Vitamin C For Runners

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Vitamin C may be an important supplement for runners. A runner's quads lengthen to slow their body's descent on landing, a type of eccentric exercise. This eccentric stress not only causes Delayed Onset Muscle Soreness (DOMS), but it also causes immediate weakness. If you've ever had problems descending stairs after a marathon, you've had DOMS. The good news is that experiencing DOMS provides a protection from future bouts, something known as the Repeated Bout Effect (RBE), which is where Vitamin C comes in. As well as being an antioxidant, Vitamin C is important in may other ways, including the production of the scaffolding that makes up muscles (collagen.) There is some evidence that Vitamin C may help with the RBE, and without sufficient Vitamin C, the ability to adapt to long runs may be impaired. While Vitamin C has been shown to interfere with the way people adapt to exercise at a biochemical level, that doesn't appear to translate into practical problems. If you take Vitamin C as a supplement, it's probably best to take it spread evenly through the day rather than a single larger dose, and the dose should be built up slowly as it can cause stomach upsets and diarrhea. It's unclear to me if the research indicates there is an increased risk of kidney stones from Vitamin C.

1 The Role of Vitamin C

Vitamin C is best known for its role as an antioxidant. However, it's not only an antioxidant, but it's also cofactor for 15 different enzymes[1], including the production of norepinephrine[2], carnitine[3], and collagen[4]. It also enhances non-heme iron absorption[5]. Increased Vitamin C may also boost the amount of Collagen synthesized[6][7]. This is especially valuable for runners, as collagen is a key structural protein, including muscle fibers[8] and tendons[9]. Even within the role as an antioxidant there is the possibility that different antioxidants may fulfill different roles. For instance, there is evidence that Vitamin C depleted plasma is susceptible to fat (lipid) oxidation, even when other anti-oxidants are present[10]. Personally, I suspect that these various roles may result in differing actions of vitamins C in differing circumstances. Vitamin C is concentrated in nearly all cells in the body above plasma levels, such as the brain with 16-18x and muscle with 4-6x, though It's unclear why many tissues concentrate Vitamin C levels well beyond the level needed for the enzymatic actions, sometimes 10-100x higher[11]. There is evidence from animal models that the Vitamin C needs may vary widely, possibly due to genetic differences[12]. This has been seen in humans, where there is wide variation in susceptibility to scurvy amongst sailors[12].

2 Vitamin C Requirements

The recommended intake for vitamins C is focused on preventing deficiency problems, primarily scurvy[13]. Vitamin C deficiency (scurvy) results in lassitude (fatigue), coiled hair, gum problems, anemia, hemorrhages, tooth loss and other problems[11]. Sometimes the only symptom of vitamins C deficiency is lassitude, even when plasma levels are below 8 uM[14]. Most animals can produce their own Vitamin C, except for humans and other primates, Guinea pigs, fruit bats, and some birds and fish[11]. The optimum dose of Vitamin C for runners is unclear based on the available research.

3 Vitamin C Intakes

Vitamin C is absorbed in the small intestine, reaching peak plasma levels in 2-3 hours, and then to extracellular fluids[11]. Over many days, the level of vitamin C in the plasma stabilizes, as shown below[14]]].

The fasting plasma Vitamin C levels of a subject given 60mg/day[14].

/ Varying doses increase the plasma levels with diminishing returns[14], giving a sigmoid (s) shaped curve. Plasma Vitamin C levels are well regulated, with even extreme oral doses (3g every 4 hours) results in peak levels of only 220 mmol/L[15][16] (note that IV Vitamin C produces vastly higher plasma levels.) /

The stable fasting plasma Vitamin C levels reached with varying doses[14]

The graphs above are from a single dose, with the measurement in the fasting state, but it's only at low doses of Vitamin C that peak and fasting levels are the same (i.e. 15 mg twice a day is 8.7 mmol/L) [11]. If you look at the graph below you can see that the time course of Vitamin C and the timing of the doses results in different areas under the curve[16]. Here you can see that while the higher doses of Vitamin C result in similar levels after 20+ hours, the levels following the doses are quite different and much higher for higher doses. Taking Vitamin C regularly though the day would result in higher average levels than a single dose. For instance, 1g/day of Vitamin C is sufficient to saturate fasting plasma levels, but levels may transiently raise higher (250+ mmol/L)[17].

Dose response over the course of a day to different doses of Vitamin C[16]

./ One study found that taking 60mg/day took ~3 weeks to reach stable plateau blood levels, and there were sharp change in blood levels up to 100mg, then far less change from 200mg up to 2,500mg[14].

4 Factors Influencing Vitamin C Needs

Both smoking and diabetes decrease Vitamin C plasma levels compared with controls, increasing intake needs[11]. Vitamin C can be reversibly or irreversibly oxidized, with irreversible oxidation consuming Vitamin C, resulting in an increased dietary need[11].

5 Distribution of Vitamin C

Vitamin C is regulated by controlling absorption in the intestine, and the balance of excretion/reabsorption in the kidney[18], as well as by recycling Vitamin C after it has functioned as an antioxidant[19]. Typically, humans only have about 1,500mg of Vitamin C in their body[20]. Because vitamin C is an anion at physiologic pH, it cannot simply diffuse across the cell membrane to extracellular fluid and must be actively transported[21], which results in different tissues having different concentrations as shown in the picture below[11]. While the level of vitamin C in skeletal muscle is lower than many other tissues[22], the size of the muscles suggests they main contain 66% of the body's vitamin C[23]. A study of Vitamin C from Kiwi fruit found for intakes between ~50-210mg/day, there was a strong correlation between plasma and muscle Vitamin C levels[24]. /

The distribution of Vitamin C at 100 mg/day[11].

6 Vitamin C, Exercise, and Aerobic Capacity

There is lots of evidence that Vitamin C changes how the human body responds to exercise, but interpreting the evidence is not straightforward. Many of the studies have found changes in enzyme levels after exercise with Vitamin C compared with placebos, but don't measure exercise outcomes such as V̇O2max[25]. I've mostly ignored these studies as they may not reflect real world impacts. In fact, one study of 54 recreationally endurance-trained individuals taking either 100mg Vitamin C plus 235 mg Vitamin E or a placebo found that cellular adaptation to exercise was hampered by the supplements, but no changes in V̇O2max or running performance[26]. I've included the studies I've found where the outcomes are measured in real world terms for aerobic capacity (primarily V̇O2max.)

  • There's strong evidence that Vitamin C deficiency results in impaired exercise ability[27][28][29]. The remainder of the studies in this section will look at Vitamin C supplementation at doses beyond those needed for the prevention of clinical deficiency.
  • Many studies do not have controls with standardized Vitamin C levels, and at low intake levels small changes in intake make a large difference in plasma levels. Interventions should have controls with low intakes of Vitamin C, as some studies have used controls where the plasma levels of Vitamin C are already near saturation[11]. For instance, in one study the Vitamin C treated group had similar plasma levels to the placebo group, rendering the identical results between the groups a bit meaningless[30] (at least they measured.)
  • 15 amateur athletes split between placebo and 90 days of 500mg Vitamin E, 30mg beta-carotene, and then 1,000mg Vitamin C for the last 15 days[31]. There was no measurement of the Vitamin C status in the subjects. The V̇O2max was 57 for the placebo group and 60 for the supplemented. The increase in V̇O2max was not significant for either group, but workload at 4 mmol/L of Lactate was higher in the supplemented group than the placebo (but not at 2 mmol/L). I found this interesting, but inconclusive given the issues of measuring Lactate, and I'd interpret this as showing no impact of Vitamin C on fitness.
  • Of 14 Sedentary men (V̇O2max < 43), 5 were given 1g/day of Vitamin C while 9 acted as controls[32]. All underwent 8 weeks of training, 3 days/week for 40 minutes, ramping up from 65% to 80% of V̇O2max. There were no statistically different changes in V̇O2max, though the average improvement was 22% in the placebo and 10.8% in the supplemented group, mostly due to the lower initial V̇O2max in the placebo group. With such a small group, it's possible that a larger study would reveal differences or that the differences would disappear. Interestingly, they also studied rats and found that Vitamin C dramatically reduced their endurance improvement, though again no significant differences in the rats' V̇O2max. (The levels of Vitamin C in the supplemented group were ~165 mmol/L and in the control group were ~45 mmol/L.)
  • A study that used "antioxidant rich foods" during altitude training found that V̇O2max increased in both treated and control groups equally, but hemoglobin concentration increased more in the treated group[33].
  • A study of 15 recreationally active men were given 1g/day of Vitamin C (n=8) or a placebo for 4 weeks of high intensity interval training, with no difference in improvement for V̇O2max, 10K time trial, or running economy[34].
  • 21 active men underwent cycling training 5 days/week for 12 weeks while 11 of them received 500mg Vitamin C and 400 IU of Vitamin E[30]. There was no statistical difference in improvement in V̇O2max, maximum power, workload at Lactate Threshold, or muscle Glycogen content.

7 Vitamin C, Exercise, and Muscular Resiliency

Unlike cycling or swimming, running involves eccentric muscular stress, with the muscles extending under load to absorb the body weight on landing[35][36], something that's exacerbated by downhill running[37]. This eccentric stress is one of the causes of muscle soreness after a marathon[38]. This damage causes Delayed Onset Muscle Soreness (DOMS), and it's particularly important to runners because while the soreness is delayed, there is muscular weakness that occurs during the damaging exercise[39]. This means the soreness you experience after a marathon involves muscular weakness during the race. There are various ways of reducing the muscle damage and treating the soreness from DOMS, but the most important is called "the repeated bout effect" (RBE). The principle of RBE is that performing exercise that causes DOMS and recovering then gives protection from similar exercise in the future[40]. There are a number of possible mechanisms behind RBE[41], including neural adaptations, changes in muscle fiber structure, changes in inflammatory response, and extracellular matrix structural remodeling. It's the extracellular matrix structural remodeling that's of interest here, as that remodeling involves collagen formation[42], and as noted above, Vitamin C is an important part in collagen formation[6][7]. There's one study that suggests that Vitamin C might be important for the Repeated Bout Effect[43] . This study used 1,000mg of Vitamin C and 400 IU Vitamin E per day on 22 moderately trained men and subjected them to two bouts of downhill running (40 min, -10%, 65-70% V̇O2max.) They found that the supplementation not only reduced DOMS after the first bout, but enhanced the RBE. Obviously, this is only one study, it used Vitamin E in addition to Vitamin C, and didn't measure strength deficits, but it's highly suggestive.

7.1 My Vitamin C Experiment

The research above mirrors my personal anecdotal experience. I've been taking Vitamin C in doses around 1g/day for many years as it seems to help my skin condition. I stopped taking Vitamin C for some months in 2018 due to the research suggesting it interferes with enzyme response to exercise. During that time without Vitamin C supplementation, I was also trying to ramp back up my Downhill Running via Treadmill Descents. I believe downhill running was a key component in my training for ultras, allowing me to race 100 miles with little muscle soreness the next day. Unfortunately, I found that 60-90 minutes of downhill running produced severe DOMS, and I couldn't get past that mark. I seemed to be stuck at that level and unable to make progress, where in previous years I'd been able to build up to marathon+ distance downhill runs. After a particularly disappointing all-day, self-supported run on Mount Mitchell in August I revisited the research on Vitamin C more comprehensively and found the study on Vitamin C and the Repeated Bout Effect. Having restarted my Vitamin C intake, and upped it to 500mg 3-5x per day, I found my ability to run downhill returned rapidly. I was able to built up to running marathon distance downhill runs at -10% within a few months, and only #1 on the DOMS scale. So for me at least, Vitamin C may be a critical component to endurance running.

7.2 Addition Eccentric Exercise Research

Sadly, most research on eccentric exercise has focused on preventing or treating causes Delayed Onset Muscle Soreness (DOMS), rather than maximizing the Repeated Bout Effect, or even limiting the immediate reduction on strength. For instance, a study showed that 3g/day of Vitamin C reduced DOMS, but not reduce muscular power[44].

8 Vitamin C and Tendons

A 2018 review of the research found that Vitamin C studies on animals improved tendon and bone healing, but that the human research at that point was limited[45]. One study found that 200 IU Vitamin E with 500 mg Vitamin C improved ACL healing (1-6 weeks) after ACL surgery, but the differences disappeared by 3 months[46].

9 Vitamin C, Running, and the Common Cold

Controlled studies suggest that Vitamin C may reduce the length of the common cold, but not prevent the colds except in those undergoing severe exercise such as a marathon[47].

10 Vitamin C and Diabetes

A full review of the research is outside the scope of this article, and further reading is encouraged. Recent reviews suggest that Vitamin C may help slow the progression of diabetes complications[48] as well as possibly reducing the risk of developing diabetes[49][50].

11 Vitamin C and Kidney Stones

There is conflicting evidence concerning Vitamin C and kidney stones, possibly because there are many things that change the risk for kidney stones. Personally, I feel that any risk for kidney stones from Vitamin C is offset by my physical activity, low body fat, good hydration, and high intakes of magnesium, potassium, and calcium. As always, read the research yourself and talk to your doctor if you have concerns.

A metabolite of Vitamin C is oxalate that is excreted in urine[51], and calcium oxalate is a common type of kidney stone[52]. Two studies found that 1,000mg of Vitamin C twice a day increased oxalate in the urine, a risk for kidney stones [53][54]. However, two other studies found that 4g/day[55] or 1, 5, 10g/day[56] didn't raise oxalate levels. One study found even found that 2g/day of Vitamin C as a supplement didn't change urine oxalate, but the same dose from Orange Juice did raise the urine oxalate[57].

Likewise, there are conflicting results from large scale prospective studies. A study of 48,850 men found that the risk of kidney stones was more than doubled with those that took more than 7 Vitamin C tablets per week[58]. The study doesn't have dosage information as it uses survey data that just ask for number of supplements taken. Another study of 45,619 men found that compared with those who consumed less than 90mg/day, 1+g/day had a 40% greater incidence of kidney stones, and even those that consume 90-249mg/day had 22% greater incidence[59]. This relationship between Vitamin C and kidney stones only emerged after adjusting for potassium intake. Potassium intake is associated with Vitamin C intake, and the risk of kidney stones goes down with potassium intake, so the two tend to "even out". This reflects the general complexity of nutrition and kidney stones, where many dietary factors may impact kidney stone formation. The contrasts with a study of 45,251 men[60] that found no relationship between Vitamin C intake and the incidence of kidney stones. (A study of 85,557 women[61] found no change in risk, but women seem to have a lower incidence of kidney stones.)

Kidney stone risk may be associated with various nutritional factors, possibly including things that might reduce the risk, such as calcium, potassium, magnesium, fluid intake[59]. Obesity may also increase the risk for kidney stones[62], with one estimate suggesting a 20% increase in risk for each 5 BMI and 12% for each 5Kg[63]. Diabetes may increase risk of kidney stones, while physical exercise may reduce the risk[63].

12 Vitamin C, Depression, and Anxiety

There is some evidence that Vitamin C may be related to depression and anxiety. More details to follow.

13 Vitamin C Conversion Factors

To convert ascorbic acid mg /100 mL to mol/L, multiply by 56.78[64]. (This will be of use if you're digging into the research papers.)

14 References

  1. ↑ S Englard, S Seifter, The Biochemical Functions of Ascorbic Acid, Annual Review of Nutrition, volume 6, issue 1, 1986, pages 365–406, ISSN 0199-9885, doi 10.1146/annurev.nu.06.070186.002053
  2. ↑ M Levine, K R Dhariwal, P W Washko, J D Butler, R W Welch, Y H Wang, P Bergsten, Ascorbic acid and in situ kinetics: a new approach to vitamin requirements, The American Journal of Clinical Nutrition, volume 54, issue 6, 1991, pages 1157S–1162S, ISSN 0002-9165, doi 10.1093/ajcn/54.6.1157s
  3. ↑ C J Rebouche, Ascorbic acid and carnitine biosynthesis, The American Journal of Clinical Nutrition, volume 54, issue 6, 1991, pages 1147S–1152S, ISSN 0002-9165, doi 10.1093/ajcn/54.6.1147s
  4. ↑ Darwin J. Prockop, Kari I. Kivirikko, Collagens: Molecular Biology, Diseases, and Potentials for Therapy, Annual Review of Biochemistry, volume 64, issue 1, 1995, pages 403–434, ISSN 0066-4154, doi 10.1146/annurev.bi.64.070195.002155
  5. ↑ Leif Hallberg, Mats Brune, Lena Rossander-Hulthén, Is There a Physiological Role of Vitamin C in Iron Absorption?, Annals of the New York Academy of Sciences, volume 498, issue 1 Third Confere, 1987, pages 324–332, ISSN 0077-8923, doi 10.1111/j.1749-6632.1987.tb23771.x
  6. ↑ 6.0 6.1 Jeffrey C. Geesin, Douglas. Darr, Russel. Kaufman, Saood. Murad, Sheldon R. Pinnell, Ascorbic Acid Specifically Increases Type I and Type III Procollagen Messenger RNA Levels in Human Skin Fibroblasts, Journal of Investigative Dermatology, volume 90, issue 4, 1988, pages 420–424, ISSN 0022202X, doi 10.1111/1523-1747.ep12460849
  7. ↑ 7.0 7.1 TA Sullivan, B Uschmann, R Hough, PS Leboy, Ascorbate modulation of chondrocyte gene expression is independent of its role in collagen secretion., The Journal of biological chemistry, volume 269, issue 36, ISSN 0021-9258, PMID 8077198, pages 22500–6
  8. ↑ V. Kovanen, H. Suominen, E. Heikkinen, Collagen of slow twitch and fast twitch muscle fibres in different types of rat skeletal muscle, European Journal of Applied Physiology and Occupational Physiology, volume 52, issue 2, 1984, pages 235–242, ISSN 0301-5548, doi 10.1007/BF00433399
  9. ↑ Marco Franchi, Alessandra Trirè, Marilisa Quaranta, Ester Orsini, Victoria Ottani, Collagen Structure of Tendon Relates to Function, The Scientific World JOURNAL, volume 7, 2007, pages 404–420, ISSN 1537-744X, doi 10.1100/tsw.2007.92
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  11. ↑ 11.0 11.1 11.2 11.3 11.4 11.5 11.6 11.7 11.8 11.9 SJ Padayatty, M Levine, Vitamin C: the known and the unknown and Goldilocks, Oral Diseases, volume 22, issue 6, 2016, pages 463–493, ISSN 1354523X, doi 10.1111/odi.12446
  12. ↑ 12.0 12.1 Man-Li S. Yew, BIOLOGICAL VARIATION IN ASCORBIC ACID NEEDS, Annals of the New York Academy of Sciences, volume 258, issue 1 Second Confer, 1975, pages 451–457, ISSN 0077-8923, doi 10.1111/j.1749-6632.1975.tb29303.x
  13. ↑ Anitra C Carr, Balz Frei, Toward a new recommended dietary allowance for vitamin C based on antioxidant and health effects in humans, The American Journal of Clinical Nutrition, volume 69, issue 6, 1999, pages 1086–1107, ISSN 0002-9165, doi 10.1093/ajcn/69.6.1086
  14. ↑ 14.0 14.1 14.2 14.3 14.4 14.5 M. Levine, C. Conry-Cantilena, Y. Wang, R. W. Welch, P. W. Washko, K. R. Dhariwal, J. B. Park, A. Lazarev, J. F. Graumlich, J. King, L. R. Cantilena, Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance., Proceedings of the National Academy of Sciences, volume 93, issue 8, 1996, pages 3704–3709, ISSN 0027-8424, doi 10.1073/pnas.93.8.3704
  15. ↑ Mark Levine, Sebastian J. Padayatty, Michael Graham Espey, Vitamin C: A Concentration-Function Approach Yields Pharmacology and Therapeutic Discoveries, Advances in Nutrition, volume 2, issue 2, 2011, pages 78–88, ISSN 2161-8313, doi 10.3945/an.110.000109
  16. ↑ 16.0 16.1 16.2 Sebastian J. Padayatty, He Sun, Yaohui Wang, Hugh D. Riordan, Stephen M. Hewitt, Arie Katz, Robert A. Wesley, Mark Levine, Vitamin C Pharmacokinetics: Implications for Oral and Intravenous Use, Annals of Internal Medicine, volume 140, issue 7, 2004, pages 533, ISSN 0003-4819, doi 10.7326/0003-4819-140-7-200404060-00010
  17. ↑ M.Cristina Polidori, Patrizia Mecocci, Mark Levine, Balz Frei, Short-term and long-term vitamin C supplementation in humans dose-dependently increases the resistance of plasma to ex vivo lipid peroxidation, Archives of Biochemistry and Biophysics, volume 423, issue 1, 2004, pages 109–115, ISSN 00039861, doi 10.1016/j.abb.2003.12.019
  18. ↑ Christopher P. Corpe, Hongbin Tu, Peter Eck, Jin Wang, Robert Faulhaber-Walter, Jurgen Schnermann, Sam Margolis, Sebastian Padayatty, He Sun, Yaohui Wang, Robert L. Nussbaum, Michael Graham Espey, Mark Levine, Vitamin C transporter Slc23a1 links renal reabsorption, vitamin C tissue accumulation, and perinatal survival in mice, Journal of Clinical Investigation, volume 120, issue 4, 2010, pages 1069–1083, ISSN 0021-9738, doi 10.1172/JCI39191
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  23. ↑ Stanley T. Omaye, Ellen E. Schaus, Mark A. Kutnink, Wayne C. Hawkes, Measurement of Vitamin C in Blood Components by High-Performance Liquid Chromatography., Annals of the New York Academy of Sciences, volume 498, issue 1 Third Confere, 1987, pages 389–401, ISSN 0077-8923, doi 10.1111/j.1749-6632.1987.tb23776.x
  24. ↑ Anitra C Carr, Stephanie M Bozonet, Juliet M Pullar, Jeremy W Simcock, Margreet CM Vissers, Human skeletal muscle ascorbate is highly responsive to changes in vitamin C intake and plasma concentrations, The American Journal of Clinical Nutrition, volume 97, issue 4, 2013, pages 800–807, ISSN 0002-9165, doi 10.3945/ajcn.112.053207
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  26. ↑ Gøran Paulsen, Kristoffer T. Cumming, Geir Holden, Jostein Hallén, Bent Ronny Rønnestad, Ole Sveen, Arne Skaug, Ingvild Paur, Nasser E. Bastani, Hege Nymo Østgaard, Charlotte Buer, Magnus Midttun, Fredrik Freuchen, Håvard Wiig, Elisabeth Tallaksen Ulseth, Ina Garthe, Rune Blomhoff, Haakon B. Benestad, Truls Raastad, Vitamin C and E supplementation hampers cellular adaptation to endurance training in humans: a double-blind, randomised, controlled trial, The Journal of Physiology, volume 592, issue 8, 2014, pages 1887–1901, ISSN 00223751, doi 10.1113/jphysiol.2013.267419
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  29. ↑ R Buzina, Z Grgić, M Jusić, J Sapunar, N Milanović, G Brubacher, Nutritional status and physical working capacity., Human nutrition. Clinical nutrition, volume 36, issue 6, 1982, ISSN 0263-8290, PMID 7161138, pages 429–38
  30. ↑ 30.0 30.1 Christina Yfanti, Thorbjörn Åkerström, Søren Nielsen, Anders R. Nielsen, Remi Mounier, Ole H. Mortensen, Jens Lykkesfeldt, Adam J. Rose, Christian P. Fischer, Bente K. Pedersen, Antioxidant Supplementation Does Not Alter Endurance Training Adaptation, Medicine & Science in Sports & Exercise, volume 42, issue 7, 2010, pages 1388–1395, ISSN 0195-9131, doi 10.1249/MSS.0b013e3181cd76be
  31. ↑ Antoni Aguiló, Pedro Tauler, Antoni Sureda, Nuria Cases, Josep Tur, Antoni Pons, Antioxidant diet supplementation enhances aerobic performance in amateur sportsmen, Journal of Sports Sciences, volume 25, issue 11, 2007, pages 1203–1210, ISSN 0264-0414, doi 10.1080/02640410600951597
  32. ↑ Mari-Carmen Gomez-Cabrera, Elena Domenech, Marco Romagnoli, Alessandro Arduini, Consuelo Borras, Federico V Pallardo, Juan Sastre, Jose Viña, Oral administration of vitamin C decreases muscle mitochondrial biogenesis and hampers training-induced adaptations in endurance performance, The American Journal of Clinical Nutrition, volume 87, issue 1, 2008, pages 142–149, ISSN 0002-9165, doi 10.1093/ajcn/87.1.142
  33. ↑ A. E. Koivisto, G. Paulsen, I. Paur, I. Garthe, E. Tønnessen, T. Raastad, N. E. Bastani, J. Hallén, R. Blomhoff, S. K. Bøhn, Antioxidant-rich foods and response to altitude training: A randomized controlled trial in elite endurance athletes, Scandinavian Journal of Medicine & Science in Sports, volume 28, issue 9, 2018, pages 1982–1995, ISSN 09057188, doi 10.1111/sms.13212
  34. ↑ Llion A. Roberts, Kris Beattie, Graeme L. Close, James P. Morton, Vitamin C Consumption Does Not Impair Training-Induced Improvements in Exercise Performance, International Journal of Sports Physiology and Performance, volume 6, issue 1, 2011, pages 58–69, ISSN 1555-0265, doi 10.1123/ijspp.6.1.58
  35. ↑ Bijker K., G. de Groot, Hollander A., Differences in leg muscle activity during running and cycling in humans, European Journal of Applied Physiology, volume 87, issue 6, 2002, pages 556–561, ISSN 1439-6319, doi 10.1007/s00421-002-0663-8
  36. ↑ A Koller, G Sumann, W Schobersberger, H Hoertnagl, C Haid, N Maffulli, Decrease in eccentric hamstring strength in runners in the Tirol Speed Marathon * COMMENTARY, British Journal of Sports Medicine, volume 40, issue 10, 2006, pages 850–852, ISSN 0306-3674, doi 10.1136/bjsm.2006.028175
  37. ↑ R G Eston, J Mickleborough, V Baltzopoulos, Eccentric activation and muscle damage: biomechanical and physiological considerations during downhill running., British Journal of Sports Medicine, volume 29, issue 2, 1995, pages 89–94, ISSN 0306-3674, doi 10.1136/bjsm.29.2.89
  38. ↑ H. Kyröläinen, T. Pullinen, R. Candau, J. Avela, P. Huttunen, P. V. Komi, Effects of marathon running on running economy and kinematics, European Journal of Applied Physiology, volume 82, issue 4, 2000, pages 297–304, ISSN 1439-6319, doi 10.1007/s004210000219
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  41. ↑ Robert D. Hyldahl, Trevor C. Chen, Kazunori Nosaka, Mechanisms and Mediators of the Skeletal Muscle Repeated Bout Effect, Exercise and Sport Sciences Reviews, volume 45, issue 1, 2017, pages 24–33, ISSN 0091-6331, doi 10.1249/JES.0000000000000095
  42. ↑ Ryo Takagi, Riki Ogasawara, Arata Tsutaki, Koichi Nakazato, Naokata Ishii, Regional adaptation of collagen in skeletal muscle to repeated bouts of strenuous eccentric exercise, Pflügers Archiv - European Journal of Physiology, volume 468, issue 9, 2016, pages 1565–1572, ISSN 0031-6768, doi 10.1007/s00424-016-1860-3
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  51. ↑ Metabolism of L-ascorbic acid-1-C14 in man., The Journal of biological chemistry, volume 230, issue 2, 1958, ISSN 0021-9258, PMID 13525409, pages 923–30
  52. ↑ Scherer, Kai, et al. "Non-invasive differentiation of kidney stone types using X-ray dark-field radiography." Scientific reports 5 (2015): 9527.
  53. ↑ Linda K. Massey, Michael Liebman, Susan A. Kynast-Gales, Ascorbate Increases Human Oxaluria and Kidney Stone Risk, The Journal of Nutrition, volume 135, issue 7, 2005, pages 1673–1677, ISSN 0022-3166, doi 10.1093/jn/135.7.1673
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