Tendinous tissue properties after short and long-term functional overload: Differences between controls, 12 weeks and 4 years of resistance training

Aim - The potential for tendinous tissues to adapt to functional overload, especially after several years of exposure to heavy resistance training is largely unexplored. This study compared the morphological and mechanical characteristics of the patellar tendon and knee-extensor tendon-aponeurosis complex between young men exposed to long-term (4 years; n=16), short-term (12 weeks; n=15) and no (untrained controls; n=39) functional overload in the form of heavy resistance training. Methods - Patellar tendon cross-sectional area, vastus-lateralis aponeurosis area and quadriceps femoris volume, plus patellar tendon stiffness and Young's modulus, and tendon-aponeurosis complex stiffness, were quantified with MRI, dynamometry and ultrasonography. Results - As expected long-term trained had greater muscle strength and volume (+58% and +56% vs untrained, both P<0.001), as well as a greater aponeurosis area (+17% vs untrained, P<0.01), but tendon cross-sectional area (mean and regional) was not different between groups. Only long-term trained had reduced patellar tendon elongation/strain over the whole force/stress range, whilst both short-term and long-term overload groups had similarly greater stiffness/Young's modulus at high force/stress (short-term +25/22%, and long-term +17/23% vs untrained; all P<0.05). Tendon-aponeurosis complex stiffness was not different between groups (ANOVA, P = 0.149). Conclusion - Despite large differences in muscle strength and size, years of resistance training did not induce tendon hypertrophy. Both short-term and long-term overload, demonstrated similar increases in high force mechanical and material stiffness, but reduced elongation/strain over the whole force/stress range occurred only after years of overload, indicating a force/strain specific time-course to these adaptations

Comparison of MRI and DXA to measure muscle size and age-related atrophy in thigh muscles.

OBJECTIVES Magnetic resonance imaging (MRI) and dual-energy x-ray absorptiometry (DXA) were used to examine the thigh lean mass in young and old men and women. METHODS A whole-body DXA scan was used to estimate thigh lean mass in young (20 men; 22.4±3.1y; 18 women; 22.1±2.0y) and older adults (25 men; 72.3±4.9y; 28 women; 72.0±4.5y). Thigh lean mass determined with a thigh scan on the DXA or full thigh MRI scans were compared. RESULTS Although the thigh lean mass quantified by DXA and MRI in young and older participants were correlated (R(2)=0.88; p<0.001) the magnitude of the differences in thigh lean mass between young and old was smaller with DXA than MRI (old vs. young men 79.5±13.1% and 73.4±11.2%; old vs. young women 88.6±11.8% and 79.4±12.3%, respectively). Detailed analysis of MRI revealed 30% smaller quadriceps muscles in the older than young individuals, while the other thigh muscles were only 18% smaller. CONCLUSIONS DXA underestimates the age-related loss of thigh muscle mass in comparison to MRI. The quadriceps muscles were more susceptible to age-related atrophy compared with other thigh muscles

Sex differences in muscle morphology of the knee flexors and knee extensors

Introduction Females experience higher risk of anterior cruciate ligament (ACL) injuries; males experience higher risk of hamstring strain injuries. Differences in injury may be partially due to sex differences in knee flexor (KF) to knee extensor (KE) muscle size ratio and the proportional size of constituent muscles. Purpose To compare the absolute and proportional size, and mass distribution, of individual KE and KF muscles, as well as overall size and balance (size ratio) of these muscle groups between the sexes. Methods T1-weighted axial plane MR images (1.5T) of healthy untrained young males and females (32 vs 34) were acquired to determine thigh muscle anatomical cross-sectional area(ACSA). Maximal ACSA (ACSAmax) ofconstituent muscles, summated for KF and KE muscle groups, and the KF:KE ratio were calculated. Results Females had 25.3% smaller KE ACSAmax (70.9±12.1 vs 93.6±10.3 cm2; P<0.001) and 29.6% smaller KF ACSAmax than males (38.8±7.3cm2 vs 55.1±7.3cm2; P<0.001).Consequently, females had lower KF:KE ACSA ratio (P = 0.031). There were sex differences in the proportional size of 2/4 KE and 5/6 KF. In females, vastus lateralis (VL), biceps femoris long-head (BFlh) and semimembranosus (SM) were a greater proportion and sartorius(SA), gracilis (GR) and biceps femoris short-head (BFsh) a smaller proportion of their respective muscle groups compared to males (All P<0.05). Conclusion Sex differences in KF:KE ACSAmax ratio may contribute to increased risk of ACL injury in females. Sex discrepancies in absolute and proportional size of SA, GR, VL and BFlh may contribute further anatomical explanations for sex differences in injury incidence

Low-Intensity Resistance Exercise with Blood Flow Restriction for Patients with Claudication: A Randomised Controlled Feasibility Trial

Background: Claudication is a common and debilitating symptom of peripheral artery disease, resulting in poor exercise performance and quality of life (QoL). Supervised exercise programmes are effective rehabilitation for patients with claudication, but they are poorly adhered in part to high pain and effort associated with walking, aerobic and resistance exercise. Low-intensity resistance exercise with blood flow restriction (BFR) represents an alternative exercise method for individuals who are intolerant to high-intensity protocols. The aim of this study was to evaluate the feasibility of a supervised BFR programme in patients with claudication. Methods: Thirty patients with stable claudication completed an 8-week supervised exercise programme and were randomised to either BFR (n = 15) or a control of matched exercise without BFR (control; n = 15). Feasibility, safety, and efficacy was assessed. Results: All success criteria of feasibility trial were met. Exercise adherence was high (BFR = 78.3%, control = 83.8%), lost to follow-up was 10%, there were no adverse events. Clinical improvement in walking was achieved in 86% of patients in BFR but only 46% of patients in the control. Time to claudication pain during walking increased by 35% for BFR but was unchanged for the control. QoL for BFR showed to have improved mobility, ability to do usual activities, pain, depression, and overall health at follow-up. Conclusion: A supervised BFR programme is feasible in patients with claudication and has potential to increase exercise performance, reduce pain, and improve QoL

Agreement between methods and terminology used to assess the kinematics of the Nordic hamstring exercise

The Nordic hamstring exercise (NHE) is employed as a component of preventative training programmes to minimise hamstring strain injury risk. Variation in the methods and terminology used to assess the NHE makes comparison between studies difficult. We aimed to compare the utility of kinetic and kinematic metrics by comparing several collected concurrently. 18 male recreational rugby union participants completed 3 bilateral NHE repetitions on a hamstring device equipped with in-line strain gauge load cells, integrated with a 3-dimensional motion tracking system. Mean break-point angle occurred after the angle at first acceleration (121.5 ± 10.4° vs. 119.2 ± 7.1°) whereas break-torque angle (BTA) occurred later in the NHE action (126.0 ± 9.8°) showing highest correlation to the angle at greatest acceleration (123.9 ± 7.9°, r = 0.85). Future research should consider movement quality as the angular velocity of the knee joint at BTA demonstrated large variation (range = 3.6–93.4 deg·s1), with high intrasubject variability of relative trunk-to-thigh angle at peak-torque (range = 0.4–44.7°). This study proposes standardisation of methods and terminology used to define the NHE. Measuring BTA is recommended to represent the point at which hamstring muscle failure occurs, specific to the proposed injury mechanism during high-speed running

Comparison of MRI and DXA to measure muscle size and age-related atrophy in thigh muscles

Objectives: Magnetic resonance imaging (MRI) and dual-energy x-ray absorptiometry (DXA) were used to examine the thigh lean mass in young and old men and women. Methods: A whole-body DXA scan was used to estimate thigh lean mass in young (20 men; 22.4±3.1y; 18 women; 22.1±2.0y) and older adults (25 men; 72.3±4.9y; 28 women; 72.0±4.5y). Thigh lean mass deter-mined with a thigh scan on the DXA or full thigh MRI scans were compared. Results: Although the thigh lean mass quantified by DXA and MRI in young and older participants were correlated (R2=0.88; p<0.001) the magnitude of the differences in thigh lean mass between young and old was smaller with DXA than MRI (old vs. young men 79.5±13.1% and 73.4±11.2%; old vs. young women 88.6±11.8% and 79.4±12.3%, respectively). Detailed analysis of MRI revealed 30% smaller quadriceps muscles in the older than young individuals, while the other thigh muscles were only 18% smaller. Conclusions: DXA underestimates the age-related loss of thigh muscle mass in comparison to MRI. The quadriceps muscles were more susceptible to age-related atrophy compared with other thigh muscles

"I want to create so much stimulus that adaptation goes through the roof": High-performance strength coaches' perceptions of planned overreaching

Functional overreaching (FOR) occurs when athletes experience improved athletic capabilities in the days and weeks following short-term periods of increased training demand. However, prolonged high training demand with insufficient recovery may also lead to non-functional overreaching (NFOR) or the overtraining syndrome (OTS). The aim of this research was to explore strength coaches' perceptions and experiences of planned overreaching (POR); short-term periods of increased training demand designed to improve athletic performance. Fourteen high-performance strength coaches (weightlifting; n = 5, powerlifting; n = 4, sprinting; n = 2, throws; n = 2, jumps; n = 1) participated in semistructured interviews. Reflexive thematic analysis identified 3 themes: creating enough challenge, training prescription, and questioning the risk to reward. POR was implemented for a 7 to 14 day training cycle and facilitated through increased daily/weekly training volume and/or training intensity. Participants implemented POR in the weeks (~5–8 weeks) preceding competition to allow sufficient time for performance restoration and improvement to occur. Short-term decreased performance capacity, both during and in the days to weeks following training, was an anticipated by-product of POR, and at times used as a benchmark to confirm that training demand was sufficiently challenging. Some participants chose not to implement POR due to a lack of knowledge, confidence, and/or perceived increased risk of athlete training maladaptation. Additionally, this research highlights the potential dichotomy between POR protocols used by strength coaches to enhance athletic performance and those used for the purpose of inducing training maladaptation for diagnostic identification

Muscle architecture and morphology as determinants of explosive strength

Purpose Neural drive and contractile properties are well-defined physiological determinants of explosive strength, the influence of muscle architecture and related morphology on explosive strength is poorly understood. The aim of this study was to examine the relationships between Quadriceps muscle architecture (pennation angle [ΘP] and fascicle length [FL]) and size (e.g. volume; QVOL), as well as patellar tendon moment arm (PTMA) with voluntary and evoked explosive knee extension torque in 53 recreationally-active young men. Method Following familiarisation, explosive voluntary torque at 50 ms intervals from torque onset (T50, T100, T150), evoked octet at 50 ms (8 pulses at 300-Hz; evoked T50), as well as maximum voluntary torque, were assessed on two occasions with isometric dynamometry. B-mode ultrasound was used to assess ΘP and FL at 10 sites throughout the quadriceps (2-3 sites per constituent muscle. Muscle size (QVOL) and PTMA were quantified using 1.5T MRI. Result There were no relationships with absolute early phase explosive voluntary torque (≤50 ms), but θP (weak), QVOL (moderate to strong) and PTMA (weak) were related to late phase explosive voluntary torque (≥100 ms). Regression analysis revealed only QVOL was an independent variable contributing to the variance in T100 (34%) and T150 (54%). Evoked T50 was also related to QVOL and θP. When explosive strength was expressed relative to MVT there were no relationships observed. Conclusion It’s likely that the weak associations of θP and PTMA with late phase explosive voluntary torque was via their association with MVT/QVOL rather than as a direct determinant

Overreaching and Overtraining in Strength Sports and Resistance Training: A Scoping Review

To date, little is known about overreaching (OR) and the overtraining syndrome (OTS) in strength sports and resistance training (RT) populations. However, the available literature may elucidate the occurrence of both conditions in these populations. A scoping review was conducted. SPORTDiscus, Scopus and Web of Science were searched in a robust and systematic manner, with relevant articles analysed. 1,170 records were retrieved during an initial search, with a total of 47 included in the review. Two broad themes were identified during data extraction: 1) overreaching in strength sports; 2) overreaching and overtraining syndrome in RT. Short-term periods of OR achieved with either high-volume or high-intensity RT can elicit functional OR (FOR) but there is also evidence that chronic high-volume and/or intensity RT can lead to nonfunctional overreaching (NFOR). There is minimal evidence to suggest that true OTS has occurred in strength sports or RT based on the studies entered during this review. More research is needed to develop robust guiding principles for practitioners. Additionally, due to the heterogeneous nature of the existing literature, future research would benefit from the development of practical tools to identify and diagnose the transition from FOR to NFOR, and subsequently OTS in strength athletes and RT populations

Comparative perceptual, affective, and cardiovascular responses between resistance exercise with and without blood flow restriction in older adults

Older adults and patients with chronic disease presenting with muscle weakness or musculoskeletal disorders may benefit from low-load resistance exercise (LLRE) with blood flow restriction (BFR). LLRE-BFR has been shown to increase muscle size, strength, and endurance comparable to traditional resistance exercise but without the use of heavy loads. However, potential negative effects from LLRE-BFR present as a barrier to participation and limit its wider use. This study examined the perceptual, affective, and cardiovascular responses to a bout of LLRE-BFR and compared the responses to LLRE and moderate-load resistance exercise (MLRE). Twenty older adults (64.3 ± 4.2 years) performed LLRE-BFR, LLRE and MLRE consisting of 4 sets of leg press and knee extension, in a randomised crossover design. LLRE-BFR was more demanding than LLRE and MLRE through increased pain (p ≤ 0.024, d = 0.8–1.4) and reduced affect (p ≤ 0.048, d = −0.5–−0.9). Despite this, LLRE-BFR was enjoyed and promoted a positive affective response (p ≤ 0.035, d = 0.5–0.9) following exercise comparable to MLRE. This study supports the use of LLRE-BFR for older adults and encourages future research to examine the safety, acceptability, and efficacy of LLRE-BFR in patients with chronic disease