ECSS Paris 2023: OP-BM16
INTRODUCTION: Single-joint knee extension (KE) and multi-joint leg press (LP) are commonly used as a resistance training exercise for the quadriceps femoris (QF). However, their comparative effectiveness for QF hypertrophy is unclear. Furthermore, although LP can theoretically train multiple muscles at the same time, it is unknown which muscles are trained/hypertrophied by LP. Therefore, this study aimed to compare the hypertrophic effects of KE and LP on QF and other lower-limb muscles. METHODS: Seventeen untrained healthy young adults (11 males and 6 females) performed KE with one leg and LP with the other leg at 50-70% of one repetition maximum (1RM) of the corresponding task. Each leg performed 5 sets of 10 repetitions per session (2 s for each of the concentric/eccentric phases), 2 sessions per week for 12 weeks. Before and after the intervention, T1-weighted axial 3-T MR images (field of view: 275×275 mm, slice thickness & gap: 5 mm) were obtained to assess muscle volume of the individual QF and gluteus muscles, as well as the whole QF, hamstrings (HAM), and adductor muscles (ADD). In a follow-up experiment, electromyograms (EMGs) during KE and LP (10 reps at 50% 1RM) were measured in eleven males from the following muscles: rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), biceps femoris long head (BFL), semitendinosus (ST), and gluteus maximum (G-max). The EMG data were normalized to those obtained during maximal voluntary contraction of each muscle (%EMGmax). RESULTS: After the intervention, muscle volume of each and the whole QF significantly increased in both conditions (P ≤ 0.002), except for the RF of the LP (P = 0.290). The changes were significantly greater for the KE than LP in the RF (+13.2% vs +1.1%) and whole QF (+7.1% vs +4.9%) (P ≤ 0.005), but similar in the vasti muscles between KE and LP (VL: +6.4% vs +6.2%, VM: +7.2% vs +6.0%, vastus intermedius: +5.0% vs +4.4%, P ≥ 0.161). The LP significantly increased muscle volume of the G-max (+13.9%), gluteus medialis (+4.1%), HAM (+3.1%), and ADD (+3.8%) (P ≤ 0.020), while no such significant changes occurred after KE (+0.2%, -0.2%, +1.5%, and -0.5%, respectively, P ≥ 0.064). Changes in total muscle volume of analyzed muscles were significantly lower in KE than LP (+2.8 vs +5.9%, P < 0.001). The EMG analysis showed that %EMGmax values during KE compared to LP were significantly higher in the RF (38.0% vs 21.7%, P < 0.001), similar in the VL (36.9% vs 37.1%) and VM (32.4% vs 35.0%) (P ≥ 0.544), and lower in the BFL (7.3% vs 13.9%), ST (8.1% vs 18.9%), and G-max (8.8% vs 41.2%) (P ≤ 0.003). CONCLUSION: KE is more effective than LP for muscle hypertrophy of the QF, which is attributed to significant and insignificant hypertrophy of the RF after KE and LP, respectively. However, LP can indeed train/hypertrophy multiple lower-limb muscles and therefore can be considered more time-efficient exercise. The unique muscle hypertrophy of both KE and LP can be explained by muscle activity during each exercise.
Read CV Momoka KinoshitaECSS Paris 2023: OP-BM16
INTRODUCTION: Muscle stretching is frequently applied in sports practice, but also in the treatment of joint contractures. The goal of stretching is to lengthen the muscle fibers, but the actual distribution of the imposed strain among the different structures is unknown. Previously, differences in length of in-series sarcomeres within muscle fibers of rat and mouse tibialis anterior (TA) muscle have been reported (Moo et al., 2016; Tijs et al., 2015). The aim of the present study is to investigate how muscle-tendon strain is distributed within the muscle belly of medial gastrocnemius (MG) muscle. METHODS: The hindlimbs of 24 adult male Wistar rats (body mass = 316±5g) were positioned in predefined ankle and knee angles (included angles 55°, 90°, 125°, 160° for both joints) and fixed in a formaldehyde solution. MG muscle was removed and whole muscle fibers were dissected from three regions: proximal, intermediate and distal. Muscle belly and mean sarcomere length were assessed. RESULTS: Increasing knee angle (i.e. extension) and decreasing ankle angle (i.e. dorsiflexion) caused lengthening of MG muscle belly and mean sarcomere length. Length changes were higher in response to changes in ankle angle than to changes in knee angle, in accordance with joint moment arms (Ettema, 1997). Mean sarcomere length did not differ between regions. Also, changes in sarcomere length in response to muscle-tendon lengthening were not different between regions. CONCLUSION: These results indicate that muscle-tendon strain caused by ankle and knee joint rotations was distributed homogeneously within the MG muscle belly. The difference with previous results in a different muscle (TA) suggests that the distribution of muscle-tendon strain is muscle specific. REFERENCES: Ettema, G.J.C., 1997. Gastrocnemius muscle length in relation to knee and ankle joint angles: verification of a geometric model and some applications. The Anatomical Record 247, 1-8. Moo, E.K., Fortuna, R., Sibole, S.C., Abusara, Z., Herzog, W., 2016. In vivo Sarcomere Lengths and Sarcomere Elongations Are Not Uniform across an Intact Muscle. Front Physiol 7, 187. Tijs, C., van Dieen, J.H., Maas, H., 2015. Effects of epimuscular myofascial force transmission on sarcomere length of passive muscles in the rat hindlimb. Physiol Rep 3.
Read CV Huub MaasECSS Paris 2023: OP-BM16
INTRODUCTION: The ability of skeletal muscles to generate force is related to their architectural properties. Plantar flexor muscles are important for running propulsion. In propulsion, sprinters have a shorter time to produce larger forces as compared to distance runners, which may be associated with different muscle architecture in sprinters and distance runners. Although some studies examined plantar flexor architecture in these populations using 2-D ultrasonography, it is likely that more advanced 3-D methods such as diffusion tensor imaging (DTI) allow further insights into architectural differences between these groups. METHODS: In this study, we recruited 15 sprinters and 15 distance runners. To date, data from 9 sprint runners (IAAF score: 977±109, 5 males) and 13 distance runners (IAAF score: 958±125, 10 males) have been processed. 3-D muscle architecture of the plantar flexor muscles was reconstructed by scanning the right leg using T1 and DTI MRI sequences. Muscle segmentation was performed based on the T1 images to establish muscle boundaries and to generate the 3D mesh of the muscles. DTI tractography was used to reconstruct the architecture of the plantar flexor muscles. Muscle volume, fascicle length, pennation angle, and physiological cross-sectional area were estimated for each of the medial and lateral gastrocnemii as well as for four compartments of the soleus muscle. Because data collection is ongoing, statistical analysis has not yet been performed. RESULTS: In medial gastrocnemius, muscle volume (268±52 vs. 273±58 cm3), fascicle length (80.41±13.12 vs. 84.51±14.20 mm), pennation angle (26.27±2.33 vs. 25.34±1.45⁰) and physiological cross-sectional area (36.3±9.3 vs. 35.8±11.3 cm2) were similar between sprint and distance runners. Similarly, no difference between groups were evident in lateral gastrocnemius muscle volume (161±35 vs. 170±31 cm3), fascicle length (72.31±11.85 vs. 73.31±7.79 mm), pennation angle (27.93±3.04 vs. 27.93±3.23⁰) or physiological cross-sectional area (22.4±5.8 vs. 23±3.6 cm2). The total soleus muscle volume (455±118 vs. 456±82 cm3) and average fascicle length (43.8±4.7 vs. 47.6±5.9 mm), pennation angle (32.7±3.9 vs. 31.7±2⁰) and the physiological cross-sectional area (104.9±29.5 vs. 100.3±24.4) were also similar between groups. CONCLUSION: Compared to data on non-trained individuals using DTI MRI(1), gastriconemii fascicles were longer in sprinters and soleus fascicles were shorter in distance runners. Seemingly, there is no obvious difference between sprinters and distance runners in the volume or architecture of plantar flexor muscles. After completing our dataset, further analysis will be performed using statistical shape modeling to test for group effects on regional differences in muscle shape and architecture. REFERENCES: 1) Bolsterlee et al., J. Biomech, 2019
Read CV Bálint KovácsECSS Paris 2023: OP-BM16