12 January - 20 June 2016

Nitrate supplementation, low oxygen training and muscle fibre composition

A study by researchers from various institutions in Belgium, UK and Australia and published in Frontiers in Physiology suggests that nitrate supplements can help change muscle fibre composition and so potentially help boost sports performance.

A study by researchers from various institutions in Belgium, UK and Australia and published in Frontiers in Physiology suggests that nitrate supplements can help change muscle fibre composition and so potentially help boost sports performance.

De Smet et al. note that interest in sprint interval training (SIT) for athletes at low oxygen levels (hypoxia) is on the increase. Previous studies have suggested that SIT can help muscle fibre adaptations towards types that can sustain power.  Other studies have shown nitrate supplementation to enhance exercise performance in hypoxia. In the current study the researchers aimed to investigate if SIT in hypoxia, with and without nitrate supplementation, increases muscle fibre adaptations from fast glycolytic fibres (type IIb – fast power, rapid fatigue) towards fast oxidative muscle (type IIa - fast power, less fatigue) and increases performance compared to SIT at normal oxygen levels (normoxia).

De Smet et al. recruited 27 “recreationally active” participants who were placed on a 5 week controlled SIT programme. Participants were assigned to one of three groups: those performing SIT in normoxia receiving a placebo supplement, those performing SIT in hypoxia receiving a placebo supplement and those performing SIT in hypoxia receiving a nitrate supplement of 6.45 mmol NaNO3. Each group performed 3 standard SIT sessions per week with supplements taken 3 hours before each session. Participants were asked to refrain from eating nitrate rich foods for the duration of the study.

Both before and after the 5-week period, participants performed exercise tests to assess a number of performance metrics.  Muscle samples were also taken and analysed for buffering capacity (the ability to neutralise acids that accumulate during exercise) and fibre composition.

De Smet et al. found that the programme, in all three group, increased “time to exhaustion” and “peak power output”. Average power output in the post-study tests was increased by 4% in the normoxia group and by 8% in the two hypoxia groups. For muscle composition, De Smet et al. discovered that while SIT reduced the proportion of fast glycolytic (type IIb) fibres in all groups, the proportion of fast oxidative fibres (type IIa) was significantly higher in the hypoxia with nitrate group, with an increase from 45% to 56%. The authors note however that there was no change in muscle buffering capacity in any of the three groups.

In discussion, De Smet et al. note that “short-term oral nitrate supplementation in conjunction with SIT may be a valid strategy to enhance performance in “glycolytic” exercise events such as a 400-meter dash, by contributing to a beneficial fibre type shift” but note that further studies would be required to attempt to discover the “cellular mechanisms by which oral nitrate intake can stimulate the conversion to type IIa muscle fibres”.

In a press release, Prof Peter Hespel, one of the study researchers, is quoted as saying that “this is probably the first study to demonstrate that a simple nutritional supplementation strategy, i.e. oral nitrate intake, can impact on training-induced changes in muscle fibre composition;".  Hespel added that “It would now be interesting to investigate whether addition of nitrate-rich vegetables to the normal daily sports diet of athletes could facilitate training-induced muscle fibre type transitions and maybe in the long term also exercise performance."

RSSL can determine nitrates in food products. For more information please contact Customer Services on +44 (0) 118 918 4076 or email enquiries@rssl.com

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