How To Get Back Training After A Long Break
Life can get busy sometimes. You may have taken some time out of your training routine for whatever reason may be.
This is okay.
In this article, you will find a few things to consider before getting stuck in.
Be Patient And Start Small
It's just as the saying goes: patience is a virtue. It can sometimes get frustrating and painful to wait to get back to a level of training that you were at before the break. It will slowly return with a few short weeks of training.
Rushing into intense workout sessions that you may have been doing before, may increase the risk of injury. To minimize the risk of injury and to increase your overall development, remember to take it slow and stick to your plan. This will ensure steady progress and allow you to reach your goals that bit sooner.
It is not uncommon for those after a break to regain muscle and strength more rapidly than normal growth. This is known as muscle memory.
Muscle memory is the result of our muscle fibres experiencing an increase in myonuclei cells. These cells help increase our muscle strength and size. The cells can be found within our muscle fibres even after weeks of inactivity, which helps with growth when returning to training. [1, 2, 3]
Don't Expect Instant Results
Taking time away from exercise will mean you may have lost some muscle bulk, strength, and cardiovascular fitness. Don't let that get you down - you won't have to start from scratch. You'll just more than likely, have to spend some time building back up to where you were. This might mean choosing a lighter weight, running a shorter distance, or running a slower time than before your break.
In a study done by McMaster et al, it was found that participants who stopped training maintained their strength for up to three weeks of detraining, but recorded noticeable levels of muscle atrophy, or wastage? after 5 to 16 weeks. 
McMaster suggests that while training age, or the amount of time you have spent training consistently increases, strength and power gains decrease. In other words, muscle and neural adaptations to resistance training reduce as you expose your body to training for a period beyond 12-24 months. The longer you train, the slower your body changes. This is completely normal, and you can see relatively significant changes at an early training age, and relatively slow changes at an older training age.
Remember You'll Be Sore
Before you jump into your workouts, remember to include a good warm-up and cool down.
These are important phases of the workout, which help you prevent muscle soreness or injury, it can also help prevent delayed onset muscle soreness (DOMS).
Delayed Onset Muscle Soreness can cause aches or stiffness in your muscles anywhere between 24 to 72 hours after you exercise. 
So, you may need some more rest to recover from this soreness. The most valuable recovery you can focus on is some quality sleep. Getting quality sleep can greatly increase your body's recovery speed. By getting sleep your body can adapt quicker and more efficiently to your workouts. [6, 7]
In a study done by Vitale et al, it was highlighted that sleep plays a vital role when it comes to recovery. In this study, it is recommended that most adults need between 7-9 hours of sleep per night. The study also suggests that those who are partaking in heavy bouts of intense exercise may need more.
Get A Trainer/Instructor
If you're having a hard time getting back into the swing of things, then it might be worthwhile getting the assistance of a personal trainer/instructor. Having someone there to hold you accountable can sometimes be the push you need to get back into a routine.
If you don't want to get a personal trainer and you're not sure where to start, these foundational exercises are ones all beginners should learn. You can check out this article, if you're looking for a routine to follow, that keeps beginners in mind.
I would highly suggest taking things slow and consult with your doctor or a physical therapist, especially if you're working with an injury, to ensure you're being safe.
To sum up...
Before you rush off into your workout routine don't make these mistakes. You can check out this article, to find tips on how to not fall into some of the common pitfalls that people fall into.
These tips will hopefully help you as you restart your workout routine. No matter what remember that it's OK to feel overwhelmed at times. Don't get discouraged, you've got this!
 Myonuclei acquired by overload exercise precede hypertrophy and are not lost on detraining. J. C. Bruusgaard, I. B. Johansen, I. M. Egner, Z. A. Rana, K. Gundersen. Proceedings of the National Academy of Sciences Aug 2010, 107 (34) 15111-15116; DOI: 10.1073/pnas.0913935107
 Ogasawara, R., Yasuda, T., Ishii, N. et al. Comparison of muscle hypertrophy following 6-month of continuous and periodic strength training. Eur J Appl Physiol 113, 975–985 (2013). https://doi.org/10.1007/s00421-012-2511-9
 PNAS August 24, 2010 107 (34) 15111-15116; https://doi.org/10.1073/pnas.0913935107
 McMaster, D. T., Gill, N., Cronin, J., & McGuigan, M. (2013). The development, retention and decay rates of strength and power in elite rugby union, rugby league and American football: a systematic review. Sports medicine (Auckland, N.Z.), 43(5), 367–384. https://doi.org/10.1007/s40279-013-0031-3
 Cheung, K., Hume, P., & Maxwell, L. (2003). Delayed onset muscle soreness: treatment strategies and performance factors. Sports medicine (Auckland, N.Z.), 33(2), 145–164. https://doi.org/10.2165/00007256-200333020-00005
 O'Donnell, S., Beaven, C. M., & Driller, M. W. (2018). From pillow to podium: a review on understanding sleep for elite athletes. Nature and science of sleep, 10, 243–253. https://doi.org/10.2147/NSS.S158598
 Vitale, K. C., Owens, R., Hopkins, S. R., & Malhotra, A. (2019). Sleep Hygiene for Optimizing Recovery in Athletes: Review and Recommendations. International journal of sports medicine, 40(8), 535–543. https://doi.org/10.1055/a-0905-3103