Effects of intensity and duration of exercise on muscular responses to training of thoroughbred racehorses

This study examined the effects of the intensity and duration of exercise on the nature and magnitude of training adaptations in muscle of adolescent (2–3 yr old) racehorses. Six thoroughbreds that had been pretrained for 2 mo performed six consecutive conditioning programs of varying lactate-guided intensities [velocities eliciting blood lactate concentrations of 2.5 mmol/l (v2.5) and 4 mmol/l (v4), respectively] and durations (5, 15, 25 min). Pre- and posttraining gluteus muscle biopsies were analyzed for myosin heavy chain content, fiber-type composition, fiber size, capillarization, and fiber histochemical oxidative and glycolytic capabilities. Although training adaptations were similar in nature, they varied greatly in magnitude among the different training protocols. Overall, the use of v4 as the exercise intensity for 25 min elicited the most consistent training adaptations in muscle, whereas the minimal training stimulus that evoked any significant change was identified with exercises of 15 min at v2.5. Within this range, muscular adaptations showed significant trends to be proportional to the exercise load of specific training programs. Taken together, these data suggest that muscular adaptations to training in horses occur on a continuum that is based on the exercise intensity and duration of training. The practical implications of this study are that exercises for 15 to 25 min/day at velocities between v2.5 and v4 can improve in the short term (3 wk) the muscular stamina in thoroughbreds. However, exercises of 5–15 min at v4 are necessary to enhance muscular features related to strength (hypertrophy).

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Energy-rich phosphates in slow and fast human skeletal muscle

AJP Cell Physiology ◽

10.1152/ajpcell.1995.268.4.c869 ◽

1995 ◽

Vol 268 (4) ◽

pp. C869-C876 ◽

Cited By ~ 53

Author(s):

K. Vandenborne ◽

G. Walter ◽

L. Ploutz-Snyder ◽

R. Staron ◽

A. Fry ◽

...

Keyword(s):

Skeletal Muscle ◽

Human Skeletal Muscle ◽

Fiber Type ◽

Phosphate Content ◽

Lateral Gastrocnemius ◽

Fiber Type Composition ◽

Type Composition ◽

Slow Twitch ◽

Gastrocnemius Muscles ◽

Muscle Biopsies

We investigated the relationship between energy-rich phosphate content and muscle fiber-type composition in human skeletal muscle using a combination of 31P-nuclear magnetic resonance spectroscopy (NMR), histochemical, and biochemical analyses of muscle biopsies. Localized 31P spectra were collected simultaneously from the predominantly slow-twitch soleus muscle and the mixed (fast-twitch and slow-twitch) medial and lateral gastrocnemius muscles, using B1-insensitive Hadamard Spectroscopic Imaging. Biopsy samples were taken from the soleus and lateral gastrocnemius muscles before NMR investigation and analyzed for fiber type composition and succinic dehydrogenase (SDH) activity. Fiber-type composition was determined based both on myofibrillar actomyosin ATPase activity combined with cross-sectional area and on myosin heavy-chain composition. Localized spectroscopy demonstrated a significantly (P < 0.001) higher P(i)/phosphocreatine ratio in the soleus muscle (0.15 +/- 0.01) compared with the medial (0.12 +/- 0.01) and lateral (0.10 +/- 0.0) gastrocnemius. However, in vitro analysis of muscle biopsies showed only a moderate relationship between the basal phosphate content and myofibrillar actomyosin ATPase-based fiber-type composition and SDH activity, respectively.

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Mitogen-Activated Protein Kinase-Activated Protein Kinases 2 and 3 Regulate SERCA2a Expression and Fiber Type Composition To Modulate Skeletal Muscle and Cardiomyocyte Function

Molecular and Cellular Biology ◽

10.1128/mcb.01692-12 ◽

2013 ◽

Vol 33 (13) ◽

pp. 2586-2602 ◽

Cited By ~ 27

Author(s):

M. Scharf ◽

S. Neef ◽

R. Freund ◽

C. Geers-Knorr ◽

M. Franz-Wachtel ◽

...

Keyword(s):

Skeletal Muscle ◽

Protein Kinase ◽

Protein Kinases ◽

Fiber Type ◽

Mitogen Activated Protein Kinase ◽

Fiber Type Composition ◽

Type Composition ◽

Mitogen Activated Protein

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Biological Determinants of Track and Field Throwing Performance

Journal of Functional Morphology and Kinesiology ◽

10.3390/jfmk6020040 ◽

2021 ◽

Vol 6 (2) ◽

pp. 40

Author(s):

Nikolaos Zaras ◽

Angeliki-Nikoletta Stasinaki ◽

Gerasimos Terzis

Keyword(s):

Fiber Type ◽

Small Body ◽

The Body ◽

Track And Field ◽

Neural Activation ◽

Biological Factors ◽

Cross Sectional ◽

Type Composition ◽

Biological Determinants

Track and field throwing performance is determined by a number of biomechanical and biological factors which are affected by long-term training. Although much of the research has focused on the role of biomechanical factors on track and field throwing performance, only a small body of scientific literature has focused on the connection of biological factors with competitive track and field throwing performance. The aim of this review was to accumulate and present the current literature connecting the performance in track and field throwing events with specific biological factors, including the anthropometric characteristics, the body composition, the neural activation, the fiber type composition and the muscle architecture characteristics. While there is little published information to develop statistical results, the results from the current review suggest that major biological determinants of track and field throwing performance are the size of lean body mass, the neural activation of the protagonist muscles during the throw and the percentage of type II muscle fiber cross-sectional area. Long-term training may enhance these biological factors and possibly lead to a higher track and field throwing performance. Consequently, coaches and athletes should aim at monitoring and enhancing these parameters in order to increase track and field throwing performance.

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Fiber type composition of four hindlimb muscles of adult Fisher 344 rats

Histochemistry and Cell Biology ◽

10.1007/s004180050341 ◽

1999 ◽

Vol 111 (2) ◽

pp. 117-123 ◽

Cited By ~ 83

Author(s):

Robert S. Staron ◽

William J. Kraemer ◽

Robert S. Hikida ◽

Andy C. Fry ◽

Jerry D. Murray ◽

...

Keyword(s):

Fiber Type ◽

Fiber Type Composition ◽

Hindlimb Muscles ◽

Type Composition

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Myostatin regulates fiber-type composition of skeletal muscle by regulating MEF2 and MyoD gene expression

AJP Cell Physiology ◽

10.1152/ajpcell.00259.2007 ◽

2009 ◽

Vol 296 (3) ◽

pp. C525-C534 ◽

Cited By ~ 104

Author(s):

Alex Hennebry ◽

Carole Berry ◽

Victoria Siriett ◽

Paul O'Callaghan ◽

Linda Chau ◽

...

Keyword(s):

Growth Factor ◽

Target Genes ◽

Fiber Type ◽

Fiber Formation ◽

Type I ◽

Mobility Shift ◽

Enhancer Activity ◽

Fiber Type Composition ◽

Nuclear Extracts ◽

Type Composition

Myostatin (Mstn) is a secreted growth factor belonging to the tranforming growth factor (TGF)-β superfamily. Inactivation of murine Mstn by gene targeting, or natural mutation of bovine or human Mstn, induces the double muscling (DM) phenotype. In DM cattle, Mstn deficiency increases fast glycolytic (type IIB) fiber formation in the biceps femoris (BF) muscle. Using Mstn null (−/−) mice, we suggest a possible mechanism behind Mstn-mediated fiber-type diversity. Histological analysis revealed increased type IIB fibers with a concomitant decrease in type IIA and type I fibers in the Mstn−/−tibialis anterior and BF muscle. Functional electrical stimulation of Mstn−/−BF revealed increased fatigue susceptibility, supporting increased type IIB fiber content. Given the role of myocyte enhancer factor 2 (MEF2) in oxidative type I fiber formation, MEF2 levels in Mstn−/−tissue were quantified. Results revealed reduced MEF2C protein in Mstn−/−muscle and myoblast nuclear extracts. Reduced MEF2-DNA complex was also observed in electrophoretic mobility-shift assay using Mstn−/−nuclear extracts. Furthermore, reduced expression of MEF2 downstream target genes MLC1F and calcineurin were found in Mstn−/−muscle. Conversely, Mstn addition was sufficient to directly upregulate MLC promoter-enhancer activity in cultured myoblasts. Since high MyoD levels are seen in fast fibers, we analyzed MyoD levels in the muscle. In contrast to MEF2C, MyoD levels were increased in Mstn−/−muscle. Together, these results suggest that while Mstn positively regulates MEF2C levels, it negatively regulates MyoD expression in muscle. We propose that Mstn could regulate fiber-type composition by regulating the expression of MEF2C and MyoD during myogenesis.

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