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Comparison of metabolic adaptations between endurance- and sprint-trained athletes in two different muscles using a 31P spectroscopic multi-slice sequence

Kevin Moll¹, Alexander Gussew¹, Maria Nisser², Martin Krämer¹, and Jürgen R. Reichenbach¹

¹Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany, ²Institute for Physiotherapy, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany

Synopsis

Due to specific training orientations athletes adapt with different metabolic responses to a given exercise. We used a 31P MR multi-slice sequence allowing a non-invasive investigation of high energy changes in two muscles. Different metabolic adaptations were shown within two muscles of different trained athletes. This may help to characterize training specific effects on energy metabolism.

Purpose

Phosphorous MR Spectroscopy (³¹P-MRS) is an important tool to investigate energy metabolism in skeletal muscles in vivo by analyzing kinetics of pH, phosphocreatine (PCr) and inorganic phosphate (Pi) during exercise and recovery¹. Specific activities like endurance training may induce metabolic adaptations as a consequence of a higher oxidative capacity². In this study, load induced metabolic changes were spectroscopically investigated in calf muscles of two differently trained groups in order to characterize training specific effects on energy metabolism.

Methods

Right calf muscles of seven active endurance- and seven sprint-trained athletes (age: 27 ± 5 years) were exercised till exhaustion by using a maximum voluntary contraction (MVC) adapted plantar flexion in a pedal ergometer³ (20% of MVC, 0.8 Hz pedal frequency). ³¹P-MR spectra were acquired in a clinical 3 T MR scanner (Magnetom PRISMA fit, Siemens, Erlangen, Germany) in m. gastrocnemius medialis (GM) and m. soleus (SOL) by using a double tuned ¹H/³¹P flexible MR coil (Rapid BioMedical) and a multi-slice FID sequence (Fig. 1). The latter enables interleaved data sampling from multiple tissue regions (TR = 5 s, 16 mm slice thickness, outer volume saturation bands over adjacent muscle regions). MR spectra series were quantified with jMRUI 4.0 software (jmrui.eu) to determine evolutions of PCr and pH.

Results

Sprint-trained athletes revealed higher MVC than endurance-trained athletes. Higher metabolic changes (PCr depletion and pH drop) were observed in the GM compared to the SOL (Table 1). PCr was completely depleted in the GM in both groups whereas the SOL showed a lower depletion especially in the sprint-trained group. With similar exercise durations among the subjects (8 ± 3.4 min vs. 7.9 ± 3.7 min) sprint-trained athletes revealed a metabolic impact mainly on the GM compared to endurance-trained athletes who showed a significant metabolic response in both muscles. In both groups a distinctly stronger pH drop was found in the GM than in the SOL. In the GM lower end-exercise pH values were determined in sprinters compared to endurance subjects. In general, the recovery of PCr was faster in the SOL than in the GM. No group specific differences were observed in the SOL. At the same time, sprinters revealed a slower PCr recovery in GM than endurance subjects (Fig. 2).

Discussion and Conclusion

In this work we showed the simultaneous non-invasive investigation of metabolic contributions in two muscles (SOL and GM) of differently trained subjects. As expected various metabolic adaptations were observed between investigated muscles as well as between the groups, which reflects different muscle fiber distributions⁴ as well as training orientations⁵. While the endurance athletes tend to stress both the SOL and the GM, the metabolic adaptation in sprint athletes remained primarily associated with the GM with a higher fraction of glycolytic fibers¹. This more efficient strategy might lead to lower anaerobic load (H⁺ and lactate production) in endurance athletes and thus provides a higher fatigue resistance during long lasting exercises⁶. A higher vascularization as a result of endurance training in this group led in a much faster PCr recovery⁷. However, sprint-trained athletes were able to afford a stronger acidification which may support their ability to perform high-intensity exercises⁴. To prove and to verify interrelations between metabolic adaptations and training status and to determine possible exhaustion avoiding strategies additional data, like lactate accumulation, buffer capacity, H⁺ efflux as well as respiration parameters, should be acquired in future studies.

Acknowledgements

This work was supported by the Competence Centre for Interdisciplinary Prevention (KIP) atthe Friedrich Schiller University Jena and the German Professional Association for Statutory AccidentInsurance and Prevention in the Foodstuffs Industry and the Catering Trade (BGN). K.M.is supported by a graduate scholarship of the Friedrich-Schiller-University Jena (Landesgraduiertenstipendium).K.M. also acknowledges support by the German Academic ExchangeService (DAAD) for a short-term international scholarship at the University of Liverpool(57044996). The authors declare to have no relevant financial interests to disclose with regard tothis study.

References

1. Kemp G. Muscle Studies by³¹P MRS. eMagRes. 2015; 4(1): 525-34.

2. Layec G et al. Short-term training alters the control of mitochondrial respiration rate before maximal oxidative ATP synthesis. Acta Physiol Scand. 2013; 208(4): 376-86.

3. Tschiesche K et al. MR-compatible pedal ergometer for reproducible exercising of the human calf muscle. Med Eng Phys. 2014; 36(7): 933-37.

4. Kemp GJ et al. Absolute quantification of phosphorus metabolite concentrations in human muscle in vivo by ³¹P MRS: a quantitative review. NMR Biomed. 2007; 20(8): 555-65.

5. Fiedler G et al. Skeletal muscle ATP synthesis and cellular H⁺ handling measured by localized ³¹P-MRS during exercise and recovery. Sci Rep. 2016; 6.

6. Maassen N et al. Physiologische "Nebenwirkung" der Milchsäure. Dtsch Z Sportmed. 2008; 59(12): 292-6.

7. Johansen L et al. ³¹P-MRS characterization of sprint and endurance trained athletes. Int J Sports Med. 2003; 24(3): 183-9.

Figures

Figure 1: Position of the two parallel spectroscopic slices covering SOL- m. soleus, GM- m. gastrocnemius medialis muscles with corresponding representative ‘stack plots’ of ³¹P-MR spectra series.

Figure 2: Mean PCr recovery in SOL (a) and GM muscle (b) for sprint-trained (blue graphs) and endurance-trained (red graphs) athletes together with the corresponding 25^th and 75^th percentiles (lower and upper boundaries of blue and red shadows).

Table 1: Mean metabolic parameters determined during the experiment (mean ± standard deviation). PCr depletion [%] indicates the percentage value to which PCr depleted.

Proc. Intl. Soc. Mag. Reson. Med. 25 (2017)

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