Reply to Li et al.
30 April 2018 (online)
We thank Prof Li and Mr Syno for their interest in our paper. We agree that our study would have been more informative had it included an assessment of hip muscle activations but the correspondents’ call for a broader study fails to appreciate the goals of the current one (assessing hamstring activation) and the limitations encountered when undertaking time consuming and expensive research. For example, when embarking on this and the other studies that were part of our broader project (Bourne et al., 2017a, 2017b & 2017c) we had to consider the pressures placed on a PhD candidate (MB) for timely completion and the budget limitations which precluded scanning a larger volume of the lower limb. However, we do hope to assess hip muscle activation in future studies and we extend an invitation to Professor Li and Mr Syno to join us in that endeavour.
Professor Li and Mr Syno have suggested that the following statement from our paper (Bourne et al. 2017c) is misleading; “During the SLB exercise, the semitendinosus is most selectively targeted and the biceps femoris long head is preferentially activated over its short head”, partly because we have not made reference to other important hip extensor muscles. However, given our paper’s title (A functional MRI exploration of hamstring activation during the supine bridge exercise), its stated purpose (“The purpose of this study was to use fMRI to explore the spatial patterns of hamstring muscle activation during the SLB exercise…”) and the methods which involved scanning of the thigh only, we believe that attentive readers will understand the context in which our statements are made. Nevertheless, we could have provided greater clarity and further minimised the risk of misunderstandings by acknowledging that these conclusions were relevant only to the hamstrings.
The correspondents also suggest that we have mischaracterised “the function of the biceps femoris short head”. We are not sure how this conclusion has been reached and do not see how we have erred in making the following statement; “During the SLB exercise… …the biceps femoris long head is preferentially activated over its short head”. The data we presented (T2 changes after exercise) clearly support our statement and we made no suggestion or inference that the biceps femoris short head is a hip extensor.
Professor Li and Mr Syno state that we “failed to present…… the actual contraction intensity of hamstring muscles in the mSLB.” We refer the correspondents to the paper that they have referenced (Bourne et al., 2017a). In our previous study we assessed the surface EMG activity of the lateral and medial hamstrings in ten exercises including the straight knee bridge. The loads employed (~10RM v 12RM) in that and the present study were similar enough for readers of both to make a reasonable judgement about the relative hamstring activations in this exercise and we saw no reason to replicate these measurements.
We also note that the second paragraph of the letter begins with an obvious error (“Single leg supine bridge is mainly an exercise for single joint hip flexors, i. e., gluteus medius and maximus”) which should have required review by the authors prior to sending it to us for a response.
- 1 Bourne MN, Williams MD, Opar DA, Al Najjar A, Kerr GK, Shield AJ. Impact of exercise selection on hamstring muscle activation. Br J Sports Med 2017; 51: 1021-1028
- 2 Bourne MN, Duhig S, Timmins RG, Williams MD, Opar DA, Najjar A, Kerr GK, Shield AJ. Impact of the Nordic hamstring and hip extension exercises on hamstring architecture and morphology: Implications for injury prevention. Br J Sports Med 2017; 51: 469-477
- 3 Bourne M, Williams M, Pizzari T, Shield A. A functional MRI exploration of hamstring activation during the supine bridge exercise. Int J Sports Med 2018; 39: 104-109