In conclusion, BFRT protocols benefit from higher occlusion pressure (80 %) when exercising at very low intensities. Conversely, occlusion pressure seems secondary to exercise intensity in more intense (40 % 1-RM) BFRT protocols. Finally, when considering muscle strength, BFRT protocols seem less effective than high-intensity RT.

PurposeThe aim of this study was to retrospectively compile normative data on the anterior cruciate ligament (ACL) in the paediatric population with magnetic resonance imaging, emphasizing the differences between men and women. MethodsIn this retrospective study, musculoskeletal radiologists evaluated length, area, coronal and sagittal inclination of the ACL and inclination of the intercondylar notch. A total of 253 MR examinations (130 males and 123 females between 6 and 18 years of age) were included. The association between measurements, sex and age was considered. Linear and fractional polynomial regression models were used to evaluate the relationships between measurements. ResultsACL length showed significant progressive growth (p < 0.001) with age in men and women, without characterization of growth peaks. ACL area in women showed more pronounced growth up to 11 years, stabilized from 11 to 14 years and then sustained a slight reduction. In men, ACL area showed more pronounced growth up to 12 years, stabilized from 12 to 15 years and then sustained slight reduction. Coronal and sagittal inclination of the ACL showed a significant progressive increase (p < 0.001) with age in both sexes, progressively verticalizing. The intercondylar roof inclination angle showed significant progressive reduction (p < 0.001) with age in both sexes. ConclusionThe area of the ACL does not accompany skeletal maturation, interrupting its growth around 11–12 years. Progressive verticalization of the ACL as well as of the intercondylar notch roof in the evaluated ages was also observed. The clinical relevance of this study is that the ACL presents different angular and morphologic changes during growth in the paediatric population. Since ACL repair is now being performed on younger children, recognition of the normal developmental changes of the ACL is of utmost importance for successful ACL graft placement. Level of evidenceIII.

Background In the pediatric gymnast, stress-related physeal injuries have been well described with characteristic imaging findings. However, a spectrum of overuse injuries, some rarely reported in the literature, can be encountered in the gymnast's hand and wrist. Objective To demonstrate the MR appearance of a spectrum of overuse injuries in the skeletally immature wrist and hand of pediatric gymnasts. Materials and methods A total of 125 MR exams of the hand and wrist in skeletally immature children were performed at our institution during a 2-year period. Clinical histories were reviewed for gymnastics participation. MR studies of that subpopulation were reviewed and abnormalities tabulated. Results Of the MR studies reviewed, ten gymnasts were identified, all girls age 12-16 years (mean age 14.2 years) who presented with wrist or hand pain. Three of these children had bilateral MR exams. Abnormalities included chronic physeal injuries in three children. Two girls exhibited focal lunate osteochondral defects. Triangular fibrocartilage tears were present in three girls, one of whom had a scapholunate ligament tear. Two girls manifested metacarpal head flattening and necrosis. Conclusion A variety of soft-tissue and osseous lesions can be encountered in the skeletally immature gymnast.Familiarity with these stress-related injuries is important for accurate diagnosis.

This study investigated the effects of different reduced strength training (RST) frequencies on half-squat 1 RM and quadriceps cross-sectional area (QCSA). Thirty-three untrained males (24.7 ± 3.9 years; 1.73 ± 0.08 m; 74.6 ± 8.4 kg) underwent a 16-week experimental period (i.e. eight weeks of strength training [ST] followed by additional eight weeks of RST). During the ST period, the participants performed 3-4 sets of 6-12 RM, three sessions/week in half-squat and knee extension exercises. Following ST, the participants were randomly allocated to one of three groups: reduced strength training with one (RST1) or two sessions per week (RST2), and ceased training (CT). Both RST1 and RST2 groups had their training frequency and total training volume-load (i.e. RST1 = 50.3% and RST2 = 57.1%) reduced, while the CT group stopped training completely. Half-squat 1 RM (RST1 = 27.9%; RST2 = 26.7%; and CT = 28.4%) and QCSA (RST1 = 6.1%; RST2 = 6.9%; and CT = 5.8%) increased significantly (p < .05) in all groups after eight weeks of ST. No significant changes were observed in 1 RM and QCSA for RST1 and RST2 groups after the RST period, while the CT group demonstrated a decrease in half-squat 1 RM (22.6%) and QCSA (5.4%) when compared to the ST period (p < .05). In conclusion, different RST frequencies applied were able to maintain muscle mass and strength performance obtained over the regular ST period. Thus, it appears that RST frequency does not affect the maintenance of muscle mass and strength in untrained males, as long as volume-load is equated between frequencies.

This study investigated the effects of non-periodized (NP), traditional periodization (TP) and daily undulating (UP) regimens on muscle strength and hypertrophy in untrained individuals. Thirty-three recreationally active males were randomly divided into four groups: NP: n = 8; TP: n = 9; UP: n = 8 and control group (C): n = 8. Experimental groups underwent a 12-week strength-training program consisting of two sessions per week. Muscle strength and quadriceps cross-sectional area (QCSA) were assessed at baseline, 6-wk (i.e. mid-point) and after 12-wk. All training groups increased squat 1RM from pre to 6-wk mid (NP: 17.02%, TP: 7.7% and UP: 12.9%, p≤0.002) and pre to post 12-wk (NP: 19.5%, TP: 17.9% and UP: 20.4%). TP was the only group that increased squat 1RM from 6-wk mid to 12-wk period (9.4%, p≤0.008). All training groups increased QCSA from pre to 6-wk mid (NP: 5.1%, TP: 4.6% and UP: 5.3%, p≤0.0006) and from pre to post 12-wk (NP: 8.1%, TP: 11.3% and UP: 8.7%). From 6-wk mid to 12-wk period, TP and UP were the only groups that increased QCSA (6.4% and 3.7%, p≤0.02). There were no significant changes for all dependent variables in C group across the time (p≥0.05). In conclusion, our results demonstrated similar training-induced adaptations after 12-wk of NP and periodized regimens. However, our findings suggest that in the latter half of the study (i.e. after the initial 6 weeks), the periodized regimens elicited greater rates of muscular adaptations compared to NP. Strength coaches and practitioners should be aware that periodized regimens might be advantageous at latter stages of training even for untrained individuals.