The science behind your plan

Updated October 27, 2026.

Comeback Strength builds every plan from training principles that are well supported by sports science research and professional guidelines. This page explains the main ones and links to the studies. Numbers in brackets, like [1], point to the reference list at the bottom.

Two things to keep in mind. The studies below looked at groups of athletes doing a type of training, not at this app. And Comeback Strength is a training app, not medical care: it doesn't diagnose or treat injuries, and your doctor or physical therapist has the final say.

Coming back is a progression, not a single day

An international consensus of sports physical therapists describes return to sport as a continuum that runs alongside recovery, rather than one yes-or-no decision at the end [1]. That's why your plan moves through phases: Re-entry, Build, Power, then Return to Play, with your sport practice stepping up alongside the lifting.

Strength training first

A review of 25 randomized trials with over 26,000 athletes found that strength training programs cut sports injuries to about a third, while stretching programs showed no protective effect [2]. Balance training also helped. So the app is built around getting strong, with balance and landing work, rather than stretching routines.

How heavy, how many, how long to rest

• Reps and weight follow the American College of Sports Medicine's guidelines: moderate weights for 8–12 reps while you find your feet, then heavier work in the 4–6 rep range for strength, and light, fast reps for power [3].
• "Finish 1–2 reps short of failure" uses the reps-in-reserve scale, a simple way to judge effort that tracks well with how fast the bar moves [4].
• When you beat the top of your rep range by 1–2 reps, the app tells you to add a little weight. That's the ACSM progression rule [3].
• The 4- and 5-day plans work each main muscle group with several hard sets across the week, because more weekly sets (up to 10 or more per muscle) were linked to more muscle growth in a meta-analysis [5].
• Rest is 2–3 minutes on main lifts and power work. Longer rest between sets led to more strength and muscle than 1 minute in trained lifters [6], and ACSM recommends 3–5 minutes for power training [3].
• Every sixth week is a lighter deload week to shed fatigue, in line with an international expert consensus on deloading [7].

Power for your sport

Jumps and throws are part of every week because plyometric training reliably improves jump height, by roughly 5–9% on average [8]. For golf, strength and conditioning programs improved clubhead speed, ball speed and distance by about 4–6% on average across studies [9]. For throwing, a review found strength training generally raises throwing velocity, though the results vary by method and no single method stands out [10].

Exercises chosen for their injury research

• Nordic hamstring curls: programs that included them had about half as many hamstring injuries across 15 studies and 8,459 athletes [11].
• Copenhagen adductor exercise: a simple one-exercise program lowered the risk of groin problems by 41% in a trial with male soccer players [12]. The app uses the same exercise, the same three levels, and the study's rule of dropping a level if groin pain goes above 3 out of 10.
• Jumping, landing, balance and strength work: programs that combine them were linked to about 50% fewer ACL injuries overall and about 67% fewer non-contact ACL injuries in female athletes [13].
• Single-leg balance training: an 8-week home program cut repeat ankle sprains by about 37% [14], and a large review supports exercise therapy for preventing ankle problems from coming back [15].
• A structured warm-up before every session: a soccer warm-up program (the FIFA 11+) led to about a third fewer injuries and nearly half as many severe injuries in young female players [16]. The app's warm-up isn't the 11+, but follows the same idea, and the app points soccer players to the 11+ itself.

Throwing and racquet athletes

In professional pitchers, weaker shoulder external rotation and supraspinatus strength before the season was linked to throwing injuries that needed surgery [17]. That's why throwers get shoulder rotation and shoulder-blade work every week. The specific arm-care exercises come from widely used programs like the Thrower's Ten and are chosen based on muscle-activation studies, not head-to-head injury trials [18].

The throwing progression follows the classic interval throwing program: start at 45 ft, build out to 180 ft, throw every other day, and only move on when a session was pain-free with no soreness the next day [19]. The same paper's interval programs for tennis and golf shaped those sports' progressions too.

Knees after ACL surgery

In a study of athletes after ACL reconstruction, those who returned to cutting and jumping sports before 9 months had about twice the rate of re-injury (39.5% vs 19.4%), and thigh strength under 90% of the other leg was linked to more re-injuries (33% vs 13%) [20]. If you tell the app when you had ACL surgery, it holds back cutting and big jumps, and keeps your sport practice at the Build level, until 9 months after. It can't measure strength, so it also reminds you to have your physical therapist test it before cutting sports.

Tendons and backs

• Painful tendons respond well to gradually heavier, slow strength work. Heavy slow resistance training gave lasting improvement for patellar tendon pain, while steroid injections helped only in the short term [21]. And Achilles tendon patients who kept running and jumping with a pain-monitoring approach did as well as those who stopped [22].
• For ongoing low back pain, exercise reduces pain compared with no treatment, but no single type of exercise has been shown to be best [23]. The app's early back choices (bracing, McGill-style core work, lighter barbell lifts at first) are a cautious approach, not a proven one.

Running

In new runners, those who raised their weekly distance by more than 30% tended to have more overuse injuries than those who kept increases under 10%, though the result fell just short of statistical certainty [24]. The app keeps increases small and steady.

What the research doesn't tell us

Many of these studies looked at specific groups, like male soccer players or professional pitchers, and results may differ for you. Some parts of the app, including the shoulder, hip and back modules, rest on expert consensus and muscle-activation research rather than injury trials. And the app itself hasn't been studied. We'll update this page as the research changes.

References

1. Ardern CL, et al. 2016 Consensus statement on return to sport from the First World Congress in Sports Physical Therapy, Bern. Br J Sports Med. 2016;50(14):853–864. Link
2. Lauersen JB, Bertelsen DM, Andersen LB. The effectiveness of exercise interventions to prevent sports injuries: a systematic review and meta-analysis of randomised controlled trials. Br J Sports Med. 2014;48(11):871–877. Link
3. American College of Sports Medicine. Position stand: Progression models in resistance training for healthy adults. Med Sci Sports Exerc. 2009;41(3):687–708. Link
4. Zourdos MC, et al. Novel resistance training-specific rating of perceived exertion scale measuring repetitions in reserve. J Strength Cond Res. 2016;30(1):267–275. Link
5. Schoenfeld BJ, Ogborn D, Krieger JW. Dose-response relationship between weekly resistance training volume and increases in muscle mass: a systematic review and meta-analysis. J Sports Sci. 2017;35(11):1073–1082. Link
6. Schoenfeld BJ, et al. Longer interset rest periods enhance muscle strength and hypertrophy in resistance-trained men. J Strength Cond Res. 2016;30(7):1805–1812. Link
7. Bell L, Strafford BW, Coleman M, Androulakis Korakakis P, Nolan D. Integrating deloading into strength and physique sports training programmes: an international Delphi consensus approach. Sports Med Open. 2023;9. Link
8. Markovic G, Newton RU. Does plyometric training improve vertical jump height? A meta-analytical review. Br J Sports Med. 2007;41(6):349. Link
9. The effects of strength and conditioning interventions on golf performance: a systematic review. J Sports Sci. 2020;38(23):2720–2731. Link
10. The effect of specific strength training on throwing velocity in overarm throwing: a systematic review. Sports Med Open. 2024;10:122. Link
11. van Dyk N, Behan FP, Whiteley R. Including the Nordic hamstring exercise in injury prevention programmes halves the rate of hamstring injuries: a systematic review and meta-analysis of 8459 athletes. Br J Sports Med. 2019;53(21):1362. Link
12. Harøy J, et al. The Adductor Strengthening Programme prevents groin problems among male football players: a cluster-randomised controlled trial. Br J Sports Med. 2019;53(3):150. Link
13. Webster KE, Hewett TE. Meta-analysis of meta-analyses of anterior cruciate ligament injury reduction training programs. J Orthop Res. 2018;36(10):2696–2708. Link
14. Hupperets MDW, Verhagen EALM, van Mechelen W. Effect of unsupervised home based proprioceptive training on recurrences of ankle sprain: randomised controlled trial. BMJ. 2009;339:b2684. Link
15. Doherty C, Bleakley C, Delahunt E, Holden S. Treatment and prevention of acute and recurrent ankle sprain: an overview of systematic reviews with meta-analysis. Br J Sports Med. 2017;51(2):113. Link
16. Soligard T, et al. Comprehensive warm-up programme to prevent injuries in young female footballers: cluster randomised controlled trial. BMJ. 2008;337:a2469. Link
17. Byram IR, et al. Preseason shoulder strength measurements in professional baseball pitchers: identifying players at risk for injury. Am J Sports Med. 2010. Link
18. Mullaney M, Nicholas S, Tyler T, Fukunaga T, McHugh M. Evidence based arm care: the Throwers 10 revisited. Int J Sports Phys Ther. 2021;16(6):1379–1386. Link
19. Reinold MM, Wilk KE, Reed J, Crenshaw K, Andrews JR. Interval sport programs: guidelines for baseball, tennis, and golf. J Orthop Sports Phys Ther. 2002;32(6):293–298. Link
20. Grindem H, Snyder-Mackler L, Moksnes H, Engebretsen L, Risberg MA. Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: the Delaware-Oslo ACL cohort study. Br J Sports Med. 2016;50(13):804. Link
21. Kongsgaard M, et al. Corticosteroid injections, eccentric decline squat training and heavy slow resistance training in patellar tendinopathy. Scand J Med Sci Sports. 2009;19(6):790–802. Link
22. Silbernagel KG, Thomeé R, Eriksson BI, Karlsson J. Continued sports activity, using a pain-monitoring model, during rehabilitation in patients with Achilles tendinopathy: a randomized controlled study. Am J Sports Med. 2007;35(6):897–906. Link
23. Hayden JA, et al. Exercise therapy for chronic low back pain. Cochrane Database Syst Rev. 2021;(9):CD009790. Link
24. Nielsen RØ, et al. Excessive progression in weekly running distance and risk of running-related injuries: an association which varies according to type of injury. J Orthop Sports Phys Ther. 2014;44(10):739–747. Link