CoChat
Sign Up
Cited by 103Cardiovascular and exercise physiologySports Performance and TrainingMuscle metabolism and nutrition

The Muscle Fiber Profiles, Mitochondrial Content, and Enzyme Activities of the Exceptionally Well-Trained Arm and Leg Muscles of Elite Cross-Country Skiers

Open access
Ørtenblad, Niels, Nielsen, Joachim, Boushel, Robert, Söderlund, Karin, Saltin, Bengt, Holmberg, Hans-Christer·2018·Frontiers in Physiology
DOI 10.3389/fphys.2018.01031PMC PMC6084043
Open this paper in CoChat — free accountOpen PDF

Abstract

As one of the most physically demanding sports in the Olympic Games, cross-country skiing poses considerable challenges with respect to both force generation and endurance during the combined upper- and lower-body effort of varying intensity and duration. The isoforms of myosin in skeletal muscle have long been considered not only to define the contractile properties, but also to determine metabolic capacities. The current investigation was designed to explore the relationship between these isoforms and metabolic profiles in the arms (triceps brachii) and legs (vastus lateralis) as well as the range of training responses in the muscle fibers of elite cross-country skiers with equally and exceptionally well-trained upper and lower bodies. The proportion of myosin heavy chain (MHC)-1 was higher in the leg (58±2% [34-69%]) than arm (40±3% [24-57%], although the mitochondrial volume-percentages (8.6±1.6 (leg) and 9.0±2.0 (arm)), and average number of capillaries per fiber (5.8±0.8 (leg) and 6.3±0.3 (arm)) were the same. In these comparable highly-trained leg and arm muscles, the maximal citrate synthase activity was the same. Still, 3-hydroxy-acyl-CoA-dehydrogenase (HAD) capacity was 52% higher (P<0.05) in the leg compared to arm muscles, suggesting a relatively higher capacity for lipid oxidation in leg muscle, which cannot be explained by the different fiber type distributions. For both limbs combined, HAD activity was correlated with the content of MHC-1 (r2= 0.32, P = 0.011), whereas citrate synthase activity was not. Thus, in these highly trained cross-country skiers capillarization of and mitochondrial volume in type 2 fiber can be at least as high as in type 1 fibers, indicating a divergence between fiber type pattern and aerobic metabolic capacity. The considerable variability in oxidative metabolism with similar MHC profiles provides a new perspective on exercise training. Furthermore, the clear differences between equally well-trained arm and leg muscles regarding HAD activity cannot be explained by training status or MHC distribution, thereby indicating an intrinsic metabolic difference between the upper and lower body. Moreover, trained type 1 and type 2A muscle fibers exhibited similar aerobic capacity regardless of whether they were located in an arm or leg muscle.

The claims and statistics of this paper haven’t been checked yet.

Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.

A few free checks a day · papers already verified open instantly · results are public

Integrity signals

Registry

Crossref · 10.3389/fphys.2018.01031

Cites

39 of 39 references verified0 citation errors · 0 not checkable

Statistics

Claims the paper makes

The claims and statistics of this paper haven’t been checked yet.

Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.

A few free checks a day · papers already verified open instantly · results are public

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Elite cross-country skiers, characterized by equally trained upper- and lower-body muscles, exhibit similar mitochondrial volume fractions, capillarization, and citrate synthase activity, despite a higher proportion of MHCII fibers in the arms.

    “Elite cross‐country skiers, who are characterized by equally trained upper‐ and lower‐body, arm and leg muscles, have been shown to exhibit similar mitochondrial volume fractions, capillarization, and citrate synthase activity, despite a higher proportion of MHCII fibers in the arms [30].”

    From Carbohydrate Storage and Supplementation Strategies for Peak Performance in Cross-Country Skiing (2026) · cites this paper as [30]

  • The greater proportion of type II fibers in upper body musculature might account for the improved bench press and inconsistent effects on squat performance after NO3− supplementation.

    “Given that there is evidence to suggest that NO3− supplementation may be more effective at enhancing physiological responses in type II muscle fibers [124] and since the proportion of type II muscle fibers may be greater in the upper body musculature, i.e., [125], this might account for the improved bench press and the inconsistent effects observed on squat performance after NO3− supplementation.”

    From Effects of Dietary Nitrate Supplementation on Weightlifting Exercise Performance in Healthy Adults: A Systematic Review (2020) · cites this paper as [125]

  • The proportion of type II muscle fibers may be greater in the upper body musculature.

    “Given that there is evidence to suggest that NO3− supplementation may be more effective at enhancing physiological responses in type II muscle fibers [124] and since the proportion of type II muscle fibers may be greater in the upper body musculature, i.e., [125], this might account for the improved bench press and the inconsistent effects observed on squat performance after NO3− supplementation.”

    From Effects of Dietary Nitrate Supplementation on Weightlifting Exercise Performance in Healthy Adults: A Systematic Review (2020) · cites this paper as [125]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

The self-check needs the paper’s full text.

Cites

Flagged first, then by citations

Research works printed but not linked: 2

  1. Saltin B. (1996). “The physiology of competitive c.c. skiing across a four decade perspective; with a note on training induced adaptations and role of training at medium altitude,” in Science and Skiing, eds Müller E. Schwameder H. Kornex E. Raschner C. (Cambridge: Chapman and Hall), 435– 469.
  2. Weibel E. R. (1980). Stereological Methods: Theoretical Foundations, Vol. 2 London: Academic Press.

Cited by

Sorted by citations

Related

Authors
Ørtenblad, N., Nielsen, J., Boushel, R., Söderlund, K., Saltin, B., & Holmberg, H.-C.
Affiliations
  • University of British Columbia (CA)
  • University of Southern Denmark (DK)
  • Swedish School of Sport and Health Sciences (SE)
  • University of Copenhagen (DK)
  • Mid Sweden University (SE)
Corresponding author
Ørtenblad, Niels
ORCID
Venue
Frontiers in Physiology
Publisher
Frontiers Media SA
Published
2018-08-02
Volume
9
Pages
1031-1031
ISSN
1664-042X (ISSN-L)
DOI
10.3389/fphys.2018.01031
PMC
PMC6084043
OpenAlex
W2883867909
Cited by
102
References
38
Citations by year
2026: 7 · 2025: 9 · 2024: 11 · 2023: 15 · 2022: 21 · 2021: 19 · 2020: 8 · 2019: 12
FWCI
13.38
Type
journal article
Language
en
Open access
Licence
Locations
  • Frontiers in Physiology (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • University of Southern Denmark Research Portal (University of Southern Denmark) (acceptedVersion, cc-by)
  • Diva portal (Dalarna University Library) (submittedVersion, other-oa)
  • KTH Publication Database DiVA (KTH Royal Institute of Technology) (submittedVersion, other-oa)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • NORA - Norwegian Open Research Archives (submittedVersion, cc-by-nc-nd)
Funders
Kulturministeriet
Topics
  • Health Sciences › Medicine › Complementary and alternative medicine › Cardiovascular and exercise physiology
  • Health Sciences › Medicine › Orthopedics and Sports Medicine › Sports Performance and Training
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › Muscle metabolism and nutrition
Keywords
cross-country skiing, myosin heavy chain isoforms, muscle fiber type distribution, mitochondrial content, capillarization, citrate synthase, 3-hydroxyacyl-CoA dehydrogenase, lipid oxidation, cardiorespiratory fitness, triceps brachii, vastus lateralis, elite athletes, exercise training response, fast-twitch muscle

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

Are you an author, or do you see a problem with this page? Request a review