Original article written by Jamie Salter, James Black, James Mallett and colleagues
Background
In a previous review, the influence of maturation on player selection in youth was highlighted [1]. More mature players are often stronger, more powerful, and faster than their less mature counterparts [2,3], and therefore these are the players selected in youth teams. However, later maturers often catch up and overtake their earlier maturing counterparts and have an increased chance of success at the adult level [4].
With this in mind, practitioners need to ensure the holistic development of all players, and bio-banding competitions, where players are organised in teams based on their biological age rather than chronological, have been introduced to achieve this [5]. This format enables the more mature players to develop their technical skills and not rely on their enhanced physical ability, and also allows late maturers the chance to become more involved in matches and not be physically dominated. While young players’ perceptions of bio-banding has been positive [6], there seems to be a lack of research on how bio-banding format influences physical exertion in young soccer players.
What the authors did
Within this study, the authors aimed to identify the impact of maturity status on acute neuromuscular performance and psycho-physiological perceptions. Fifty-five young soccer players from an EPPP academies U12-U16 teams participated in the study (mean ±SD; age 13.8 ±1.4 years; stature 164.3 ±11.5cm; body mass 52.7 ±10.3 kg; percentage of predicted adult height (PAH%) 91.3 ±5.3).
Data was collected over a 6-week period during normal training sessions. The study involved three consecutive weeks of chronological SSGs, followed by three consecutive weeks of bio-banded SSGs, played at the same time of evening each week and on the same surface. Players performed the 30–15IFT test, with starting velocity set at 10 km·h-1, prior to the SSGs. The SSGs consisted of five bouts of 5-min 6v6 (including GK) on a playing area 45×36 m, each bout separated by 2-min passive recovery. Where there were more than 6 players assigned to a team, extras were included as “bounce” players on the sides of the playing area, and rolling subs were used throughout to keep non-playing time minimal. Following the SSGs, the same 30–15IFT sub-maximal running protocol was repeated to measure acute changes in neuromuscular movement patterns.
A foot-mounted inertial measurement unit (IMU) (PlayerMakerTM, Tel Aviv, Israel) was attached to the lateral ankle of players to assess movement profiles. The PlayerMakerTM system was used to measure Reactive Strength Index (RSI) (equation 1) during the 30–15IFT, as well as absolute, and relative leg stiffness. Absolute leg stiffness (kN·m−1) was calculated using equation 2, and relative leg stiffness was calculated by dividing leg length and body mass by absolute leg stiffness.
RSI = jump height (m)/ ground contact time (s) [1]
Kleg = [M∗p (Tf + Tc )]/Tc2 [(Tf + Tc /p) − (Tc /4)] [2]
where Kleg refers to leg stiffness, M is total body mass, Tc refers to ground contact time and Tf is equal to flight time.
Finally, to assess psycho-physiological perceptions of intensity, sessional rating of perceived exertion (sRPE) was utilised. Additionally, differential rating of perceived exertion (d-RPE) for breathlessness (RPE-B), leg muscle exertion (RPE-L) and cognitive/technical (RPE-T) demands was also collected.
What the authors found
The authors found that players experienced different stress-responses according to their maturity status, despite being exposed to the exact same training session. For example, following the SSGs, all maturity groups experienced a moderate (pre-PHV) or large (mid and post-PHV) within-session increase in absolute stiffness assessed during the 30–15IFT test. However, no other variables were altered following the SSGs other than stride length decreasing in the pre-PHV cohort. The increase in stiffness may lead to increased loading rates and peak forces for the lower extremity, which ultimately would increase the mechanical stress on bony structures and musculotendinous unit, potentially causing a pathway for injury.
Interestingly, bio-banded training sessions produced significantly different findings to chronological sessions in terms of pre to post response, with a lesser change in absolute stiffness, and cadence, but a greater increase in stride length.
These findings could support the use of bio-banded training formats for load management, with relatively smaller pre–post changes seeming to stabilise the negative stress-response from training in chronological age groups. The largest impact of bio-banded formats was on absolute stiffness, which may have indirectly, positively impacted contact time, RSI, and stride length to stimulate less “shock” to the athletes and therefore ultimately moderating injury risk.
Players subjective perception of exertion during bio-banded play was also lower then chronological age training, but this opposes previous work [7] so may require further research in this area. In the current study, pre- and post-PHV players rated all components of differential RPE less intense during bio-banded SSGs, versus chronologically aged. Similarly, circa-PHV players identified sRPE and RPE-T lower during bio-banded play, but rated RPE-L more intense during bio-banded sessions.
Limitations
This study has made a significant contribution to the understanding of bio-banding, identifying how it could possibly be used to modulate neuromuscular load on players, however, as with all studies it has minor limitations. The first being that three weeks of chronological SSGs were performed followed by three weeks of bio-banded groupings. This could have had an effect on the results, and a more randomised structure may have been better. However, the researchers may have been limited by using academy players, with training session structure being designed by coaches. The number of “bounce” players used as subs may also have altered the load for different teams, dependent on how many there were. Players from larger squads would have had greater rest periods in the SSGs, altering load. Finally, a measure of central fatigue would have been good to see the influence on the CNS system. For example, performing a drop jump prior to, and following the SSGs, alongside the sub-maximal run, may have given a clearer picture of the influence on fatigue as a whole.
What this means for coaches
The main takeaway for practitioners is that bio-banding can be used to reduce the training load on players during the week, as they perceive it to be less fatiguing than chronological aged-matched training, and it has a reduced neuromuscular load on players, especially absolute stiffness. This could have injury reduction benefits, so should be considered alongside the benefits for developing technical performance.
Reviewer’s comments
This is a really interesting paper looking at the influence of bio-banding on the neuromuscular profile of players. It is one of the first studies that have aimed to quantify load of bio-banded training. It would be interesting to now see more research in this area, as well as looking at the influence of bio-banding on technical performance, for example pass completion, scanning rates etc.
Recommended resources
Read – Working with youth athletes; monitoring maturation, biobanding and training through rapid growth – Sean Cumming