Hi Linda- doing workouts outside is an excellent way to train all the skills we work on. I do as much of my workouts outdoors as I can weather and family schedule permitting.
Without a power meter you could use RPE (Rate of Perceived Exertion) or HR (hear rate), as I discussed in a recent post (excerpt below):
Rate of Perceived Exertion (RPE)
Using RPE can be helpful for the new athlete who does not have the tools to measure power. It can also be useful when an athlete has taken significant time off the bike due to injury or illness and needs to get back into training in a more conservative and progressive manner instead of doing workouts at the pre-illness power numbers.
Rate of Perceived Exertion, or RPE, is one of the methods used to prescribe workouts. It is a subjective scale of 0-10 or 6-20, used to measure the intensity of intervals.
Heart Rate (HR)
It is also possible to train using heart rate (HR) zones. These are calculated using a person’s maximum heart rate (Max HR), which is the upper limit of what your cardiovascular system can handle during physical activity.
Using the popular formula 220 minus your age is not recommended, because each person’s maximum heart rate is unique, and that formula is rarely accurate.
The workouts would then be designed by using a % of Max HR. The downside of using this method is that a person’s HR does not follow the exact trajectory as their effort/power output. There is a lag in HR increase, and therefore there is great likelihood that the athlete following HR only would fall short of the desired effort measured in watts.
As you can see, these methods can be tricky because they are not as accurate, and you could fall short or be over your targets on all intervals.
Have you considered getting a used Power Meter? I can also see if I can get you one at a discount. It does not have to be anything fancy.