Functional and Muscle-Size Effects of Flywheel Resistance Training with Eccentric-Overload in Professional Handball Players

Effects of Inertial Flywheel Training vs. Accentuated Eccentric Loading Training on Strength, Power, and Speed in Well-Trained Male College Sprinters

This study aimed to evaluate and compare the effects of inertial flywheel training and accentuated eccentric loading training on the neuromuscular performance of well-trained male college sprinters. Fourteen sprinters were recruited and randomly assigned to either the flywheel training (FWT, n = 7) group or the accentuated eccentric loading training (AELT, n = 7) group. The FWT group completed four sets of 2 + 7 repetitions of flywheel squats, whereas the AELT group performed four sets of seven repetitions of barbell squats (concentric/eccentric: 80%/120% 1RM). Both groups underwent an eight-week squat training program, with two sessions per week. A two-way repeated ANOVA analysis was used to find differences between the two groups and between the two testing times (pre-test vs. post-test). The results indicated significant improvements in all measured variables for the FWT group: 1RM (5.0%, ES = 1.28), CMJ (13.3%, ES = 5.42), SJ (6.0%, ES = 2.94), EUR (6.5%, ES = 4.42), SLJ (2.9%, ES = 1.77), and 30 m sprint (-3.4%, ES = -2.80); and for the AELT group: 1RM (6.3%, ES = 2.53), CMJ (7.4%, ES = 3.44), SJ (6.4%, ES = 2.21), SLJ (2.2%, ES = 1.20), and 30 m sprint (-3.0%, ES = -1.84), with the exception of EUR (0.9%, ES = 0.63, p = 0.134), showing no significant difference. In addition, no significant interaction effects between group and time were observed for 1RM back squat, SJ, SLJ, and 30 m sprint (p > 0.05). Conversely, a significant interaction effect between group and time was observed for both CMJ and EUR (p < 0.001); post hoc analysis revealed that the improvements in CMJ and EUR were significantly greater in the FWT group compared to the AELT group (p < 0.001). These findings indicate that both FWT and AELT are effective at enhancing lower-body strength, power, and speed in well-trained male college sprinters, with FWT being particularly more effective in promoting elastic energy storage and the full utilization of the stretch-shortening cycle.

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.

Pumping up the Fight against Multiple Sclerosis: The Effects of High-Intensity Resistance Training on Functional Capacity, Muscle Mass, and Axonal Damage

BACKGROUND

Resistance training (RT) has been recognized as a beneficial non-pharmacological intervention for multiple sclerosis (MS) patients, but its impact on neurodegeneration is not fully understood. This study aimed to investigate the effects of high-intensity RT on muscle mass, strength, functional capacity, and axonal damage in MS patients.

METHODS

Eleven relapsing-remitting MS patients volunteered in this within-subject counterbalanced intervention study. Serum neurofilament light-chain (NfL) concentration, vastus lateralis thickness (VL), timed up-and-go test (TUG), sit-to-stand test (60STS), and maximal voluntary isometric contraction (MVIC) were measured before and after intervention. Participants performed 18 sessions of high-intensity RT (70-80% 1-RM) over 6 weeks.

RESULTS

Significant (p < 0.05) differences were observed post-intervention for VL (ES = 2.15), TUG (ES = 1.98), 60STS (ES = 1.70), MVIC (ES = 1.78), and NfL (ES = 1.43). Although moderate correlations between changes in VL (R = 0.434), TUG (R = -0.536), and MVIC (R = 0.477) and changes in NfL were observed, only the correlation between VL and MVIC changes was significant (R = 0.684, p = 0.029).

CONCLUSIONS

A 6-week RT program significantly increased muscle mass, functional capacity, and neuromuscular function while also decreasing serum NfL in MS patients. These results suggest the effectiveness of RT as a non-pharmacological approach to mitigate neurodegeneration while improving functional capacity in MS patients.

The effect of flywheel complex training with eccentric-overload on muscular adaptation in elite female volleyball players

This study aimed to compare the effects of 8 weeks (24 sessions) between flywheel complex training with eccentric overload and traditional complex training of well-trained volleyball players on muscle adaptation, including hypertrophy, strength, and power variables. Fourteen athletes were recruited and randomly divided into the flywheel complex training with an eccentric-overload group (FCTEO, n = 7) and the control group (the traditional complex training group, TCT, n = 7). Participants performed half-squats using a flywheel device or Smith machine and drop jumps, with three sets of eight repetitions and three sets of 12 repetitions, respectively. The variables assessed included the muscle thickness at the proximal, mid, and distal sections of the quadriceps femoris, maximal half-squats strength (1RM-SS), squat jump (SJ), countermovement jump (CMJ), and three-step approach jump (AJ). In addition, a two-way repeated ANOVA analysis was used to find differences between the two groups and between the two testing times (pre-test vs. post-test). The indicators of the FCTEO group showed a significantly better improvement (p < 0.05) in CMJ (height: ES = 0.648, peak power: ES = 0.750), AJ (height: ES = 0.537, peak power: ES = 0.441), 1RM-SS (ES = 0.671) compared to the TCT group and the muscle thicknes at the mid of the quadriceps femoris (ES = 0.504) after FCTEO training. Since volleyball requires lower limb strength and explosive effort during repeated jumps and spiking, these results suggest that FCTEO affects muscular adaptation in a way that improves performance in well-trained female volleyball players.

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.

Effects of single and repeated bouts of flywheel exercise on jump performance and muscle damage in athletes and non athletes

BACKGROUND

Although recent studies have investigated the effects of flywheel (FW) training on muscle function, the effects of transient FW exercise on jump performance in athletes are unknown. This study examined the effects of single and repeated bouts of FW squat exercises on jump performance and muscle damage in male collegiate basketball players.

METHODS

The participants were 10 healthy college-age men (nonathletes) and 11 male basketball players (athletes). The intervention involved 100 squat exercises (10 repetitions × 10 sets) using an FW device. To examine the repeated-bout effects, the protocol was conducted again after a 2-week interval. Squat jumps, countermovement jumps, drop jumps, and rebound jumps were evaluated as jump performance, while isometric maximal voluntary contraction (MVC) torque in knee extension, muscle soreness, range of motion, thigh circumference, muscle thickness, and echo intensity were evaluated as markers of muscle damage. Measurements were taken at baseline, immediately after exercise, 24 h later, and 72 h later.

RESULTS

The jump performance of nonathletes decreased after exercise (p < 0.05), while that of the athletes did not. The results were similar for muscle soreness. MVC torque decreased significantly after the first exercise in both groups (p < 0.05) and was significantly lower in the nonathletes versus athletes. Significant repeated-bout effects were found for muscle soreness in nonathletes but not athletes.

CONCLUSIONS

These results suggest that a single bout of FW exercise reduces jump performance in male nonathletes but not basketball players.

Effect of the Intrasession Exercise Order of Flywheel Resistance and High-Intensity Interval Training on Maximal Strength and Power Performance in Elite Team-Sport Athletes

Petré, H, Ovendal, A, Westblad, N, Ten Siethoff, L, Rosdahl, H, and Psilander, N. Effect of the intrasession exercise order of flywheel resistance and high-intensity interval training on maximal strength and power performance in elite team-sport athletes. J Strength Cond Res 37(12): 2389–2396, 2023—This study aimed to investigate the effect of intrasession exercise order of maximal effort flywheel resistance training (RT; 4 × 6 repetitions [rep]) and high-intensity interval training (HIIT, 2–4 × 8 rep of 20 second at 130% of Watt at V̇o 2max [wV̇o 2max]), on the development of maximal strength and power in elite team-sport athletes. A 7-week training intervention involving 2 training sessions per week of either HIIT followed by RT (HIIT + RT, n = 8), RT followed by HIIT (RT + HIIT, n = 8), or RT alone (RT, n = 7) was conducted in 23 elite male bandy players (24.7 ± 4.3 years). Power and work were continuously measured during the flywheel RT. Isometric squat strength (ISq), countermovement jump, squat jump, and V̇o 2max were measured before and after the training period. Power output during training differed between the groups (p = 0.013, η p 2 = 0.365) with RT producing more power than HIIT + RT (p = 0.005). ISq improved following RT + HIIT (∼80%, d = 2.10, p = 0.001) and following HIIT + RT (∼40%, d = 1.64, p = 0.005), and RT alone (∼70%, d = 1.67, p = 0.004). V̇o 2max increased following RT + HIIT and HIIT + RT (∼10%, d = 1.98, p = 0.001 resp. d = 2.08, p = 0.001). HIIT before RT reduced power output during RT in elite team-sport athletes but did not lead to blunted development of maximal strength or power after a 7-week training period. During longer training periods (>7-weeks), it may be advantageous to schedule RT before HIIT because the negative effect of HIIT + RT on training quality increased during the final weeks of training. In addition, the largest training effect on maximal strength was observed following RT + HIIT.

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 submaximal and supramaximal accentuated eccentric loading on mass and function

Introduction: Eccentric-overload (EO) resistance training emerges as an alternative to more optimally prescribe intensity relative to the force generation capabilities of the eccentric muscle contraction. Given the difficulties to individually prescribe absolute eccentric loads relative to each person's eccentric ability, setting the load relative to the concentric one-repetition maximum (1-RM) is the most used EO training approach. Therefore, we investigated the effects of submaximal and supramaximal (i.e., eccentric loads above 100% of 1-RM) accentuated eccentric training on changes in lean mass, anabolic hormonal responses and muscle function. Methods: Physically active university students (n = 27) were randomly assigned to two training groups. Participants in the training groups performed dominant leg isotonic training twice a week for 10 weeks (four sets of eight repetitions). Isotonic resistance was generated by an electric-motor device at two different percentages of 1-RM for the eccentric phase; 90% submaximal load, SUB group) and 120% (supramaximal load, SUPRA group). Concentric load was the same for both groups (30% of 1-RM). Changes in total thigh lean mass (TTLM), anabolic hormonal responses (growth hormone, IGF-1, IL-6, and total testosterone), unilateral leg-press 1-RM, maximal voluntary isometric contractions (MVIC), local muscle endurance (XRM), muscle power at 40 (PP40), 60 (PP60) and 80% (PP80) of the 1-RM, and unilateral vertical jump height before and after training were compared between groups. Results: After training, both SUB and SUPRA groups showed similar increases (p < 0.05) in MVIC (19.2% and 19.6%), XRM (53.8% and 23.8%), PP40 (16.2% and 15.7%), TTLM (2.5% and 4.2%), IGF-1 (10.0% and 14.1%) and IL-6 (58.6% and 28.6%). However, increases in 1-RM strength (16.3%) and unilateral vertical jump height (10.0%-13.4%) were observed for SUPRA only. Indeed, SUPRA was shown to be more favorable than SUB training for increasing 1-RM [ES = 0.77 (1.49-0.05)]. Unilateral muscle power at medium and high intensity (10.2% and 10.5%) also increased in SUB but without significant differences between groups. Discussion: Similar functional and structural effects were demonstrated after 10 weeks EO training with submaximal and supramaximal eccentric loads. Although supramaximal loading might be superior for increasing 1-RM, the use of this approach does not appear to be necessary in healthy, active individuals.

Effects of Flywheel vs. Free-Weight Squats and Split Squats on Jumping Performance and Change of Direction Speed in Soccer Players

The objective of this study was to compare (i) The effects of a flywheel and free-weight resistance training program; and (ii) The effects of performing lateral and frontal split squats as part of a flywheel-resistance training program on jumping performance, the 5-0-5 change of direction test time, and the one-repetition maximum (1RM) back squat in soccer players. Twenty-four male amateur soccer players participated in this study and were randomly and equally assigned to one of three different test groups: forward split-squat group (FSQ); lateral split-squat group (LSQ); and free-weight training group (TRAD). Athletes in the FSQ group performed a squat and a forward split squat on a flywheel device, while those in the LSQ group performed a squat and a lateral split squat (instead of a forward split squat) on a flywheel device. Each training lasted 4 weeks. The main finding was that all training groups, such as TRAD, FSQ, and LSQ, significantly improved broad jump length (p = 0.001; effect size [ES] = 0.36), 5-0-5 COD time with a turn on the dominant limb (p = 0.038; ES = 0.49), and 1RM back squat (p = 0.001; ES = 0.4). In turn, both flywheel-resistance training groups (FSQ and LSQ) significantly improved their counter-movement jump height (p = 0.001; ES = 0.8 and p = 0.002; ES = 0.58; respectively) with no effect in the TRAD (p = 0.676; ES = 0.07) training group. Both free-weight and flywheel-resistance training lasting 4 weeks performed in-season contributed to significant improvement in 1RM back squat, broad jump performance, and 5-0-5 change of direction testing time, while flywheel-resistance training might be superior in counter-movement jump height enhancement in soccer players. Moreover, the manner in which split squats were performed was not a factor influencing the obtained results.

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.

Effect of Flywheel versus Traditional Resistance Training on Change of Direction Performance in Male Athletes: A Systematic Review with Meta-Analysis

Objective: This study aimed to systematically review and meta-analyze the effect of flywheel resistance training (FRT) versus traditional resistance training (TRT) on change of direction (CoD) performance in male athletes. Methods: Five databases were screened up to December 2021. Results: Seven studies were included. The results indicated a significantly larger effect of FRT compared with TRT (standardized mean difference [SMD] = 0.64). A within-group comparison indicated a significant large effect of FRT on CoD performance (SMD = 1.63). For TRT, a significant moderate effect was observed (SMD = 0.62). FRT of ≤2 sessions/week resulted in a significant large effect (SMD = 1.33), whereas no significant effect was noted for >2 sessions/week. Additionally, a significant large effect of ≤12 FRT sessions (SMD = 1.83) was observed, with no effect of >12 sessions. Regarding TRT, no significant effects of any of the training factors were detected (p > 0.05). Conclusions: FRT appears to be more effective than TRT in improving CoD performance in male athletes. Independently computed single training factor analyses for FRT indicated that ≤2 sessions/week resulted in a larger effect on CoD performance than >2 sessions/week. Additionally, a total of ≤12 FRT sessions induced a larger effect than >12 training sessions. Practitioners in sports, in which accelerative and decelerative actions occur in quick succession to change direction, should regularly implement FRT.

Internal Validity in Resistance Training Research: A Systematic Review

Ensuring internal validity is the key procedure when planning the study design. Numerous systematic reviews have demonstrated that considerations for internal validity do not receive adequate attention in the primary research in sport sciences. Therefore, the purpose of this study was to review methodological procedures in current literature where the effects of resistance training on strength, speed, and endurance performance in athletes were analyzed. A computer-based literature searches of SPORTDiscus, Scopus, Medline, and Web of Science was conducted. The internal validity of individual studies was assessed using the PEDro scale. Peer-reviewed studies were accepted only if they met all the following eligibility criteria: (a) healthy male and female athletes between the ages of 18-65 years; (b) training program based on resistance exercises; (c) training program lasted for at least 4 weeks or 12 training sessions, with at least two sessions per week; (d) the study reported maximum strength, speed, or endurance outcomes; and (e) systematic reviews, cohort studies, case-control studies, cross-sectional studies were excluded. Of the 6,516 articles identified, 133 studies were selected for rating by the PEDro scale. Sixty-eight percent of the included studies used random allocation to groups, but only one reported concealed allocation. Baseline data are presented in almost 69% of the studies. Thirty-eight percent of studies demonstrated adequate follow-up of participants. The plan to follow the intention-to-treat or stating that all participants received training intervention or control conditions as allocated were reported in only 1.5% of studies. The procedure of blinding of assessors was also satisfied in only 1.5% of the studies. The current study highlights the gaps in designing and reporting research in the field of strength and conditioning. Randomization, blinding of assessors, reporting of attrition, and intention-to-treat analysis should be more fully addressed to reduce threats to internal validity in primary research.

Quadriceps electromyography during flywheel-based inertial training (FIT) and dynamic constant external resistance (DCER) squats at similar tempo

Flywheel-based iso-inertial training (FIT) has been purported to provide enhanced adaptations to muscle overload compared to dynamic constant external resistance (DCER), but previous studies have not controlled for exercise intensity. We compared quadriceps electromyography (EMG) amplitude between FIT- and DCER-squats with similar tempo. Eleven (5 M and 6F) resistance-trained participants completed sets of five maximal velocity FIT (0.025 kg∙m2) and DCER (55 ± 15 %1RM) squats. Sagittal plane knee joint angles and surface EMG activity of the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) were measured. Repetition time and peak knee angles were similar between FIT and DCER squats. Mean knee angular velocity during the concentric (122.2 ± 23.6 vs. 108.9 ± 22.9, p = 0.022, Cohen's D: 0.820), but not eccentric, phase was significantly greater during FIT. Peak VM (210.4 ± 49.3 vs. 177.5 ± 56.3 %MVIC, p = 0.001; Cohen's D: 1.416), but not VL or RF, EMG amplitude was significantly greater in FIT compared to DCER. Mean EMG amplitude was significantly (p < 0.001) greater during the concentric than the eccentric phase for the VL and VM but not RF. Mean EMG amplitude was not significantly different between modes during either the concentric or eccentric phase. Quadriceps EMG amplitude is largely similar between FIT and DCER squats when matched for movement velocity.

The Importance of Posture And Body Composition for the Stability and Selected Motor Abilities of Professional Handball Players

The aim of the research was to analyze body composition, body posture and postural stability of professional male handball players and to determine the differences between players with correct and incorrect body posture, considering power of the lower limbs and agility, speed, and change of direction deficit. The study comprised 16 professional handball players. Body composition analysis was performed using the method of electrical bioimpedance. Body posture was examined using the Diers formetric III 4D optoelectronic method. Postural stability was tested via the Biodex Balance System. Players performed the following fitness tests assessing lower limb muscle power (LP, HS, CMJ), linear speed (SLS 20 m), and COD speed (Zig-Zag test, COD deficit). Only 31.25% of players demonstrated body posture with correct physiological curvatures, while 68.75% showed changes in body asymmetry. The group with correct body posture performed better in SLS 20m than the group with incorrect posture, yet in the Zig-Zag agility test, the difference in the results was not significant and this affected the COD deficit, which was higher. The vast majority of participants demonstrated postural defects and incorrect physiological curvatures of the spine. The occurrence of scoliotic posture was also observed. The body deflection angles indicated that athletes’ postural stability was good. However, it is worth noting that the majority demonstrated a tendency towards asymmetrical body deflections to the right or to the left, backwards direction. One-sided sports specialization leads to disturbances in the statics of the body, therefore, it becomes necessary to include postural re-education exercises in training.

Comparison of Flywheel and Pneumatic Training on Hypertrophy, Strength, and Power in Professional Handball Players

Purpose: The mechanical properties of resistance-training machines are a variable that may help to optimize sports performance and injury prevention protocols. The purpose of this study was to examine two non-gravity-dependent training modalities on muscle structure and function. Methods: Eighteen professional handball players were randomly divided into two experimental groups: 1) iso-inertial flywheel training (FW) and 2) pneumatic resistance training (PN). Participants in both groups completed twelve training sessions in six weeks consisting of three movements (lateral raise, internal and external rotation). Four sets of seven repetitions for each movement were performed during each session. Before and after training subscapularis and deltoid (anterior, middle, posterior) muscle thickness was measured. Isokinetic torque and power during internal and external rotation at 60, 180, and 240 deg·s^-1 was measured as well. Throwing speed was assessed before and after training while both sitting and standing situations. Results: Both groups showed similar significant increases in throwing speed and internal and external rotation peak torque, average and peak power at all angular velocities. Anterior and middle deltoid muscle thickness changes were greater after training in FW (20 and 22%) in comparison to PN (14 and 7%, respectively). Conclusions: In summary, both flywheel and pneumatic training resulted in similar increases in shoulder strength and power and throwing speed. However, flywheel training appeared to possibly result in a slightly greater level of muscle hypertrophy of the anterior and middle deltoid. Non-gravity dependent training appears to induce changes that would be beneficial to sports performance and perhaps injury prevention.

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 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.

Effects of Inertial Load on Sagittal Plane Kinematics of the Lower Extremity During Flywheel-Based Squats

ABSTRACT

Worcester, KS, Baker, PA, and Bollinger, LM. Effects of inertial load on sagittal plane kinematics of the lower extremity during flywheel-based squats. J Strength Cond Res 36(1): 63-69, 2022-Increasing load increases flexion of lower extremity joints during weighted squats; however, the effects of inertial load on lower extremity kinematics during flywheel-based resistance training (FRT) squats remain unclear. The purpose of this study was to evaluate sagittal plane kinematics of lower extremity joints during FRT squats at various inertial loads. Nine recreationally resistance-trained subjects (3M, 6F) completed a bout of FRT squats with inertial loads of 0.050, 0.075, and 0.100 kg·m2. Two-dimensional sagittal plane kinematics were monitored with retroreflective markers at a rate of 60 Hz. Joint angles and angular velocities of the knee, trunk + hip, trunk inclination, and ankle were quantified throughout concentric and eccentric actions. Effects of inertial load were determined by repeated-measures analysis of variance with α = 0.05. Average power and average vertical velocity decreased with increasing inertial load, whereas average force increased. Minimal and maximal sagittal plane joint angles of the knee, trunk + hip, trunk inclination, and ankle were not significantly different among inertial loads. However, peak joint angular velocities of the knee and trunk + hip tended to decrease with increasing inertial load. Conversely trunk inclination and ankle dorsiflexion velocities were not significantly different among inertial loads. Increasing inertial load from 0.050 to 0.100 kg·m2 significantly reduces average power during FRT squats primarily by decreasing movement velocity, which seems to be specific to the knee and hip joints. It is possible that lower concentric energy input at high inertial loads prevents increased joint flexion during FRT squats.

The Maximum Flywheel Load: A Novel Index to Monitor Loading Intensity of Flywheel Devices

BACKGROUND

The main aim of this study was (1) to find an index to monitor the loading intensity of flywheel resistance training, and (2) to study the differences in the relative intensity workload spectrum between the FW-load and ISO-load.

METHODS

twenty-one males participated in the study. Subjects executed an incremental loading test in the squat exercise using a Smith machine (ISO-load) or a flywheel device (FW-load). We studied different association models between speed, power, acceleration, and force, and each moment of inertia was used to find an index for FW-load. In addition, we tested the differences between relative workloads among load conditions using a two-way repeated-measures test.

RESULTS

the highest r2 was observed using a logarithmic fitting model between the mean angular acceleration and moment of inertia. The intersection with the x-axis resulted in an index (maximum flywheel load, MFL) that represents a theoretical individual maximal load that can be used. The ISO-load showed greater speed, acceleration, and power outcomes at any relative workload (%MFL vs. % maximum repetition). However, from 45% of the relative workload, FW-load showed higher vertical forces.

CONCLUSIONS

MFL can be easily computed using a logarithmic model between the mean angular acceleration and moment of inertia to characterize the maximum theoretical loading intensity in the flywheel squat.

Cross-education effects of unilateral accentuated eccentric isoinertial resistance training on lean mass and function

PURPOSE

We investigated the effects of three different unilateral isoinertial resistance training protocols with eccentric overload on changes in lean mass and muscle function of trained (TL) and contralateral non-trained (NTL) legs.

METHODS

Physically active university students were randomly assigned to one of three training groups or a control group (n = 10/group). Participants in the training groups performed dominant leg isoinertial squat training twice a week for 6 weeks (4 sets of 7 repetitions) using either an electric-motor device with an eccentric phase velocity of 100% (EM100) or 150% (EM150) of concentric phase velocity or a conventional flywheel device (FW) with the same relative inertial load. Changes in thigh lean mass, unilateral leg-press one-repetition maximum (1-RM), muscle power at 40-80% 1-RM, and unilateral vertical jump height before and after training were compared between the groups and between TL and NTL.

RESULTS

No changes in any variable were found for the control group. In TL, all training groups showed similar increases (p < 0.05) in 1-RM strength (22.4-30.2%), lean tissue mass (2.5-5.8%), muscle power (8.8-21.7%), and vertical jump height (9.1-32.9%). In NTL, 1-RM strength increased 22.0-27.8% without significant differences between groups; however, increases in lean mass (p < 0.001) were observed for EM150 (3.5%) and FW (3.8%) only. Unilateral vertical jump height (6.0-32.9%) and muscle power (6.8-17.5%) also increased in NTL without significant differences between training groups.

CONCLUSION

The three eccentric-overload resistance training modalities produced similar neuromuscular changes in both the trained and non-trained legs, suggesting that strong cross-education effects were induced by the eccentric-overload training.

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.

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.

Ipsilateral Lower-to-Upper Limb Cross-Transfer Effect on Muscle Strength, Mechanical Power, and Lean Tissue Mass after Accentuated Eccentric Loading

Background and Objectives: To investigate the effects of unilateral accentuated eccentric loading (AEL) on changes in lean mass and function of leg trained (TL) and ipsilateral non-trained arm (NTA) in young men and women. Materials and Methods: In a prospective trial, 69 Physically active university students (20.2 ± 2.2 years) were randomly placed into a training group (n = 46; 27 men, 19 women) or a control group without training (n = 23; 13 men, 10 women). Participants in the training group performed unilateral AEL in the leg press exercise of the dominant leg twice a week for 10 weeks. An electric motor device-generated isotonic resistance at different intensities for both concentric (30% of 1-RM) and eccentric contractions (105% of 1-RM). Changes in thigh and arm lean tissue mass, unilateral leg press and unilateral elbow flexion maximal concentric (1-RM) and isometric strength (MVIC), and unilateral muscle power at 40, 60, and 80% 1-RM for both leg press and elbow flexion exercises before and after intervention were compared between groups, between sexes and between TL and NTA. Results: Both men and women in the training group showed increases (p < 0.05) in lean tissue mass, 1-RM, MVIC, and muscle power for TL. In NTA, 1-RM, MVIC, and muscle power increased without significant differences between sexes, but neither in men nor women changes in lean tissue mass were observed. In addition, men showed greater changes in TL, but changes in NTA were similar between sexes. No gains in any variable were found for the control group. Conclusions: AEL protocol produced similar neuromuscular changes in TL and ipsilateral NTA, which suggests that strong ipsilateral lower-to-upper limb cross-transfer effects were induced by the eccentric-overload training. However, early ipsilateral increases in muscle force and power were not associated with lean mass gains. Both men and women experienced similar changes in NTA; however, men showed greater changes in TL.

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.

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 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.

Validity of an inertial system for measuring velocity, force, and power during hamstring exercises performed on a flywheel resistance training device

Background

Inertial hamstring exercises promote functional changes leading to lower rates of hamstring injuries. However, variable training measurement systems have not been specifically validated for hamstring exercises. Accordingly, this study aimed to evaluate the validity of the Inertial Measurement System (IMS) to measure the velocity, force, and power during the performance of different hamstring exercises on a flywheel resistance training device.

Methods

Fifteen males (average age: 22.4 ± 2.5 years; body mass: 77.3 ± 9.8 kg; height: 179.5 ± 7.4 cm; weekly physical activity: 434.0 ± 169.2 min; years of strength training: 4.3 ± 2.2 years) performed the bilateral stiff-leg deadlift (SDL), 45° hip extension (HE), and unilateral straight knee bridge (SKB) in two sessions (familiarization and evaluation) with a 1-week interval between them. The velocity, force, and power (average and peak values) in the concentric and eccentric phases for each of the exercises were recorded simultaneously with IMS and MuscleLab.

Results

Consistency between IMS and MuscleLab was good to excellent for all variables, with r ranges from 0.824 to 0.966 in SDL, from 0.822 to 0.971 in HE, and from 0.806 to 0.969 in SKB. Acceptable levels of agreement between devices were observed in general for all exercises, the “bias” ranging from 1.1% to 13.2%. Although MuscleLab showed higher values than IMS for peak velocity, force and power values, the effect size was only relevant for 5 of the 36 parameters. IMS is a new and valid system to monitor inertial hamstring exercises on a new flywheel device. In this way, IMS could have potential practical applications for any professional or athlete who wants to monitor inertial hamstring exercises.

Effect of Volume on Eccentric Overload-Induced Postactivation Potentiation of Jumps

PURPOSE

To investigate the postactivation potentiation (PAP) effects of different eccentric overload (EOL) exercise volumes on countermovement-jump (CMJ) and standing-long-jump (LJ) performance.

METHODS

In total, 13 male university soccer players participated in a crossover design study following a familiarization period. Control (no PAP) CMJ and LJ performances were recorded, and 3 experimental protocols were performed in a randomized order: 1, 2, or 3 sets of 6 repetitions of flywheel EOL half-squats (inertia = 0.029 kg·m2). Performance of CMJ and LJ was measured 3 and 6 minutes after all experimental conditions. The time course and magnitude of the PAP were compared between conditions.

RESULTS

Meaningful positive PAP effects were reported for CMJ after 2 (Bayes factor [BF10] = 3.15, moderate) and 3 (BF10 = 3.25, moderate) sets but not after 1 set (BF10 = 2.10, anecdotal). Meaningful positive PAP effects were reported for LJ after 2 (BF10 = 3.05, moderate) and 3 (BF10 = 3.44, moderate) sets but not after 1 set (BF10 = 0.53, anecdotal). The 2- and 3-set protocols resulted in meaningful positive PAP effects on both CMJ and LJ after 6 minutes but not after 3 minutes.

CONCLUSION

This study reported beneficial effects of multiset EOL exercise over a single set. A minimum of 2 sets of flywheel EOL half-squats are required to induce PAP effects on CMJ and LJ performance of male university soccer players. Rest intervals of around 6 minutes (>3 min) are required to maximize the PAP effects via multiple sets of EOL exercise. However, further research is needed to clarify the optimal EOL protocol configurations for PAP response.

Influence of the Strap Rewind Height During a Conical Pulley Exercise

The use of flywheel devices has increased in popularity within resistance training programs. However, little is known about modifiable variables which may affect power output responses, as the rope length and the height level used in a conical pulley device. The aim of this study was to assess the influence of using three different rope lengths (1.5, 2.5 and 3.5 meters) and four different height levels (L1, L2, L3 and L4) on concentric peak power (PPconc), eccentric peak power (PPecc) and eccentric overload (eccentric/concentric PP ratio; EO) during conical pulley exercises (i.e. seated and stand-up row). A total of 29 recreationally trained subjects (25.3±7.1 years; 1.74±0.06 m; 72.5±8.3 kg) took part in the study. Testing sessions consisted of 1 set of 10 repetitions under each condition; experiment 1: seated row exercise using the three different rope lengths; experiment 2: stand-up row exercise using four different height levels of the conical pulley. Results from experiment 1 did not show differences between rope lengths, although a trend for greater PPecc (ES=0.36-0.38) and EO (ES=0.40-0.41) was found when using longer rope lengths (2.5 and 3.5). Experiment 2 showed significant increases in both PPconc and PPecc as the height level used was closer to the cone base (L4). In contrast, EO values were significantly greater when using upper height levels (L1). These results suggest that the height level used during conical pulley exercises highly influences power output responses. Therefore, this variable should be carefully managed depending on the training goal (e.g. power vs hypertrophy).

The Effects of Different Types of Eccentric Overload Training on Strength, Speed, Power and Change of Direction in Female Basketball Players

The aim of this study was to investigate the effect of two types of eccentric (ECC) overload training on strength, speed, power and change of direction in female basketball players. Twenty amateur basketball players (mean ± SD: age: 23.67 ± 6.05 years; height: 1.73 ± 0.05 m; body mass: 80.28 ± 17.67 kg) participated in a randomized trial. The players performed either flywheel inertial training (FIT) (n = 11) or tempo ECC training (TET) (n = 9) for 4 weeks, performing two sessions weekly. Performance characteristics, one repetition back squat (1RM), counter-movement jump (CMJ), squat jump (SJ), 10-metre sprint (10 m), change of direction (COD) and sit and reach flexibility (S&R) were tested pre and post intervention. Post-hoc testing revealed significant improvements in the FIT group for 1RM (p ≤ 0.001; ES = 0.59), 10 m (p = 0.003; ES = -0.54) and CMJ (p ≤ 0.001; ES = 1.04), while significant improvements were revealed in the TET group for 1RM (p = 0.007; ES = 0.71) and S&R (p ≤ 0.001; ES = 0.58). In conclusion, both FIT and TET groups demonstrated a positive training stimulus for increasing muscular strength. FIT may produce superior adaptions in CMJ and 10-m sprint, while TET may produce superior adaptions in S&R. Neither group achieved increases in either SJ or COD.

How Are Mechanical, Physiological, and Perceptual Variables Affected by the Rest Interval Between Sets During a Flywheel Resistance Session?

The use of flywheel devices has increased in popularity during the last few years. Flywheel training is an attractive alternative to traditional resistance exercise because it allows for the loading stimulus to be manipulated. Some of the benefits associated with flywheel training include increases in muscle hypertrophy, muscular strength and reductions in injury risk. Nevertheless, there is a lack of research about how basic training variables [i.e., rest intervals (RI) between sets], or variables associated with manipulation of the loading stimulus (i.e., different inertial loads), influence the acute responses during a flywheel session. Thus, the aim of this study was to assess the influence of three different RI between sets (1, 2, or 3 min), during a flywheel squat session with two different inertial loads: light (0.025 kg⋅m²) and high (0.075 kg⋅m²). Twenty-three participants performed six exercise sessions (two inertial loads × three RI) consisting of four sets of 11 repetitions. Concentric and eccentric power, lactate concentration ([La]) and ratings of perceived exertion (RPE) were measured during the exercise session, and delayed onset muscular soreness (DOMS) were recorded 24 h post-exercise. Both concentric (9.1 and 22.1% at light and high load respectively; p = 0.022 and 0.005) and eccentric peak power (17.5% at high load; p = 0.02) decreased across sets when the 1 min RI was used. Concentric peak power was decreased (11.1%, p = 0.041) from the 2 min RI only with the high inertial load. RPE was higher during the 1 min compared with the 3 min RI protocol when using the high inertial load (p = 0.028). [La] was higher when using the 2 min RI compared with the 3 min RI at light load (p = 0.03). In conclusion, during flywheel training sessions, a short RI (1 min) was insufficient to maintain power output across all four sets and was linked to greater perceptual variables. A 2 min RI allowed for power to be maintained, but only when training with light inertial loads. Based on these results, coaches should consider prescribing 3 min RI’s when performing flywheel squat exercises regardless the inertial load. In contrast, when using 2 min RI’s the inertial load should be light.

Eccentric-Overload Production During the Flywheel Squat Exercise in Young Soccer Players: Implications for Injury Prevention

This study aimed to evaluate the differences in power production between movement phases (i.e., concentric and eccentric) during the execution of resistance exercises with a flywheel device, differentiating between execution regimes (i.e., bilateral, unilateral dominant leg and unilateral non-dominant leg). Twenty young elite soccer players (U-17) performed two sets of six repetitions of the bilateral half-squat (inertia 0.025 kg·m-2) and the lateral-squat exercise (inertia 0.010 kg·m-2) on a flywheel device. During the testing sessions, mean and peak power in concentric (MPcon) and eccentric (MPecc) phases were recorded. The non-dominant leg showed higher values in all power variables measured, although substantial differences were only found in MPecc (ES = 0.40, likely) and PPcon (ES = 0.36, possibly). On the other hand, for both exercises, MPcon was higher than MPecc (ES = -0.57 to -0.31, possibly/likely greater), while only PPecc was higher than PPcon in the dominant lateral-squat (ES = 0.44, likely). These findings suggest that young soccer players have difficulty in reaching eccentric-overload during flywheel exercises, achieving it only with the dominant leg. Therefore, coaches should propose precise preventive programs based on flywheel devices, attending to the specific characteristics of each limb, as well as managing other variables to elicit eccentric-overload.

Brachial Plexus Injuries in Sport Medicine: Clinical Evaluation, Diagnostic Approaches, Treatment Options, and Rehabilitative Interventions

The brachial plexus represents a complex anatomical structure in the upper limb. This "network" of peripheral nerves permits the rearrangement of motor efferent fibers, coming from different spinal nerves, in several terminal branches directed to upper limb muscles. Moreover, afferent information coming from different cutaneous regions in upper limb are sorted in different spinal nerves through the brachial plexus. Severe brachial plexus injuries are a rare clinical condition in the general population and in sport medicine, but with dramatic consequences on the motor and sensory functions of the upper limb. In some sports, like martial arts, milder injuries of the brachial plexus can occur, with transient symptoms and with a full recovery. Clinical evaluation represents the cornerstone in the assessment of the athletes with brachial plexus injuries. Electrodiagnostic studies and imaging techniques, like magnetic resonance and high-frequency ultrasound, could be useful to localize the lesion and to define an appropriate treatment and a functional prognosis. Several conservative and surgical techniques could be applied, and multidisciplinary rehabilitative programs could be performed to guide the athlete toward the recovery of the highest functional level, according to the type of injury.

The relationship between the relative age effect and performance among athletes in World Handball Championships

This study examines the relative age effect (RAE) and its impact on the performance of elite male (n = 3,358) and female (n = 3,273) handball players in the U-19 (n = 2,188), U-21 (n = 2,031), and senior (n = 2,412) categories of the 2013/2014, 2015/2016 and 2017/2018 World Handball Championships organised by the International Handball Federation (IHF). The distribution of the players´ birth dates (by quartile: Q, and semester: S) by categories, handball playing positions, and membership of continental federations, were analysed for each of the three two-year periods in which the World Handball Championships took place. Differences between the observed and expected birth dates were tested using a chi-square goodness of fit test, and subsequent calculations were tested using odds ratios. The Spearman's correlation coefficient was applied to test the correlation between the relative age of the athletes and (their) performance parameters. The results revealed a prevalence of the RAE on both male and female in the U-19 and U-21 categories (p<0.001), and a stabilisation of the RAE throughout the period analysed (2013/14-2017/2018). The RAE was not found in the female senior category (2013, 2015 and 2017) or male senior category (2013) (p>0.05). All playing positions were impacted by the RAE (p<0.001), and especially strong effect sizes were noted for male pivots (Vc = 0.66/0.68/0.60) and female center backs (Vc = 0.71/0.65/0.71). In our analysis of the handball continental federations, the RAE was found in all regions, except Oceania (p>0.05). The RAE also affected athlete performance: the oldest athletes played more minutes and achieved better performances. The RAE was associated with the final placement of the teams in each championship category, except in the male youth category. The findings clearly demonstrated that the RAE has a significant impact on the selection of male and female athletes to international competitions and the performance of both men and women in international handball. The potential implications of these findings for policy and practice are discussed.

Effect of eccentric overload through isoinertial technology in basketball players

Abstract The present study investigated the effect of eccentric overload on professional basketball players. Participants were 8 players aged 18-25 years who play in a Leb Oro League team. There was an 8 week training cycle with 1 weekly session of half squats. The control group performed training following a traditional methodology –using free weights– whereas the experimental group used inertial technology, that is, the ProSquat machine from Proinertial®. Both vertical jump and 30-meter sprint were assessed before and after intervention. The following conclusions were reached: a) strength training with vertical vector improves the 30-meter sprint test and also the vertical jump; b) training program that affects the eccentric overload of the movement results in more improvements than traditional training with the same duration; c) training in the vertical vector also has an impact on the way force is manifested in the horizontal vector, showing improvements in the 30-meter sprint.

Eccentric Resistance Training in Youth: Perspectives for Long-Term Athletic Development

The purpose of this narrative review is to discuss the role of eccentric resistance training in youth and how this training modality can be utilized within long-term physical development. Current literature on responses to eccentric exercise in youth has demonstrated that potential concerns, such as fatigue and muscle damage, compared to adults are not supported. Considering the importance of resistance training for youth athletes and the benefits of eccentric training in enhancing strength, power, speed, and resistance to injury, its inclusion throughout youth may be warranted. In this review we provide a brief overview of the physiological responses to exercise in youth with specific reference to the different responses to eccentric resistance training between children, adolescents, and adults. Thereafter, we discuss the importance of ensuring that force absorption qualities are trained throughout youth and how these may be influenced by growth and maturation. In particular, we propose practical methods on how eccentric resistance training methods can be implemented in youth via the inclusion of efficient landing mechanics, eccentric hamstrings strengthening and flywheel inertia training. This article proposes that the use of eccentric resistance training in youth should be considered a necessity to help develop both physical qualities that underpin sporting performance, as well as reducing injury risk. However, as with any other training modality implemented within youth, careful consideration should be given in accordance with an individual's maturity status, training history and technical competency as well as being underpinned by current long-term physical development guidelines.

Eccentric Training Interventions and Team Sport Athletes

Eccentric resistance training has been shown to improve performance outcomes in a range of populations, making it a popular choice for practitioners. Evidence suggests that neuromuscular adaptations resulting from eccentric overload (EO) and accentuated eccentric loading (AEL) methods could benefit athletic populations competing in team sports. The purpose of this review was to determine the effects of eccentric resistance training on performance qualities in trained male team sport athletes. A systematic review was conducted using electronic databases PubMed, SPORTDiscus and Web of Science in May 2019. The literature search resulted in 1402 initial articles, with 14 included in the final analysis. Variables related to strength, speed, power and change of direction ability were extracted and effect sizes were calculated with a correction for small sample size. Trivial, moderate and large effect sizes were reported for strength (-0.17 to 1.67), speed (-0.08 to 1.06), power (0.27 to 1.63) and change of direction (0.48 to 1.46) outcomes. Eccentric resistance training appears to be an effective stimulus for developing neuromuscular qualities in trained male team sport athletes. However, the range of effect sizes, testing protocols and training interventions suggest that more research is needed to better implement this type of training in athletic populations.

Implementing Eccentric Resistance Training-Part 2: Practical Recommendations

The purpose of this review is to provide strength and conditioning practitioners with recommendations on how best to implement tempo eccentric training (TEMPO), flywheel inertial training (FIT), accentuated eccentric loading (AEL), and plyometric training (PT) into resistance training programs that seek to improve an athlete's hypertrophy, strength, and power output. Based on the existing literature, TEMPO may be best implemented with weaker athletes to benefit positional strength and hypertrophy due to the time under tension. FIT may provide an effective hypertrophy, strength, and power stimulus for untrained and weaker individuals; however, stronger individuals may not receive the same eccentric (ECC) overload stimulus. Although AEL may be implemented throughout the training year to benefit hypertrophy, strength, and power output, this strategy is better suited for stronger individuals. When weaker and stronger individuals are exposed to PT, they are exposed to an ECC overload stimulus as a result of increases in the ECC force and ECC rate of force development. In conclusion, when choosing to utilize ECC training methods, the practitioner must integrate these methods into a holistic training program that is designed to improve the athlete's performance capacity.