If you have been a trainer long enough, this will eventually happen. To that extent it is normal. 99% of the time it is just a hypoglycemic issue (using all available glucose, and lacking available glycogen stores to make up the difference). Nothing dangerous in fact, but very uncomfortable, and potentially scary for the novice trainer. This is something that should not necessarily make you feel bad, but it should make you reevaluate how hard you chose to train that client, and others to come. This physiological response is much more likely to happen to newer unfit clients than more experienced fit clients. Any serious athlete has probably experienced this at some point, but it shouldn’t be something that our clients have to go through. Furthermore, this response can happen even when you are training a client well beneath the “easy level,” due to their own physiological issue(s) at the time that you may not be aware of, and have no way of being aware of.
Having said all of the above, I will say that if a clients gets to the vomiting stage, the trainer will have completely missed critical prior stages to vomiting that should have been noticed. If a client is training beyond their ability to function within normal physiological responses, there are certain early signs to look for. They first the client can start to yawn. Following yawning, the client can turn green or pale look. The trainer should be keenly aware if any of these symptoms develop, then immediately stop the exercise session until the client feels better. If the condition gets worse, they client will feel dizzy or nauseous. If this happens, I would recommend terminating the exercise session immediately. Even if you let a client rest a few minutes until they feel better, as soon as they begin to exercise again, they usually get dizzy and nauseous again relatively quickly. This is because the blood glucose level takes more time to fully recover, and any level of exercise will throw them back into a hypoglycemic condition. Beyond the dizzy and nauseous point however, the client can vomit. Again, the vomiting stage is the last stage of this process, and an aware trainer should have picked up on the warning signs far before this point. If the clients vomits,the session is definitely OVER. If a session is terminated for any of the above mentioned reasons, I recommend spending the remaining time stretching with your client, and discussing what just happened.
I have some basic rules that every trainer should adhere to with respect to this issue:
1- Until you get to know a clients response(s) to exercise, train them well below their physical capabilities. Increase intensity slowly over time, once you know how they handle exercise. If a client starts to yawn, gets dizzy or nauseous, you overshot the mark.
2- If a client says they are dizzy or nauseous, make the client continue to walk around, swinging their arms and legs, as this keeps their blood pumping, and keeps it from pooling. Or, you can lie them down with their feet up, as this evens out the blood flow and allows them to recover better. In either case, I would recommend that you get them out of the view of other members. Simply put, you don’t want other members to think you are traumatizing people. Just a marketing tip. 🙂
3- If a client says they are dizzy or nauseous, the workout is over. Spend the rest of your time stretching.
4- To minimize the chance of this happening next time, have the client warm-up better, and adding more time to the warm-up. I would also have the client increase their blood sugar level just prior to the workout. You can have them drink a fruit juice or eat an apple or banana. This usually increases their blood sugar level and helps them get through the early phase workouts until their body learns to burn more fat and store more sugar naturally.
In summary, this was a great question. Trainers should be well versed in how to handle a client yawning, getting dizzy or nauseous, or even vomiting. If you have been a trainer long enough, at some point it may happen. No problem. Just learn from it. Reevaluate your training program, and, always train client easy until you know how they can handle exercise.