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Comment on Dissociation between running economy and running performance in elite Kenyan distance runners a
a
Jordan Santos-Concejero & Ross Tucker a
UCT/MRC Research Unit for Exercise Science and Sports Medicine, Human Biology, University of Cape Town, Cape Town 7700, South Africa Published online: 29 Oct 2014.
Click for updates To cite this article: Jordan Santos-Concejero & Ross Tucker (2014): Comment on Dissociation between running economy and running performance in elite Kenyan distance runners, Journal of Sports Sciences, DOI: 10.1080/02640414.2014.971048 To link to this article: http://dx.doi.org/10.1080/02640414.2014.971048
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Journal of Sports Sciences, 2014 http://dx.doi.org/10.1080/02640414.2014.971048
LETTER TO THE EDITOR
Comment on Dissociation between running economy and running performance in elite Kenyan distance runners
JORDAN SANTOS-CONCEJERO & ROSS TUCKER
Downloaded by [University of Otago] at 08:16 05 July 2015
UCT/MRC Research Unit for Exercise Science and Sports Medicine, Human Biology, University of Cape Town, Cape Town 7700, South Africa (Accepted 26 September 2014)
Abstract Mooses and colleagues suggest that running economy alone does not explain superior distance running performance in elite Kenyan runners. Whilst we agree with the multi-factorial hypothesis for Kenyan running success, we do not believe that running economy can be overlooked to the extent that it was based on this particular study. Based on the methods used and the range of athletes tested, in this response letter we question whether this study provides any basis for downplaying the influence of running economy or suggesting that other factors compensate for it to enable superior performance. Keywords: metabolic cost, African runners, association, anthropometry, middle-distance runners
Mooses and colleagues recently argued that since they found no association between running economy (RE) and running performance in elite Kenyan distance runners, a superior RE per se could not account for the superior performance of the East African runners, and that RE is compensated for by other factors to enable superior distance running performance (Mooses et al., 2014). Whilst we agree with the multi-factorial hypothesis for Kenyan running success, as acknowledged by Mooses et al. (2014) and argued elsewhere (Larsen, 2003; Tucker, Santos-Concejero, & Collins, 2013; Wilber & Pitsiladis, 2012), we do not believe that RE can be overlooked or even downplayed to the extent that it was based on this particular study. Previous research in African runners in general (Weston, Mbambo, & Myburgh, 2000), and East African runners in particular (Lucia et al., 2006; Saltin et al., 1995) has shown that African runners are more metabolically economical than elite European runners. Even studies that did not find RE differences between elite Kenyan and European runners reported that RE, together with VO2max and the fraction of the VO2max that can be sustained over
a race distance, are strong predictors of performance (Tam et al., 2012). The absence of such an association in the study of Mooses et al. (2014) may be the result of a number of method related issues which must be acknowledged before any conclusions regarding RE can be made. First, Mooses et al. (2014) apply a questionable standard to the definition of “homogenous” when defining their elite athlete sample, with respect to both ability and the events they excel in. They analysed the best performances of 32 elite Kenyan runners, competing in distances ranging from 800 m to the marathon. Even if we accept, for example, that runners with 800 m personal best performances ranging from 1:47 to 1:53 are homogenous, it seems conflicting to group together and analyse athletes from distances as different as 800 m and the marathon. Further, we would also question the characterisation of the athletes tested by Mooses et al. (2014) as “elite”. The athletes are certainly competitive and superior to almost all those studied in previous research, but may fall slightly below the elite level (La Torre, Vernillo, Agnello, Berardelli, & Rampinini, 2011). We do not however consider this difference to affect the veracity of the
Correspondence: Jordan Santos-Concejero, UCT/MRC Research Unit for Exercise Science and Sports Medicine, Human Biology, University of Cape Town, 3º Floor Sports Sciences Institute of South Africa, Boundary Road, Newlands, Cape Town 7700, South Africa. E-mail: [email protected] © 2014 Taylor & Francis
Downloaded by [University of Otago] at 08:16 05 July 2015
2
J. Santos-Concejero & R. Tucker
conclusions made by Mooses et al. (2014), and suggest that the lack of homogeneity is the key factor undermining their conclusions. This is not a trivial matter, for the contribution of RE to performance is different for an 800-m athlete and a marathon runner, as is the method by which RE would be used to predict performance (Saunders, Pyne, Telford, & Hawley, 2004). First, it is widely known that the metabolic cost and pulmonary VO2 kinetics differ between middleand long-distance runners (Chapman et al., 2012; Kilding, Fysh, & Winter, 2007). Second, it is known that the speeds at which runners are tested influences laboratory measures of RE, as middle-distance runners are more economical at faster speeds and long-distance runners at slower speeds (Daniels & Daniels, 1992). Since Mooses et al. (2014) tested all runners at a speed of 16 km · h−1, we would question whether this satisfies the relative-speed range of runners in the sample group, and would suggest that it explains why this apparently homogenous group had a range of VO2 from 55 to 67 ml · kg−1 · min−1 at that particular speed. In events such as in 800 m, the accumulated oxygen deficit alone can actually predict up to 89% of running performance (Nevill, Ramsbottom, Nevill, Newport, & Williams, 2008). Similarly, whereas for the 800–m, aerobic pathways contribute approximately 60% of total energy (Duffield, Dawson, & Goodman, 2005), the marathon is almost exclusively aerobic (~100%) and its performance can be almost entirely predicted by the following equation (Tam et al., 2012): ðV O2max V O2max fraction that can be sustained during the marathonÞ RE1 RE and VO2max can also explain up to 95% of the variance in middle-distance running performance, but since the predicting model for middle-distance running is different – a proportional curvilinear ratio of VO2max divided by RE (Ingham et al., 2008) – analysing marathon and middle-distance runners as part of the same group would hide any existing trend for the different events separately. Therefore, since 13 of the 32 participants tested were 800- or 1500-m runners, we would question (a) the simple method and resultant lack of association as an artefact of the group and testing model and (b) whether there was a basis for testing a RE-performance hypothesis in such different athletes in the first instance. Ideally, what Mooses et al. (2014) might have done is to identify which runners in the sample belong to the middle-distance compared to longdistance category, so that either a different method of testing or performance prediction might be used. However, we appreciate that such a distinction
would likely have decreased sample sizes to the point of being statistically underpowered. The treatment of all runners in one group may however lead to falsely concluding that RE is not related to performance. Further method issues may also influence the findings. One of the findings of Mooses et al. (2014) was that incremental running performance to exhaustion was not correlated with RE. However, the protocol used in this incremental test is unusual and, we would argue, not valid for the range of athletes tested. First, the speed was increased only to 17 km · h−1, relatively slow for an elite group. Thereafter, the load was increased by means of increasing gradient. The data on the final gradients reached are not provided, but we would expect this calibre of athlete to reach very high gradients at which point the biomechanical changes of steep uphill running may begin to confound the performance as the muscle activation profiles dramatically differ between horizontal and uphill running (Sloniger, Cureton, Prior, & Evans, 1997). Finally, whilst this study may be the first to systematically explore the relationships of a vast number of anthropometric parameters and RE in “elite” Kenyan runners, it is not the first to analyse the major putative anthropometric parameters that may explain RE and running performance in a homogenous group of competitive Kenyan runners, as is claimed. Vernillo and colleagues recently reported a comprehensive range of directly measured anthropometrical variables, including skindfolds, upper and lower body lengths, breadths, girths and even the somatotype (Vernillo et al., 2013). They did not link these to RE, as Mooses et al. (2014) have done, but this existing contribution cannot be overlooked. In conclusion, the findings of Mooses et al. (2014) suggest that RE alone does not explain superior distance running performance in elite Kenyan runners. This was never in question, since Kenyan running success is widely accepted as a multi-factorial phenomenon. However, based on the methods used, and the range of athletes tested, we would question whether this study provides any basis for downplaying the influence of RE, suggesting that other factors compensate for it to enable superior performance.
References Chapman, R. F., Laymon, A. S., Wilhite, D. P., McKenzie, J. M., Tanner, D. A., & Stager, J. M. (2012). Ground contact time as an indicator of metabolic cost in elite distance runners. Medicine & Science in Sports & Exercise, 44, 917–925. Daniels, J., & Daniels, N. (1992). Running economy of elite male and elite female runners. Medicine & Science in Sports & Exercise, 24, 483–489.
Downloaded by [University of Otago] at 08:16 05 July 2015
Running economy and performance in Kenyan runners Duffield, R., Dawson, B., & Goodman, C. (2005). Energy system contribution to 400-metre and 800-metre track running. Journal of Sports Sciences, 23, 299–307. Ingham, S. A., Whyte, G. P., Pedlar, C., Bailey, D. M., Dunman, N., & Nevill, A. M. (2008). Determinants of 800-m and 1500m running performance using allometric models. Medicine & Science in Sports & Exercise, 40, 345–350. Kilding, A. E., Fysh, M., & Winter, E. M. (2007). Relationships between pulmonary oxygen uptake kinetics and other measures of aerobic fitness in middle- and long-distance runners. European Journal of Applied Physiology, 100, 105–114. La Torre, A., Vernillo, G., Agnello, L., Berardelli, C., & Rampinini, E. (2011). Is it time to consider a new performance classification for high-level male marathon runners? Journal of Strength and Conditioning Research, 25, 3242–3247. Larsen, H. B. (2003). Kenyan dominance in distance running. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 136, 161–170. Lucia, A., Esteve-Lanao, J., Oliván, J., Gómez-Gallego, F., San Juan, A. F., Santiago, C., … Foster, C. (2006). Physiological characteristics of the best Eritrean runners-exceptional running economy. Applied Physiology & Nutrition Metabolism, 31, 530– 540. Mooses, M., Mooses, K., Haile, D. W., Durussel, J., Kaasik, P., & Pitsiladis, Y. P. (2014). Dissociation between running economy and running performance in elite Kenyan distance runners. Journal of Sports Sciences, 11, 1–9. Nevill, A. M., Ramsbottom, R., Nevill, M. E., Newport, S., & Williams, C. (2008). The relative contributions of anaerobic and aerobic energy supply during track 100-, 400- and 800-m
3
performance. Journal of Sports Medicine & Physical Fitness, 48, 138–142. Saltin, B., Larsen, H., Terrados, N., Bangsbo, J., Bak, T., Kim, C. K., … Rolf, C. J. (1995). Aerobic exercise capacity at sea level and at altitude in Kenyan boys, junior and senior runners compared with Scandinavian runners. Scandinavian Journal of Medicine & Science in Sports, 5, 209–221. Saunders, P. U., Pyne, D. B., Telford, R. D., & Hawley, J. A. (2004). Factors affecting running economy in trained distance runners. Sports Medicine, 34, 465–485. Sloniger, M. A., Cureton, K. J., Prior, B. M., & Evans, E. M. (1997). Lower extremity muscle activation during horizontal and uphill running. Journal of Applied Physiology, 83, 2073–2079. Tam, E., Rossi, H., Moia, C., Berardelli, C., Rosa, G., Capelli, C., & Ferretti, G. (2012). Energetics of running in top-level marathon runners from Kenya. European Journal of Applied Physiology, 112, 3797–3806. Tucker, R., Santos-Concejero, J., & Collins, M. (2013). The genetic basis for elite running performance. British Journal of Sports Medicine, 47, 545–549. Vernillo, G., Schena, F., Berardelli, C., Rosa, G., Galvani, C., Maggioni, M., … La Torre, A. (2013). Anthropometric characteristics of top-class Kenyan marathon runners. Journal of Sports Medicine & Physical Fitness, 53, 403–408. Weston, A. R., Mbambo, Z., & Myburgh, K. H. (2000). Running economy of African and Caucasian distance runners. Medicine & Science in Sports & Exercise, 32, 1130–1134. Wilber, R. L., & Pitsiladis, Y. P. (2012). Kenyan and Ethiopian distance runners: What makes them so good? International Journal of Sports Medicine, 7, 92–102.
Journal of Sports Sciences Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/rjsp20
Comment on Dissociation between running economy and running performance in elite Kenyan distance runners a
a
Jordan Santos-Concejero & Ross Tucker a
UCT/MRC Research Unit for Exercise Science and Sports Medicine, Human Biology, University of Cape Town, Cape Town 7700, South Africa Published online: 29 Oct 2014.
Click for updates To cite this article: Jordan Santos-Concejero & Ross Tucker (2014): Comment on Dissociation between running economy and running performance in elite Kenyan distance runners, Journal of Sports Sciences, DOI: 10.1080/02640414.2014.971048 To link to this article: http://dx.doi.org/10.1080/02640414.2014.971048
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Journal of Sports Sciences, 2014 http://dx.doi.org/10.1080/02640414.2014.971048
LETTER TO THE EDITOR
Comment on Dissociation between running economy and running performance in elite Kenyan distance runners
JORDAN SANTOS-CONCEJERO & ROSS TUCKER
Downloaded by [University of Otago] at 08:16 05 July 2015
UCT/MRC Research Unit for Exercise Science and Sports Medicine, Human Biology, University of Cape Town, Cape Town 7700, South Africa (Accepted 26 September 2014)
Abstract Mooses and colleagues suggest that running economy alone does not explain superior distance running performance in elite Kenyan runners. Whilst we agree with the multi-factorial hypothesis for Kenyan running success, we do not believe that running economy can be overlooked to the extent that it was based on this particular study. Based on the methods used and the range of athletes tested, in this response letter we question whether this study provides any basis for downplaying the influence of running economy or suggesting that other factors compensate for it to enable superior performance. Keywords: metabolic cost, African runners, association, anthropometry, middle-distance runners
Mooses and colleagues recently argued that since they found no association between running economy (RE) and running performance in elite Kenyan distance runners, a superior RE per se could not account for the superior performance of the East African runners, and that RE is compensated for by other factors to enable superior distance running performance (Mooses et al., 2014). Whilst we agree with the multi-factorial hypothesis for Kenyan running success, as acknowledged by Mooses et al. (2014) and argued elsewhere (Larsen, 2003; Tucker, Santos-Concejero, & Collins, 2013; Wilber & Pitsiladis, 2012), we do not believe that RE can be overlooked or even downplayed to the extent that it was based on this particular study. Previous research in African runners in general (Weston, Mbambo, & Myburgh, 2000), and East African runners in particular (Lucia et al., 2006; Saltin et al., 1995) has shown that African runners are more metabolically economical than elite European runners. Even studies that did not find RE differences between elite Kenyan and European runners reported that RE, together with VO2max and the fraction of the VO2max that can be sustained over
a race distance, are strong predictors of performance (Tam et al., 2012). The absence of such an association in the study of Mooses et al. (2014) may be the result of a number of method related issues which must be acknowledged before any conclusions regarding RE can be made. First, Mooses et al. (2014) apply a questionable standard to the definition of “homogenous” when defining their elite athlete sample, with respect to both ability and the events they excel in. They analysed the best performances of 32 elite Kenyan runners, competing in distances ranging from 800 m to the marathon. Even if we accept, for example, that runners with 800 m personal best performances ranging from 1:47 to 1:53 are homogenous, it seems conflicting to group together and analyse athletes from distances as different as 800 m and the marathon. Further, we would also question the characterisation of the athletes tested by Mooses et al. (2014) as “elite”. The athletes are certainly competitive and superior to almost all those studied in previous research, but may fall slightly below the elite level (La Torre, Vernillo, Agnello, Berardelli, & Rampinini, 2011). We do not however consider this difference to affect the veracity of the
Correspondence: Jordan Santos-Concejero, UCT/MRC Research Unit for Exercise Science and Sports Medicine, Human Biology, University of Cape Town, 3º Floor Sports Sciences Institute of South Africa, Boundary Road, Newlands, Cape Town 7700, South Africa. E-mail: [email protected] © 2014 Taylor & Francis
Downloaded by [University of Otago] at 08:16 05 July 2015
2
J. Santos-Concejero & R. Tucker
conclusions made by Mooses et al. (2014), and suggest that the lack of homogeneity is the key factor undermining their conclusions. This is not a trivial matter, for the contribution of RE to performance is different for an 800-m athlete and a marathon runner, as is the method by which RE would be used to predict performance (Saunders, Pyne, Telford, & Hawley, 2004). First, it is widely known that the metabolic cost and pulmonary VO2 kinetics differ between middleand long-distance runners (Chapman et al., 2012; Kilding, Fysh, & Winter, 2007). Second, it is known that the speeds at which runners are tested influences laboratory measures of RE, as middle-distance runners are more economical at faster speeds and long-distance runners at slower speeds (Daniels & Daniels, 1992). Since Mooses et al. (2014) tested all runners at a speed of 16 km · h−1, we would question whether this satisfies the relative-speed range of runners in the sample group, and would suggest that it explains why this apparently homogenous group had a range of VO2 from 55 to 67 ml · kg−1 · min−1 at that particular speed. In events such as in 800 m, the accumulated oxygen deficit alone can actually predict up to 89% of running performance (Nevill, Ramsbottom, Nevill, Newport, & Williams, 2008). Similarly, whereas for the 800–m, aerobic pathways contribute approximately 60% of total energy (Duffield, Dawson, & Goodman, 2005), the marathon is almost exclusively aerobic (~100%) and its performance can be almost entirely predicted by the following equation (Tam et al., 2012): ðV O2max V O2max fraction that can be sustained during the marathonÞ RE1 RE and VO2max can also explain up to 95% of the variance in middle-distance running performance, but since the predicting model for middle-distance running is different – a proportional curvilinear ratio of VO2max divided by RE (Ingham et al., 2008) – analysing marathon and middle-distance runners as part of the same group would hide any existing trend for the different events separately. Therefore, since 13 of the 32 participants tested were 800- or 1500-m runners, we would question (a) the simple method and resultant lack of association as an artefact of the group and testing model and (b) whether there was a basis for testing a RE-performance hypothesis in such different athletes in the first instance. Ideally, what Mooses et al. (2014) might have done is to identify which runners in the sample belong to the middle-distance compared to longdistance category, so that either a different method of testing or performance prediction might be used. However, we appreciate that such a distinction
would likely have decreased sample sizes to the point of being statistically underpowered. The treatment of all runners in one group may however lead to falsely concluding that RE is not related to performance. Further method issues may also influence the findings. One of the findings of Mooses et al. (2014) was that incremental running performance to exhaustion was not correlated with RE. However, the protocol used in this incremental test is unusual and, we would argue, not valid for the range of athletes tested. First, the speed was increased only to 17 km · h−1, relatively slow for an elite group. Thereafter, the load was increased by means of increasing gradient. The data on the final gradients reached are not provided, but we would expect this calibre of athlete to reach very high gradients at which point the biomechanical changes of steep uphill running may begin to confound the performance as the muscle activation profiles dramatically differ between horizontal and uphill running (Sloniger, Cureton, Prior, & Evans, 1997). Finally, whilst this study may be the first to systematically explore the relationships of a vast number of anthropometric parameters and RE in “elite” Kenyan runners, it is not the first to analyse the major putative anthropometric parameters that may explain RE and running performance in a homogenous group of competitive Kenyan runners, as is claimed. Vernillo and colleagues recently reported a comprehensive range of directly measured anthropometrical variables, including skindfolds, upper and lower body lengths, breadths, girths and even the somatotype (Vernillo et al., 2013). They did not link these to RE, as Mooses et al. (2014) have done, but this existing contribution cannot be overlooked. In conclusion, the findings of Mooses et al. (2014) suggest that RE alone does not explain superior distance running performance in elite Kenyan runners. This was never in question, since Kenyan running success is widely accepted as a multi-factorial phenomenon. However, based on the methods used, and the range of athletes tested, we would question whether this study provides any basis for downplaying the influence of RE, suggesting that other factors compensate for it to enable superior performance.
References Chapman, R. F., Laymon, A. S., Wilhite, D. P., McKenzie, J. M., Tanner, D. A., & Stager, J. M. (2012). Ground contact time as an indicator of metabolic cost in elite distance runners. Medicine & Science in Sports & Exercise, 44, 917–925. Daniels, J., & Daniels, N. (1992). Running economy of elite male and elite female runners. Medicine & Science in Sports & Exercise, 24, 483–489.
Downloaded by [University of Otago] at 08:16 05 July 2015
Running economy and performance in Kenyan runners Duffield, R., Dawson, B., & Goodman, C. (2005). Energy system contribution to 400-metre and 800-metre track running. Journal of Sports Sciences, 23, 299–307. Ingham, S. A., Whyte, G. P., Pedlar, C., Bailey, D. M., Dunman, N., & Nevill, A. M. (2008). Determinants of 800-m and 1500m running performance using allometric models. Medicine & Science in Sports & Exercise, 40, 345–350. Kilding, A. E., Fysh, M., & Winter, E. M. (2007). Relationships between pulmonary oxygen uptake kinetics and other measures of aerobic fitness in middle- and long-distance runners. European Journal of Applied Physiology, 100, 105–114. La Torre, A., Vernillo, G., Agnello, L., Berardelli, C., & Rampinini, E. (2011). Is it time to consider a new performance classification for high-level male marathon runners? Journal of Strength and Conditioning Research, 25, 3242–3247. Larsen, H. B. (2003). Kenyan dominance in distance running. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 136, 161–170. Lucia, A., Esteve-Lanao, J., Oliván, J., Gómez-Gallego, F., San Juan, A. F., Santiago, C., … Foster, C. (2006). Physiological characteristics of the best Eritrean runners-exceptional running economy. Applied Physiology & Nutrition Metabolism, 31, 530– 540. Mooses, M., Mooses, K., Haile, D. W., Durussel, J., Kaasik, P., & Pitsiladis, Y. P. (2014). Dissociation between running economy and running performance in elite Kenyan distance runners. Journal of Sports Sciences, 11, 1–9. Nevill, A. M., Ramsbottom, R., Nevill, M. E., Newport, S., & Williams, C. (2008). The relative contributions of anaerobic and aerobic energy supply during track 100-, 400- and 800-m
3
performance. Journal of Sports Medicine & Physical Fitness, 48, 138–142. Saltin, B., Larsen, H., Terrados, N., Bangsbo, J., Bak, T., Kim, C. K., … Rolf, C. J. (1995). Aerobic exercise capacity at sea level and at altitude in Kenyan boys, junior and senior runners compared with Scandinavian runners. Scandinavian Journal of Medicine & Science in Sports, 5, 209–221. Saunders, P. U., Pyne, D. B., Telford, R. D., & Hawley, J. A. (2004). Factors affecting running economy in trained distance runners. Sports Medicine, 34, 465–485. Sloniger, M. A., Cureton, K. J., Prior, B. M., & Evans, E. M. (1997). Lower extremity muscle activation during horizontal and uphill running. Journal of Applied Physiology, 83, 2073–2079. Tam, E., Rossi, H., Moia, C., Berardelli, C., Rosa, G., Capelli, C., & Ferretti, G. (2012). Energetics of running in top-level marathon runners from Kenya. European Journal of Applied Physiology, 112, 3797–3806. Tucker, R., Santos-Concejero, J., & Collins, M. (2013). The genetic basis for elite running performance. British Journal of Sports Medicine, 47, 545–549. Vernillo, G., Schena, F., Berardelli, C., Rosa, G., Galvani, C., Maggioni, M., … La Torre, A. (2013). Anthropometric characteristics of top-class Kenyan marathon runners. Journal of Sports Medicine & Physical Fitness, 53, 403–408. Weston, A. R., Mbambo, Z., & Myburgh, K. H. (2000). Running economy of African and Caucasian distance runners. Medicine & Science in Sports & Exercise, 32, 1130–1134. Wilber, R. L., & Pitsiladis, Y. P. (2012). Kenyan and Ethiopian distance runners: What makes them so good? International Journal of Sports Medicine, 7, 92–102.
