Clinical Applications of Iso-Inertial, Eccentric-Overload (YoYo™) Resistance Exercise

In the quest for a viable non-gravity dependent method to “lift weights” in space, our laboratory introduced iso-inertial resistance (YoYo™) exercise using spinning flywheel(s), more than 25 years ago. After being thoroughly tested in individuals subjected to various established spaceflight analogs, a multi-mode YoYo™ exercise apparatus was eventually installed on the International Space Station in 2009. The method, applicable to any muscle group, provides accommodated resistance and optimal muscle loading through the full range of motion of concentric actions, and brief episodes of eccentric overload. This exercise intervention has found terrestrial applications and shown success in enhancing sports performance and preventing injury and aiding neurological or orthopedic rehabilitation. Research has proven that this technique offers unique physiological responses not possible with other exercise hardware solutions. This paper provides a brief overview of research that has made use, and explored the efficacy, of this method in healthy sedentary or physically active individuals and populations suffering from muscle wasting, disease or injury. While the collective evidence to date suggests YoYo™ offers a potent stimulus to optimize the benefits of resistance exercise, systematic research to support clinical use of this method has only begun to emerge. Thus, we also offer perspectives on unresolved issues, unexplored applications for clinical conditions, and how this particular exercise paradigm could be implemented in future clinical research and eventually being prescribed. Fields of particular interest are those aimed at promoting muscle health by preventing injury or combating muscle wasting and neurological or metabolic dysfunction due to aging or illness, or those serving in rehabilitation following trauma and/or surgery

The International Olympic Committee framework on fairness, inclusion and nondiscrimination on the basis of gender identity and sex variations does not protect fairness for female athletes

The International Olympic Committee (IOC) recently published a framework on fairness, inclusion, and nondiscrimination on the basis of gender identity and sex variations. Although we appreciate the IOC's recognition of the role of sports science and medicine in policy development, we disagree with the assertion that the IOC framework is consistent with existing scientific and medical evidence and question its recommendations for implementation. Testosterone exposure during male development results in physical differences between male and female bodies; this process underpins male athletic advantage in muscle mass, strength and power, and endurance and aerobic capacity. The IOC's “no presumption of advantage” principle disregards this reality. Studies show that transgender women (male-born individuals who identify as women) with suppressed testosterone retain muscle mass, strength, and other physical advantages compared to females; male performance advantage cannot be eliminated with testosterone suppression. The IOC's concept of “meaningful competition” is flawed because fairness of category does not hinge on closely matched performances. The female category ensures fair competition for female athletes by excluding male advantages. Case-by-case testing for transgender women may lead to stigmatization and cannot be robustly managed in practice. We argue that eligibility criteria for female competition must consider male development rather than relying on current testosterone levels. Female athletes should be recognized as the key stakeholders in the consultation and decision-making processes. We urge the IOC to reevaluate the recommendations of their Framework to include a comprehensive understanding of the biological advantages of male development to ensure fairness and safety in female sports

The Impact of Coronavirus (COVID-19) Related Public-Health Measures on Training Behaviours of Individuals Previously Participating in Resistance Training: A Cross-Sectional Survey Study

Introduction Understanding the impact of lockdown upon resistance training (RT), and how people adapted their RT behaviours, has implications for strategies to maintain engagement in similar positive health behaviours. Further, doing so will provide a baseline for investigation of the long-term effects of these public health measures upon behaviours and perceptions, and facilitate future follow-up study. Objectives To determine how the onset of coronavirus (COVID-19), and associated ‘lockdown’, affected RT behaviours, in addition to motivation, perceived effectiveness, enjoyment, and intent to continue, in those who regularly performed RT prior to the pandemic. Methods We conducted an observational, cross-sectional study using online surveys in multiple languages (English, Danish, French, German, Italian, Portuguese, Slovakian, Swedish, and Japanese) distributed across social media platforms and through authors’ professional and personal networks. Adults (n = 5389; median age = 31 years [interquartile range (IQR) = 25, 38]), previously engaged in RT prior to lockdown (median prior RT experience = 7 years [IQR = 4, 12]) participated. Outcomes were self-reported RT behaviours including: continuation of RT during lockdown, location of RT, purchase of specific equipment for RT, method of training, full-body or split routine, types of training, repetition ranges, exercise number, set volumes (per exercise and muscle group), weekly frequency of training, perception of effort, whether training was planned/recorded, time of day, and training goals. Secondary outcomes included motivation, perceived effectiveness, enjoyment, and intent to continue RT. Results A majority of individuals (82.8%) maintained participation in RT during-lockdown. Marginal probabilities from generalised linear models and generalised estimating equations for RT behaviours were largely similar from pre- to during-lockdown. There was reduced probability of training in privately owned gyms (~ 59% to ~ 7%) and increased probability of training at home (~ 18% to ~ 89%); greater probability of training using a full-body routine (~ 38% to ~ 51%); reduced probability of resistance machines (~ 66% to ~ 13%) and free weight use (~ 96% to ~ 81%), and increased probability of bodyweight training (~ 62% to ~ 82%); reduced probability of moderate repetition ranges (~ 62–82% to ~ 55–66%) and greater probability of higher repetition ranges (~ 27% to ~ 49%); and moderate reduction in the perception of effort experienced during-training (r = 0.31). Further, individuals were slightly less likely to plan or record training during lockdown and many changed their training goals. Additionally, perceived effectiveness, enjoyment, and likelihood of continuing current training were all lower during-lockdown. Conclusions Those engaged in RT prior to lockdown these behaviours with only slight adaptations in both location and types of training performed. However, people employed less effort, had lower motivation, and perceived training as less effective and enjoyable, reporting their likelihood of continuing current training was similar or lower than pre-lockdown. These results have implications for strategies to maintain engagement in positive health behaviours such as RT during-restrictive pandemic-related public health measures

Muscle damage responses and adaptations to eccentric-overload resistance exercise in men and women

Purpose: This study assessed markers of muscle damage and training adaptations to eccentric-overload flywheel resistance exercise (RE) in men and women. Methods: Dynamic strength (1 RM), jump performance, maximal power at different percentages of 1 RM, and muscle mass in three different portions of the thigh were assessed in 16 men and 16 women before and after 6 weeks (15 sessions) of flywheel supine squat RE training. Plasma creatine kinase (CK) and lactate dehydrogenase (LDH) concentrations were measured before, 24, 48 and 72 h after the first and the last training session. Results: After training, increases in 1 RM were somewhat greater (interaction P &lt; 0.001) in men (25 %) than in women (20 %). Squat and drop jump height and power performance at 50, 60, 70 and 80 % of 1 RM increased after training in both sexes (P &lt; 0.05). Power improvement at 80 % of 1 RM was greater (interaction P &lt; 0.02) in men than women. Muscle mass increased ~5 % in both groups (P &lt; 0.05). CK increased in men after the first training session (P &lt; 0.001), whereas the response in women was unaltered. In both sexes, LDH concentration was greater after the first training session compared with basal values (P &lt; 0.05). After the last session, CK and LDH remained at baseline in both groups. Conclusions: These results suggest that although improvements in maximal strength and power at high loads may be slightly greater for men, eccentric-overload RE training induces comparable and favorable gains in strength, power, and muscle mass in both men and women. Equally important, it appears muscle damage does not interfere with the adaptations triggered by this training paradigm. © 2014 Springer-Verlag Berlin Heidelberg.Language of Original Document: English</p

Threshold-automated CT measurements of muscle size and radiological attenuation in multiple lower-extremity muscles of older individuals

Muscle atrophy and fat infiltration, two indicators of deconditioning and weakness in elderly frail patients, are typically assessed by means of manual image analysis from computed tomography (CT) scans. As this time-consuming image analysis limits its wider use in clinical studies, the use of tissue thresholds to semi-automatically assess muscle composition has been suggested. Here, we aimed to investigate the relationship between manual and semi-automated analysis of both cross-sectional area (CSA) and radiological attenuation (RA), in multiple muscles of the lower extremities in aged (77 +/- 6 years) sedentary individuals (n = 40). The participants underwent CT scans of their lower limbs, including hip, thigh and calf muscles. The subsequent analysis of CSA and RA was conducted using both manual segmentation and semi-automatic thresholds (-30 to +150 Hounsfield units). Automated measurements were generally strongly correlated with manually encircled CSA in all muscle groups (R = 0.79-0.99, p &lt; .05) and shortened the analysis time by 70% (p &lt; .05). In m. iliopsoas, however, the CSA became overestimated (15%, p &lt; .05) with thresholded measurements, while the assessment of both CSA and RA was underestimated in muscles with high-fat content (i.e., the gluteal muscles) and in individuals with high-fat infiltration. In conclusion, using the semi-automated technique with conventional thresholds is a time-saving method that delivers accurate gross size of the muscle groups, particularly in the thigh. However, caution should be exercised when using semi-automated techniques for assessing CSA and fat infiltration in muscles with high-fat content

Relationship between maximal oxygen uptake, within-set fatigue and between-set recovery during resistance exercise in resistance-trained men and women

Abstract Background The primary aim of this study was to examine the relationship between maximal oxygen update (V̇O2max) and within-set fatigue and between-set recovery during resistance exercise in men and women. Methods We examined the relationship between V̇O2max and various indices of fatigue and recovery during parallel squats (3 sets, 90 s rest, 70% of 1RM to failure) and isokinetic knee extensions (3 × 10 maximal repetitions at 60 deg/s, 45 s rest) in 28 (age 27.0 ± 3.6 years) resistance-trained subjects (14 men and 14 women). We also examined whether there were sex differences in within-set fatigue and between-set recovery. Results V̇O2max was weakly related to recovery and fatigue in both men and women (range of P-values for V̇O2max as a covariate; 0.312–0.998, range of R-values, 0.005–0.604). There were no differences between the sexes in fatigue within a set for the squat, but men showed less within-set fatigue than women in the first set of the isokinetic knee extension exercise (~ 8% torque loss difference, main effect of sex P = 0.034). Regarding recovery between sets, men showed greater relative peak power (P = 0.016) and peak torque (P = 0.034) loss between sets in both exercises, respectively, compared to women. Women also tended to complete more repetitions than men (main effect of sex, P = 0.057). Loss of peak torque between sets in knee extension was evident in both absolute and relative (%) values in men but not in women. Conclusions Our study suggests that aerobic capacity is weakly associated with within-set fatigue and between-set recovery in resistance training in both men and women. Women and men show comparable levels of within-set fatigue in the multi-joint squat, but women show more within-set fatigue during the single-joint isokinetic knee extension compared with men. In contrast, women recover better than men between sets in both exercises

Regional and muscle-specific adaptations in knee extensor hypertrophy using flywheel versus conventional weight-stack resistance exercise

This study compared the effects of the most frequently employed protocols of flywheel vs. weight-stack resistance exercise (RE) on regional and muscle-specific adaptations of the knee extensors. Sixteen men (n=8) and women (n=8) performed 8 weeks (2-3 days/wk) of knee extension RE employing flywheel technology (FW) on one leg (4x7 repetitions), while the contralateral leg performed regular weight-stack (WS) training (4x8-12 repetitions). Maximal strength (1RM in WS) and peak FW power were determined before and after training for both legs. Partial muscle volume of vastus lateralis (VL), vastus medialis (VM), vastus intermedius (VI) and rectus femoris (RF) were measured using magnetic resonance imaging (MRI). Additionally, quadriceps (QF) cross-sectional area was assessed at a proximal and a distal site. There were no differences (P>0.05) between FW vs. WS in muscle hypertrophy of the QF (8% vs. 9%), VL (10% vs. 11%), VM (6% vs. 8%) or VI (5% vs. 5%). Muscle hypertrophy tended (P=0.09) to be greater at the distal compared with the proximal site, but there was no interaction with exercise method. Increases in 1RM and FW peak power were similar across legs, yet the increase in 1RM was greater in men (31%) than in women (20%). These findings suggest that FW and WS training induce comparable muscle-specific hypertrophy of the knee extensors. Given that these robust muscular adaptations were brought about with markedly fewer repetitions in the FW compared with WS, it seems FW training can be recommended as a particularly time-efficient exercise paradigm.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Three months of bed rest induce a residual transcriptomic signature resilient to resistance exercise countermeasures

This study explored the muscle genome-wide response to long-term unloading (84-day bed rest) in 21 men. We hypothesized that a part of the bed rest-induced gene expression signature would be resilient to a concurrent flywheel resistance exercise (RE) countermeasure. Using DNA microarray technology analyzing 35 345 gene-level probe-sets, we identified 335 annotated probe-sets that were downregulated, and 315 that were upregulated after bed rest (P &amp;lt; .01). Besides a predictable differential expression of genes and pathways related to mitochondria (downregulation; false-discovery rates (FDR) &amp;lt;1E-04), ubiquitin system (upregulation; FDR = 3E-02), and skeletal muscle energy metabolism and structure (downregulation; FDR &amp;lt;= 3E-03), 84-day bed rest also altered circadian rhythm regulation (upregulation; FDR = 3E-02). While most of the bed rest-induced changes were counteracted by RE, 209 transcripts were resilient to the exercise countermeasure. Genes upregulated after bed rest were particularly resistant to training (P &amp;lt; .001 vs downregulated, non-reversed genes). Specifically, "Translation Factors," "Proteasome Degradation," "Cell Cycle," and "Nucleotide Metabolism" pathways were not normalized by RE. This study provides an unbiased high-throughput transcriptomic signature of one of the longest unloading periods in humans to date. Classical disuse-related changes in structural and metabolic genes/pathways were identified, together with a novel upregulation of circadian rhythm transcripts. In the context of previous bed rest campaigns, the latter seemed to be related to the duration of unloading, suggesting the transcriptomic machinery continues to adapt throughout extended disuse periods. Despite that the RE training offset most of the bed rest-induced muscle-phenotypic and transcriptomic alterations, we contend that the human skeletal muscle also displays a residual transcriptomic signature of unloading that is resistant to an established exercise countermeasure.Funding Agencies|Swedish National Space Agency; European Space Agency (ESA)European Space Agency; Swedish National Center for Research in Sports</p