented non-significant small and possibly greater improvement in CMJ (ES = 0.4) and CMJwA (ES = 0.4) than ER players at T2. These data indicate that early recruitment is not likely to result in greater physical performance improvement at the age of 18.

Association of walking pace and handgrip strength with all-cause, cardiovascular, and cancer mortality: a UK Biobank observational study

Aims

To quantify the association of self-reported walking pace and handgrip strength with all-cause, cardiovascular, and cancer mortality.

Methods and results

A total of 230 670 women and 190 057 men free from prevalent cancer and cardiovascular disease were included from UK Biobank. Usual walking pace was self-defined as slow, steady/average or brisk. Handgrip strength was assessed by dynamometer. Cox-proportional hazard models were adjusted for social deprivation, ethnicity, employment, medications, alcohol use, diet, physical activity, and television viewing time. Interaction terms investigated whether age, body mass index (BMI), and smoking status modified associations. Over 6.3 years, there were 8598 deaths, 1654 from cardiovascular disease and 4850 from cancer. Associations of walking pace with mortality were modified by BMI. In women, the hazard ratio (HR) for all-cause mortality in slow compared with fast walkers were 2.16 [95% confidence interval (CI): 1.68–2.77] and 1.31 (1.08–1.60) in the bottom and top BMI tertiles, respectively; corresponding HRs for men were 2.01 (1.68–2.41) and 1.41 (1.20–1.66). Hazard ratios for cardiovascular mortality remained above 1.7 across all categories of BMI in men and women, with modest heterogeneity in men. Handgrip strength was associated with cardiovascular mortality in men only (HR tertile 1 vs. tertile 3 = 1.38; 1.18–1.62), without differences across BMI categories, while associations with all-cause mortality were only seen in men with low BMI. Associations for walking pace and handgrip strength with cancer mortality were less consistent.

Conclusion

A simple self-reported measure of slow walking pace could aid risk stratification for all-cause and cardiovascular mortality within the general population.

Relation Between Training Load and Recovery-Stress State in High-Performance Swimming

Background: The relation between training load, especially internal load, and the recovery-stress state is of central importance for avoiding negative adaptations in high-performance sports like swimming. The aim of this study was to analyze the individual time-delayed linear effect relationship between training load and recovery-stress state with single case time series methods and to monitor the acute recovery-stress state of high-performance swimmers in an economical and multidimensional manner over a macro cycle. The Acute Recovery and Stress Scale (ARSS) was used for daily monitoring of the recovery-stress state. The methods session-RPE (sRPE) and acute:chronic workload-ratio (ACWR) were used to compare different methods for quantifying the internal training load with regard to their interrelationship with the recovery-stress state. Methods: Internal load and recovery-stress state of five highly trained female swimmers [with a training frequency of 13.6 ± 0.8 sessions per week and specializing in sprint (50 and 100 m), middle-distance (200 and 400 m), or long distance (800 and 1,500 m) events] were daily documented over 17 weeks. Two different types of sRPE were applied: RPE^∗duration (sRPE^h) and RPE^∗volume (sRPE^km). Subsequently, we calculated the ratios ACWR^h and ACWR^km (sRPE last week: 4-week exponentially weighted moving average). The recovery-stress state was measured by using the ARSS, consisting of eight scales, four of which are related to recovery [Physical Performance Capability (PPC), Mental Performance Capability (MPC), Emotional Balance (EB), Overall Recovery (OR)], and four to stress [Muscular Stress (MS), Lack of Activation (LA), Negative Emotional State (NES), Overall Stress (OS)]. To examine the relation between training load and recovery-stress state a cross correlation (CCC) was conducted with sRPE^h, sRPE^km, ACWR^h, and ACWR^km as lead and the eight ARSS-scales as lag variables. Results: A large variation of training load can be observed in the individual week-to-week fluctuations whereby the single fluctuations can significantly differ from the overall mean of the group. The range also shows that the CCC individually reaches values above 0.3, especially with sRPE^km as lead variable. Overall, there is a large range with significant differences between the recovery and stress dimensions of the ARSS and between the training load methods, with sRPE^km having the largest span (Range = 1.16). High inter-individual differences between the athletes lie in strength and direction of the correlation | 0.66|≤ CCC ≥|-0.50|. The time delayed effects (lags 0-7) are highly individual, however, clear patterns can be observed. Conclusion: The ARSS, especially the physical and overall-related scales (PPC, OR, MS, OS), is a suitable tool for monitoring the acute recovery-stress state in swimmers. MPC, EB, LA, and NES are less affected by training induced changes. Comparably high CCC and Ranges result from the four internal load methods, whereby sRPE, especially sRPE^km, shows a stronger relation to recovery-stress state than ACWR. Based on these results and the individual differences in terms of time delay in training response, we recommend for swimming to use sRPE to monitor the internal training load and to use the ARSS, with a focus at the physical and overall-scales, to monitor the recovery-stress state.

Inter-Individual Responses of Maximal Oxygen Uptake to Exercise Training: A Critical Review

It has recently been reported how to quantify inter-individual differences in the response to an exercise intervention using the standard deviation of the change scores, as well as how to appraise these differences for clinical relevance. In a parallel-group randomised controlled trial, the key trigger for further investigation into inter-individual responses is when the standard deviation of change in the intervention sample is substantially larger than the same standard deviation derived from a suitable comparator sample. 'True' and clinically relevant inter-individual differences in response can then be plausibly expected, and potential moderators and mediators of the inter-individual differences can be explored. We now aim to critically review the research on the inter-individual differences in response to exercise training, focusing on maximal oxygen uptake (VO₂max). A literature search through the relevant bibliographic databases resulted in the identification of six relevant studies that were published prior to the influential HEalth, RIsk factors, exercise Training And GEnetics (HERITAGE) Family Study. Only one of these studies was found to include a comparator arm. Re-analysis of the data from this study, accounting for random within-subjects variation, revealed an absence of clinically important inter-individual differences in the response of VO₂max to exercise training. The standard deviation of change was, in fact, larger (±5.6 mL/kg/min) for the comparator than the intervention group (±3.7 mL/kg/min). We located over 180 publications that resulted from the HERITAGE Family Study, but we could not find a comparator arm in any of these studies. Some authors did not explain this absence, while others reasoned that only inter-individual differences in exercise response were of interest, thus the intervention sample was investigated solely. We also found this absence of a comparator sample in on-going studies. A perceived high test-retest reliability is offered as a justification for the absence of a comparator arm, but the test-retest reliability analysis for the HERITAGE Family Study was over a much shorter term than the length of the actual training period between baseline and follow-up measurements of VO₂max. We also scrutinised the studies in which twins have been investigated, resulting in concerns about how genetic influences on the magnitude of general within-subjects variability has been partitioned out (again in the absence of a comparator no-training group), as well as with the intra-class correlation coefficient approach to data analysis. Twin pairs were found to be sometimes heterogeneous for the obviously influential factors of sex, age and fitness, thereby inflating an unadjusted coefficient. We conclude that most studies on inter-individual differences in VO₂max response to exercise training have no comparator sample. Therefore, true inter-individual differences in response cannot be quantified, let alone appraised for clinical relevance. For those studies with a comparator sample, we found that the inter-individual differences in training response were not larger than random within-subjects variation in VO₂max over the same time period as the training intervention.

Using a site-specific technical error to establish training responsiveness: a preliminary explorative study

BACKGROUND

Even though cardiorespiratory fitness (CRF) training elicits numerous health benefits, not all individuals have positive training responses following a structured CRF intervention. It has been suggested that the technical error (TE), a combination of biological variability and measurement error, should be used to establish specific training responsiveness criteria to gain further insight on the effectiveness of the training program. To date, most training interventions use an absolute change or a TE from previous findings, which do not take into consideration the training site and equipment used to establish training outcomes or the specific cohort being evaluated. The purpose of this investigation was to retrospectively analyze training responsiveness of two CRF training interventions using two common criteria and a site-specific TE.

METHODS

Sixteen men and women completed two maximal graded exercise tests and verification bouts to identify maximal oxygen consumption (VO2max) and establish a site-specific TE. The TE was then used to retrospectively analyze training responsiveness in comparison to commonly used criteria: percent change of >0% and >+5.6% in VO2max.

RESULTS

The TE was found to be 7.7% for relative VO2 max. χ2 testing showed significant differences in all training criteria for each intervention and pooled data from both interventions, except between %Δ >0 and %Δ >+7.7% in one of the investigations. Training nonresponsiveness ranged from 11.5% to 34.6%.

CONCLUSION

Findings from the present study support the utility of site-specific TE criterion to quantify training responsiveness. A similar methodology of establishing a site-specific and even cohort specific TE should be considered to establish when true cardiorespiratory training adaptations occur.

Resting sympatho-vagal balance is related to 10 km running performance in master endurance athletes

Relationships between heart rate recovery after exercise (HRR, baseline heart rate variability measures (HRV), and time to perform a 10Km running trial (t10Km) were evaluated in "master" athletes of endurance to assess whether the measured indexes may be useful for monitoring the training status of the athletes. Ten “master” athletes of endurance, aged 40-60 years, were recruited. After baseline measures of HRV, the athletes performed a graded maximal test on treadmill and HRR was measured at 1 and 2 minutes from recovery. Subsequently they performed a 10Km running trial and t10Km was related to HRV and HRR indexes. The time to perform a 10Km running trial was significantly correlated with baseline HRV indexes. No correlation was found between t10Km and HRR. Baseline HRV measures, but not HRR, were significantly correlated with the time of performance on 10km running in “master” athletes. The enhanced parasympathetic function at rest appears to be a condition to a better performance on 10km running. HRV can be simple and useful measurements for monitoring the training stratus of athletes and their physical condition in proximity of a competition.

Understanding Personalized Training Responses: Can Genetic Assessment Help?

Background:

Traditional exercise prescription is based on the assumption that exercise adaptation is predictable and standardised across individuals. However, evidence has emerged in the past two decades demonstrating that large inter-individual variation exists regarding the magnitude and direction of adaption following exercise.

Objective:

The aim of this paper was to discuss the key factors influencing this personalized response to exercise in a narrative review format.

Findings:

Genetic variation contributes significantly to the personalized training response, with specific polymorphisms associated with differences in exercise adaptation. These polymorphisms exist in a number of pathways controlling exercise adaptation. Environmental factors such as nutrition, psycho-emotional response, individual history and training programme design also modify the inter-individual adaptation following training. Within the emerging field of epigenetics, DNA methylation, histone modifications and non-coding RNA allow environmental and lifestyle factors to impact genetic expression. These epigenetic mechanisms are themselves modified by genetic and non-genetic factors, illustrating the complex interplay between variables in determining the adaptive response. Given that genetic factors are such a fundamental modulator of the inter-individual response to exercise, genetic testing may provide a useful and affordable addition to those looking to maximise exercise adaption, including elite athletes. However, there are ethical issues regarding the use of genetic tests, and further work is needed to provide evidence based guidelines for their use.

Conclusion:

There is considerable inter-individual variation in the adaptive response to exercise. Genetic assessments may provide an additional layer of information allowing personalization of training programmes to an individual’s unique biology.

Can the ability to adapt to exercise be considered a talent-and if so, can we test for it?

Talent identification (TI) is a popular and hugely important topic within sports performance, with an ever-increasing amount of resources dedicated to unveiling the next sporting star. However, at present, most TI processes appear to select high-performing individuals at the present point in time, as opposed to identifying those individuals with the greatest capacity to improve. This represents a potential inefficiency within the TI process, reducing its effectiveness. In this article, we discuss whether the ability to adapt favorably, and with a large magnitude, to physical training can be considered a talent, testing it against proposed criteria. We also discuss whether, if such an ability can be considered a talent, being able to test for it as part of the TI process would be advantageous. Given that such a capacity is partially heritable, driven by genetic variation between individuals that mediate the adaptive response, we also explore whether the information gained from genetic profiling can be used to identify those with the greatest capacity to improve. Although there are some ethical hurdles which must be considered, the use of genetic information to identify those individuals with the greatest capacity appears to hold promise and may improve both the efficiency and effectiveness of contemporary TI programmes.

The gene SMART study: method, study design, and preliminary findings

The gene SMART (genes and the Skeletal Muscle Adaptive Response to Training) Study aims to identify genetic variants that predict the response to both a single session of High-Intensity Interval Exercise (HIIE) and to four weeks of High-Intensity Interval Training (HIIT). While the training and testing centre is located at Victoria University, Melbourne, three other centres have been launched at Bond University, Queensland University of Technology, Australia, and the University of Brighton, UK. Currently 39 participants have already completed the study and the overall aim is to recruit 200 moderately-trained, healthy Caucasians participants (all males 18-45 y, BMI < 30). Participants will undergo exercise testing and exercise training by an identical exercise program. Dietary habits will be assessed by questionnaire and dietitian consultation. Activity history is assessed by questionnaire and current activity level is assessed by an activity monitor. Skeletal muscle biopsies and blood samples will be collected before, immediately after and 3 h post HIIE, with the fourth resting biopsy and blood sample taken after four weeks of supervised HIIT (3 training sessions per week). Each session consists of eight to fourteen 2-min intervals performed at the pre-training lactate threshold (LT) power plus 40 to 70% of the difference between pre-training lactate threshold (LT) and peak aerobic power (W_peak). A number of muscle and blood analyses will be performed, including (but not limited to) genotyping, mitochondrial respiration, transcriptomics, protein expression analyses, and enzyme activity. The participants serve as their own controls. Even though the gene SMART study is tightly controlled, our preliminary findings still indicate considerable individual variability in both performance (in-vivo) and muscle (in-situ) adaptations to similar training. More participants are required to allow us to better investigate potential underlying genetic and molecular mechanisms responsible for this individual variability.