Effects of a 10-week in-season eccentric-overload training program on muscle-injury prevention and performance in junior elite soccer players

Comparing the Effect of Isoinertial Flywheel Training and Traditional Resistance Training on Maximal Strength and Muscle Power in Healthy People: A Systematic Review and Meta-Analysis

BACKGROUND

This systematic review and meta-analysis aimed to analyze whether isoinertial flywheel training (FWT) is superior to traditional resistance training (TRT) in enhancing maximal strength and muscle power in healthy individuals.

METHODS

Electronic searches were conducted in the Web of Science, PubMed, Cochrane Library, SPORTDiscus, and Scopus databases up to 21 April 2024. Outcomes were analyzed as continuous variables using either a random or fixed effects model to calculate the standardized mean difference (SMD) and 95% confidence intervals (CI).

RESULTS

A total of sixteen articles, involving 341 subjects, met the inclusion criteria and were included in the statistical analyses. The pooled results indicate no statistically significant differences between FWT and TRT in developing maximal strength in healthy individuals (SMD = 0.24, 95% CI [-0.26, 0.74], p = 0.35). Additionally, the pooled outcomes showed a small-sized effect in muscle power with FWT (SMD = 0.47, 95% CI [0.10, 0.84]), which was significantly higher than that with TRT (p = 0.01) in healthy individuals. Subgroup analysis revealed that when the total number of FWT sessions is between 12 and 18 (1-3 times per week), it significantly improves muscle power (SMD = 0.61, 95% CI [0.12, 1.09]). Significant effects favoring FWT for muscle power were observed in both well-trained (SMD = 0.58, 95% CI [0.04, 1.13]) and untrained individuals (SMD = 1.40, 95% CI [0.23, 2.57]). In terms of exercise, performing flywheel training with squat and lunge exercises significantly enhances muscle power (SMD = 0.43; 95% CI: 0.02-0.84, and p = 0.04). Interestingly, FWT was superior to weight stack resistance training (SMD = 0.61, 95% CI [0.21, 1.00]) in enhancing muscle power, while no significant differences were found compared to barbell free weights training (SMD = 0.36, 95% CI [-0.22, 0.94]).

CONCLUSIONS

This meta-analysis confirms the superiority of FWT compared to TRT in promoting muscle power in both healthy untrained and well-trained individuals. Squats and lunges for FWT are more suitable for improving lower limb explosive power. It is recommended that coaches and trainers implement FWT for six weeks, 2-3 times per week, with at least a 48 h interval between each session. Although FWT is not superior to free weights training, it is advisable to include FWT in sport periodization to diversify the training stimuli for healthy individuals.

Effects of variable intensity and constant intensity flywheel resistance training programs on specific soccer players' performance

Resistance training programs play a crucial role in optimizing soccer performance. The aim of this study is to compare performance outcomes in sport-specific tasks after implementing two different flywheel resistance training (FRT) programs: variable intensity (VI) and constant intensity (CI). Seventeen (n = 17) amateur footballers were divided into VI and CI groups with the same training volume. For the VI group, a decrease in inertial load was implemented every four sessions, whereas the CI group maintained a constant load during the entire program. After different familiarization sessions and testing (sprint, change of direction, jump, one-repetition maximum and flywheel strength variables), ten sessions of FRT were performed over 5 weeks. Both groups showed similar improvements in the one-repetition maximum (p < 0.01) but the CI group had significant improvements in the 10-m sprint (p = 0.04; ES = 0.72), emphasizing the potential benefits of medium inertial loads to maximize power and specificity in sport tasks. However, no significant differences were observed in the countermovement jump, change of direction and 30-m sprint, possibly attributed to neuromuscular fatigue from a high-volume training schedule and friendly matches. The study highlights the importance of considering training load distribution in FRT programs. The findings emphasize the need for complementary training to maximize the jump and change of direction abilities and caution against high-volume training and friendly match scenarios. In conclusion, FRT programs, whether varying in intensity or not, can yield medium-term performance improvements for soccer players.

Bodily Practices and Meanings Articulated in the Physical Exercise of Older Adults in Santiago de Chile Post-COVID-19

This article presents the results of almost nine months of ethnographic research on the relationship between physical exercise and health in older people in the post-COVID-19 context. Via exploratory-descriptive qualitative research and the use of a convenient sample, I shed light on this relationship using the stories and life experiences of 40 older people (10 men and 30 women, including two women instructors for senior classes) who exercise regularly. The meanings they attributed to physical exercise during COVID-19 and after it are explained, emphasising first that there is no health in a context of not feeling safe; once there is a feeling of security, the most relevant meanings can be exposed in three directions. First, exercise produces a sense of identity linked to "being an athlete" and "belonging to a group". Second, exercising is valued as participating in something meaningful (the meanings range from self-realisation, independence, and autonomy to feelings of happiness). Finally, and linked to the sense of identity, those who train alone show more commitment and total hours spent in physical exercise and physical activity than those who train in groups. Even though older people are not a homogeneous group, they generally faced the pandemic as an ageist situation that affected their lives and how they saw sports and health. This article describes the strategies they used during COVID-19 related to exercise and well-being and those used once the pandemic restrictions were no longer present. The qualitative aspects that physical exercise brings to this population are highlighted. The research results give voice to older people, showing their heterogeneity and the meanings and practices that unite them. These inputs are rich material for studies on physical activity, older people, and well-being.

Force Production and Electromyographic Activity during Different Flywheel Deadlift Exercises

This study aimed to characterize and compare force production and muscle activity during four flywheel deadlift exercises (bilateral [Bi] vs. unilateral [Uni]) with different loading conditions (vertical [Ver] vs. horizontal [Hor]). Twenty-three team-sport athletes underwent assessments for exercise kinetics (hand-grip force), along with surface electromyography (sEMG) of the proximal (BFProx) and medial biceps femoris (BFMed), semitendinosus (ST), and gluteus medius (GM). Mean and peak force were highest (p < 0.001) in Bi + Ver compared with Bi + Hor, Uni + Ver, and Uni + Hor. Although no significant differences were observed between Bi + Hor and Uni + Ver, both variants showed higher (p < 0.001) average force and peak eccentric force when compared with Uni + Hor. The presence of eccentric overload was only observed in the vertically loaded variants. Bi + Ver and Uni + Ver showed higher (p < 0.05) sEMG levels in BFProx and BFMed compared with the Uni + Hor variant. In addition, Uni + Ver registered the largest GM and ST sEMG values. In conclusion, the vertical variants of the flywheel deadlift exercise led to higher muscle force production and sEMG compared with their horizontal counterparts. Both Bi + Ver and Uni + Ver may be effective in promoting an increase in hamstring muscles activity and muscle force at long muscle length, while the Uni + Ver variant may be more effective in promoting GM and ST involvement.

Current Guidelines for the Implementation of Flywheel Resistance Training Technology in Sports: A Consensus Statement

BACKGROUND

Flywheel resistance training has become more integrated within resistance training programs in a variety of sports due to the neuromuscular, strength, and task-specific enhancements reported with this training.

OBJECTIVE

This paper aimed to present the consensus reached by internationally recognized experts during a meeting on current definitions and guidelines for the implementation of flywheel resistance training technology in sports.

METHODS

Nineteen experts from different countries took part in the consensus process; 16 of them were present at the consensus meeting (18 May 2023) while three submitted their recommendations by e-mail. Prior to the meeting, evidence summaries were developed relating to areas of priority. This paper discusses the available evidence and consensus process from which recommendations were made regarding the appropriate use of flywheel resistance training technology in sports. The process to gain consensus had five steps: (1) performing a systematic review of systematic reviews, (2) updating the most recent umbrella review published on this topic, (3) first round discussion among a sample of the research group included in this consensus statement, (4) selection of research group members-process of the consensus meeting and formulation of the recommendations, and (5) the consensus process. The systematic analysis of the literature was performed to select the most up-to-date review papers available on the topic, which resulted in nine articles; their methodological quality was assessed according to AMSTAR 2 (Assessing the Methodological Quality of Systematic Review 2) and GRADE (Grading Recommendations Assessment Development and Evaluation). Statements and recommendations scoring 7-9 were considered appropriate.

RESULTS

The recommendations were based on the evidence summary and researchers' expertise; the consensus statement included three statements and seven recommendations for the use of flywheel resistance training technology. These statements and recommendations were anonymously voted on and qualitatively analyzed. The three statements reported a score ranging from 8.1 to 8.8, and therefore, all statements included in this consensus were considered appropriate. The recommendations (1-7) had a score ranging from 7.7 to 8.6, and therefore, all recommendations were considered appropriate.

CONCLUSIONS

Because of the consensus achieved among the experts in this project, it is suggested that practitioners and researchers should adopt the guidelines reported in this consensus statement regarding the use of flywheel resistance technology in sports.

From Theory to Practice: A Worldwide Cross-Sectional Survey About Flywheel Training in Basketball

PURPOSE

This study aimed to comprehensively investigate the global implementation of flywheel training (FT) by basketball strength and conditioning (S&C) coaches in various contexts, encompassing daily practice, games, and sessions.

METHODS

Survey data were collected from 117 basketball S&C coaches who participated in a 24-question online survey. The survey was structured into 6 key areas, including country and competition, S&C coach context, training methodology, flywheel and competition, postactivation performance enhancement, and recovery.

RESULTS

Notably, all respondents emphasized the necessity of a familiarization period with flywheel technology, with a substantial 96% indicating that FT yielded improved player performance on the court. The predominant mention was the conical pulley system. During the season, the prevalent approach involved integrating FT into training twice a week, allocating <15 minutes per session, often in conjunction with traditional strength training. A diverse array of lower-body closed kinetic chain exercises were reported, encompassing squats, decelerations, and backward lunges. Intriguingly, FT implementation on match days was unlikely (77%), with the primary aims cited as injury prevention (34%) and enhancing players' strength levels during various phases of the regular season (27%).

CONCLUSIONS

Recognizing its inherent limitations, this descriptive study provides valuable contextual insights and practical applications for professional basketball practitioners grappling with the utilization of FT.

Six Weeks of Unilateral Flywheel Hip-Extension and Leg-Curl Training Improves Flywheel Eccentric Peak Power but Does Not Enhance Hamstring Isokinetic or Isometric Strength

PURPOSE

This preregistered trial investigated how 6 weeks of unilateral flywheel leg-curl and hip-extension training impact isokinetic, isometric, and flywheel strength and power outcomes.

METHODS

The study involved 11 male university athletes (age 22 [2] y; body mass 77.2 [11.3] kg; height 1.74 [0.09] m) with one leg randomly allocated to flywheel training and one leg to control. Unilateral eccentric and isometric knee-flexion torque and flywheel unilateral leg-curl and hip-extension peak power were tested. Training intensity and volume (3-4 sets of 6 + 2 repetitions) were progressively increased.

RESULTS

The intervention enhanced hip-extension concentric (P < .01, d = 1.76, large) and eccentric (P < .01, d = 1.33, large) peak power more than the control (significant interaction effect). Similarly, eccentric (P = .023, d = 1.05, moderate) peak power was enhanced for the leg curl. No statistically significant differences between conditions were found for isokinetic eccentric (P = .086, d = 0.77, moderate) and isometric (P = .431, d = 0.36, small) knee-flexor strength or leg-curl concentric peak power (P = .339, d = 0.52, small). Statistical parametric mapping analysis of torque-angle curves also revealed no significant (P > .05) time-limb interaction effect at any joint angle.

CONCLUSION

Unilateral flywheel hamstring training improved knee-flexor eccentric peak power during unilateral flywheel exercise but not flywheel concentric, isokinetic eccentric, or isometric (long-lever) knee-flexor strength.

Resistance Training Practices of Brazilian Olympic Sprint and Jump Coaches: Toward a Deeper Understanding of Their Choices and Insights (Part III)

In the final part of this three-article collection on the training strategies of Brazilian Olympic sprint and jump coaches, we provide a detailed description of the resistance training methods and exercises most commonly employed by these speed experts. Always with the objective of maximizing the sprint and jump capabilities of their athletes, these experienced coaches primarily utilize variable, eccentric, concentric, machine-based, isometric, complex, and isoinertial resistance training methods in their daily practices. Squats (in their different forms), Olympic weightlifting, ballistics, hip thrusts, lunges, calf raises, core exercises, leg curls, stiff-leg deadlifts, and leg extension are the most commonly prescribed exercises in their training programs, during both the preparatory and competitive periods. Therefore, the current manuscript comprehensively describes and examines these methods, with the additional aim of extrapolating their application to other sports, especially those where sprint speed is a key performance factor.

Is a Maximal Strength-Training Program Effective on Physical Fitness, Injury Incidence, and Injury Burden in Semi-Professional Soccer Players? A Randomized Controlled Trial

The aims of the study were to analyze the effects of a 12-week maximal strength- training program on injury incidence, injury burden, and physical fitness in semi-professional soccer players and to compare the perceived exertion load and well-being state between injured and non-injured soccer players. Twenty semi-professional male soccer players participated in this study. Participants were randomly allocated to an experimental group (EG, n = 10 players), who performed a maximal strength-training program, or to a control group (CG, n = 10 players), who only performed their regular soccer training. Physical fitness was measured at baseline and after the training program. In addition, the injury incidence, burden, training/match load, and the state of well-being of the players were recorded. The EG showed significant improvements in vertical jumps, change in direction ability, linear sprints, repeated sprint ability, isometric strength (p < 0.003; effect size = 1.78-11.86), and quadriceps-hamstring imbalance in both legs (p < 0.001; effect size = 2.37-3.71) in comparison to the CG. In addition, the EG players showed a significantly (p < 0.05) lower injury burden (p < 0.001, relative risk = 5.05, 95% confidence interval = 3.27-7.79). This study demonstrated the beneficial effects of a 12-week maximal strength-training program on physical fitness attributes and injury burden in semi-professional soccer players.

Stable vs. variable eccentric load. Do they induce different training and physical performance outcomes?

Since most movements on the field require athletes to produce forces in variable and unpredictable contexts, the use of training programs based on identical repetitions of an exercise may not be optimal for movement transference. Therefore, the aim of this study was to analyse the effects of unexpected eccentric load variability during resistance training in team sport players. Sixty-three men were randomly allocated to two experimental groups (Variable (VTG) and stable (STG) training group) and control group: (CG) volunteered to participate in this study. Experimental groups trained with the same average load of half-squat exercise twice a week for six weeks using rotary inertial devices (RIDs) with (VTG) and without (STG) an unexpected variability of the load. The squat force was measured for every session with force plates. Counter-movement jump (CMJ), sprint, and change of direction performances were measured pre and post-test. CMJ performance improved for VTG (p = .014; ES = 0.7) and STG (p = .005; ES = 0.79) but not for CG. Exposure to high eccentric forces with RIDs lead athletes to improve physical performance in the trained force vector but, since RIDs induce in high levels of variability per se, increasing the level of variability of the exercise will not add benefits to physical performance and training outcomes.HIGHLIGHTSThe relevance of the study is to analyse if increasing the variability of the load will improve the athlete output to different physical performance tests.The exposure to eccentric overload with RIDs during the squat exercise allows to greater CMJ height improvements than those seen in the literature with RIDs without overloading the eccentric contraction.RIDs induce in high level of variability per se. Therefore, increasing the level of variability of the exercise will not add benefits to physical performance and training outcomes.

Stojanović MD, Bird SP, Calleja-González J. Effectiveness of Eccentric Overload Training in Basketball Players: A Systematic Review

Several studies have confirmed the efficacy of flywheel eccentric overload training in order to improve or increase muscle volume and strength, as well as several performance-related fitness attributes, but to date, there are no studies that have reviewed the effects of these training methods in basketball. Therefore, the present systematic review aimed to collect the updated information about the influence of flywheel training on performance of basketball players. A search in four electronic databases (PubMed, SCOPUS, Web of Science, and Google Scholar) was conducted up to November 20, 2022. Articles were selected as valid for review if: (i) they were an experimental trial published in English; (ii) participants were basketball players without illnesses or injuries, and (iii) a rotational inertial overload method was used as a performance-dependent variable. A total of 93 articles were found. After filtering procedures, only seven studies were considered in this systematic review. In the selected studies, 203 participants were included, 58 females and 145 males. Focusing on basketball related performance variables, all the studies included the countermovement jump (CMJ), while five included sprinting and a change of direction test (COD). The results showed an improvement in performance-related variables associated with basketball (sprint, CMJ, and COD) through the use of inertial methods. Improvements were reported in professional, semi-professional and amateur players as well as both male and female players. However, given the low number of studies, additional investigations on this topic are warranted before a "clear picture" can be drawn concerning the effects of flywheel eccentric overload training in basketball players.

Effects of body mass-based resistance training on measures of physical fitness and musculotendinous injury incidence and burden in U16 male soccer players

This study examined the effects of body mass-based resistance training (bmRT) on selected measures of physical fitness and injury incidence and burden in soccer players. Forty-six U16 male soccer players were randomly assigned to an control (CG; n = 26) or experimental group (EG; n = 20) Countermovement jump (CMJ), change of direction (CoD) (i.e., 20 m with one CoD), and linear sprint over 30 m were assessed before and after a 15-weeks training. Any type of musculotendinous injury that occurred throughout the intervention period was recorded. Between-group difference was noted at post-test for CMJ (p = 0.008). Pre-to-post training values increased in the EG (effect size [ES] = 1.01) while in the CG no pre-to-post changes were detected (ES = 0.27). No between-group differences at post-test were observed for sprint and CoD tests. Differences in injury burden were reported (33.28 [CG] vs. 9.55 [EG] absence days/1,000 hours exposure, rate ratio = 3.49, 95% CI 2.03-6.00, p < 0.001), but not in injury incidence. A bmRT programis suitable for improving jumping height but not linear and CoD speed performance. Additionally, bmRT may reduce injury burden, and therefore, the severity of musculotendinous injuries in U16 male soccer players.

Effects of eccentric-emphasized leg curl intervention on muscle strength imbalance markers in professional soccer players during pre-season

BACKGROUND

The effects of strength training on muscle strength imbalance are unclear in professional soccer players. As a result, this study examined the effects of an 8-week strength training program comprising eccentric-emphasized prone leg curl adjusted according to the individual strength imbalance status.

METHODS

Ten professional soccer players (26.0 ± 3.6 yrs) participated in the study. Players who had a ≥ 10% contralateral imbalance in knee flexors eccentric peak torque (n = 6) performed two additional repetitions per set in the low-strength limb (high-volume, HV) compared to the high-strength limb (low-volume, LV). Isokinetic concentric knee extension and concentric and eccentric knee flexion peak torque (PT) and derived contralateral imbalances and conventional and functional hamstring-to-quadriceps ratios (H:Q) were assessed at baseline and after 8 weeks. Differences at baseline were assessed using paired-sample T-tests, and a two-way (limb x time) repeated measures analysis of covariance (ANCOVA) for changes over time.

RESULTS

A significant improvement in the eccentric knee flexion PT was observed in both limbs after 8 weeks (P < 0.05), with greater effects observed in the HV limb (25.0 N m, 95% CI: 15.1-34.9 N m). Significant decreases were also observed in the contralateral imbalances from concentric knee extension and flexion and eccentric knee flexion PT (P < 0.05). Differences were not observed in concentric knee extension and flexion PT (P > 0.05).

CONCLUSIONS

A short-term eccentric-emphasized leg curl intervention adjusted by the initial knee flexors eccentric strength was an efficient method to improve knee flexors strength imbalance in professional soccer players.

Intra- and Inter-Day Reliability of Inertial Loads with Cluster Sets When Performed during a Quarter Squat on a Flywheel Device

The aims of this study were to (i) estimate the intra- and inter-day reliability of mean concentric (CON) and eccentric (ECC) power at different inertial loads during a flywheel quarter-squat using a cluster set approach and (ii) to determine the acute effect of internal and external attentional focus on mean power when performing the flywheel quarter squat. Twelve collegiate field sport male athletes (age 22.4 ± 3.2 years, weight 81.4 ± 10.3 kg, height 1.81 ± 0.06 m) attended four cluster set testing sessions separated by 7 days. Sessions consisted of 4 sets of 15 repetitions using 4 inertial loads (0.025, 0.050, 0.075, and 0.100 kg·m²). A cluster block consisted of 5 repetitions, including "momentum repetitions" (4 × 5 + 5 + 5). Mean power (MP), CON power, ECC power, and ECC overload were recorded for both internal and external attentional focus groups. The external instructional group attained familiarization after two flywheel sessions (ES = 0.03-0.15) with little volatility between performance measures (CV% = 3.39-9.22). The internal instructional group showed large differences in MP output from session 2 to session 3 for all loads (ES = 0.59-1.25). In conclusion, the flywheel cluster set approach is a reliable training modality for maintaining MP output during all repetitions.

Building for the Future: A Systematic Review of the Effects of Eccentric Resistance Training on Measures of Physical Performance in Youth Athletes

BACKGROUND

Eccentric resistance training is recognised as an effective stimulus for enhancing measures of muscular strength and power in adult populations; however, its value in youth athletes is currently not well understood.

OBJECTIVE

The aim of this systematic review was to critically appraise the effects of eccentric resistance training on measures of physical performance (i.e. muscular strength, jump, sprint and change of direction) in youth athletes 18 years of age and under.

METHODS

Original journal articles published between 1950 and June 2022 were retrieved from electronic search engines of PubMed, SPORTDiscus and Google Scholar's advanced search option. Full journal articles investigating the acute and chronic effects of eccentric resistance training on measures of physical performance in youth athletes (i.e. a person 18 years of age or under who competes in sport) were included. The methodological quality and bias of each study were assessed prior to data extraction using a modified Downs and Black checklist.

RESULTS

The search yielded 749 studies, of which 436 were duplicates. Three-hundred studies were excluded based upon title and abstract review and a further 5 studies were removed following the modified Downs and Black checklist. An additional 14 studies were identified during backward screening. Accordingly, 22 studies were included in our systematic review. The Nordic hamstring exercise and flywheel inertial training were the most frequently used eccentric resistance training methods in youth athletes. Improvements in physical performance following the Nordic hamstring exercise are dependent upon an increase in the breakpoint angle, rather than training volume (sets and repetitions), and are further elevated with the addition of hip extension exercises or high-speed running. A minimum of 3 familiarisation trials is necessary to elicit meaningful adaptations following flywheel inertial training. Furthermore, an emphasis should be placed upon decelerating the rotating flywheel during the final one to two thirds of the eccentric phase, rather than gradually throughout the entire eccentric phase.

CONCLUSIONS

The findings of this systematic review support the inclusion of eccentric resistance training in youth athletes to improve measures of muscular strength, jump, sprint and change of direction performance. The current eccentric resistance training methods are predominantly limited to the Nordic hamstring exercise and flywheel inertial training; however, the efficacy of accentuated eccentric loading to improve jump performance warrants attention in future investigations.

A Systematic Review of Flywheel Training Effectiveness and Application on Sport Specific Performances

The objective of this systematic review was to examine the effectiveness of flywheel training, which allows for the replication of specific sports movements, overloading both the concentric and eccentric phases. Inclusion criteria were injury prevention outcomes; ability in terms of strength, power, sprinting, jumping and change of direction; competitive athletes; and RCTs. Exclusion criteria were a lack of a control group and lack of baseline and/or follow-up data. The databases used were Web of Science, Scopus, PubMed, Cochrane Library, and Sage. The revised Cochrane risk-of-bias tool was used to assess the quality of the selected RCTs. The Oxford Centre for Evidence-Based Medicine 2011 Levels of Evidence was used. A PICOS (participants, intervention, comparators, study outcomes, and study design) approach was used to evaluate eligibility. A total of 21 RCTs with 8 to 54 participants in each study analyzed flywheel technology and its application in nine sports. The results showed that flywheel training is a good strategy to improve sports performance, providing variation in training methodologies and athletes’ adherence. Further studies are needed to define guidelines on training modality, weekly frequency, volume, and inertia load. Only a few studies have applied the flywheel device directly to overload specific multidirectional movements at different joint angles. This method is not exempt from criticalities, such as the cost and the ability to carry out only individual training.

Effects of Flywheel Resistance Training on Muscle Function and Sport-Specific Performance in Collegiate Club Water Polo Players

Purpose: This study investigated the effects of flywheel squat training on lower body muscle function adaptations and sport-specific performance in collegiate club water polo players. Methods: Thirteen collegiate club water polo athletes (5 women, 8 men) performed flywheel squat training for 4 weeks. Isokinetic knee extension (KE) peak power (PP) and peak torque (PT), flywheel squat peak power (FPP) and mean power (FMP), countermovement jump (CMJ), in-water jump height (WJH) and foot speed were assessed at baseline (Pre1), 4 weeks (Pre2), and 8 weeks (Post) with the first 4 week block being a control period and the second 4 week block being the experimental training. Throughout the training period muscle soreness was assessed using a VAS scale, and FPP and FMP were assessed during every other session. Results: Isokinetic KE PP and PT increased from Pre1 to Post, and FPP and FMP increased between Pre1 and Post, and Pre2 and Post. CMJ and foot speed were unchanged. WJH displayed a change between Pre1 and Post. FPP increased 19% from session 2 to 4 and FMP increased 27% from session 2 to 6, and each remained elevated through session 8. Conclusion: 4 weeks of flywheel squat training in collegiate club water polo players elicited large gains (47-52%) in flywheel-specific squat power, but did not influence sport-specific performance measures including CMJ, WJH, and foot speed. Water-based exercises and stretch-shortening cycle movements (plyometrics) in combination with effective resistance training programs, which may include flywheel-based training, are likely needed for marked sport skill improvements.

Perception and use of flywheel resistance training amongst therapists in sport

Flywheel (isoinertial) resistance training is a valid strength training method that has been incorporated in sport for decades, yet little is known about how therapists working in sport apply flywheel resistance training. We aimed to describe and understand current application and perception of flywheel resistance training amongst therapists working in sport. Seventy- three therapists (13 ± 10 years of experience) started part of this survey with 52 completing the entire electronic questionnaire. Nine multiple choice questions on application and perceptions of flywheel training (prerequisites, use of technology, barriers, and upper- and lower-body exercises) preceded two 6-point Likert scale statements on strength and reduction of injury likelihood. Most therapists (47/73) either used or intended to use flywheel training with their athletes and stated familiarisation would be a priority prior to initiating training. Although more than half suggested they were confident flywheel training could enhance strength (27/52) and muscular prehabilitation outcomes (40/52), many remained unsure. Nonetheless, it appears that therapists would mostly include flywheel training within prehabilitation (40/52) or during the later stages of rehabilitation (37/52). To monitor progress, therapists slightly prefer power (30/52) over velocity outputs, while few would not use them at all. Although therapists would prescribe most exercises - the squat, rotational exercise, and unilateral leg curl would be the most selected. Meanwhile, therapists reported remain most unsure or would avoid prescribing the lateral squat and unilateral hip extension. The biggest perceived barriers to flywheel training are equipment cost/space, evidence, and scheduling. The investigation provides valuable insight into the application and perception of flywheel training amongst therapists working in sport.

Wearable technology in the sports medicine clinic to guide the return-to-play and performance protocols of athletes following a COVID-19 diagnosis

The coronavirus disease 2019 (COVID-19) pandemic has enabled the adoption of digital health platforms for self-monitoring and diagnosis. Notably, the pandemic has had profound effects on athletes and their ability to train and compete. Sporting organizations worldwide have reported a significant increase in injuries manifesting from changes in training regimens and match schedules resulting from extended quarantines. While current literature focuses on the use of wearable technology to monitor athlete workloads to guide training, there is a lack of literature suggesting how such technology can mediate the return to sport processes of athletes infected with COVID-19. This paper bridges this gap by providing recommendations to guide team physicians and athletic trainers on the utility of wearable technology for improving the well-being of athletes who may be asymptomatic, symptomatic, or tested negative but have had to quarantine due to a close exposure. We start by describing the physiologic changes that occur in athletes infected with COVID-19 with extended deconditioning from a musculoskeletal, psychological, cardiopulmonary, and thermoregulatory standpoint and review the evidence on how these athletes may safely return to play. We highlight opportunities for wearable technology to aid in the return-to-play process by offering a list of key parameters pertinent to the athlete affected by COVID-19. This paper provides the athletic community with a greater understanding of how wearable technology can be implemented in the rehabilitation process of these athletes and spurs opportunities for further innovations in wearables, digital health, and sports medicine to reduce injury burden in athletes of all ages.

Hypertrophic adaptations to a 6-week in-season barbell vs. flywheel squat added to regular soccer training

BACKGROUND

The aim of this study was to compare the hypertrophic adaptations to barbell or flywheel squat exercise added to regular in-season soccer training.

METHODS

Quadriceps' (rectus femoris [RF], vastus medialis [VM] and vastus lateralis [VL]) cross-sectional area (CSA) in its portions (proximal [PROX], middle [MID], and distal [DIST]) was measured on both legs before and after a 6-week barbell (80 to 90% one-maximum repetition; N.=7) or flywheel (0.0611 to 0.0811 kg·m²; N.=7) in an U19 professional soccer team using a 3T magnetic resonance imaging. Both groups underwent 5 sets × 6 reps per session of squat separated by 3-min rest, while controlling the time under tension (within 0.5 and 0.8 s).

RESULTS

The barbell squat group experienced moderate CSA increments in the VM<inf>MID</inf> and the VL<inf>DIST</inf> of the right leg (d=0.98-0.99). Additionally, the flywheel group experience large CSA increments in the RF<inf>MID</inf>, VL<inf>PROX</inf> and VL<inf>MID</inf> of the right leg (d=1.00-1.84). On average, flywheel squat training largely produced greater force during exercise compared to the barbell squat training (29.2 vs. 12.2 N·kg^-1; d=5.95), whereas the barbell squat training produced moderately greater power output (10.5 vs. 9.7; d=0.52).

CONCLUSIONS

Barbell squat training seems to be more effective for VM hypertrophy whereas flywheel squat triggers greater RF and VL hypertrophy as complementary to regular field-based soccer practice and competition within a short range of time (6 weeks) during the in-season. These findings can be considered also from either strength or reconditioning perspective based on the increase in the quadriceps muscles' CSA as mechanism underlying strength/power adaptations.

The Effects of a Compensatory Training Program Adding an Isoinertial Device in the Shoulder Function on Young Tennis Players

ABSTRACT

Fernandez-Fernandez, J, Moreno-Perez, V, Cools, A, Nakamura, FY, Teixeira, AS, Ellenbecker, T, Johansson, F, and Sanz-Rivas, D. The effects of a compensatory training program adding an isoinertial device in the shoulder function on young tennis players. J Strength Cond Res 37(5): 1096-1103, 2023-The aim of this study was to analyze whether a compensatory training program, including isoinertial flywheel training, could reduce shoulder imbalances in a group of asymptomatic young tennis players. After an initial evaluation, 26 young tennis players were assigned to either a supervised flywheel training group (FTG, n = 13) or a control group (CG, n = 13). Shoulder passive internal (IR) and external rotation (ER) range of motion (ROM) as well as shoulder IR and ER maximal isometric strength were measured before and after a 12-week training intervention, performed 3 times per week. After the intervention, results showed significant changes for IR ( p < 0.001, effect size [ES] = 1.83) and ER ( p < 0.001, ES = 1.77) on the dominant (D) side, and IR on the nondominant (ND) side ( p < 0.001, ES = 2.24) in the FTG compared with the CG. Regarding the ROM values, results showed that the FTG achieved significantly greater increases for the IR ROM ( p < 0.001, ES = 3.32) and total ROM (TROM) ( p = 0.004, ES = 1.39) on the D and ND sides (IR ROM: p = 0.002, ES = 1.53; TROM: p < 0.001, ES = 2.35) than the CG. Moreover, the CG displayed larger decrements in ER ROM ( p = 0.016, ES = 1.12) on the ND side after the training period than the FTG. The conducted compensatory training program was effective to increase the ER strength and IR mobility of the FTG players, which led to a reduction in the glenohumeral imbalances.

The soccer season: performance variations and evolutionary trends

The physiological demands of soccer challenge the entire spectrum of the response capacity of the biological systems and fitness requirements of the players. In this review we examined variations and evolutionary trends in body composition, neuromuscular and endurance-related parameters, as well as in game-related physical parameters of professional players. Further, we explore aspects relevant for training monitoring and we reference how different training stimulus and situational variables (e.g., competition exposure) affect the physiological and performance parameters of players. Generally, improvements of small magnitude in non- (non-CMJ) and countermovement-based jumps (CMJBased) and in the sprint acceleration (ACCPhase) and maximal velocity phase (MVPhase) are observed from start of preparation phase (PPS) to beginning of competition phase (BCP). A greater magnitude of increases is observed in physiological and endurance performance measures within this period; moderate magnitude in sub-maximal intensity exercise (velocity at fixed blood lactate concentrations; V2-4mmol/l) and large magnitude in VO2max, maximal aerobic speed (MAS) and intense intermittent exercise performance (IE). In the middle of competition phase (MCP), small (CMJBased and ACCPhase), moderate (non-CMJ; MVPhase; VO2max; sub-maximal exercise) and large (MAS and IE) improvements were observed compared to PPS. In the end of competition period (ECP), CMJBased and MVPhase improve to a small extent with non-CMJ, and ACCPhase, VO2max, MAS, sub-maximal intensity exercise and IE revealing moderate increments compared to PPS. Although less investigated, there are generally observed alterations of trivial magnitude in neuromuscular and endurance-related parameters between in-season assessments; only substantial alterations are examined for IE and sub-maximal exercise performance (decrease and increase of small magnitude, respectively) from BCP to MCP and in VO2max and IE (decrements of small magnitude) from MCP to ECP. Match performance may vary during the season. Although, the variability between studies is clear for TD, VHSR and sprint, all the studies observed substantial increments in HSR between MCP and ECP. Finally, studies examining evolutionary trends by means of exercise and competition performance measures suggests of a heightened importance of neuromuscular factors. In conclusion, during the preseason players "recover" body composition profile and neuromuscular and endurance competitive capacity. Within in-season, and more robustly towards ECP, alterations in neuromuscular performance seem to be force-velocity dependent, and in some cases, physiological determinants and endurance performance may be compromised when considering other in-season moments. Importantly, there is a substantial variability in team responses that can be observed during in-season. Consequently, this informs on the need to both provide a regular training stimulus and adequate monitorization throughout the season.

Effects of Vest and Sled Resisted Sprint Training on Sprint Performance in Young Soccer Players: A Systematic Review and Meta-analysis

ABSTRACT

Fernández-Galván, LM, Casado, A, García-Ramos, A, and Haff, GG. Effects of vest and sled resisted sprint training on sprint performance in young soccer players: A systematic review and meta-analysis. J Strength Cond Res XX(X): 000-000, 2022-The aim of the meta-analysis was to determine the effect of resisted sprint training (RST) on sprint performance in young (<20 years) soccer players and to analyze whether the training equipment (sled or vest) and magnitude of the resistive load (above or below 20% of body mass [BM]) influences the long-term adaptations in sprint performance. Resisted sprint training reduced the acceleration phase time [standardized mean difference (SMD) = -0.41], with greater reduction in sprint time occurring in response to applying resistance with a vest (SMD = -0.70) when compared with a sled (SMD = -0.27). Similar reductions were determined for resistive loads <20% (SMD = -0.55) and ≥20% of BM (SMD = -0.31). Full sprint time showed a small reduction after RST (SMD = -0.36), regardless of the training equipment (sled: SMD = -0.44; vest: SMD = -0.26) and resistive load (<20% of BM: SMD = -0.40 ≥ 20% of BM: SMD = -0.21). There was a small and nonsignificant reduction in the maximum-velocity phase after RST (SMD = -0.25), which was comparable when the training was performed with vest (SMD = -0.34) or sled (SMD = -0.22). No significant differences in the changes of the acceleration phase time (SMD = 0.05) or full sprint time (SMD = 0.08) were observed between the experimental (sled or vest RST) and control groups (only soccer or unresisted sprint training). In conclusion, RST is effective to improve sprint performance in young soccer players, but the improvements are not superior to unresisted sprint training.

The effect of flywheel training on strength and physical capacities in sporting and healthy populations: An umbrella review

The aim of this umbrella review was to provide a detailed summary of how flywheel training enhances strength and physical capacities in healthy and athletic populations. The eleven reviews included were analyzed for methodological quality according to the Assessing the Methodological Quality of Systematic Review 2 (AMSTAR 2) and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) criteria. Two were systematic reviews, six were systematic reviews with meta-analyses and three were narrative reviews. Although the included reviews support use of flywheel training with athletic and healthy populations, the umbrella review highlights disparity in methodological quality and over-reporting of studies (38 studies were included overall). Flywheel post-activation performance enhancement protocols can effectively enhance strength and physical capacities acutely with athletes and healthy populations. All relevant reviews support flywheel training as a valid alternative to traditional resistance training for enhancing muscular strength, power, and jump performance with untrained and trained populations alike. Similarly, reviews included report flywheel training enhances change of direction performance—although conclusions are based on a limited number of investigations. However, the reviews investigating the effect of flywheel training on sprint performance highlight some inconsistency in attained improvements with elite athletes (e.g., soccer players). To optimize training outcomes, it is recommended practitioners individualize (i.e., create inertia-power or inertia-velocity profiles) and periodize flywheel training using the latest guidelines. This umbrella review provides an analysis of the literature’s strengths and limitations, creating a clear scope for future investigations.

The Flywheel Device Shaft Shape Determines Force and Velocity Profiles in the Half Squat Exercise

Flywheel resistance training devices can be classified by their shaft shape. The objective of this study was to analyze whether using two flywheel resistance training devices shaft shapes can influence force and velocity production, regardless of the inertia used. Thirty-nine (n = 39) healthy active men participated in this study. They were randomized to perform 3 sets of 7 repetitions at maximal concentric voluntary execution, followed by a break in the last third of the eccentric phase in the half squat exercise. A progressive rotational inertial setting of 0.11, 0.22, and 0.33 kg·m² was used. Force- and velocity-time profiles were captured using two force plates and a synchronized linear encoder. Statistical parametric mapping was used to compare biomechanical output between the flywheel devices. The level of significance was set at p < 0.05. Force application was significantly higher in the horizontal cylinder-shaped device for the three moments of inertia used in the eccentric phase (p < 0.001). In the concentric phase, force application was significantly higher in the horizontal cylinder-shaped device in 0.11 (p < 0.001) and 0.22 kg·m² (p < 0.001). The resultant speed was higher in the vertical cone-shaped device in the concentric phase and the eccentric phase for the three moments of inertia (p < 0.001). In conclusion, the flywheel shaft type determines the mechanical output of the half squat exercise, regardless of the moment of inertia used. While a horizontal cylinder-shaped device is more suitable to achieve higher forces, especially in the eccentric phase, a vertical cone-shaped device can be used to achieve higher speeds during the execution of the exercise.

Sprint Performance and Mechanical Force-Velocity Profile among Different Maturational Stages in Young Soccer Players

The aim of the present study was to determine the influence of maturation status on the components of the sprint force-velocity (F-V) profile in young soccer players. Sixty-two young male soccer players from the same professional soccer academy took part in the present study. A cross-sectional design was implemented to compare the main components of the sprint F-V profile (i.e., maximal theoretical force (F₀), velocity (V₀), power (P_max), and ratio of horizontal-to-resultant force (RF_peak), and decrease in the ratio of horizontal-to-resultant force (DRF)) and sprint performance (5, 20, and 30 m sprint time) among participants’ maturation stages (i.e., pre-, mid- and post-peak height velocity (PHV) groups). The results show that the ES of differences in 5 min sprint performance, F₀, and RF_peak (i.e., strength- and acceleration-related components of the sprint F-V profile) were greater between pre- and mid-PHV groups than those between mid- and post-PHV groups (i.e., large and very large effects (1.24 ≤ ES ≤ 2.42) vs. moderate, small, and zero effects (0 ≤ ES ≤ 0.69), respectively). However, the ES of differences in V₀ and DRF (i.e., peak speed-related components of the sprint F-V profile) were greater between mid- and post-PHV groups than those between pre- and mid-PHV groups (i.e., large effects (1.54 ≤ ES ≤ 1.92) vs. moderate effects (−0.59 ≤ ES ≤ 1), respectively). Once the strength development is achieved to a great extent from the pre- to mid-PHV groups, specific strength training methods may be used for young soccer players to improve their sprint performance.

Effects of Six Weeks of Flywheel Single-Leg Romanian Deadlift Training on Speed, Jumping and Change of Direction Performance

Several studies have confirmed the efficacy of flywheel training, mainly in the bilateral half-squat exercise. The aim of the present study was to analyze the effects of single-leg Romanian deadlift flywheel training on speed, jumping and change of direction performance. Seventeen young healthy males underwent two periods of 3-week training based on two weekly sessions of 3 sets × 7 repetitions or 4 sets × 7 repetitions of single-leg Romanian deadlifts (0.037 kg/m² moment inertia) with their dominant and non-dominant leg. After the first three weeks of the program, the CMJ, the 10 m, 30 m and total sprint times, as well as the COD-90 test, presented likely substantial beneficial effects and a small decrease in the relationship between the sprint and COD-90 test performance. After the second period of the three-week training, likely detrimental effects were observed in some of the change of direction conditions and an increase in the relationship between the sprint and the COD-180 performance. It could be hypothesized that most of the flywheel training effects reported in the traditional protocols lasting a minimum of 5–6 weeks would occur in the first weeks of training.

The Efficacy of Flywheel Inertia Training to Enhance Hamstring Strength

The purpose of this narrative review is to examine the efficacy of flywheel inertia training to increase hamstring strength. Hamstring strain injury is common in many sports, and baseline strength deficits have been associated with a higher risk of hamstring strain injury. As a result, strength and conditioning professionals actively seek additional techniques to improve hamstring strength with the aim of minimising the incidence of hamstring strain injury. One method of strength training gaining popularity in hamstring strength development is flywheel inertia training. In this review, we provide a brief overview of flywheel inertia training and its supposed adaptions. Next, we discuss important determinants of flywheel inertia training such as familiarisation, volume prescription, inertia load, technique and specific exercise used. Thereafter, we investigate its effects on hamstring strength, fascicle length and hamstring strain injury reduction. This article proposes that hamstring specific flywheel inertia training can be utilised for strength development, but due to the low number of studies and contrary evidence, more research is needed before a definite conclusion can be made. In addition, as with any training modality, careful consideration should be given to flywheel inertia training determinants. This review provides general recommendations of flywheel inertia training determinants that have value when integrating flywheel inertia training into a hamstring strengthening program.

The use of real-time monitoring during flywheel resistance training programmes: how can we measure eccentric overload? A systematic review and meta-analysis

This systematic review and meta-analysis aimed to analyse the technologies and main training variables used in the literature to monitor flywheel training devices in real time. In addition, as the main research question, we investigated how eccentric overload can be effectively monitored in relation to the training variable, flywheel shaft type device and the moment of inertia selected. The initial search resulted in 11,621 articles that were filtered to twenty-eight and seventeen articles that met the inclusion criteria for the systematic review and meta-analysis, respectively. The main technologies used included force sensors and rotary/linear encoders, mainly to monitor peak or mean force, power or speed. An eccentric overload was not always achieved using flywheel devices. The eccentric overload measurement was related to the main outcome selected. While mean force (p = 0.011, ES = -0.84) and mean power (p < 0.001, ES = -0.30) favoured the concentric phase, peak power (p < 0.001, ES = 0.78) and peak speed (p < 0.001, ES = 0.37) favoured the eccentric phase. In addition, the lower moments of inertia (i.e., from 0.01 to 0.2 kg·m²) and a cylindrical shaft type (i.e., vs conical pulley) showed higher possibilities to achieve eccentric overload. A wide variety of technologies can be used to monitor flywheel devices, but to achieve eccentric overload, a flywheel cylindrical shaft type with low moments of inertia is advised to be used.

Relationship Between Interlimb Asymmetries and Speed and Change of Direction Speed in Youth Handball Players

ABSTRACT

Madruga-Parera, M, Bishop, C, Beato, M, Fort-Vanmeerhaeghe, A, Gonzalo-Skok, O, and Romero-Rodríguez, D. Relationship between inter-limb asymmetries and speed and change of direction speed in youth handball players. J Strength Cond Res 35(12): 3482-3490, 2021-The aims of the present study were to quantify interlimb asymmetry from jumping, change of direction speed (CODS), and iso-inertial tests and to establish the association between those asymmetry scores and performance during speed and CODS tests in youth handball athletes. Twenty-six youth handball players (age: 16.2 ± 0.9 years) volunteered to participate in this study and performed single-leg countermovement jumps, single-leg broad jumps, single-leg lateral jumps, CODS tests at 180° (CODS180) and 90° (CODS90), change of direction actions with iso-inertial overload (crossover step [CRO] and lateral shuffle step), and a 20-m sprint test. Excellent intraclass correlation coefficient (ICC) values were found for all tests (ICC = 0.96-1.00) with the exception of the dominant limb during the CODS90 test (ICC = 0.69). Interlimb asymmetry scores ranged from 3.66 to 12.67%. Iso-inertial asymmetry values were higher than those found during jumping tasks (9.8-12.7% vs. 3.66-8.76%). Spearman's r correlations showed significant relationships between CRO asymmetry and CODS90 performance on both limbs (r = 0.48-0.51; p < 0.05) and CODS180 (r = 0.41-0.51; p < 0.05) and a sprint test (r = 0.46; p < 0.05). These results show the test-specific nature of asymmetries in youth handball players, with iso-inertial device and CODS deficit presenting the greatest magnitude of asymmetries. Furthermore, interlimb differences during iso-inertial device (CRO) were associated with reduced CODS and sprint performance. These results suggest that the use of iso-inertial devices for the detection of interlimb asymmetry may be more effective than the total time during traditional CODS tests and that larger imbalances are associated with reduced athletic performance in youth handball players.

Short and Long-Term Effects of a Simple-Strength-Training Program on Injuries Among Elite U-19 Soccer Players

Purpose: The aim of this study was to examine the short and long-term effects of a simple strength training program on muscle injury prevention in soccer players. Methods: Twenty-seven U-19 elite male soccer players participated in the study. The investigation was conducted over two consecutive and similar seasons (e.g., the same staff, players, weekly training schedule), the first being the control and the second the experimental season. The strength program was carried out 2 times per week, for 10 weeks, during part of the preseason and in-season. Injury incidence and absence days were compared between both seasons, according to the injury rate ratio (IRR), with 95% CI and the Z test. Results: A lower number of total and hamstring injuries were recorded during the experimental (9 and 2, respectively) compared to the control (15 and 7, respectively) period. During the 10 weeks intervention period, the injury rate ratio (IRR) was lower in the experimental season than in the control season (IRR = 8.12; 95% CI: 1.00-66.03; effect size (ES) = 3.30, large). In addition, there was a decline in absence days per injury and in the number of absence days/1000 h (IRR = 2.44; 95% CI: 1.90-3.14; ES = 1.12) during the experimental season. Conclusion: The results of this study suggest that this simple strength-training program could reduce the muscle injury incidence during its application period in young soccer players.

Comparison of Joint and Muscle Biomechanics in Maximal Flywheel Squat and Leg Press

The aim was to compare the musculoskeletal load distribution and muscle activity in two types of maximal flywheel leg-extension resistance exercises: horizontal leg press, during which the entire load is external, and squat, during which part of the load comprises the body weight. Nine healthy adult habitually strength-training individuals were investigated. Motion analysis and inverse dynamics-based musculoskeletal modelling were used to compute joint loads, muscle forces, and muscle activities. Total exercise load (resultant ground reaction force; rGRF) and the knee-extension net joint moment (NJM) were slightly and considerably greater, respectively, in squat than in leg press (p ≤ 0.04), whereas the hip-extension NJM was moderately greater in leg press than in squat (p = 0.03). Leg press was performed at 11° deeper knee-flexion angle than squat (p = 0.01). Quadriceps muscle activity was similar in squat and leg press. Both exercise modalities showed slightly to moderately greater force in the vastii muscles during the eccentric than concentric phase of a repetition (p ≤ 0.05), indicating eccentric overload. That the quadriceps muscle activity was similar in squat and leg press, while rGRF and NJM about the knee were greater in squat than leg press, may, together with the finding of a propensity to perform leg press at deeper knee angle than squat, suggest that leg press is the preferable leg-extension resistance exercise, both from a training efficacy and injury risk perspective.

Inertial flywheel vs heavy slow resistance training among athletes with patellar tendinopathy: A randomised trial

OBJECTIVES

To compare the efficacy of inertial flywheel and heavy slow resistance training in reducing pain and improving function in patellar tendinopathy.

DESIGN

Randomised clinical trial.

METHODS

Fourty two participants (1 woman, 41 men) with longstanding (>3 months) patellar tendinopathy were randomised into inertial flywheel resistance (N = 21) or heavy slow resistance (N = 21) group. Both programmes consisted of three supervised inertial flywheel or heavy slow resistance exercise sessions per week in a fitness center during 12 weeks. Primary outcome was pain and function, assessed by the Spanish Victorian Institute of Sport Assessment for Patella (VISA-P) score at 6 and 12 weeks. Secondary outcomes were activity limitation using Patient Specific Functional Scale (PSFS), health status (EuroQol-5D), patient impression of change on pain and function, adherence, adverse events, pain provocation test for the patellar tendon (numerical rating score of pain between 0 and 10), physical test, patellar tendon thickness and doppler signal on ultrasound. Secondary outcomes were taken at 0 and 12 weeks.

RESULTS

Both groups showed significant improvements in VISA-P scores from 0 to 12 weeks but there was not statistically significant between-group difference (P = 0.506). No adverse events or side effects occurred in any of the groups during the intervention period.

CONCLUSIONS

Inertial flywheel resistance three times a week during 12 weeks resulted in similar pain and function benefit at 12 weeks compared with the heavy slow resistance training among people with patellar tendinopathy. Flywheel training is another exercise option for managing people with patellar tendinopathy. CLINICALTRIALS.

GOV REGISTRY

NCT03917849.

A systematic review of resistance training methodologies for the development of lower body concentric mean power, peak power, and mean propulsive power in team-sport athletes

This study aimed to systematically review training methods prescribed to develop lower-body power, determine their effectiveness for the development of lower-body mechanical power and their implementation in an annual training cycle amongst team-sport athletes. The absolute and relative outcome values of concentric mean power, peak power and mean propulsive power were extracted from 19 studies. Outcomes were assessed using baseline to post intervention percent change, effect sizes, and the level of evidence concerning the method's effectiveness. A thorough analysis of the literature indicated that, based on the high level of evidence, traditional (e.g., strength training alone) and combination training (e.g., complex and contrast) methods should be considered. Further, optimal load and velocity-based training can be implemented if coaches have access to the appropriate equipment to monitor movement velocity and mechanical power in every session. This is of particular importance in periods of the season where high volumes of technical-tactical training and congested fixture periods are present. Also, flywheel, eccentric overload and weightlifting methods have been shown to be effective although the level of evidence is low. Future research should expand on current training practices whilst adequately reporting actual training loads from sport-specific training and games alongside strength-power training protocols.

Chronic effects of flywheel training on physical capacities in soccer players: a systematic review

The aims of the current systematic review were to evaluate the current literature surrounding the chronic effect of flywheel training on the physical capacities of soccer players, and to identify areas for future research to establish guidelines for its use.Studies were identified following a search of electronic databases (PubMed and SPORTDiscus) in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA).Eleven studies met the inclusion criteria and were included. The methodological quality of the included studies ranged between 10 and 18 with an average score of 15 points using the PEDro scale. The training duration ranged from 6 weeks to 27 weeks, with volume ranging from 1 to 6 sets and 6 to 10 repetitions, and frequency from 1 to 2 times a week. This systematic review reported that a diverse range of flywheel training interventions can effectively improve strength, power, jump, and changes of direction in male soccer players of varying levels.Flywheel training interventions improve the physical capacities of soccer players of varying levels. Nonetheless, the current literature suggests contrasting evidence regarding flywheel training induced changes in sprint speed and acceleration capacity of soccer players.

Comparison of flywheel versus traditional resistance training in elite academy male Rugby union players

This study investigated the effects of flywheel inertia training (FIT) vs traditional resistance training (TRT) over four weeks in academy male rugby union (RU) players. Sixteen elite male academy RU players (age = 18.0 ± 1.0 years, body mass = 93.0 ± 13.1 kg) were allocated into either FIT (n = 8) or TRT (n = 8) groups. Pre and post measures of countermovement jump (CMJ), squat jump (SJ) and drop jump (DJ) were completed. Relative peak force (PF), relative peak power (PP) and jump height (H) were measured for CMJ and SJ with reactive strength index measured for the DJ. Both groups showed improvements in all measures, except for SJ peak power, following TRT. Within-group analysis showed significant increases following TRT in CMJ-H (2.79 cm, 90% CI = -0.70, 4.89 cm; p = 0.002; ES = 0.51) and SJ-H (3.68 cm, 90% CI = 1.25, 6.11 cm; p = 0.002; ES = 0.88) with a significant improvement following FIT for CMJ-PP (1.96Wkg-1, 90% CI = -0.89, 4.80 Wkg-1; p = 0.022; ES = 0.55). No significant between-group differences (p > 0.05) were evident. These findings suggest both FIT and TRT are effective for developing lower-body strength and power qualities in male academy RU players.

Comparison of Electromyographic Activity During Hip Extension Exercises Under Gravitational or Inertial Loading Conditions

BACKGROUND

Hamstring injury prevention programs include strengthening, especially eccentric exercises using both gravitational and inertial loading. Inertial exercises are characterized by eccentric contractions of high intensity and velocity. This study aimed to analyze the muscular activation of the biceps femoris (BF), semitendinosus (ST), gluteus maximus (GM), and gracilis (GC) muscles during hip extension (HE) exercises performed under both gravitational and inertial loading conditions.

HYPOTHESIS

Inertial training would generate a greater activation of HE muscles than gravitational training.

STUDY DESIGN

Cross-sectional study.

LEVEL OF EVIDENCE

Level 4.

METHODS

Fifteen resistance-trained men performed the unilateral straight knee bridge (SKB), 45° of HE, and stiff-leg deadlift (SDL) exercises under gravitational and inertial loading conditions. Concentric and eccentric phases were identified with a linear encoder. Differences between load types, exercises, and their interaction were examined to establish the electromyographic (EMG) activity of each muscle and BF/ST ratio.

RESULTS

In the concentric phase, inertial loading showed a higher normalized EMG than gravitational loading for BF, ST, and GM. SKB and HE activated BF and ST between 9.6% and 24.3% more than SDL. In the eccentric phase, the inertial modality achieved greater GM activation than the gravitational form (18.1%). BF activation was increased with HE and SKB as compared with SDL (24.4% and 16.4%, respectively), while ST activation was likewise enhanced with HE as compared with SDL (15.1%).

CONCLUSION

Inertial training is more effective than gravitational training for the concentric activation of the hamstring muscles while SDL showed lower hamstring activation than HE and SKB. Therefore, HE and SKB with inertial loading should be taken into account in hamstring training programs.

CLINICAL RELEVANCE

Inertial training is more effective than gravitational training for the concentric activation of the hamstring muscles. HE and SKB with inertial loading should be taken into account in hamstring training programs.

The effects of free weights and iso-inertial resistance during semi-squatting exercise on amateur soccer players' physical performance indicators: a randomized controlled study

BACKGROUND

The aim was to compare the effects of two lower extremity strengthening programs using iso-inertial resistance or free weights on amateur soccer players' physical performance indicators.

METHODS

Thirty-five amateur soccer players (average age 22.6±5.1 years) were randomly assigned to iso-inertial group (n=11) or free-weight group (n=11), or control group (n=13). The groups performed two training sessions per week for six weeks. Before and after the strengthening implementation, physical performance indicators were evaluated, including the isokinetic knee extensors and flexors' strength, power, speed, and agility. The significance level was set at p<0.05.

RESULTS

The iso-inertial training resistance led to an increase in the hamstrings' eccentric strength at 60°/s and 150°/s (p<0.05) compared to the free-weight resistance (p>0.05) and the controls (p>0.05). No other significant adaptations were observed in the other isokinetic strength, power, speed (10-m, p=0.052) and agility measurements (Illinois agility test, p=0.059). In ratio (knee flexors/knee extensors) the only differences observed was at 150 o/s for iso-inertial group (p<0.05).

CONCLUSIONS

Iso-inertial resistance training during semi squatting can enhance the hamstrings' eccentric performance andthe soccer players' speed and agility compared to the classic free-weight training program, which should considered when designing strength and injury prevention programs.

Injury Prevention Programs Based on Flywheel vs. Body Weight Resistance in Recreational Athletes

ABSTRACT

Monajati, A, Larumbe-Zabala, E, Sampson, MG, and Naclerio, F. Injury prevention programs based on flywheel vs. body weight resistance in recreational athletes. J Strength Cond Res 35(2S): S188-S196, 2021-This study compares the effect of an isoinertial flywheel technology vs. a traditional gravity-dependent exercise protocol on modifiable factors associated with the incidence of hamstring strain (HAM) and anterior cruciate ligament (ACL) injuries. Furthermore, the effect on repeated sprint ability was also considered. Eighteen recreationally trained volleyball players completed one of the following 6-week protocols: (a) flywheel (FY) included 3 exercises using a YoYo isoinertial-squat machine and 3 exercises with a Versa-Pulley isoinertial device, and (b) gravity-dependent (GT) involved 6 similar exercises with no external resistance (participants' body weight). Both programs consisted in 2 sessions·wk-1 performing 2 sets of 8 repetitions with 2 minutes of rest. Outcomes included a 10-second tuck jump assessment (TJA), landing knee valgus score, hamstring and quadriceps concentric and eccentric isokinetic 60°·s-1 peak torque, optimal peak torque localization, conventional and functional hamstring-to-quadriceps ratio, and 30-m repeated shuttle sprint ability (RSSA) test. FY improved TJA (-2, interquartile range [IQR] = -3 to -1) and valgus (-1, IQR = -1 to 0) scores, hamstring eccentric (20.37, 95% confidence interval [CI] = 9.27-31.47 N·m) and concentric (17.87, 95% CI = 0.40-35.34 N·m) peak torque, as well as the RSSA (-0.28, 95% CI = -0.45 to -0.10 seconds), whereas GT only improved hamstring eccentric peak torque (21.41, 95% CI = 9.00-33.82 N·m). A 6-week protocol using flywheel technology seems to elicit better positive adaptations to protect athletes from HAM and ACL injuries and to enhance RSSA performance compared to exercising with no external resistance other than athletes' body weight.

Exercise-Based Strategies to Prevent Muscle Injury in Elite Footballers: A Systematic Review and Best Evidence Synthesis

BACKGROUND

Exercise-based strategies are used to prevent muscle injuries in football and studies on different competitive-level populations may provide different results.

OBJECTIVES

To evaluate the effectiveness of exercise-based muscle injury prevention strategies in adult elite football.

METHODS

A systematic search was conducted in PubMed (MEDLINE), Web of Science, Cochrane Library, and SPORTDiscuss (EBSCO). We considered only elite adult (> 16 year-old) football players with no distinction for gender; the intervention to be any exercise/s performed with the target to prevent lower-limb muscle injuries; the comparison to be no injury prevention exercise undertaken; the outcome to be the number of injuries, injury incidence, and severity. We searched systematic reviews, randomized-controlled trials (RCTs), and non-randomized-controlled trials (NRCTs), limited for English language. Risk of bias was assessed using the Risk of Bias in Systematic Reviews tool, the Cochrane Collaboration's Tool for assessing risk of bias in RCTs, and the Risk of Bias in NRCTs of Interventions tool.

RESULTS

15 studies were included. Three systematic reviews showed inconsistent results, with one supporting (high risk of bias) and two showing insufficient evidence (low risk of bias) to support exercise-based strategies to prevent muscle injuries in elite players. Five RCTs and seven NRCTs support eccentric exercise, proprioception exercises, and a multi-dimensional component to an injury prevention program; however, all were deemed to be at high/critical risk of bias. Only one RCT was found at low risk of bias and supported eccentric exercise for preventing groin problems.

CONCLUSION

We found limited scientific evidence to support exercise-based strategies to prevent muscle injury in elite footballers.

TRIAL REGISTRATION NUMBER

PROSPERO CRD42017077705.

The Effect of Autoregulated Flywheel and Traditional Strength Training on Training Load Progression and Motor Skill Performance in Youth Athletes

Background: The effects of flywheel resistance training (FRT) on youth are relatively unknown. The aim of this study was to compare the effects of autoregulated FRT with traditional strength training (TST) on jumping, running performance and resistance training load progression in youth athletes. Thirty youth athletes (11.8 ± 0.9 yr) were matched for peak height velocity (PHV) status and block-randomised into two groups: FRT (n = 15, PHV −0.8 ± 1.6) and TST (n = 15, PHV −0.8 ± 1.5). Twelve resistance training sessions over a six-week intervention with flywheel or barbell squats were performed using autoregulated load prescription. Squat jump (SJ); countermovement jump (CMJ); and 10 m, 20 m and 30 m sprints were assessed pre- and post-intervention. The external load increased similarly for FRT and TST (z = 3.8, p = 0.06). SJ increased for both groups (p < 0.05) but running performance was unaffected (p > 0.05). Conclusions: FRT resulted in similar load progression and motor skill development in youth athletes as TST, but the perceived exertion was less. Autoregulation is a practical method for adjusting training load during FRT and should be considered as an alternative to autoregulated TST.

Muscle Activation Sequence in Flywheel Squats

Background: Muscle coordination is important for rational and effective planning of therapeutic and exercise interventions using equipment that mimics functional movements. Our study was the first to assess muscle coordination during flywheel (FW) squats. Methods: Time-of-peak electromyographic activation order was assessed separately for 8, 4, and 3 leg muscles under four FW loads. A sequential rank agreement permutations tests (SRA) were conducted to assess activation order and Kendall’s tau was used to assess the concordance of activation order across subjects, loads and expected order of activation. Results: SRA revealed a latent muscle activation order at loads 0.05, 0.075, and 0.1, but not at 0.025 kg·m². Kendall’s tau showed moderate-to-strong concordance between the expected (proximal-to-distal) and the observed muscle activation order only at a load 0.025 kg·m², regardless of the number of muscles analyzed. Muscle activation order was highly concordant between loads 0.05, 0.075, and 0.1 kg·m². Conclusions: The results show a specific role of each muscle during the FW squat that is load-dependent. While the lowest load follows the proximal-to-distal principle of muscle activation, higher loads lead to a reorganization of the underlying muscle coordination mechanisms. They require a specific and stable muscle coordination pattern that is not proximal-to-distal.

Effects of an eccentric overload and small-side games training in match accelerations and decelerations performance in female under-23 soccer players

BACKGROUND

The aims of this study were: 1) to investigate the impacts that an eccentric overload training (EOT) and a small-side game training (SSGT) have on the characteristics of the accelerations (ACC) and decelerations (DCC) of the players in a soccer match; and 2) to determine if EOT and SSGT could affect the ACC and DCC reduction over time in a soccer match.

METHODS

Twenty-three female soccer players from a Spanish professional club were split into three groups: a small-sided game training group (SGG), an eccentric overload training group (EOG) and a control group (CG).

RESULTS

The SSG improved the high intensity distance performed (ES [CI]=0.72 [0.22; 1.22]), the number of high intensity actions (ES [CI]=0.65 [0.01; 1.29]), the percentage of repeated high intensity actions (ES [CI]=0.54 [-0.17; 1.25]), the initial velocity of the ACC (ES [CI]=0.55 [-0.08; 1.17]) and the percentage of repeated accelerations (ES [CI]=0.87 [-0.18; 1.91]) with respect to the control group. The EOG obtained better results in distance travelling accelerating (ES [CI]=0.84 [0.09; 1.60]) and decelerating (ES [CI]=0.87 [0.23; 1.51]) above 3 m/s², maximum ACC (ES [CI]=1.92 [0.90; 2.94]) and DCC (ES [CI]=1.29 [0.44; 2.14]) and the average of maximum ACC (ES [CI]=0.89 [0.23; 1.54]) and DCC (ES [CI]=1.08 [0.62; 1.55]) with respect to the CG. A decrement in the ACC and DCC performance was observed between the first and last 15 minutes of the competition, except for the EOG.

CONCLUSIONS

The SSG obtained mainly improvements in variables related with efforts repetitions and the capacity of maintaining the ACC and the DCC over time, while improvements in the EOG were related to intensity in the ACC and DCC.

Implementing Strength Training Strategies for Injury Prevention in Soccer: Scientific Rationale and Methodological Recommendations

Due to the negative effects that injuries have on performance, club finances, and long-term player health (permanent disability after a severe injury), prevention strategies are an essential part of both sports medicine and performance. Purpose: To summarize the current evidence regarding strength training for injury prevention in soccer and to inform its evidence-based implementation in research and applied settings. Conclusions: The contemporary literature suggests that strength training, proposed as traditional resistance, eccentric, and flywheel training, may be a valid method to reduce injury risk in soccer players. Training strategies involving multiple components (eg, a combination of strength, balance, plyometrics) that include strength exercises are effective at reducing noncontact injuries in female soccer players. In addition, the body of research currently published supports the use of eccentric training in sports, which offers unique physiological responses compared with other resistance exercise modalities. It seems that the Nordic hamstring exercise, in particular, is a viable option for the reduction of hamstring injuries in soccer players. Moreover, flywheel training has specific training peculiarities and advantages that are related to the combination of both concentric and eccentric contraction, which may play an important role in injury prevention. It is the authors’ opinion that strength and conditioning coaches should integrate the strength training methods proposed here in their weekly training routine to reduce the likelihood of injuries in their players; however, further research is needed to verify the advantages and disadvantages of these training methods to injury prevention using specific cohorts of soccer players.

Eccentric Resistance Training in Youth: A Survey of Perceptions and Current Practices by Strength and Conditioning Coaches

BACKGROUND

Eccentric resistance training (ERT) in youth is advocated for aiding performance and injury risk. However, research investigating the applied practices of ERT in youth is in its infancy. In this study, we surveyed the perceptions and practices of practitioners utilizing ERT in youth to provide an understanding of its current application in practice.

METHODS

Sixty-four strength and conditioning coaches completed an online survey reporting their current use of ERT in youth using both open and closed questions.

RESULTS

Coaches deemed the inclusion of ERT important in youth with its inclusion based upon factors such as maturation status, training age and strength levels. Coaches also displayed an awareness of the physiological responses to eccentric exercise in youth compared to adults. ERT was primarily used for injury prevention, with the majority of coaches using body-weight and tempo exercises. Furthermore, utilizing eccentric hamstrings exercises was reported as highly important. The frequency of ERT tended to increase in older age groups and coaches mainly prescribed self-selected rest intervals. Finally, the need for further research into the training guidelines of ERT in youth was highlighted, in which coaches require more information on how maturation influences training adaptations and the fatigue-recovery responses.

CONCLUSION

Coaches emphasized the importance of including ERT for both performance and injury prevention factors in youth although further research is required to generate practical guidelines for coaches in order to support its inclusion within practice.

Sports Medicine Considerations During the COVID-19 Pandemic

The outbreak of the novel coronavirus (COVID-19) has resulted in upward of 14 million confirmed cases and >597,000 deaths worldwide as of July 19, 2020. The current disruption in sports activities caused by COVID-19 presents a challenge to physicians, coaches, and trainers in discerning best practices for a safe return to sport. There is a distinct need to develop and adopt consistent measures for resumption of sports activities, including training and competition, in a way that places the health and well-being of athletes at the forefront while also protecting coaches, allied staff, and spectators. This article provides an overview of the effects of COVID-19 in the athletic population and presents considerations for training during the pandemic, as well as guidelines for return to sports as restrictions are lifted.

Effects of Flywheel Resistance Training on Sport Actions. A Systematic Review and Meta-Analysis

The purpose of the present meta-analysis was to examine the effect of flywheel resistance training (FRT) on main sport action (i.e., jumping performance, sprinting time and change of direction performance) improvements in athletes and healthy active people. A Boolean search strategy adapted for each of the databases employed was conducted to identify all studies measuring change in sport actions performance after FRT interventions up to July 2019. Outcomes were analysed using an average effect size (D₊) and a 95% confidence interval (CI), which was calculated assuming a random-effects model. A total of 9 studies with 283 participants met the inclusion criteria and were selected for the analysis. The mean quality score (PEDro scale) of the articles included in the meta-analysis was 5.67. The meta-analysis showed significant positive effects on jumping performance (SMC 0.65; 95% CI, 0.11-1.19; p = 0.02), sprinting time (SMC 1.33; 95% CI, 0.39-2.28; p < 0.01) and change of direction performance (SMC 1.36; 95% CI, 0.58-2.14; p < 0.01) after FRT interventions compared to control/traditional resistance training groups. The results of the present meta-analysis provide evidence of the usefulness of FRT to improve variables related to sport performance in both athletes and healthy population.

Greater Power but Not Strength Gains Using Flywheel Versus Equivolumed Traditional Strength Training in Junior Basketball Players

The main aim of the present study was to compare the effects of flywheel strength training and traditional strength training on fitness attributes. Thirty-six well trained junior basketball players (n = 36; 17.58 ± 0.50 years) were recruited and randomly allocated into: Flywheel group (FST; n = 12), traditional strength training group (TST; n = 12) and control group (CON; n = 12). All groups attended 5 basketball practices and one official match a week during the study period. Experimental groups additionally participated in the eight-week, 1–2 d/w equivolume intervention conducted using a flywheel device (inertia = 0.075 kg·m⁻²) for FST or free weights (80%1 RM) for TST. Pre-to post changes in lower limb isometric strength (ISOMET), 5 and 20 m sprint time (SPR5m and SPR20m), countermovement jump height (CMJ) and change of direction ability (t-test) were assessed with analyses of variance (3 × 2 ANOVA). Significant group-by-time interaction was found for ISOMET (F = 6.40; p = 0.000), CMJ (F = 7.45; p = 0.001), SPR5m (F = 7.45; p = 0.010) and T test (F = 10.46; p = 0.000). The results showed a significantly higher improvement in CMJ (p = 0.006; 11.7% vs. 6.8%), SPR5m (p = 0.001; 10.3% vs. 5.9%) and t-test (p = 0.045; 2.4% vs. 1.5%) for FST compared to the TST group. Simultaneously, th FST group had higher improvement in ISOMET (p = 0.014; 18.7% vs. 2.9%), CMJ (p = 0.000; 11.7% vs. 0.3%), SPR5m (p = 0.000; 10.3% vs. 3.4%) and t-test (p = 0.000; 2.4% vs. 0.6%) compared to the CON group. Players from the TST group showed better results in CMJ (p = 0.006; 6.8% vs. 0.3%) and t-test (p = 0.018; 1.5% vs. 0.6%) compared to players from the CON group. No significant group-by-time interaction was found for sprint 20 m (F = 2.52; p = 0.088). Eight weeks of flywheel training (1–2 sessions per week) performed at maximum concentric intensity induces superior improvements in CMJ, 5 m sprint time and change of direction ability than equivolumed traditional weight training in well trained junior basketball players. Accordingly, coaches and trainers could be advised to use flywheel training for developing power related performance attributes in young basketball players.