Are muscle fibres of body builders intrinsically weaker? A comparison with single fibres of aged‐matched controls

Abstract

Aim Skeletal muscles of Body Builders (BB) represent an interesting model to study muscle mass gains in response to high volume resistance training. It is debated whether muscle contractile performance improves in proportion to mass. Here, we aim to assess whether muscle hypertrophy does not occur at the expense of performance. Methods Six BB and Six untrained controls (CTRL) were recruited. Cross‐sectional area (CSA) and maximum voluntary contraction (MVC) of quadriceps femoris muscle (QF) and CSA and architecture of vastus lateralis (VL) were determined. Moreover, a biopsy was taken from VL mid‐portion and single fibres were analysed. Results QF CSA and MVC were 32% (n.s., P = .052) and 58% (P = .009) higher in BB than in CTRL, respectively. VL CSA was 37% higher in BB (P = .030). Fast 2A fibres CSA was 24% (P = .048) greater in BB than in CTRL, when determined in immunostained sections of biopsy samples. Single permeabilized fast fibres CSA was 37% (n.s., P = .052) higher in BB than in CTRL, and their force was slightly higher in BB (n.s.), while specific tension (P0) was 19% (P = .024) lower. The lower P0 was not explained either by lower myosin content or by impaired calcium diffusion. Conversely, the swelling caused by skinning‐induced permeabilization was different and, when used to correct P0, differences between populations disappeared. Conclusions The results show that high degree of muscle hypertrophy is not detrimental for force generation capacity, as increases in fibre size and force are strictly proportional once the differential swelling response is accounted for.

Emphasizing Task-Specific Hypertrophy to Enhance Sequential Strength and Power Performance

“…Such adaptations may also increase fCSA while only promoting suboptimal strength improvements. We agree with Jorgenson et al [ 29 ] that the paper by Haun et al [ 179 ], as well as other studies, do not represent the whole population regarding sarcoplasmic hypertrophic adaptations; however, there is still evidence provided indicating that sarcoplasmic hypertrophy may take place, contributing to myofibrillar growth and function [ 190 ].…”

“…It is possible that resistance training-induced sarcoplasmic hypertrophy may occur as an initial “precursor” to myofibrillar hypertrophy to enlarge available intracellular space, or as a response to increased metabolism [ 180 ]. While it is often thought that sarcoplasmic hypertrophy as a result of bodybuilding style training is associated with nonfunctional adaptions (i.e., increase in noncontractile elements), when accounting for cellular swelling, the force generated by a single fiber is proportional to the increase in fiber size [ 190 ]. This theory is also controversial, as it has been suggested that sarcoplasmic hypertrophy does not make a substantive contribution to the mechanical load-induced growth of myofibers [ 29 ].…”

Implementing Ultrasound Imaging for the Assessment of Muscle and Tendon Properties in Elite Sports: Practical Aspects, Methodological Considerations and Future Directions

“…In addition, the isolated practice of a specific sport can induce changes in muscle and tendon morphological and mechanical properties. Differences in muscle dimensions and architecture [84][85][86][87][88] as well as tendon features [85,86,89,90] have been observed in cross-sectional studies comparing athletes practising different sports with non-athletes. Moreover, muscle architecture [91,92], muscle stiffness [93], tendon stiffness and ACSA [94][95][96], and capacity to use tendon elastic energy [97] have been shown to differ in relation to chronic sportsspecific loading exposure.…”

Significant significance?

“…[19][20][21] Then, there are research questions which require investigation of whole body morphological or behavioural traits which can only be observed in living animals 22 and lastly, there are the research questions which depend on human subjects of research and the heaps of models related to research in humans. 23,24 It is a hard task to choose the correct model and in many cases, only a combination of multiple models can lead to insightful results. Interpreting those models based on P-values only will lead to described false positive and negative interpretations.…”