RED-S, dysmenorrhoea, peak height velocity, spondylolysis, GIRD: 42 definitions with the figure, the population it was measured in and the source. BAB’s glossary.
Amenorrhoea
The absence of menstruation; in sport it is not a harmless side effect of training but a possible warning signal.
Ankle sprain
Injury to the ankle ligaments, typically the lateral compartment, caused by movement exceeding the joint’s range. It is the most frequent injury in girls’ youth sport: the ankle accounts for 23% of all injuries, ahead of the knee (16%) and thigh (13%) (Beech et al., 2024). Incidence is higher in females than males (13.6 vs 6.94 per 1,000 exposures) and higher in younger athletes (Doherty et al., 2014).
Anterior cruciate ligament (ACL)
The ligament stabilising the knee; its rupture is the injury that most often ends a girl’s sporting career. In high-school sport, female athletes sustain 1.40 times the ruptures of their male peers (0.084 vs 0.060 per 1,000 exposures), with the widest gap in basketball (RR 4.14) (Bram et al., 2021).
Biological maturation
How far a body’s development has progressed, as distinct from chronological age. In young female athletes the evidence linking maturation status to injury is limited, while the evidence linking it to knee risk factors in jumping and landing is moderate (Zoellner and Whatman, 2026). It is estimated through repeated height measurements and maturity-offset equations (Moore et al., 2015): these are estimates with wide margins of error, useful for planning load, not for labelling an athlete.
Bone health and peak bone mass
The bone capital accumulated during growth. Total bone mineral content plateaus on average 6 years after peak height velocity, i.e. around age 18 in girls (Baxter-Jones et al., 2011); lifestyle factors — physical activity, nutrition, calcium, vitamin D — account for 20-40% of it (Weaver et al., 2016). It is a window that closes: bone is built in adolescence, not afterwards.
Chronic ankle instability
The condition in which, after one or more sprains, the ankle keeps giving way and hurting beyond tissue healing. Among athletes aged 14-18 the prevalence is 20.0%: 23.6% in girls against 16.3% in boys, with lower ankle sport function (FAAM-Sport 87.0 vs 97.7) and lower perceived quality of life, at the same level of physical activity (Donovan et al., 2020). It is the outcome that the phrase «it’s just a twist» makes invisible.
Circadian rhythm
The internal biological clock regulating sleep and wakefulness. With puberty its timing shifts later: the need for sleep does not decrease, what changes is the hour at which the body can fall asleep — and that collides with school start times (Carskadon, 2011).
Concussion in sport
A functional brain injury induced by biomechanical forces: it requires neither a visible blow to the head nor loss of consciousness. In high-school football (soccer), female athletes sustain 1.88 times the concussions of male peers (95% CI 1.69-2.09), and the leading mechanism is contact with an object (41.9%) rather than with another player (Bretzin et al., 2021). Where concussion is suspected the athlete must be removed from play immediately.
Deliberate play (free play)
Unstructured physical activity, chosen and governed by the children themselves, distinct from organised training. It is not wasted time: when the ratio of organised sport to free play exceeds 2:1 hours per week, the odds of a serious overuse injury rise to 1.87 times (Jayanthi et al., 2015).
Drop-out from girls’ sport
Leaving sport during adolescence: among girls registered with a club aged 10-14, 71% drop out without ever returning (Eime et al., 2020). It is not a dip in motivation but the result of an environment that stops working when the body changes.
Dysmenorrhoea (period pain)
Pain associated with menstruation. It is the most widespread form of recurrent pain among school-age girls: estimated prevalence among young women under 25 is 71.1%, with 20.1% reporting absence from school or university and 40.9% an impact on concentration and performance (Armour et al., 2019). Among athletes it is the most frequent menstrual disorder, with a prevalence of 32.3% and a very wide range across studies, 7.8-85.6% (Taim et al., 2023). It is classed as primary (no underlying pelvic pathology, by far the most common form in adolescents) or secondary.
Early sport specialisation
Playing a single sport for more than 8 months a year, choosing it as the main sport and quitting the others: the three criteria defining high specialisation on the 3-point scale used in the literature. Among athletes aged 13-18, highly specialised girls report a history of injury 2.93 times as often as low-specialisation peers (Okoruwa et al., 2022); the American Academy of Pediatrics recommends playing multiple sports at least until puberty (Brenner and AAP, 2016).
Endometriosis
The presence of endometrium-like tissue outside the uterine cavity; it is the leading cause of secondary dysmenorrhoea in adolescents. The clinical guidance dedicated to this age group advises investigating secondary causes when period pain does not improve within 3-6 months of starting treatment (ACOG Committee Opinion No. 760, 2018). In a sporting context the point is not to diagnose, but not to normalise pain that keeps costing training sessions and school days.
Energy availability
The energy left to the body for its vital functions after the cost of training has been covered. When it is too low the body downregulates functions such as the menstrual cycle, bone health and recovery: this is the mechanism underlying RED-S.
GIRD (glenohumeral internal rotation deficit)
Loss of internal rotation in the dominant shoulder compared with the other side, a typical adaptation in those who work overhead. In a case-control study of 123 high-school volleyball players (mean age 15.8), 38.2% had GIRD, but in that same sample no relationship emerged with history of shoulder injury; males tended towards hypomobility and females towards hypermobility (Mizoguchi et al., 2022).
Growth plate (physis)
The cartilaginous zone from which a long bone lengthens during growth, mechanically weaker than mature bone and therefore at the heart of the fear that weights «stunt growth». That fear is not borne out: supervised protocols have no negative effect on growth and maturation (Malina, 2006). The documented risk concerns load without supervision, without technique and with improvised progressions.
Iron deficiency
Insufficient iron stores, measured through ferritin; it can be present without anaemia. Among adolescent female athletes the prevalence of mild deficiency (ferritin ≤30 µg/L) is 53% (Nicotra et al., 2023). It is established with a blood test, not assumed.
Load management
Dosing training load progressively instead of alternating complete rest with full resumption. In adolescent patellofemoral pain it is the approach with the best results: 12 weeks of activity modification, strengthening and graded return to sport produced 86% positive outcomes at 12 weeks and 81% at 12 months in 151 boys and girls aged 10-14 (Rathleff et al., 2019); adding supervised exercise to education doubles the odds of recovery at 24 months (OR 2.52; Rathleff et al., 2015).
Low back pain in youth sport
Pain in the lumbar region in athletes aged 10-19. It is common: estimated 12-month prevalence is 42% (95% CI 29-55%), 3-month prevalence 46% and point prevalence 16% (Wall et al., 2022; 80 studies, 60 sports, heterogeneity I² up to 98% because no shared definition exists). Reported risk factors include training volume and intensity, concurrent lower-limb pain, being overweight, later adolescent age, family history and female sex. The morphology most often described in this age band is spondylolysis, not the disc.
Menarche
The first menstrual period; its timing is associated with several health outcomes in adolescence and adulthood.
Menstrual cycle
The female hormonal cycle; in youth sport it is a health signal to be recognised, not a clinical measure to be diagnosed.
Osgood-Schlatter disease
Pain localised over the tibial tuberosity, where the patellar tendon inserts just below the kneecap; typical of the growing adolescent. It does not simply require waiting: in a prospective cohort of 51 adolescents aged 10-14 (51% girls), a load-progression ladder with strengthening exercises produced 80% positive outcomes at 12 weeks and 90% at 12 months, albeit without a control group (Rathleff et al., 2020).
Overhead sports
Disciplines whose defining movement happens above the head — volleyball, swimming, handball, tennis, badminton. The load concentrates on a shoulder that in an adolescent has not finished growing: the proximal humeral growth plate provides roughly 80% of the humerus’s growth in length and closes between 18 and 21 (Casadei and Kiel, StatPearls). The systematic review of risk factors in these sports concludes that the evidence is still limited or conflicting (Asker et al., 2018).
Overuse injury
Damage from repeated load with no single identifiable trauma: it accumulates over time and is therefore noticed late. In highly specialised athletes the risk is 1.81 times that of low-specialisation athletes (Bell et al., 2018), and those training more hours per week than their age in years have 2.07 times the odds of a serious overuse injury (Jayanthi et al., 2015).
Pain
A sensory and emotional experience whose underlying mechanisms change during puberty; clinical pain tends to increase in this age band.
Patellofemoral pain
Diffuse pain around or behind the kneecap, provoked by loading the knee in flexion: stairs, squatting, jumping, running and long periods sitting. It is not pinpoint pain on the bone and does not arise from a single trauma: in the Danish cohort, 68.3% of adolescent knee pain had an insidious onset (Rathleff et al., 2013). Estimated annual prevalence in adolescents is 28.9% (Smith et al., 2018) and it is not self-limiting: at 2 years 55.9% still have pain (Rathleff et al., 2016), at 5 years 40.5%, with 60% of those having stopped or cut back on sport (Rathleff et al., 2019).
Peak height velocity (PHV)
The moment when height increases at its fastest rate during puberty. In young female athletes the estimated mean age is 11.18 years, but with a 90% credible interval running from 8.62 to 12.94 years (Lima et al., 2024): two athletes in the same age category can be years apart biologically. Peak bone mineral accrual arrives roughly 6 months later (Bailey et al., 1999), so for a period the bone is longer but not yet as dense.
Pelvic floor
The group of muscles supporting the bladder and pelvic organs and contributing to continence. In repeated-impact sport it is loaded at every jump and landing: among adolescent female athletes the mean prevalence of urinary incontinence is 48.58% (Rial Rebullido et al., 2021).
Preventive neuromuscular training
A structured warm-up with landing stabilisation, strength and pelvic control. It reduces ACL rupture risk from roughly 1 in 54 to 1 in 111 (OR 0.51), with a stronger effect among athletes aged 13-19 (OR 0.38) (Petushek et al., 2019). It only works above roughly 66% adherence (Sugimoto et al., 2012).
Proprioception and balance training
The ability to sense the position and movement of one’s own body in space, trainable with balance and single-leg control exercises. In youth sport, programmes including it reduce ankle injuries by roughly 26% (IRR 0.74; 95% CI 0.60-0.91) with 15-20 minutes twice a week for 3-6 months (Berkey et al., 2024); in a randomised study of 765 high-school athletes, 523 of them girls, the balance-training group recorded 1.13 sprains per 1,000 exposures against 1.87 (McGuine and Keene, 2006).
Puberty
The developmental phase in which the body matures; the window in which most of the physiological changes relevant to young female athletes emerge.
RED-S (Relative Energy Deficiency in Sport)
A syndrome of low energy availability in sport: when energy intake does not cover the cost of training, with effects on the menstrual cycle, bone, the immune system and mood.
Return to sport
The graded pathway bringing an athlete back to activity after injury. After a concussion, the Amsterdam 2022 international consensus sets out 24-48 hours of relative (not absolute) rest, 4 return-to-learn steps and 6 return-to-sport steps of at least 24 hours each, with full return to school preceding unrestricted return to sport and final clearance resting with a healthcare professional (Patricios et al., 2023).
Scapular dyskinesis
Altered movement of the shoulder blade during arm elevation, often proposed as a shoulder screening test. Its predictive value is contested: a meta-analysis of 5 studies and 419 athletes estimates a 43% greater risk of shoulder pain (RR 1.43; 95% CI 1.05-1.93) (Hickey et al., 2018), while a larger one of 7 studies and 923 athletes finds no statistically significant association (RR 1.07; 95% CI 0.85-1.34; p=0.59) (Hogan et al., 2021). On its own it does not identify who will get injured.
Shoulder pain in youth sport
Pain and functional problems of the shoulder joint linked to repeated overhead movement. In a prospective study of 471 elite handball players aged 15-18 monitored every week, 23% reported substantial shoulder problems in one season and 43% of those for at least 3 consecutive weeks; prevalence was 1.46 times higher in girls (95% CI 1.04-2.06) (Asker et al., 2018). In swimming, the 15-17 age band reports the highest shoulder-pain rate of all ages considered, 91.3% (self-reported prevalence; Feijen et al., 2020).
Sleep in adolescence
Night-time rest in the 13-18 age band, for which the consensus recommendation is 8-10 hours per night (Paruthi et al., 2016). In adolescent athletes, sleeping less than 8 hours is associated with being injured 1.7 times as often (Milewski et al., 2014). It is not optional recovery: it is part of growing.
A stress fracture of the pars interarticularis, the bony bridge joining a vertebra’s posterior joints, almost always in the lower lumbar spine. It arises from repeated loading of the spine in extension and rotation, not from a single trauma. It is the cause that separates the adolescent back from the adult one: in a direct comparison it explained 47% of cases in athletes aged 12-18 against 5% in adults, while the disc explained 11 cases in 100 against 48 (Micheli and Wood, 1995 — a specialist-clinic sample). Among non-elite adolescent athletes with low back pain the share is 30% (Selhorst et al., 2019). Return to competition is estimated at 92.2% with conservative treatment (Overley et al., 2018).
Sports bra
A garment supporting the breast during movement. Breast tissue has no muscle of its own to support it: at 13-14, 51% of girls say their breasts affect their participation in sport, yet only 10% always wear one (Scurr et al., 2016).
Stress fracture (bone stress injury)
Bone damage from repeated load without a single trauma: it presents as pain in one precise spot, appearing under load and, over time, arriving ever earlier in the session. In high-school sport, female athletes sustain 2.22 per 100,000 exposures against 1.27 in male peers (a ratio of 1.75) and account for 63.3% of all cases (Changstrom et al., 2015); recurrence in adolescent athletes runs as high as 21% (Beck and Drysdale, 2021).
Tanner stages
The clinical scale describing the steps of pubertal development. It is useful because many phenomena track pubertal stage rather than chronological age: insomnia symptoms in girls, for example, rise from 3.4% to 12.2% between stage 1 and stage 5 (Zhang et al., 2016).
Urinary incontinence in sport
Involuntary loss of urine during physical activity, typically in jumps, sprints and changes of direction. It is common but not physiological: 87% of adolescent female athletes say they would not mention it to their coach and up to 90% have never heard of pelvic floor training (Rial Rebullido et al., 2021).
Youth resistance training
Resistance training performed before skeletal maturity. Consensus statements consider it safe and effective when appropriately designed and supervised (Lloyd et al., 2014; Stricker et al., AAP 2020): in a review of 22 experimental programmes in children and preadolescents it did not affect growth in height or weight, with injury rates estimated between 0.053 and 0.176 per 100 hours of participation (Malina, 2006). The effect on strength is large (effect size 1.12; 95% CI 0.9-1.3) and grows with maturation, without a surge at puberty (Behringer et al., 2010).