Due to certain pieces of research that I have read over the last few years, I have naturally developed a negative feeling towards this training aid and this discussion outlines all of that research. Therefore, this discussion is biased and is not intended to be a balanced critical review of the subject, although as far as I have found there is only one benefit to the use of this aid which is stated within the discussion. Unfortunately there have been no studies conducted on the effect of this training aid on mobility and strengthening, which is surprising as these are are widely suggested to be the benefits in its use. Nevertheless, one well known distributor of this aid has described it as being "designed to encourage your horse to work effectively over his back in a natural way”. Let's delve into the facts behind this statement through the use of the most relevant scientific evidence that is available, to provide us with some idea of what the effects of this aid might be.
In 2018, Russel Guire of Centaur Biomechanics and team published a study that found that consistent local back pressure in the area indicated X caused by a non-gulleted roller created pressures that were greater than those which have previously been shown to cause pain in horses (13). A roller is more or less fixed in position and so it can be reasonably assumed then that the side-side movement of the rope part of this lunging aid caused by forelimb movement, could cause additional discomfort and potential for injury. Any pressure in this region is likely to reduce the horses willingness to 'lift' their back, the opposite being thoracic extension (dropping of the back). Prolonged or repeated thoracic extension is thought to contribute to the occurrence of overriding dorsal spinous processes (kissing spines), which coincidentally, commonly affects the spinous processes directly underneath and caudal to (behind) the area marked X (1) (7) (11) (12). This suggests that until we have evidence supporting the use of this specific training aid, at the very least it should not be used on kissing spine cases. It should be mentioned here that a low head carriage has been shown to increase thoracic flexion resulting in widening of the inter-DSP spaces (1). However, there are other methods to induce a slightly lowered head carriage that do not require the horse's mouth to be strapped to their withers via a rope that is wrapped around their [moving] elbows.
In 2013 Murray, Guire, Fisher & Fairfax published a study showing that poorly fitting girths caused peak pressures in the location marked X in the image above and below (18). These pressures were the same or greater than those associated with clinical signs of pain in horses. This pressure point is also in the location associated with girth galls which have been attributed to pressure or friction. Again, this was found when investigating girths - which are more or less fixed in position. It could reasonably be assumed then that the training aid in question might cause a greater degree of pressure as it is being pulled forwards by its attachment to the bit and an even greater degree of friction due to the side-side movement caused by shoulder and elbow movement.
Common sense suggests that this training aid is likely to cause pressure and restrictions behind the elbows. It is possible that this will result in reduced elbow mobility that will have a direct impact on shoulder mobility, and indeed mobility of the entire forelimb. Although this needs directly investigating, the aforementioned study by Murray, Guire, Fisher & Fairfax (2013) found that poorly fitting girths caused decreased forelimb protraction (18). The training aid in question crosses the underside of the horse and in relation to girths, Murray, Guire, Fisher & Fairfax (2013) explain that this location is a junction of various extrinsic muscles of the forelimbs that are involved in forelimb movement and flexion and lifting of the of thoracic, lumbar and sacral (back) regions whilst also contributing to protraction of the hindlimbs. It is clear to see that any overt pressure or restrictions in this location will have far-reaching consequences for the horse's entire musculoskeletal system that are likely to be opposite to the common goal in the use of this training aid.
No matter your feelings on bits, it is a fact that rein pressure is used as a form of negative reinforcement, where rein tension is released as a ‘reward’ once the horse has provided the correct response (14). If you would like to learn about positive/negative reinforcement/ punishment please follow reference 23. The problem with training aids is that the pressure cannot be released at the correct time, resulting in confusion and a negative impact on welfare (16). However, this training aid in particular is at risk of ‘jabbing’ and ‘yanking’ the horse's mouth due to its direct connection to the the elbows and due to the side-side effect on the bit caused by the left-right movement of the forelimbs. Overt pressures on the bit have been strongly evidenced to cause pain, fear, fight and flight responses, facial neuralgia, cervical (neck) pathologies, tongue injury, tongue retraction, bulging of the tongue and tooth damage (2) (3) (5) (6) (8) (9) (14). Additionally, critics point out that training aids force the horse into an outline (at any tension) rather than training them in self-carriage (14). When the horse's head is held down, the muscles of the neck and topline can not ‘‘suspend’’ the head and neck correctly and therefore the topline muscles can not strengthen. Further, training aids that fix the head and neck in position and do not allow the natural biomechanical movement of the head forwards and backward (undulation) in the walk and the canter, and therefore cause 'stilted' gaits (17).
As we have seen, there is likely to be a negative impact caused by this training aid on the withers elbows, shoulders and mouth; all of which surround and neighbour the horses neck; it is possible then that a compensatory effect will occur within the neck. The commonly discussed and so-called ‘broken neck’ is not a reference to a fractured vertebral column but instead is a description of the horses neck when flexed artificially by force (e.g., through training aids) which can cause over-flexion at the junctions of C3, 4, and 5 (17). It is unfortunate that this area (specifically C5, 6 and 7) has also been shown to be the area of the neck most commonly affected by arthritic changes (10). The combination of these factors in unison with the negative effect on supporting musculature due to prolonged use of training aids such as this may therefore contribute to the development of cervical dysfunction over time. We do not as yet know what the immediate effect of this training aid is, so why risk these potential long-term effects when there are other training options available?
Finally, it is interesting that it was not felt necessary to include the horses hind end in this image advertising this training aid. As we all know, correct hind end engagement and action is essential in the correct movement of the whole horse, but how? The ‘bow and string’ concept of the horse's back (illustrated below), demonstrates the connection between the limbs and the back (4) (22). Sufficient hindlimb protraction and forelimb retraction contribute to flexion (lifting) of the horses back, and subsequent improvements in core strength and ‘topline’ over time. As we have established, it is likely that the training aid in question will inhibit forelimb movement (at any tension) and therefore is likely to limit the horses ability to truly lift through their back.
So how can we safely instigate (and not inhibit) this type of movement? A four week study investigating the effects of elastic hindquarter and abdominal bands (Equiband™) on horses trotting found increased dynamic thoracolumbar stability in the trotting horse in-hand and on the lunge that may have been caused by activation of core musculature (19). Although muscle activation needs investigating in this scenario, this is a training method that does not provide any of the negative effects that have been highlighted throughout this particular discussion. Further, a doctoral thesis published by Marie Rhodin in 2008 demonstrated improved equine biomechanics as a result of long-reining due to the handlers ability to ‘engage’ the horse's hind end (21). These are just a couple of brief examples but the literature is out there if you wish to investigate alternative methods to train your horse and improve his way of going.
References
(1) Berner, D., Winter, K., Brehm, W., & Gerlach, K. (2012). Influence of head and neck position on radiographic measurement of intervertebral distances between thoracic dorsal spinous processes in clinically sound horses.Equine Veterinary Journal,44, 21-26. doi: 10.1111/j.2042-3306.2012.00678.x
(2) Cook, W. (2003). Bit-induced pain: a cause of fear, flight, fight und facial neuralgia in the horse. Pferdeheilkunde Equine Medicine, 19(1), 75-82. doi: 10.21836/pem20030111
(3) Cook, W., & Kibler, M. (2018). Behavioural assessment of pain in 66 horses, with and without a bit. Equine Veterinary Education, 31(10), 551-560. doi: 10.1111/eve.12916
(4) Denoix, J.M. (1999) Spinal biomechanics and functional anatomy. Vet. Clin. N. Am.: Equine Pract. 15, 27-6
(5) Doherty, O., Casey, V., McGreevy, P., McLean, A., Parker, P., & Arkins, S. (2017). An analysis of visible patterns of horse bit wear. Journal Of Veterinary Behavior, 18, 84-91. doi: 10.1016/j.jveb.2016.12.007
(6) Eisersiö, M., Rhodin, M., Roepstorff, L., & Egenvall, A. (2015). Rein tension in 8 professional riders during regular training sessions. Journal Of Veterinary Behavior, 10(5), 419-426. doi: 10.1016/j.jveb.2015.05.004
(7) ERICHSEN, C., EKSELL, P., HOLM, K., LORD, P., & JOHNSTON, C. (2010). Relationship between scintigraphic and radiographic evaluations of spinous processes in the thoracolumbar spine in riding horses without clinical signs of back problems.Equine Veterinary Journal,36(6), 458-465. doi: 10.2746/0425164044877341
(8) Guire, R., Mathie, H., Fisher, M., & Fisher, D. (2016). Riders' Perception of Symmetrical Pressure on the Ischial Tuberosities and Rein Contact Whilst Sitting on a Static Object. Equine Veterinary Journal, 48, 9-9. doi: 10.1111/evj.07_12595
(9) Hawson, L., Salvin, H., McLean, A., & McGreevy, P. (2014). Riders' application of rein tension for walk-to-halt transitions on a model horse. Journal Of Veterinary Behavior, 9(4), 164-168. doi: 10.1016/j.jveb.2014.04.001
(10) Hett, A., Busato, A., & Ueltschi, G. (2006). Radiographic measurements of the equine cervical spine with arthrotic alterations - a retrospective statistical study. Pferdeheilkunde Equine Medicine, 22(3), 241-249. doi: 10.21836/pem20060301
(11) Jeffcott, L. (1979). Radiographic Examination of the Equine Vertebral Column.Veterinary Radiology,20(3-6), 135-139. doi: 10.1111/j.1740-8261.1979.tb01191.x
(12) Jeffcott, L. (1979). Radiographic Features of the Normal Equine Thoracolumbar Spine.Veterinary Radiology,20(3-6), 140-147. doi: 10.1111/j.1740-8261.1979.tb01192.x
(13) Mackechnie-Guire, R., Mackechnie-Guire, E., Bush, R., Fisher, D., Fisher, M., & Weller, R. (2018). Local Back Pressure Caused by a Training Roller During Lunging With and Without a Pessoa Training Aid. Journal Of Equine Veterinary Science, 67, 112-117. doi: 10.1016/j.jevs.2018.03.018
(14) Manfredi, J., Rosenstein, D., Lanovaz, J., Nauwelaerts, S., & Clayton, H. (2009). Fluoroscopic study of oral behaviours in response to the presence of a bit and the effects of rein tension. Comparative Exercise Physiology, 6(04), 143-148. doi: 10.1017/s1755254010000036
(15) Martin, P., Cheze, L., Pourcelot, P., Deswuilbet, L., Duray, L., & Chateau, H., (2017) Effects of Large Saddle Panels on the Biomechanics of the Equine Back During Rising Trot: Preliminary Results. Journal of Equine Veterinary Science, 48, 15-22
(16) McLean, A., & McGreevy, P. (2010). Horse-training techniques that may defy the principles of learning theory and compromise welfare. Journal Of Veterinary Behavior, 5(4), 187-195. doi: 10.1016/j.jveb.2010.04.002
(17) McLean, A., & McGreevy, P. (2010). Horse-training techniques that may defy the principles of learning theory and compromise welfare. Journal Of Veterinary Behavior, 5(4), 187-195. doi: 10.1016/j.jveb.2010.04.002
(18) Murray, R., Guire, R., Fisher, M., & Fairfax, V. (2013). Girth pressure measurements reveal high peak pressures that can be avoided using an alternative girth design that also results in increased limb protraction and flexion in the swing phase. The Veterinary Journal, 198(1), 92-97. doi: 10.1016/j.tvjl.2013.07.028
(19) Pfau, T., Simons, V., Rombach, N., Stubbs, N., & Weller, R. (2017). Effect of a 4-week elastic resistance band training regimen on back kinematics in horses trotting in-hand and on the lunge. Equine Veterinary Journal, 49(6), 829-835. doi: 10.1111/evj.12690
(20) Reswick, J., Rogers, J. (1976). Experience at Rancho Los AMigos Hospital with devices and techniques to prevent pressure sores.
(21) Rhodin, M. (2008). A Biomechanical Analysis of Relationship Between the Head and Neck Position, Vertebral Column and Limbs in the Horse at Walk and Trot (Doctoral Thesis). Uppsala, Sweden.
(22) Slijper, E.J. (1946) Comparative biologic anatomical investigations on the vertebral column and spinal musculature of mammals. Proc. K. Ned. Acad. Wetensch. 42, 1-128.