Fascicle length of leg muscles is greater in sprinters than distance runners. (2000).
PURPOSE: The purpose of this study was to compare architectural characteristics of leg muscles of sprinters and distance runners. METHODS: Skeletal muscle architectural characteristics were studied in 23 elite male 100-m sprinters (SPR, 10.0-10.9 s for 100 m), 24 elite male distance runners (DR, 13.5-14.5 min for 5000 m), and 24 untrained male controls. Fascicle pennation angle and isolated muscle thickness of the vastus lateralis and gastrocnemius medialis and lateralis muscles were measured in vivo by ultrasound, and fascicle length was estimated. RESULTS: Standing height and upper and lower limb lengths were similar among the groups. Body weight was significantly greater in SPR than in either DR or controls, which were similar. Muscle thickness of the vastus lateralis and gastrocnemius medialis and lateralis muscles was significantly greater in SPR than in either DR or controls, which were similar. In all muscles, pennation angle was similar between SPR and controls, but less than DR. Fascicle length of the vastus lateralis muscle (absolute and relative to limb length) was greatest in SPR and least in DR with control values being between the athlete groups. Fascicle length of the gastrocnemius medialis muscle (absolute and relative to limb length) was greater in SPR than in either DR or controls, which were similar. Fascicle length of the gastrocnemius lateralis muscle (absolute and relative to limb length) was significantly greater in SPR than DR. Absolute fascicle length in gastrocnemius lateralis muscle was similar between DR and controls; however, relative to limb length DR was significantly less. CONCLUSION: Greater fascicle length and lesser pennation angle observed in leg muscles of SPR, compared with DR, would appear to favor shortening velocity as required for greater running speed.
Sprint performance is related to muscle fascicle length in male 100-m sprinters. (2000).
The purpose of this study was to investigate the relationship between muscle fascicle length and sprint running performance in 37 male 100-m sprinters. The sample was divided into two performance groups by the personal-best 100-m time: 10.00-10.90 s (S10; n = 22) and 11.00-11.70 s (S11; n = 15). Muscle thickness and fascicle pennation angle of the vastus lateralis and gastrocnemius medialis and lateralis muscles were measured by B-mode ultrasonography, and fascicle length was estimated. Standing height, body weight, and leg length were similar between groups. Muscle thickness was similar between groups for vastus lateralis and gastrocnemius medialis, but S10 had a significantly greater gastrocnemius lateralis muscle thickness. S10 also had a greater muscle thickness in the upper portion of the thigh, which, given similar limb lengths, demonstrates an altered "muscle shape." Pennation angle was always less in S10 than in S11. In all muscles, S10 had significantly greater fascicle length than did S11, which significantly correlated with 100-m best performance (r values from -0.40 to -0.57). It is concluded that longer fascicle length is associated with greater sprinting performance.
Effects of physical training and detraining, immobilisation, growth and aging on human fascicle geometry. (2006).
In addition to its size and the extent of its neural activation, a muscle's geometry (the angles and lengths of its fibres or fascicles) strongly influences its force production characteristics. As with many other tissues within the body, muscle displays significant plasticity in its geometry. This review summarises geometric differences between various athlete populations and describes research examining the plasticity of muscle geometry with physical training, immobilisation/detraining, growth and aging. Typically, heavy resistance training in young adults has been shown to cause significant increases in fascicle angle of vastus lateralis and triceps brachii as measured by ultrasonography, while high-speed/plyometrics training in the absence of weight training has been associated with increases in fascicle length and a reduction in angles of vastus lateralis fascicles. These changes indicate that differences in geometry between various athletic populations might be at least partly attributable to their differing training regimes. Despite some inter-muscular differences, detraining/unloading is associated with decreases in fascicle angle, although little change was shown in muscles such as vastus lateralis and triceps brachii in studies examining the effects of prolonged bed rest. No research has examined the effects of other interventions such as endurance or chronic stretching training. Few data exist describing geometric adaptation during growth and maturation, although increases in gastrocnemius fascicle angle and length seem to occur until maturation in late adolescence. Although some evidence suggests that a decrease in both fascicle angle and length accompanies the normal aging process, there is a paucity of data examining the issue; heavy weight training might attenuate the decline, at least in fascicle length. A significant research effort is required to more fully understand geometric adaptation in response to physical training, immobilisation/detraining, growth and aging.
Effects of dynamic resistance training on fascicle length and isometric strength. (2006).
The aims of this study were to assess changes in muscle architecture, isometric and dynamic strength of the leg extensor muscles, resulting from dynamic resistance training, and the relationships between strength and muscle architecture variables. The participants (n = 30) were randomly assigned to one of two groups. The training group (n = 16; age 21.8 +/- 2.3 years, body mass 74.8 +/- 9.2 kg, height 1.75 +/- 0.08 m) performed dynamic resistance training for 13 weeks. The control group (n = 14; age 19.9 +/- 1.5 years, body mass 74.0 +/- 8.5 kg, height 1.76 +/- 0.05 m) did not perform any resistance training. Maximal dynamic and isometric strength were tested in both groups, before and after the training period. The members of the training group used the free-weight squat lift (90 degrees ) as their training exercise. The concentric phase of the squat was performed explosively. Skeletal muscle architecture of the vastus lateralis was visualized using ultrasonography. At the end of the study, significant increases in vastus lateralis muscle thickness (+6.9%, P < 0.001), fascicle length (+10.3%, P < 0.05), one-repetition maximum (+8.2%, P < 0.05), rate of force development (+23.8%, P < 0.05) and average force produced in the first 500 ms (+11.7%, P < 0.05) were seen only in the training group. Adaptations to the muscle architecture in the training group limited the loss of fibre force, and improved the capacity for developing higher velocities of contraction. The architectural changes in the training group were similar to those seen in studies where high-speed training was performed. In conclusion, dynamic resistance training with light loads leads to increases in muscle thickness and fascicle length, which might be related to a more efficient transmission of fibre force to the tendon.
Adaptation to chronic eccentric exercise in humans: the influence of contraction velocity. (2001).
We compared changes in muscle fibre composition and muscle strength indices following a 10 week isokinetic resistance training programme consisting of fast (3.14 rad x s(-1)) or slow (0.52 rad x s(-1)) velocity eccentric muscle contractions. A group of 20 non-resistance trained subjects were assigned to a FAST (n = 7), SLOW (n = 6) or non-training CONTROL (n = 7) group. A unilateral training protocol targeted the elbow flexor muscle group and consisted of 24 maximal eccentric isokinetic contractions (four sets of six repetitions) performed three times a week for 10 weeks. Muscle biopsy samples were obtained from the belly of the biceps brachii. Isometric torque and concentric and eccentric torque at 0.52 and 3.14 rad x s(-1) were examined at 0, 5 and 10 weeks. After 10 weeks, the FAST group demonstrated significant [mean (SEM)] increases in eccentric [29.6 (6.4)%] and concentric torque [27.4 (7.3)%] at 3.14 rad x s(-1), isometric torque [21.3 (4.3)%] and eccentric torque [25.2 (7.2)%] at 0.52 rad x s(-1). The percentage of type I fibres in the FAST group decreased from [53.8 (6.6)% to 39.1 (4.4)%] while type IIb fibre percentage increased from [5.8 (1.9)% to 12.9 (3.3)%; P < 0.05]. In contrast, the SLOW group did not experience significant changes in muscle fibre type or muscle torque. We conclude that neuromuscular adaptations to eccentric training stimuli may be influenced by differences in the ability to cope with chronic exposure to relatively fast and slow eccentric contraction velocities. Possible mechanisms include greater cumulative damage to contractile tissues or stress induced by slow eccentric muscle contractions.
Changes in muscle strength, muscle fibre size and myofibrillar gene expression after immobilization and retraining in humans. (2000).
Changes in muscle strength, vastus lateralis fibre characteristics and myosin heavy-chain (MyoHC) gene expression were examined in 48 men and women following 3 weeks of knee immobilization and after 12 weeks of retraining with 1866 eccentric, concentric or mixed contractions. 2. Immobilization reduced eccentric, concentric and isometric strength by 47 %. After 2 weeks of spontaneous recovery there still was an average strength deficit of 11 %. With eccentric and mixed compared with concentric retraining the rate of strength recovery was faster and the eccentric and isometric strength gains greater. 3. Immobilization reduced type I, IIa and IIx muscle fibre areas by 13, 10 and 10 %, respectively and after 2 weeks of spontaneous recovery from immobilization these fibres were 5 % smaller than at baseline. Hypertrophy of type I, IIa and IIx fibres relative to baseline was 10, 16 and 16 % after eccentric and 11, 9 and 10 % after mixed training (all P < 0.05), exceeding the 4, 5 and 5 % gains after concentric training. Type IIa and IIx fibre enlargements were greatest after eccentric training. 4. Total RNA/wet muscle weight and ty I, IIa and IIx MyoHC mRNA levels did not change differently after immobilization and retraining. Immobilization downregulated the expression of type I MyoHC mRNA to 0.72-fold of baseline and exercise training upregulated it to 0.95 of baseline. No changes occurred in type IIa MyoHC mRNA. Immobilization and exercise training upregulated type IIx MyoHC mRNA 2.9-fold and 1.2-fold, respectively. For the immobilization segment, type I, IIa and IIx fibre area and type I, IIa and IIx MyoHC mRNA correlated (r = 0.66, r = 0.07 and r = -0.71, respectively). 5. The present data underscore the role muscle lengthening plays in human neuromuscular function and adaptation.
Electromyostimulation training effects on neural drive and muscle architecture. (2005).
PURPOSE: The purpose of the study was to investigate the effect of 4 and 8 wk of electromyostimulation (EMS) training on both muscular and neural adaptations of the knee extensor muscles. METHODS: Twenty males were divided into the electrostimulated group (EG, N = 12) and the control group (CG, N =
. The training program consisted of 32 sessions of isometric EMS over an 8-wk period. All subjects were tested at baseline (B) and retested after 4 (WK4) and 8 (WK8) wk of EMS training. The EMG activity and muscle activation obtained under maximal voluntary contractions (MVC) was used to assess neural adaptations. Torque and EMG responses obtained under electrically evoked contractions, muscle anatomical cross-sectional area (ACSA), and vastus lateralis (VL) pennation angle, both measured by ultrasonography imaging, were examined to analyze muscular changes. RESULTS: At WK8, knee extensor MVC significantly increased by 27% (P < 0.001) and was accompanied by an increase in muscle activation (+6%, P < 0.01), quadriceps muscle ACSA (+6%, P < 0.001), and VL pennation angle (+14%, P < 0.001). A significant increase in normalized EMG activity of both VL and vastus medialis (VM) muscles (+69 and +39%, respectively, P < 0.001) but not of rectus femoris (RF) muscle was also found at WK8. The ACSA of the VL, VM, and vastus intermedius muscles significantly increased at WK8 (5-8%, P < 0.001) but not at WK4, whereas no changes occurred in the RF muscle. CONCLUSION: We concluded that the voluntary torque gains obtained after EMS training could be attributed to both muscular and neural adaptations. Both changes selectively involved the monoarticular vastii muscles.
Differential Adaptations to Eccentric versus Conventional Resistance Training in Older Humans. (2009).
We hypothesised that training with eccentric contractions only (therefore utilising higher loads) would yield greater muscle structural and strength gains compared to conventional resistance training. Nine older adults (mean +/- SD age: 74 +/- 3 years) were assigned to a conventional (CONV) resistance training group performing both concentric and eccentric contractions and 10 (age: 67 +/- 2 years) to an eccentric-only (ECC) resistance training group. Both groups trained 3 times per week for 14 weeks at 80% of the 5-repetition maximum, specific to each training mode. Maximum knee extensor torque was assessed during isometric, concentric and eccentric contractions across a range of angular velocities (0-3.49 rad.(-1)). Vastus lateralis muscle architecture (fascicle length, pennation angle and muscle thickness) was assessed in vivo at rest using ultrasonography. Training increased fascicle length in both groups, but the increase was significantly greater in the ECC (20% increase) than the CONV (8% increase) group. Conversely, pennation angle significantly increased in the CONV (35%), but not in the ECC (5%) group. Muscle thickness increased to a similar extent in both groups (~12%). In the ECC group, eccentric knee extensor torque increased by 9-17% across velocities, but concentric torque was unchanged. Conversely, in the CONV group, concentric torque increased by 22-37% across velocities, but eccentric torque was unchanged. Instead, isometric torque increased similarly in both groups (~8%). Thus, the two training regimens resulted in differential adaptations in muscle architecture and strength. These results suggest the stimulus for adding sarcomeres in-series and in-parallel may be different, which implies different myogenic responses induced by the two different training methods.
Effects of eccentric strength training on biceps femoris muscle architecture and knee joint range of movement. (2009).
The aim was to determine whether eccentric strengthening changed the muscle architecture of human biceps femoris and consequently, knee range of motion. Twenty-two subjects were randomly assigned to control and experimental groups. The experimental group completed an eccentric strengthening programme for 8 weeks. Outcome measures included hamstring muscle strength (one repetition maximum), the passive knee extension test (PKE) (knee joint angle at which the onset of passive tension occurs), fascicle length (FL) and pennation angle (PA). One repetition maximum increased by 34% (P < 0.01), the PKE test revealed a 5% increase in joint range of motion (P = 0.01), FL increased by 34% (P = 0.01) and PA did not change (P = 0.38). This is the first report of an increase in FL in the biceps femoris following eccentric resistance training. In addition, the results might imply that this fascicle lengthening could lead to an increase in the range of motion of the knee. Clinical implications for rehabilitation and injury prevention are discussed.
Differential serial sarcomere number adaptations in knee extensor muscles of rats is contraction type dependent. (2005).
Sarcomerogenesis, or the addition of sarcomeres in series within a fiber, has a profound impact on the performance of a muscle by increasing its contractile velocity and power. Sarcomerogenesis may provide a beneficial adaptation to prevent injury when a muscle consistently works at long lengths, accounting for the repeated-bout effect. The association between eccentric exercise, sarcomerogenesis and the repeated-bout effect has been proposed to depend on damage, where regeneration allows sarcomeres to work at shorter lengths for a given muscle-tendon unit length. To gain additional insight into this phenomenon, we measured fiber dynamics directly in the vastus lateralis (VL) muscle of rats during uphill and downhill walking, and we measured serial sarcomere number in the VL and vastus intermedius (VI) after chronic training on either a decline or incline grade. We found that the knee extensor muscles of uphill walking rats undergo repeated active concentric contractions, and therefore they suffer no contraction-induced injury. Conversely, the knee extensor muscles during downhill walking undergo repeated active eccentric contractions. Serial sarcomere numbers change differently for the uphill and downhill exercise groups, and for the VL and VI muscles. Short muscle lengths for uphill concentric-biased contractions result in a loss of serial sarcomeres, and long muscle lengths for downhill eccentric-biased contractions result in a gain of serial sarcomeres.
