Motion Sickness

Although motion sickness is a widespread problem that seems to have been around forever, there is a tendency to play down its significance. There are those who suggest that it does not play a vital role in the community as a whole or in the military in particular. Others describe it as “wimpish” and not worthy of attention. These attitudes are quite wrong. Motion sickness, is a motion adaptation syndrome, that should be recognised for what it is, namely, a maladaptation to novel provocative motion environments. It is a normal protective mechanism that can be managed effectively if we make the effort to understand its various features. It is also important to realise that these efforts will pay significant dividends in terms of time and money. Those who are fortunate have an easy transition to various forms of travel, whereas others have some difficulty in adapting to the protective responses that are incurred. With understanding and help, these problems can be overcome. I propose to begin this review of motion sickness by examining the very basic aspects of this syndrome that can beset us when we venture to travel other than on our own two feet and, when exposed to “vehicular” motion, begin to adapt to this new world.

Now that we have a basic understanding of what the term “motion sickness” means and how it affects the individual, we can examine the problem in more detail. We shall begin by getting a feel for just how common motion sickness has been found to occur in various forms of provocative motion. I am sure that these numbers will convince you that this response is prevalent across the population. This in itself would support what I said in the last chapter, namely, that this is a perfectly normal protective response and we should not be surprised at the high incidence that is associated with the various modes of transport. It should also alert us to the fact that motion sickness can have a significant effect on crew performance and operational efficiency. Although I seem to stress the military situation, one must not forget that this malady is also equally common in both commercial and social settings.

The incidence of motion sickness can be affected by a number of individual factors. In this chapter, I propose to introduce you to some of the personal features that have been identified as having a bearing on the response to provocative motion, namely: age; sex of the subject; race or culture; and physical fitness. Some of these can have an impact on military personnel; as you will see, there are no hard and fast rules. More work is needed to investigate these suggested correlates both to confirm the relationship and better understand the underlying reason for these associations to exist.

A considerable amount of work has been performed in an attempt to identify the characteristics of motion that provoke motion sickness. As you will see, this has ranged from studies in the laboratory to others that have taken place in environments more akin to the real world. Apart from giving us a better understanding of the mechanism of motion sickness, these data provide valuable design criteria to reduce provocative vehicular responses; in addition, however, we must not forget the operator’s personality and cognition. This is an example of the value of recognising the need to design with the human operator or traveller in mind from day one.

In this chapter, I shall try to provide an overview of the changes that have taken place during the last fifty years in terms of identifying the physiological mechanisms underlying the motion sickness response. Despite the fact that much effort has gone into this search, we still do not have a definitive explanation for this syndrome. I suggest that we may well find that there is no single explanation and that perhaps a number of these current concepts are relevant. Fortunately, this lack of a clear model for the aetiology of motion sickness has not prevented us from making progress in terms of dealing with the condition.

From the beginning of my research into motion sickness in the military, I have believed that there must be a psychological component in the aetiology of this malady. I have based this opinion on the notion that individuals whose careers are in jeopardy are most likely to have an arousal overlay when confronted with their provocative motion environment. This is also likely to happen to the majority of people outside the military if previous motion experiences have been uncomfortable. That does not mean to infer that motion sickness is entirely “psychological.” It merely suggests that the psychological component, based on memories of previous motion discomfort and/or the effect that motion sickness may have on future aspirations, contribute to an individual’s inability to adapt to provocative motion. In addition, I also believe that the situation is made worse for high achievers, as we shall see later.

The question of adaptation is a key issue in dealing with motion sickness. It is generally accepted that most people should be capable of adapting to provocative motion. In that case, why do so many people suffer from chronic motion sickness? As I have said in the previous chapter, I believe that this is due to a psychological component based upon unpleasant motion responses in the past; perhaps as a result of individual motion experiences from a young age. Early and continued exposure to provocative motion may either sensitise a person or allow that person to adapt. This will depend upon the duration, character and frequency of exposure to whatever form of motion. In a sense it may be entirely fortuitous and depend on social and/or geographical circumstances. I shall return to this question later in Chap. 12, when discussing cognitive-behavioural training.

It is very appealing to try to predict susceptibility to motion sickness. Very many before me and no doubt many after, will pursue this goal. As you will see, my experiences have been very disappointing. I spent many years evaluating motion sickness history questionnaires and the seemingly predictive test of cupulometry—all to no avail. The more time I spend with people who suffer from chronic motion sickness, the more intrigued I am by their stories. These stories frequently seem illogical in terms of apparently widely different responses to stimuli that seem to be very similar. Suffice to say that in our laboratory we are frequently surprised by the responses of individuals. Those with a seemingly “bad” history often do better on our motion devices than others whose history seems less severe. We still have a lot to learn.

There are many and various ways that we can prevent, or at least reduce, the likelihood and severity of motion sickness. We can start by avoiding exposure to motion profiles that have been shown to be particularly provocative and in some cases we can control the duration of exposure. We can also do our best to distract those who are inexperienced travelers so that they are less likely to dwell on the idea that they might become motion sick. As I have heard local sport fishermen say, “If the fish are biting, I don’t get seasick!” Well-controlled increased exposure to provocative motion together with supportive cognitive-behavioural training can go a long way to helping people get their “sea legs” and adapt to other forms of provocative motion on land, sea and in the air; I have been very successful in training people to overcome their motion sickness, whatever the cause.

Practically everything has been tried at one time or another to treat motion sickness. There are a number of medications that are quite effective, although most have some unwanted side effects and some adversely affect performance. Scopolamine and promethazine are still considered to be the most effective anti-motion sickness medications. Perhaps the most disturbing feature of the anti-motion sickness drug story is that nothing new and effective has appeared in the last forty years or so. Recently, drugs that have effective anti-emetic properties in certain clinical settings have not been found to be effective in a motion environment. If you are treating passengers, make your choice of medication according to circumstances such as duration and severity of exposure and individual idiosyncrasies. When dealing with operators of potentially hazardous equipment or those performing certain skilled tasks, the choice is more difficult and it may be better to avoid drugs all together.

There are a number of non-pharmacological forms of therapy for managing motion sickness. These have had varying degrees of success over the years. The biggest problem I see in comparing the results of these various desensitising programmes is that all but mine excluded an undisclosed number of potential candidates who showed less than desirable enthusiasm for continuing to fly. Despite the fact that my cognitive-behavioural desensitisation training programme had no such pre-selection criteria, it was found to have the highest success rate. Most of the other desensitisation training programmes involved biofeedback. I do not support that approach because it relies on mental relaxation techniques to control the individual’s physiological state, whereas I believe that the subject’s mind should be both strongly focused and targeted elsewhere; that alone can protect against provocative motion. In addition it is my strongly held opinion that it is better to avoid the need to record physiological responses, for two reasons. First, it seems to conflict with the idea that motion sickness is a normal protective response. Second, military professionals and astronauts tend to be suspicious of physiological recordings lest they have an adverse effect on their medical status.

When I devised the cognitive-behavioural desensitisation training programme some years ago, it was and still is based on the concept that chronic motion sickness could well have both physiological and psychological features. My earlier dismal experience with trying to identify successful predictors left me with the feeling that in any given person, I was unable to decide whether his or her problem with motion sickness was more physiological or more psychological. For those reasons, I avoided the issue by planning to cater for both of these characteristics in parallel, on the basis that each individual would get whatever quantum of each type of help that was needed. I am bound to say that in retrospect, I could often have made the correct judgment about the likelihood of success after the training was completed. Does that really matter, however? I think not. You will make your own decision on that point.

When I first proposed my course of cognitive-behavioural desensitisation training, it generated its fair share of adverse comments. For a start, the naysayers believed that I was only putting off the evil day and all of my clients would fall by the wayside sooner or later with a resumption of motion sickness. The programme would simply waste time and money. Others believed that it was merely a behavioural desensitising programme and there was no point in the so-called cognitive component. I would very much like to have addressed the latter issue at that time, but was convinced that both were necessary and above all, my clients only had one shot for success. As to the former question, only time would tell. Finally, there was no question of having a control group for ethical reasons. I am pleased to tell you that I have been able to address these issues since then and the answers are to be found in this chapter.

I am sure that you will have already concluded that I am very much a psychophysiologist at heart and that my approach to the solution of a problem lies in dealing with the whole person; no doubt that is another reason why I am teaching ‘Human Factors Engineering’. So the contents of this last chapter will come as no surprise. I believe most strongly that many, if not most, stressors can best be dealt with by using the various component techniques that lie within the cognitive-behavioural training concept that I have described. I am equally sure that many of you, if you so desire, will find that you will be as successful as I have been, or more so, in dealing with a wide variety of psychophysiological problems. In this last chapter, I shall sum up briefly and in addition, I propose to describe some of my experiences with these techniques other than in the realm of motion sickness. You will find that I have used many of my cognitive-behavioural training strategies quite successfully during sessions of high altitude decompression training at altitude in a decompression chamber, as well as in a clinical setting, while performing coronary arteriography and implanting cardiac pacemakers. I have also included some information from a different field on a relatively recent neurophysiological approach, which others have described, for the management of tinnitus. I am sure that you will be interested to note the similarity with my motion sickness prevention training programme.