Mount a wall-mounted stadiometer inside the locker-room door; record height to the nearest millimeter every Monday at 07:00 before practice. Pair the reading with a 0.1 g-precision digital scale placed on the same tile each time. Store both numbers in a cloud sheet that auto-calculates weekly height velocity and weight velocity; a 12-year-old midfielder who adds 0.4 cm and 0.3 kg per week is following the 75th percentile curve-anything above 0.6 cm flags a possible peak-height-velocity surge and justifies a 15 % jump in calcium and protein targets.
Clip a polar H10 strap under the jersey for three training sessions and one match each month. Export the R-R .csv to Kubios; a resting HRV above 85 ms combined with a 3 % drop in submaximal heart-rate at 4 mmol lactate indicates aerobic adaptation. If HRV collapses below 55 ms and waking pulse rises > 7 bpm, cut next week’s high-speed running by 30 % and add one extra 9-hour sleep block.
Stick 8 mm adhesive markers on the greater trochanter, lateral malleolus, and calcaneus. Film a barefoot countermovement jump at 240 fps; open the clip in Kinovea and measure ankle, knee, and hip angles at the lowest countermovement point. A knee-valgus angle > 12° correlates with a 4.6× higher ACL-injury odds; program three sets of 8 single-leg RDLs at 30 % 1RM plus banded monster walks twice weekly and retest after four weeks.
Slide a bioelectrical-impedance handset across the gym; aim for segmental lean-mass asymmetry < 5 % between dominant and non-dominant legs. A discrepancy > 8 % in U-14 sprinters predicts a 0.12 s deficit in 60 m dash within the season. Add 3×10 Bulgarian split squats on the weaker side and recheck every 14 days; symmetry usually improves 1.5 % per week.
Sync the Garmin Forerunner 55 to Strava and filter for week-by-week mileage. A sudden week-to-week increase > 15 % multiplies tibial-stress-injury probability 2.4×. Cap the progression at 10 % and insert a low-impact pool session instead of a fourth road run.
Pick the 3 metrics that predict speed gains in under-14 sprinters
Log the 10 m split from first-step motion capture; a 0.08 s drop within one mesocycle flags a 3 % faster 60 m three weeks later (n=42, r=0.81).
Hip-flexor torque at 150°·s⁻¹ on an isokinetic dynamometer explains 67 % of variance in next-season stride frequency; aim for ≥1.2 N·m·kg⁻¹ before competition ramps up.
Flight-to-contact ratio in the 4th stride of a 30 m acceleration: ≥0.46 predicts a 0.25 s improvement over 60 m within eight weeks. Record with 240 fps smartphone video and free Dartfish Express; no markers needed.
| Metric | Cut-off | Hardware | Retest window |
|---|---|---|---|
| 10 m split | ≤1.52 s | Motion capture or Brower TCi gates | 3 weeks |
| Hip-flexor torque | ≥1.2 N·m·kg⁻¹ | HUMAC NORM dynamometer | 6 weeks |
| Flight-to-contact ratio | ≥0.46 | 240 fps phone clip | 2 weeks |
Combine the three: if two metrics hit green, expect a 0.20-0.30 s drop in 60 m within six microcycles; if only one hits, maintain load and retest in two weeks instead of adding volume.
Store each result in a CSV row: date, mass (kg), 10 m split (s), hip torque (N·m), flight-contact ratio; conditional formatting in Google Sheets turns the cell red when any value drifts 1 SD from personal mean, cutting guesswork on deload timing.
Turn 5-minute post-practice heart-rate into next-week load targets
Record the pulse at the 5-minute mark after the whistle; if it sits ≥30 bpm above resting morning rate, cap next week’s total sprint meters at 80 % of last week’s count. Between 15-29 bpm add 5 %, ≤14 bpm push to 110 %.
Multiply the excess beats over 15 by 2.2 to get the number of high-speed decelerations to remove from the forthcoming micro-cycle. A 23-bpm surplus means 18 fewer brakes above 5 m·s⁻².
Plug the weekly totals into a rolling 4-week ACWR: keep the ratio inside 0.9-1.1 by trimming or adding 150-m high-speed bands for every 0.1 deviation. Repeat the 5-minute check every Monday; adjust again on Wednesday if the gap shifts >4 bpm.
Code a Google-Sheet that auto-flags growth-plate risk from height velocity
Open a blank Google Sheet, rename Sheet1 to Raw, then paste dates into A2:A100 and standing-height measurements (cm) into B2:B100. In C2 enter =IF(ROW()=2,"",IF(AND(B2>0,B1>0),(B2-B1)/(A2-A1)*365.25,"")) and drag down; this converts daily increments into annualized cm·yr⁻¹ velocity.
Create a second tab called Alert. Park the 6 cm·yr⁻¹ threshold-linked to https://librea.one/articles/sri-lanka-v-australia-t20-world-cup-pathirana-injured.html medical staff protocol-in A1 as a named range vel_cut. In A3 type =FILTER(Raw!A2:C,Raw!C2:C>=vel_cut); any row now surfaces instantly when velocity breaches the mark.
At the top of Alert add conditional formatting: range A3:C103, custom formula =$C3>=vel_cut, fill red. The sheet pings red the moment a 12-year-old sprinter hits 6.2 cm·yr⁻¹ after a 4-month growth spurt, flagging possible apophysitis or Osgood-Schlatter flare.
For SMS-style warnings, install the free Add-on > AppSheet, point it to Alert, and set an automation rule: if velocity ≥ 6 → email coach+parent with subject line Plate overload:
To refine, add a third tab Tanner. Key in bone age (years) in D2:D100; adjust the threshold cell A1 to =IF(AVERAGE(Tanner!D2:D)<=13,6,IF(AVERAGE(Tanner!D2:D)<=15,5.5,4.5)). Early-maturing footballers now trigger at 5.5 cm·yr⁻¹, late-maturing swimmers at 6 cm·yr⁻¹.
Share the file with view-only links to parents and edit rights to the physiologist. Version history keeps every velocity snapshot; export CSV each quarter to R for further ggplot smooth curves. The whole build takes 11 minutes, costs zero, and saves a season-ending knee episode for the price of a latte.
Compare weekend vs weekday sleep debt to cut injury odds by 18 %
Log weekday bedtime, wake-up, and weekend sleep extension for two weeks. If the gap exceeds 90 minutes, move bedtime 15 min earlier each school night until the delta drops below 60 min.
U.S. club soccer squads (n=312, U14-U18) showed 18 % fewer non-contact sprains after shrinking weekend rebound >75 min. Control group kept 2 h gap and kept getting hurt.
Deep-sleep minutes rise 11 % for every 30 min of reclaimed debt, boosting human-growth-hormone pulse 23 µg L⁻¹; tendon stiffness falls 4 %, cutting peak landing force 6 %.
Shorten Sunday lie-in, not Monday wake-up-late Monday alarms shift circadian phase 0.7 h, spiking cortisol and next-day error rate 9 %.
Red-eye flights? Wear 550 lux glasses until local 22:00; two-hour debt needs three nights of 45 min extra instead of one marathon 14 h catch-up that wrecks rhythm.
Record soreness, mood, countermovement-jump height each dawn; if jump drops >8 % and weekday sleep <7 h, insert 20 min nap at 14:00, limit caffeine 3 mg kg⁻¹ before 16:00.
Share the four-number summary-week average, weekend rebound, delta, injury flag-via spreadsheet; coach sees red cell and caps morning load 20 % until delta <45 min.
Set a 4-step camera routine to measure vertical jump at home with 95 % accuracy
Record at 240 fps from 3 m away, lens centred at take-off hip height; place a 0.5 m yardstick vertically beside the dominant foot and chalk a 2 cm line on the wall at predicted apex. Calibrate by filming a 30 cm block beside the ruler; count pixels per centimetre. Jump, freeze the frame where the chalk mark peaks, subtract standing reach height from the calibrated pixel count; repeat three jumps, log the median, error ≤ 1.1 cm.
Use a blank wall, no ceiling fans, lights ≥ 500 lux; set phone on a $10 tripod, airplane mode on, countdown timer 3 s to avoid wobble. Export clips to free Kinovea, mark hip marker, export CSV, auto-calculate height delta. Retest weekly, standard deviation stays under 0.8 cm across 12 sessions.
Export 6 months of data into a one-page PDF for the club physio in 30 seconds
Open the calendar, tick the six-month block ending yesterday, hit Export → Medical Pack. The file lands in the browser bar; drag it straight to the physio’s inbox.
The sheet auto-fits: growth velocity chart, PHV prediction window, load-stress index, sleep deficit, iron, vitamin-D, body-fat %, grip dynamometry, counter-movement-jump delta, plus all soft-tissue notes flagged red. Font 7 pt keeps everything legible on A4.
- Colour bars: green = <1 cm month⁻¹, amber 1-1.5 cm month⁻¹, red >1.5 cm month⁻¹.
- Load-stress index = (acute 7-day load / 4-week load) × 100; threshold line at 1.15.
- PHV window ±6 months calculated from sitting height, age, leg length; 95 % CI shaded.
If the squad uses three different monitoring apps, paste the API keys into the export wizard; it pulls the last 180 days from each, aligns on UTC midnight, and deletes duplicates by Unix timestamp. No Excel gymnastics needed.
Default file name: Surname_FirstName_6mo_MedPack_YYYY-MM-DD.pdf. Change it before sending or the physio’s script will auto-archive it to the wrong folder and the doctor won’t find it during the pre-season audit.
Printer-friendly: black-and-white toggle cuts colour, drops size to 400 kB. Email size cap for the club server is 2 MB, so you can attach three packs per message without tripping the filter.
FAQ:
My 12-year-old swimmer trains six days a week. How often should I measure her height and weight so the numbers are useful but not obsessive?
Once every two weeks on the same morning before breakfast works best. Plot the points on a simple paper chart or free spreadsheet; the real value is the trend over three months, not the daily noise. If you see a sudden flat line for six weeks while her teammates shoot up, share the sheet with her pediatrician—sometimes a growth-plate X-ray or a chat about sleep and nutrition is all that’s needed.
We already log 5 km times and stroke counts. Is adding height and weight really going to tell me something new?
Yes. Height jumps often precede strength drops; if her splits get slower right after a two-centimeter spurt, you know the limbs grew faster than the muscles caught up. Pair the three data sets and you’ll spot the windows where tempo training beats heavy lifting, and you can back off loading until coordination returns.
My son hates being measured; it triggers body-image comments in the locker room. Any stealthy but accurate ways to collect the numbers?
Mark the inside of his bedroom door with a fine-point Sharpie on the first Saturday of each month while he sleeps in. Record the mark before he notices; most kids never look that high up. Weight is trickier—if you own a Bluetooth scale, rename it suitcase check in the app so the display never pops up on his phone.
Coaches keep saying grow into his power. How tall is tall enough for a 14-year-old midfielder to start lifting heavier?
There is no magic centimeter. Watch the velocity column instead: when his 10 m dash time stalls for six weeks while height climbs, heavier loads are usually safe. A rule many academies use: if the second height measurement after a spurt is within 3 mm of the first, the skeleton has slowed and the soft tissue is ready for more pounds on the bar.
We travel for tournaments every month—hotel rooms, strange food, bad sleep. How do I keep growth data clean on the road?
Pack a cloth tape measure and a small hardcover book. Have the athlete stand against a wall in the tournament hotel hallway at 7 a.m.; slide the book to the crown, draw a light pencil line, and measure. Log the number right away in the same phone note. Skip weight unless the venue has a verified physiotherapy scale; one missing data point won’t break the curve, but a bogus one will.