Impaired muscle Ca2+ and K+ regulation contribute to poor exercise performance post-lung transplantation

2003 ◽  
Vol 95 (4) ◽  
pp. 1606-1616 ◽  
Author(s):  
Michael J. McKenna ◽  
Steve F. Fraser ◽  
Jia L. Li ◽  
Xiao N. Wang ◽  
Michael F. Carey ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Atpase Activity ◽  
Phosphatase Activity ◽  
Vastus Lateralis ◽  
Buffering Capacity ◽  
Peak Oxygen Consumption ◽  
Vastus Lateralis Muscle ◽  
Ouabain Binding ◽  
Potassium Regulation ◽  
Lung Transplant Recipients

Lung transplant recipients (LTx) exhibit marked peripheral limitations to exercise. We investigated whether skeletal muscle Ca2+ and K+ regulation might be abnormal in eight LTx and eight healthy controls. Peak oxygen consumption and arterialized venous plasma [K+] (where brackets denote concentration) were measured during incremental exercise. Vastus lateralis muscle was biopsied at rest and analyzed for sarcoplasmic reticulum Ca2+ release, Ca2+ uptake, and Ca2+-ATPase activity rates; fiber composition; Na+-K+-ATPase (K+-stimulated 3- O-methylfluorescein phosphatase) activity and content ([3H]ouabain binding sites); as well as for [H+] and H+-buffering capacity. Peak oxygen consumption was 47% less in LTx ( P < 0.05). LTx had lower Ca2+ release (34%), Ca2+ uptake (31%), and Ca2+-ATPase activity (25%) than controls ( P < 0.05), despite their higher type II fiber proportion (LTx, 75.0 ± 5.8%; controls, 43.5 ± 2.1%). Muscle [H+] was elevated in LTx ( P < 0.01), but buffering capacity was similar to controls. Muscle 3- O-methylfluorescein phosphatase activity was 31% higher in LTx ( P < 0.05), but [3H]ouabain binding content did not differ significantly. However, during exercise, the rise in plasma [K+]-to-work ratio was 2.6-fold greater in LTx ( P < 0.05), indicating impaired K+ regulation. Thus grossly subnormal muscle calcium regulation, with impaired potassium regulation, may contribute to poor muscular performance in LTx.

Chronic intermittent hypoxia and incremental cycling exercise independently depress muscle in vitro maximal Na+-K+-ATPase activity in well-trained athletes

2005 ◽  
Vol 98 (1) ◽  
pp. 186-192 ◽  
Author(s):  
R. J. Aughey ◽  
C. J. Gore ◽  
A. G. Hahn ◽  
A. P. Garnham ◽  
S. A. Clark ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Vastus Lateralis ◽  
Incremental Exercise ◽  
Peak Oxygen Consumption ◽  
Vastus Lateralis Muscle ◽  
Minor Effect ◽  
Moderate Altitude ◽  
Ouabain Binding ◽  
Before And After

Athletes commonly attempt to enhance performance by training in normoxia but sleeping in hypoxia [live high and train low (LHTL)]. However, chronic hypoxia reduces muscle Na+-K+-ATPase content, whereas fatiguing contractions reduce Na+-K+-ATPase activity, which each may impair performance. We examined whether LHTL and intense exercise would decrease muscle Na+-K+-ATPase activity and whether these effects would be additive and sufficient to impair performance or plasma K+ regulation. Thirteen subjects were randomly assigned to two fitness-matched groups, LHTL ( n = 6) or control (Con, n = 7). LHTL slept at simulated moderate altitude (3,000 m, inspired O2 fraction = 15.48%) for 23 nights and lived and trained by day under normoxic conditions in Canberra (altitude ∼600 m). Con lived, trained, and slept in normoxia. A standardized incremental exercise test was conducted before and after LHTL. A vastus lateralis muscle biopsy was taken at rest and after exercise, before and after LHTL or Con, and analyzed for maximal Na+-K+-ATPase activity [K+-stimulated 3- O-methylfluorescein phosphatase (3- O-MFPase)] and Na+-K+-ATPase content ([3H]ouabain binding sites). 3- O-MFPase activity was decreased by −2.9 ± 2.6% in LHTL ( P < 0.05) and was depressed immediately after exercise ( P < 0.05) similarly in Con and LHTL (−13.0 ± 3.2 and −11.8 ± 1.5%, respectively). Plasma K+ concentration during exercise was unchanged by LHTL; [3H]ouabain binding was unchanged with LHTL or exercise. Peak oxygen consumption was reduced in LHTL ( P < 0.05) but not in Con, whereas exercise work was unchanged in either group. Thus LHTL had a minor effect on, and incremental exercise reduced, Na+-K+-ATPase activity. However, the small LHTL-induced depression of 3- O-MFPase activity was insufficient to adversely affect either K+ regulation or total work performed.

Depressed Na+-K+-ATPase activity in skeletal muscle at fatigue is correlated with increased Na+-K+-ATPase mRNA expression following intense exercise

2005 ◽  
Vol 289 (1) ◽  
pp. R266-R274 ◽  
Author(s):  
A. C. Petersen ◽  
K. T. Murphy ◽  
R. J. Snow ◽  
J. A. Leppik ◽  
R. J. Aughey ◽  
...  
Keyword(s):  
Gene Expression ◽  
Atpase Activity ◽  
Mrna Expression ◽  
Binding Sites ◽  
Time Course ◽  
Acute Exercise ◽  
Vastus Lateralis ◽  
Vastus Lateralis Muscle ◽  
Ouabain Binding ◽  
Atpase Gene

We investigated whether depressed muscle Na+-K+-ATPase activity with exercise reflected a loss of Na+-K+-ATPase units, the time course of its recovery postexercise, and whether this depressed activity was related to increased Na+-K+-ATPase isoform gene expression. Fifteen subjects performed fatiguing, knee extensor exercise at ∼40% maximal work output per contraction. A vastus lateralis muscle biopsy was taken at rest, fatigue, 3 h, and 24 h postexercise and analyzed for maximal Na+-K+-ATPase activity via 3- O-methylfluorescein phosphatase (3- O-MFPase) activity, Na+-K+-ATPase content via [3H]ouabain binding sites, and Na+-K+-ATPase α1-, α2-, α3-, β1-, β2- and β3-isoform mRNA expression by real-time RT-PCR. Exercise [352 (SD 267) s] did not affect [3H]ouabain binding sites but decreased 3- O-MFPase activity by 10.7 (SD 8)% ( P < 0.05), which had recovered by 3 h postexercise, without further change at 24 h. Exercise elevated α1-isoform mRNA by 1.5-fold at fatigue ( P < 0.05). This increase was inversely correlated with the percent change in 3- O-MFPase activity from rest to fatigue (%Δ3- O-MFPaserest-fatigue) ( r = −0.60, P < 0.05). The average postexercise (fatigue, 3 h, 24 h) α1-isoform mRNA was increased 1.4-fold ( P < 0.05) and approached a significant inverse correlation with %Δ3- O-MFPaserest-fatigue ( r = −0.56, P = 0.08). Exercise elevated α2-isoform mRNA at fatigue 2.5-fold ( P < 0.05), which was inversely correlated with %Δ3- O-MFPaserest-fatigue ( r = −0.60, P = 0.05). The average postexercise α2-isoform mRNA was increased 2.2-fold ( P < 0.05) and was inversely correlated with the %Δ3- O-MFPaserest-fatigue ( r = −0.68, P < 0.05). Nonsignificant correlations were found between %Δ3- O-MFPaserest-fatigue and other isoforms. Thus acute exercise transiently decreased Na+-K+-ATPase activity, which was correlated with increased Na+-K+-ATPase gene expression. This suggests a possible signal-transduction role for depressed muscle Na+-K+-ATPase activity with exercise.

Fatigue depresses maximal in vitro skeletal muscle Na+-K+-ATPase activity in untrained and trained individuals

2002 ◽  
Vol 93 (5) ◽  
pp. 1650-1659 ◽  
Author(s):  
Steve F. Fraser ◽  
Jia L. Li ◽  
Michael F. Carey ◽  
Xiao N. Wang ◽  
Termboon Sangkabutra ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Phosphatase Activity ◽  
Important Determinant ◽  
Vastus Lateralis ◽  
Ouabain Binding ◽  
Isokinetic Contractions ◽  
Lower Ratio ◽  
Muscle Biopsies ◽  
Training State

This study investigated whether fatiguing dynamic exercise depresses maximal in vitro Na+-K+-ATPase activity and whether any depression is attenuated with chronic training. Eight untrained (UT), eight resistance-trained (RT), and eight endurance-trained (ET) subjects performed a quadriceps fatigue test, comprising 50 maximal isokinetic contractions (180°/s, 0.5 Hz). Muscle biopsies (vastus lateralis) were taken before and immediately after exercise and were analyzed for maximal in vitro Na+-K+-ATPase (K+-stimulated 3- O-methylfluoroscein phosphatase) activity. Resting samples were analyzed for [3H]ouabain binding site content, which was 16.6 and 18.3% higher ( P < 0.05) in ET than RT and UT, respectively (UT 311 ± 41, RT 302 ± 52, ET 357 ± 29 pmol/g wet wt). 3- O-methylfluoroscein phosphatase activity was depressed at fatigue by −13.8 ± 4.1% ( P < 0.05), with no differences between groups (UT −13 ± 4, RT −9 ± 6, ET −22 ± 6%). During incremental exercise, ET had a lower ratio of rise in plasma K+ concentration to work than UT ( P < 0.05) and tended ( P = 0.09) to be lower than RT (UT 18.5 ± 2.3, RT 16.2 ± 2.2, ET 11.8 ± 0.4 nmol · l−1 · J−1). In conclusion, maximal in vitro Na+-K+-ATPase activity was depressed with fatigue, regardless of training state, suggesting that this may be an important determinant of fatigue.

Glucose supplements increase human muscle in vitro Na+-K+-ATPase activity during prolonged exercise

2007 ◽  
Vol 293 (1) ◽  
pp. R354-R362 ◽  
Author(s):  
H. J. Green ◽  
T. A. Duhamel ◽  
K. P. Foley ◽  
J. Ouyang ◽  
I. C. Smith ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Prolonged Exercise ◽  
Serum Insulin ◽  
Vastus Lateralis ◽  
Oral Glucose ◽  
Vastus Lateralis Muscle ◽  
Ouabain Binding ◽  
Similar Time ◽  
Phosphatase Assay

Regulation of maximal Na+-K+-ATPase activity in vastus lateralis muscle was investigated in response to prolonged exercise with (G) and without (NG) oral glucose supplements. Fifteen untrained volunteers (14 males and 1 female) with a peak aerobic power (V̇o2peak) of 44.8 ± 1.9 ml·kg−1·min−1; mean ± SE cycled at ∼57% V̇o2peak to fatigue during both NG (artificial sweeteners) and G (6.13 ± 0.09% glucose) in randomized order. Consumption of beverage began at 30 min and continued every 15 min until fatigue. Time to fatigue was increased ( P < 0.05) in G compared with NG (137 ± 7 vs. 115 ± 6 min). Maximal Na+-K+-ATPase activity (Vmax) as measured by the 3- O-methylfluorescein phosphatase assay (nmol·mg−1·h−1) was not different between conditions prior to exercise (85.2 ± 3.3 or 86.0 ± 3.9), at 30 min (91.4 ± 4.7 vs. 91.9 ± 4.1) and at fatigue (92.8 ± 4.3 vs. 100 ± 5.0) but was higher ( P < 0.05) in G at 90 min (86.7 ± 4.2 vs. 109 ± 4.1). Na+-K+-ATPase content (βmax) measured by the vanadate facilitated [3H]ouabain-binding technique (pmol/g wet wt) although elevated ( P < 0.05) by exercise (0<30, 90, and fatigue) was not different between NG and G. At 60 and 90 min of exercise, blood glucose was higher ( P < 0.05) in G compared with NG. The G condition also resulted in higher ( P < 0.05) serum insulin at similar time points to glucose and lower ( P < 0.05) plasma epinephrine and norepinephrine at 90 min of exercise and at fatigue. These results suggest that G results in an increase in Vmax by mechanisms that are unclear.

Unchanged [3H]ouabain binding site content but reduced Na+-K+ pump α2-protein abundance in skeletal muscle in older adults

2012 ◽  
Vol 113 (10) ◽  
pp. 1505-1511 ◽  
Author(s):  
Michael J. McKenna ◽  
Ben D. Perry ◽  
Fabio R. Serpiello ◽  
Marissa K. Caldow ◽  
Pazit Levinger ◽  
...  
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Oxygen Consumption ◽  
Binding Site ◽  
Total Content ◽  
Peak Oxygen Consumption ◽  
Vastus Lateralis Muscle ◽  
Protein Abundance ◽  
Membrane Excitability ◽  
Ouabain Binding

Aging is associated with reduced muscle mass, weakness, and increased fatigability. In skeletal muscle, the Na+-K+ pump (NKA) is important in regulating Na+-K+ gradients, membrane excitability, and thus contractility, but the effects of aging on muscle NKA are unclear. We investigated whether aging is linked with reduced muscle NKA by contrasting muscle NKA isoform gene expression and protein abundance, and NKA total content in 17 Elderly (66.8 ± 6.4 yr, mean ± SD) and 16 Young adults (23.9 ± 2.2 yr). Participants underwent peak oxygen consumption assessment and a vastus lateralis muscle biopsy, which was analyzed for NKA α1-, α2-, α3-, β1-, β2-, and β3-isoform gene expression (real-time RT-PCR), protein abundance (immunoblotting), and NKA total content ([3H]ouabain binding sites). The Elderly had lower peak oxygen consumption (−36.7%, P = 0.000), strength (−36.3%, P = 0.001), NKA α2- (−24.4%, 11.9 ± 4.4 vs. 9.0 ± 2.7 arbitrary units, P = 0.049), and NKA β3-protein abundance (−23.0%, P = 0.041) than Young. The β3-mRNA was higher in Elderly compared with Young ( P = 0.011). No differences were observed between groups for other NKA isoform mRNA or protein abundance, or for [3H]ouabain binding site content. Thus skeletal muscle in elderly individuals was characterized by decreased NKA α2- and β3-protein abundance, but unchanged α1 abundance and [3H]ouabain binding. The latter was likely caused by reduced α2 abundance with aging, preventing an otherwise higher [3H]ouabain binding that might occur with a greater membrane density in smaller muscle fibers. Further study is required to verify reduced muscle NKA α2 with aging and possible contributions to impaired exercise capability and daily living activities.

scholarly journals Cardiovascular and skeletal muscle health with lifelong exercise

2018 ◽  
Vol 125 (5) ◽  
pp. 1636-1645 ◽  
Author(s):  
Kevin J. Gries ◽  
Ulrika Raue ◽  
Ryan K. Perkins ◽  
Kaleen M. Lavin ◽  
Brittany S. Overstreet ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Oxygen Consumption ◽  
Aerobic Exercise ◽  
Muscle Biopsy ◽  
Citrate Synthase ◽  
Vastus Lateralis ◽  
Metabolic Phenotype ◽  
Vastus Lateralis Muscle ◽  
Metabolic Fitness ◽  
Lifelong Exercise

The purpose of this study was to examine the effects of aerobic lifelong exercise (LLE) on maximum oxygen consumption (V̇o2max) and skeletal muscle metabolic fitness in trained women ( n = 7, 72 ± 2 yr) and men ( n = 21, 74 ± 1 yr) and compare them to old, healthy nonexercisers (OH; women: n = 10, 75 ± 1 yr; men: n = 10, 75 ± 1 yr) and young exercisers (YE; women: n = 10, 25 ± 1 yr; men: n = 10, 25 ± 1 yr). LLE men were further subdivided based on intensity of lifelong exercise and competitive status into performance (LLE-P, n = 14) and fitness (LLE-F, n = 7). On average, LLE exercised 5 day/wk for 7 h/wk over the past 52 ± 1 yr. Each subject performed a maximal cycle test to assess V̇o2maxand had a vastus lateralis muscle biopsy to examine capillarization and metabolic enzymes [citrate synthase, β-hydroxyacyl-CoA dehydrogenase (β-HAD), and glycogen phosphorylase]. V̇o2maxhad a hierarchical pattern (YE > LLE > OH, P < 0.05) for women (44 ± 2 > 26 ± 2 > 18 ± 1 ml·kg−1·min−1) and men (53 ± 3 > 34 ± 1 > 22 ± 1 ml·kg−1·min−1) and was greater ( P < 0.05) in LLE-P (38 ± 1 ml·kg−1·min−1) than LLE-F (27 ± 2 ml·kg−1·min−1). LLE men regardless of intensity and women had similar capillarization and aerobic enzyme activity (citrate synthase and β-HAD) as YE, which were 20%–90% greater ( P < 0.05) than OH. In summary, these data show a substantial V̇o2maxbenefit with LLE that tracked similarly between the sexes, with further enhancement in performance-trained men. For skeletal muscle, 50+ years of aerobic exercise fully preserved capillarization and aerobic enzymes, regardless of intensity. These data suggest that skeletal muscle metabolic fitness may be easier to maintain with lifelong aerobic exercise than more central aspects of the cardiovascular system.NEW & NOTEWORTHY Lifelong exercise (LLE) is a relatively new and evolving area of study with information especially limited in women and individuals with varying exercise intensity habits. These data show a substantial maximal oxygen consumption benefit with LLE that tracked similarly between the sexes. Our findings contribute to the very limited skeletal muscle biopsy data from LLE women (>70 yr), and similar to men, revealed a preserved metabolic phenotype comparable to young exercisers.

Effects of prior exercise and a low-carbohydrate diet on muscle sarcoplasmic reticulum function during cycling in women

2006 ◽  
Vol 101 (3) ◽  
pp. 695-706 ◽  
Author(s):  
T. A. Duhamel ◽  
H. J. Green ◽  
J. G. Perco ◽  
J. Ouyang
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Vastus Lateralis ◽  
Phase 1 ◽  
Vastus Lateralis Muscle ◽  
Low Carbohydrate Diet ◽  
Hill Slope ◽  
Low Carbohydrate ◽  
Exercise Induced

The effects of exercise and diet on sarcoplasmic reticulum Ca2+-cycling properties in female vastus lateralis muscle were investigated in two groups of women following four different conditions. The conditions were 4 days of a low-carbohydrate (Lo CHO) and glycogen-depleting exercise plus a Lo CHO diet (Ex + Lo CHO) ( experiment 2) and 4 days of normal CHO (Norm CHO) and glycogen-depleting exercise plus Norm CHO (Ex + Norm CHO) ( experiment 1). Peak aerobic power (V̇o2peak) was 38.1 ± 1.4 (SE); n = 9 and 35.6 ± 1.4 ml·kg−1·min−1; n = 9, respectively. Sarcoplasmic reticulum properties measured in vitro in homogenates (μmol·g protein−1·min−1) indicated exercise-induced reductions ( P < 0.05) in maximal Ca2+-ATPase activity (0 > 30, 60 min > fatigue), Ca2+ uptake (0 > 30 > 60 min, fatigue), and Ca2+ release, both phase 1 (0, 30 > 60 min, fatigue) and phase 2 (0 > 30, 60 min, fatigue; 30 min > fatigue) in Norm CHO. Exercise was without effect in altering the Hill slope ( nH), defined as the slope of relationship between Ca2+-ATPase activity and Ca2+ concentration. No differences were observed between Norm CHO and Ex+Norm CHO. Compared with Norm CHO, Lo CHO resulted in a lower ( P < 0.05) Ca2+ uptake, phase 1 Ca2+ release (30 min), and nH. Ex + Lo CHO resulted in a greater ( P < 0.05) Ca2+ uptake and nH compared with Lo CHO. The results demonstrate that Lo CHO alone can disrupt SR Ca2+ cycling and that, with the exception of Ca2+ release, a glycogen-depleting session of exercise before Lo CHO can reverse the effects.

Human and rodent muscle Na(+)-K(+)-ATPase in diabetes related to insulin, starvation, and training

1994 ◽  
Vol 76 (5) ◽  
pp. 2140-2146 ◽  
Author(s):  
T. A. Schmidt ◽  
S. Hasselbalch ◽  
P. A. Farrell ◽  
H. Vestergaard ◽  
K. Kjeldsen
Keyword(s):  
Diabetes Mellitus ◽  
Insulin Treatment ◽  
Vastus Lateralis ◽  
Insulin Dependent Diabetes Mellitus ◽  
Insulin Dependent Diabetes ◽  
Dependent Diabetes Mellitus ◽  
Vastus Lateralis Muscle ◽  
Ouabain Binding ◽  
Partial Pancreatectomy ◽  
Insulin Dependent

As determined by vanadate-facilitated [3H]ouabain binding to intact samples, semistarvation and untreated streptozotocin- or partial pancreatectomy-induced diabetes reduced rat soleus muscle Na(+)-K(+)-adenosinetriphosphatase (Na(+)-K(+)-ATPase) concentration by 12–21% (P < 0.05). Conversely, insulin treatment of rats with streptozotocin-induced diabetes induced an increase of 18-26% above control (P < 0.05). Treadmill training diminished the reduction in muscle [3H]ouabain binding site concentration induced by untreated diabetes to only 2–5%. No significant variation was observed in rat cerebral cortex Na(+)-K(+)-ATPase concentration as a result of diabetes, semistarvation, or insulin treatment. In human subjects, Na(+)-K(+)-ATPase concentration in vastus lateralis muscle biopsies was 17 and 22% greater (P < 0.05), respectively, in patients with treated non-insulin-dependent diabetes mellitus (n = 24) and insulin-dependent diabetes mellitus (n = 7) than in control subjects (n = 8). A positive linear correlation between muscle Na(+)-K(+)-ATPase and plasma insulin concentrations was observed (r = 0.50, P = 0.006; n = 29). Thus, insulin seems a regulator of muscle Na(+)-K(+)-ATPase concentration, reduction of muscle Na(+)-K(+)-ATPase concentration with untreated diabetes bears similarities with undernourishment, and physical conditioning may ameliorate the muscle Na(+)-K(+)-ATPase concentration decrease induced by diabetes.

Adaptation of actomyosin ATPase in different types of muscle to endurance exercise

1975 ◽  
Vol 229 (2) ◽  
pp. 422-426 ◽  
Author(s):  
KM Baldwin ◽  
WW Winder ◽  
JO Holloszy
Keyword(s):  
Atpase Activity ◽  
Specific Activity ◽  
Vastus Lateralis ◽  
Close Correlation ◽  
Treadmill Running ◽  
Vastus Lateralis Muscle ◽  
Actomyosin Atpase ◽  
Different Types ◽  
Phosphofructokinase Activity ◽  
Fast Twitch

Higher concentrations of actomyosin were found in the red portion of the vastus lateralis and in the white portion of the vastus lateralis muscle than in the soleus or heart in rats. A strenuous program of treadmill running lasting 18 wk or longer did not significantly affect the amount of actomyosin recovered from the different types of muscle. No changes in actomyosin ATPase occurred in fast-twitch white (white vastus) or heart muscles in response to the exercise training. In contrast, a decrease of approximately 20% occurred in the specific activity of actomyosin ATPase of fast-twitch red (red vastus) muscle (0.635 +/- 0.029 mumol Pi/min per milligram for sedentary vs. 0.529 +/- 0.021 mumol Pi/min per milligram for trained), while the actomyosin ATPase activity of slow-twitch red (soleus) muscle increased about 20% (0.209 +/- 0.033 vs. 0.257 +/- 0.031 mumol Pi/min per milligram). There was a close correlation (r = 0.99, P less than 0.001) between actomyosin ATPase activity and phosphofructokinase activity in the three types of skeletal muscles and in heart muscle of exercise-trained and untrained animals, providing further evidence in support of the concept that the glycogenolytic capacity of a muscle and its actomyosin ATPase activity are regulated in parallel.

Muscle cellular properties in the ice hockey player: a model for investigating overtraining?

2012 ◽  
Vol 90 (5) ◽  
pp. 567-578 ◽  
Author(s):  
Howard J. Green ◽  
Aziz Batada ◽  
Bill Cole ◽  
Margaret E. Burnett ◽  
Helen Kollias ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
G Protein ◽  
Vastus Lateralis ◽  
Succinic Dehydrogenase ◽  
Maximal Activity ◽  
Ice Hockey ◽  
Peak Oxygen Consumption ◽  
Cross Sectional ◽  
Hockey Players ◽  
Wet Weight

In this study, we hypothesized that athletes involved in 5–6 months of sprint-type training would display higher levels of proteins and processes involved in muscle energy supply and utilization. Tissue was sampled from the vastus lateralis of 13 elite ice hockey players (peak oxygen consumption = 51.8 ± 1.3 mL·kg–1·min–1; mean ± standard error) at the end of a season (POST) and compared with samples from 8 controls (peak oxygen consumption = 45.5 ± 1.4 mL·kg–1·min–1) (CON). Compared with CON, higher activities were observed in POST (p < 0.05) only for succinic dehydrogenase (3.32 ± 0.16 mol·(mg protein)–1·min–1 vs. 4.10 ± 0.11 mol·(mg protein)–1·min–1) and hexokinase (0.73 ± 0.05 mol·(mg protein)–1·min–1 vs. 0.90 ± 0.05mol·(mg protein)–1·min–1) but not for phosphorylase, phosphofructokinase, and creatine phosphokinase. No differences were found in Na+,K+-ATPase concentration (βmax: 262 ± 36 pmol·(g wet weight)–1 vs. 275 ± 27 pmol·(g wet weight)–1) and the maximal activity of the sarcoplasmic reticulum Ca2+-ATPase (98.1 ± 6.1 µmol·(g protein)–1·min–1 vs. 102 ± 3.3 µmol·(g protein)–1·min–1). Cross-sectional area was lower (p < 0.05) in POST but only for the type IIA fibres (6312 ± 684 μm2 vs. 5512 ± 335 μm2), while the number of capillary counts per fibre and the capillary to fibre area ratio were generally higher (p < 0.05). These findings suggest that elite trained ice hockey players display elevations only in support of glucose-based aerobic metabolism that occur in the absence of alterations in excitation–contraction processes.

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