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Rehabilitation after anterior cruciate ligament (ACL) reconstruction has focused over the past decade on closed kinetic chain (CKC) exercises due to presumably less strain on the graft than with isokinetic open kinetic chain exercises (OKC); however, recent reports suggest that there are only minor differences in ACL strain values between some CKC and OKC exercises. We studied anterior knee laxity, thigh muscle torque, and return to preinjury sports level in 44 patients with unilateral ACL; group 1 carried out quadriceps strengthening only with CKC while group 2 trained with CKC plus OKC exercises starting from week 6 after surgery. Anterior knee laxity was determined with a KT‐1000 arthrometer; isokinetic concentric and eccentric quadriceps and hamstring muscle torque were studied with a Kin‐Com dynamometer before and 6 months after surgery. At an average of 31 months after surgery the patients answered a questionnaire regarding their current knee function and physical activity/sports to determine the extent and timing of their recovery. No significant differences in anterior knee laxity were noted between the groups 6 months postsurgery. Patients in group 2 increased their quadriceps torque significantly more than those in group 1, but no differences were found in hamstring torque between the groups. A significantly higher number of patients in group 2 (n=12) than in group 1 (n=5) returned to sports at the same level as before the injury (P<0.05). Patients from group 2 who returned to sports at the same level did so 2 months earlier than those in group 1. Thus the addition of OKC quadriceps training after ACL reconstruction results in a significantly better improvement in quadriceps torque without reducing knee joint stability at 6 months and also leads to a significantly higher number of athletes returning to their previous activity earlier and at the same level as before injury.

Background: Knee osteoarthritis is one of the most common musculoskeletal problems in the elderly, characterized by pain, stiffness, and decreased joint function, all of which negatively affect quality of life. Objective: To examine the effect of CKC and OKC exercises on dynamic balance and health status among elderly patients with knee osteoarthritis. Methods: This study employed a quasi-experimental design with a pretest-posttest two-group approach. The sample consisted of 30 elderly individuals aged ≥60 years with a medical diagnosis of knee osteoarthritis, selected using purposive sampling. Respondents were divided into two groups: 15 participants performed CKC exercises and 15 participants performed OKC exercises for two weeks with a frequency of three sessions per week. The Western Ontario and McMaster Osteoarthritis Index (WOMAC) was used to assess health status, and the Time Up and Go Test (TUG) was used to assess dynamic balance. Data were analyzed using paired t-tests with SPSS software. Results: There was a significant reduction in WOMAC scores in both the CKC group (38.47 ± 8.16 to 32.60 ± 9.43; p < 0.001) and the OKC group (37.53 ± 7.97 to 34.40 ± 8.40; p < 0.001). TUG performance also improved significantly in the CKC group (12.80 ± 1.08 to 11.20 ± 1.47; p < 0.001) and the OKC group (12.80 ± 1.21 to 11.27 ± 1.28; p < 0.001). Overall, improvements in health status were greater in the CKC group compared to the OKC group. Conclusion: Both CKC and OKC exercises are effective in improving dynamic balance and health status among elderly patients with knee osteoarthritis. CKC exercises tend to provide greater benefits in overall functional improvement. Antecedentes: La artrosis de rodilla es uno de los problemas musculoesqueléticos más comunes en las personas mayores, caracterizada por dolor, rigidez y disminución de la función articular, lo que afecta negativamente la calidad de vida. Objetivo: Examinar el efecto de los ejercicios en cadena cinética cerrada (CKC) y cadena cinética abierta (OKC) sobre el equilibrio dinámico y el estado de salud en pacientes mayores con artrosis de rodilla. Métodos: Este estudio empleó un diseño cuasi-experimental con un enfoque de pretest-postest en dos grupos. La muestra estuvo compuesta por 30 adultos mayores de ≥60 años con diagnóstico médico de artrosis de rodilla, seleccionados mediante muestreo intencional. Los participantes se dividieron en dos grupos: 15 realizaron ejercicios CKC y 15 realizaron ejercicios OKC durante dos semanas con una frecuencia de tres sesiones por semana. El índice de osteoartritis de Western Ontario y McMaster (WOMAC) se utilizó para evaluar el estado de salud, y la prueba Time Up and Go (TUG) se empleó para evaluar el equilibrio dinámico. Los datos se analizaron mediante pruebas t pareadas utilizando el software SPSS. Resultados: Se observó una reducción significativa en los puntajes WOMAC tanto en el grupo CKC (de 38.47 ± 8.16 a 32.60 ± 9.43; p < 0.001) como en el grupo OKC (de 37.53 ± 7.97 a 34.40 ± 8.40; p < 0.001). El desempeño en la prueba TUG también mejoró significativamente en el grupo CKC (de 12.80 ± 1.08 a 11.20 ± 1.47; p < 0.001) y en el grupo OKC (de 12.80 ± 1.21 a 11.27 ± 1.28; p < 0.001). En general, las mejoras en el estado de salud fueron mayores en el grupo CKC en comparación con el grupo OKC. Conclusión: Tanto los ejercicios CKC como OKC son efectivos para mejorar el equilibrio dinámico y el estado de salud en pacientes mayores con artrosis de rodilla. Los ejercicios CKC tienden a proporcionar mayores beneficios en la mejora funcional general. Introdução: A osteoartrose do joelho é um dos problemas músculo-esqueléticos mais comuns nos idosos, caracterizada por dor, rigidez e diminuição da função articular, o que impacta negativamente a qualidade de vida. Objectivo: Examinar o efeito dos exercícios em cadeia cinética fechada (CCF) e em cadeia cinética aberta (CCA) no equilíbrio dinâmico e no estado de saúde em doentes idosos com osteoartrose do joelho. Métodos: Este estudo utilizou um desenho quase experimental com uma abordagem pré-teste-pós-teste em dois grupos. A amostra foi constituída por 30 idosos com idade ≥60 anos e diagnóstico médico de osteoartrose do joelho, selecionados por amostragem intencional. Os participantes foram divididos em dois grupos: 15 realizaram exercícios em CCF e 15 realizaram exercícios em CCA durante duas semanas, com uma frequência de três sessões por semana. O Índice de Osteoartrite Western Ontario-McMaster (WOMAC) foi utilizado para avaliar o estado de saúde, e o teste Time Up and Go (TUG) foi utilizado para avaliar o equilíbrio dinâmico. Os dados foram analisados ​​através de testes t emparelhados, utilizando o software SPSS. Resultados: Observou-se uma redução significativa dos scores do WOMAC tanto no grupo CKC (de 38,47 ± 8,16 para 32,60 ± 9,43; p < 0,001) como no grupo OKC (de 37,53 ± 7,97 para 34,40 ± 8,40; p < 0,001). O desempenho no teste TUG também melhorou significativamente no grupo CKC (de 12,80 ± 1,08 para 11,20 ± 1,47; p < 0,001) e no grupo OKC (de 12,80 ± 1,21 para 11,27 ± 1,28; p < 0,001). No geral, as melhorias no estado de saúde foram maiores no grupo CKC em comparação com o grupo OKC. Conclusão: Tanto os exercícios CKC como OKC são eficazes na melhoria do equilíbrio dinâmico e do estado de saúde em doentes idosos com OA do joelho. Os exercícios CKC tendem a proporcionar maiores benefícios na melhoria funcional global.

Knee extensor resistance training using open kinetic chain (OKC) exercise for patients recovering from anterior cruciate ligament reconstruction (ACLR) surgery has lost favour mainly because of research indicating that OKC exercise causes greater ACL strain than closed kinetic chain (CKC) exercise. In this prospective, randomized clinical trial the effects of these two regimes on knee laxity were compared in the early period after ACLR surgery. Thirty‐six patients recovering from ACLR surgery (29 males, 7 females; age mean=30) were tested at 2 and 6 weeks after ACLR with knee laxity measured using the Knee Signature System arthrometer. Between tests subjects trained using either OKC or CKC resistance of their knee and hip extensors in formal physical therapy sessions three times per week. Following adjustment for site of treatment, pretraining injured knee laxity, and untreated knee laxity at post‐training, the use of OKC exercise, when compared to CKC exercise, was found to lead to a 9% increase in looseness with a 95% confidence interval of –8% to +29%. These results indicate that the great concern about the safety of OKC knee extensor training in the early period after ACLR surgery may not be well founded.

To determine whether quadriceps and hamstring strengthening in a rehabilitation program involving early open kinetic chain (OKC) and/or closed kinetic chain (CKC) knee joint exercises had an influence on graft laxity at 1, 3, and 6 months after anterior cruciate ligament reconstruction (ACLR). Retrospective study. Two groups (n = 53) of ACLR patients (combination of OKC and CKC exercises group compared to a CKC exercise group) were recruited. OKC protocol was introduced at 2 weeks post-operatively without external resistance and progressed at 4 weeks with load. Comparative ACL graft laxity measurement and isokinetic strength testing were prospectively performed up to 6 months in both groups. No significant differences were observed in the knee laxity at 1 (p = 0.263), 3 (p = 0.263), and 6 months (p = 0.256) follow up between the groups. Similarly, no significant results were observed in within-group knee laxity between 1 and 6 months after ACLR in the intervention (p = 0.155) and control group (p = 0.690). The early initiation of OKC along with CKC exercises doesn't seem to increase the ACLR graft laxity as compared to a rehabilitation program with only CKC exercises. •Early OKC can be used in full ROM and seems to be safe•Early OKC following specific inclusion criteria did not show any complications•Early high volume training should be introduced with OKC and CKC after surgery•Early high volume training seems to be safe

Trampoline bounces are performed on a bed of a jumping surface that is stretched over the trampoline apparatus. The jumping motion is divided into a descent phase, i.e., from the landing to the maximum depth, and an ascent phase, from the maximum depth to the takeoff. Most studies on muscle activity during jumping have investigated muscle activity during the same phase between groups or between landing and release; however, no studies have investigated muscle activity between phases. Therefore, this study aimed to investigate muscle activity during the descent and ascent phases and obtain basic data on the jumping motion. For the trials, participants were instructed to perform 15 consecutive jumps on the trampoline bed from a standing still position, as high as possible, straight and straight up in the center of the trampoline bed. The muscle activities of the rectus femoris, tibialis anterior, and lateral gastrocnemius revealed significant increases and larger effect sizes in the descent phase than in the ascent phase (p < 0.01). The muscle activities of the sternocleidomastoid, trapezius, and biceps femoris demonstrated significant increases and medium effect sizes in the descent phase in contrast to the ascent phase (p < 0.01). Pushing down the bed by the muscular activity of the lower extremities is most pursued in the descent phase. Then, participants maintain a straight vertical posture for the body to receive the rebound force from the maximum depth of the bed. This suggests that the sternocleidomastoid and trapezius muscles were significantly active in controlling the head position. A high jump is achieved by pushing the bed down for a deep descent and maintaining a straight posture at the maximum depth. The elastic bed is similar to an Open Kinetic Chain in the descent phase because the load incrementally increases, and to a Closed Kinetic Chain in the ascent phase because the load begins at the maximum depth of the bed. Separating the elements of the jumping motion required in the descent and ascent phases is important in athletic training

Closed kinetic chain (CKC) exercises are the gold standard for rehabilitation after anterior cruciate ligament reconstruction (ACL-R). Open kinetic chain (OKC) exercises may provide benefits, but their use in the early stages remains controversial. To determine the effect of OKC exercises during the first weeks of rehabilitation after ACL-R. Systematic review and meta-analysis. A comprehensive literature search was conducted according to PRISMA guidelines from inception to April 2024. The methodological quality of the included studies was assessed using the ROBINS I and RoB-2 tools. The changes in outcomes from pre-to post-intervention were quantified using standardized mean differences. Overall, the methodological quality was low and the population, intervention, comparison, outcome, time (PICOT) criteria were heterogeneous. However, OKC was found to have beneficial effects on patient reported outcomes (PROMs), strength, function, and return to play, especially when performed at least four weeks after surgery in rehabilitation programs that began with CKC exercises. The evidence suggests that OKC exercises may provide benefits and no adverse effects in the early stages of rehabilitation after ACL-R, particularly when initiated after CKC exercises. These findings are consistent with current clinical practice guideline recommendations for the inclusion of OKC in rehabilitation programs. •High study heterogeneity limits strong conclusions and recommendations about early OKC in ACL-R rehabilitation•OKC benefits PROMs, knee flexor and extensor strength, and return to play•Early OKC (<4 weeks, 90-30° knee flexion ROM) may increase knee laxity but not graft failure•Best results were seen when OKC was introduced 4–6 weeks after ACL surgery•Standardized research on OKC progression, loads, and graft types is needed

Background: Open kinetic chain (OKC) exercise is an effective method to improve muscle function during rehabilitation after anterior cruciate ligament reconstruction (ACLR); however, there is controversy about its use in the early phase of rehabilitation. Purpose: To determine (1) whether the use of OKC and closed kinetic chain (CKC) exercises improves quadriceps and hamstring strength in the early phase of rehabilitation after ACLR and (2) whether the early use of OKC exercise affects graft laxity at 3 and 6 months postoperatively in patients with a hamstring tendon graft. Study Design: Cohort study; Level of evidence, 3. Methods: This study included an intervention group that underwent OKC + CKC exercises (n = 51) and a control group that underwent CKC exercise only (n = 52). In the intervention group, OKC exercise for the quadriceps and hamstring was started at 4 weeks after ACLR. At 3 and 6 months postoperatively, isokinetic testing was performed to calculate the limb symmetry index (LSI) and the peak torque to body weight ratio (PT/BW) for the quadriceps and hamstring. Anterior knee laxity was measured by an arthrometer. Results: At 3 and 6 months postoperatively, quadriceps strength was higher in the intervention group than in the control group for the LSI (3 months: 76.14% ± 0.22% vs 46.91% ± 0.21%, respectively; 6 months: 91.05% ± 0.18% vs 61.80% ± 0.26%, respectively; P < .001 for both) and PT/BW (3 months: 1.81 ± 0.75 vs 0.85 ± 0.50 N·m/kg, respectively; 6 months: 2.40 ± 0.73 vs 1.39 ± 0.70 N·m/kg, respectively; P < .001 for both). There were similar findings regarding hamstring strength for the LSI (3 months: 86.13% ± 0.22% vs 64.26% ± 0.26%, respectively; 6 months: 91.90% ± 0.17% vs 82.42% ± 0.24%, respectively; P < .001 at three months, P = .024 at 6 months) and PT/BW (3 months: 1.09 ± 0.36 vs 0.67 ± 0.39 N·m/kg, respectively; 6 months: 1.42 ± 0.41 vs 1.07 ± 0.39 N·m/kg, respectively; P < .001 for both). No significant difference in laxity was observed between the intervention and control groups at 3 or 6 months. Conclusion: Early use of OKC exercise for both the quadriceps and the hamstring, in addition to conventional CKC exercise, resulted in better correction of quadriceps and hamstring strength deficits without increasing graft laxity.

Background: Hamstring tendon autografts are frequently used for anterior cruciate ligament reconstruction (ACLR), but they are associated with persistent hamstring strength deficits and delayed functional recovery. Current rehabilitation guidelines often delay open kinetic chain (OKC) hamstring exercises due to safety concerns, despite the limited supporting evidence. This uncontrolled, underpowered, and exploratory study aimed to evaluate the safety and effectiveness of introducing OKC hamstring strengthening exercises as early as three weeks after ACLR. Methods: An exploratory retrospective observational study was conducted at a single physiotherapy center on 13 patients (aged 18–35) who underwent primary ACLR with semitendinosus–gracilis grafts. Participants followed a standardized rehabilitation program including isometric leg curls at 60° and 90° knee flexion and long-lever glute bridges twice weekly, starting from postoperative week 3. Safety was assessed through predefined “safety flags” (pain > 4/10, hematoma, clinical hamstring strain). Strength outcomes, including isometric knee flexion strength at 60° and 90°, limb symmetry index (LSI), and endurance tests, were assessed at 6 and 12 weeks. Results: All participants completed the program without major adverse events. Pain remained consistently low (median 2.5/10), with only one transient episode exceeding the threshold. No other complications were recorded. Isometric knee flexion strength significantly improved between week 6 and week 12 at both 60° (p = 0.018) and 90° (p = 0.003), with large effect sizes. LSI at 90° also increased significantly (p = 0.006), whereas improvements at 60° did not reach significance. Endurance testing showed functional gains as early as 6 weeks. Conclusions: The early introduction of OKC hamstring strengthening exercises three weeks after ACLR with hamstring autografts appears safe and promotes clinically meaningful improvements in strength and endurance. These findings, while from a small uncontrolled study, challenge conservative rehabilitation protocols and support the reconsideration of early hamstring loading. Given the retrospective, uncontrolled, and underpowered design, these findings are hypothesis-generating and not generalizable beyond young adults with hamstring autografts; larger randomized trials are required.

Background After an anterior cruciate ligament reconstruction (ACLR), mounting evidence suggests that open kinetic chain (OKC) strengthening is safe, reduces the risk of anterior knee pain, and significantly improves the quadriceps strength. However, clinicians are reluctant to use OKC knee strengthening exercises mainly due to the strong beliefs that they might increase graft laxity. The objective of this scoping review is to identify the key criteria employed in the scientific literature for the safe introduction of OKC quadriceps strengthening following ACLR. Methods A scoping review of the literature was conducted on the online databases MEDLINE (PubMed), ScienceDirect, Embase and CINAHL Library online. Data regarding time-based criteria and/or clinical based criteria allowing OKC exercises introduction following ACLR were searched for. Only studies involving patients who performed quadriceps strengthening using any type of OKC exercises were included, regardless of the type, resistance location, load magnitude, type of muscle contraction, knee range of motion, or duration of the strengthening protocol. Results Twenty-six studies met the inclusion criteria. Twenty-one employed time-based criteria for the introduction of OKC exercise. The median time from when OKC was permitted was 15 postoperative days (range 1–270 days), while the mean time was 31.6 ± 56.7 postoperative days. In 30.7% of the studies additional clinical examination components were used. These components included range of motion (0-100°), numeric pain scale score < 2 or 3, absence of joint effusion (assess by the stroke test), full knee active extension (assess by the straight leg raise), and walking without crutches for the decision-making regarding OKC exercise introduction. Conclusion Less than one study in 3 reported clinical criteria for the introduction of OKC exercise. This highlights the absence of consensus among surgeons and physiotherapists, thereby hindering their ability to make informed decisions based on scientific evidence. Although the use of OKC exercise appears to be safe, precautions to maintain the integrity of the surgical repair need to be implemented. The establishment of valid criteria is crucial to support evidence-based decision-making. Key Points Open kinetic chain (OKC) exercises are generally safe and can significantly improve quadriceps strength without increasing the risk of graft laxity after anterior cruciate ligament reconstruction (ACLR). The majority of studies (80.7%) used time-based criteria for introducing OKC exercises, with a median time of 15 postoperative days. Combining clinical and temporal criteria ensures safe and effective integration of OKC exercises in ACLR rehabilitation.

Hop tests are functional tests that reportedly require strength, power, and postural stability to perform. The extent to which a triple-hop distance (THD) test measures each of these characteristics is relatively unknown. To determine the extent to which the THD predicts performance on clinical measures of power, strength, and balance in athletic individuals. Within-subjects correlational study. Station-based, preseason screening of athletes. Forty National Collegiate Athletic Association Division I-AA men's and women's soccer student-athletes (20 women, 20 men; age = 20.0 +/- 1.4 years, height = 172.8 +/- 9.2 cm, mass = 71.9 +/- 8.9 kg). As part of a comprehensive preseason screening of athletes, participants completed the Balance Error Scoring System (BESS) test, 3 trials each of the THD and vertical jump, and 5 repetitions each of concentric isokinetic quadriceps and hamstrings strength testing at 60 degrees /s and 180 degrees /s. Bivariate correlations and linear regression analyses determined the extent to which THD (cm) predicted each of the strength, power, and balance measures. Maximal vertical jump height (cm), total BESS error scores, and quadriceps (Quad(60), Quad(180)) and hamstrings (Ham(60), Ham(180)) isokinetic maximum peak torque (Nm) at 60 degrees /s and 180 degrees /s, respectively. Triple-hop distance was a strong predictor of vertical jump height, explaining 69.5% of the variance (P < .01). THD also predicted 56.7% of the variance in Ham(60) (P < .01), 55.5% of the variance in Ham(180) (P < .01), 49.0% of the variance in Quad(60) (P < .01), and 58.8% of the variance in Quad(180) (P < .01). No relationships between THD and BESS scores were noted. Triple-hop distance is a useful clinical test to predict an athlete's lower extremity strength and power. Although THD was not a predictor of static balance, further research is needed to examine its relationship with more dynamic balance tests.