This study looked at whether the order of two different types of muscle-and-connective-tissue ("myofascial chain") training affects how young football players improve their jumping power and balance.

Forty male football players, aged 15 to 16, took part. Players were split into two groups by chance. One group did "posterior chain" training first, then switched to "spiral chain" training. The other group did the trainings in the opposite order. Each training phase lasted six weeks, and players kept doing their normal team practice at the same time.

Jumping power and balance were measured four times: before training started, after the first six weeks, after the second six weeks, and again four weeks after training ended.

The goal was to find out if starting with one type of training instead of the other leads to bigger, faster, or longer-lasting improvements. This information may help coaches design better training programs for young athletes.

Myofascial chains are interconnected lines of muscle and connective tissue that transmit force across body segments, contributing to movement efficiency, joint stability, and elastic energy storage. Among the chains described in fascial anatomy literature, the posterior chain is considered a primary contributor to explosive force production, while the spiral chain contributes to rotational control and dynamic balance. Despite growing interest in fascia-informed training approaches, no prior study has examined whether the sequence in which these chains are trained influences the magnitude, time-course, or persistence of performance adaptations in youth athletes.

To address this gap, the study employed a randomized crossover design. Participants were randomly allocated in a 1:1 ratio to one of two sequence groups: the Posterior Chain First Group (PCFG) or the Spiral Chain First Group (SCFG). Both groups continued their regular club training throughout the entire study period.

The intervention consisted of two consecutive six-week training blocks separated by a mid-test assessment. In the first block, each group performed their assigned myofascial chain protocol; following the crossover, groups switched protocols for the second block. Each training session lasted 30 minutes and was completed in addition to routine club practice. Outcomes were assessed at four time points - baseline, after the first block, after the second block, and at a four-week follow-up - to capture both the progression and persistence of adaptations.

The primary aim was to determine whether initiating training with the posterior chain versus the spiral chain produces differential adaptation trajectories, which may inform evidence-based sequencing decisions in youth athlete development programs.

IInclusion Criteria:

• Male, aged 15-16 years (U15-U16 category)
• Holding an active football player license and currently competing with a club team
• Regularly participating in routine club training sessions
• Free from any injury or musculoskeletal condition that could affect performance testing at the time of enrollment
• Parental/legal guardian consent and participant assent obtained

Exclusion Criteria:

• Presence of any musculoskeletal injury, recent surgery, or medical condition affecting lower-limb function within the past 6 months
• Inability to attend the required training sessions or assessment time points
• Unwillingness or inability of parents/legal guardians to provide informed consent

De-identified individual participant data underlying the results reported in this article (CMJ and Y-Balance Test scores at all four assessment time points), along with the study protocol.

Beginning 3 months and ending 5 years after article publication

Investigators who provide a methodologically sound proposal, for use in achieving the aims of the approved proposal. Requests should be directed to the corresponding author.