Physical activity plays important role in our healthspan, chronic diseases, mood, cognition and learning. Current scientific evidence points to U-shaped curve - too low or too much might be not good for health. Overtraining leads to suppressed immunity, which cause infections, inflammation. Physical capacity and muscle mass degrades during aging. Sedentary lifestyle promotes a couple of chronic diseases, including metabolic, cardiovascular etc.
What can we do to combat these issues and prolong our healthspan?
Analyzing physical activity can answer important questions:
Physical activity is a complex measure. In general, we can split our activity like that
Here we have a category-specific metrics and shared metrics.
There is a large research field focused on professional athletes and measuring their training load, performance, mood, fatigue, stress, recovery etc by objective metrics and subjective questionnaires     . Also measures categorized by nature: internal or external
Session Rating of Perceived Exertion (sRPE) seams to be easiest and widely used train load (TL) assessment in research, professional sport and sport medicine . After each training, within 10 minutes i'm answering simple question:
After answering i'm simply multiply time of training by RPE and see my sRPE train load in au (Arbitrary Units). For example, moderate run for 30 minutes rated as RPE of 5 will result in sRPE = 30 * 5 = 150 au.
I'm doing all my training sessions with Polar H10 which provides heart rate with 1-second resolution. For each session Banister's TRIMP (Training Impulse) is calculated. TRIMP describes how much cardio load happens during session .
T is a time, dHR is a percentage of average HR Reserve for given time T.
There also alternative and newer method called HR-EPOC, but i'm not using it.
For most of people implementing TRIMP / EPOC calculation into their train regime is unnecessary, because sRPE correlates very well (r=0.73-0.98) with TRIMP, proving consistency. So, if you are casual user, then stick with sRPE for simplicity.
In addition to internal load (sRPE, TRIMP), i measure external load variables:
I'm not a professional athlete and i dont need to precisely measure (which requires more measurements - watts, cadence, gps etc) and hardly optimize my exercise performance. I'm more focused on just achieving enough train load distributed into various exercises.
Same as for aerobic.
Resistance training well described in this article and in addition to session RPE, i've decided to measure physical work with equation 5 formula mechanical work in joules per 1kg of body weight = (load weight / body weight) * distance * repetitions * sets.
Since i'm doing ~20 different exercises (squats, push ups etc) for each of these i need to measure:
For example, in squats, my legs not only pushing up a loaded barbell, but also pushing up upper part of my body (for squats its about 77% ). With my body weight of 60kg and doing squats with 50kg barbell my legs pushing up 50kg + 0.77 * 60kg = 96.2kg and since i'm moving for 80cm distance for a single repetition mechanical work is 96.2 * g = 96.2 * 0.8 * 9.8 = 754J. Since i'm doing 3 sets with 10 reps each total job done is 664 * 3 * 10 = 22 620 J for squats. If my weight is 60kg, i'm doing 22 620 J / 60 kg = 377 J per 1 kg body weight. Since body weight changes over time, we account for that and can compare different time points.
Date, time, exercise type, sets, reps, equipment weight is stored for future analysis of training load. Note that these numbers only comparable between resistance trainings and cant be directly compared to aerobic training by simple joule to kcal conversion.
My yearly resistant work looks like that:
This is a total work (without accounting for body weight). The 50kJ ones is a squat sessions and 15-20k is a benchpress sessions.
Yoga & Stretching: sRPE (duration & RPE). i'm not using Polar H10 to get my HR, relying only on Fibit Charge 4 / Polar Vantage V2.
General daily activity mostly consist of walking.
I did a few 10 000 step walks and measured duration & RPE, getting around RPE = 2.5 and duration = 40 minutes resulting in 100 au for 10k walk. Now, since i know sRPE for 10k steps walk is a 100 au, then 1 step provides a 100 au / 10 000 steps = 0.01 au of sRPE. Finally, sRPE for general activity for given day is a steps per day multiplied by 0.01 (or just divide by 100).
TRIMP for walking can be calculated same way, providing amount of TRIMP per step.
Other activities like sauna can be also tracked in terms of sRPE.
Since i have all my general and training activities described in sRPE units, then i can calculate total train load for each day.
Here is my total daily sRPE for a year
As you can see a lot of days i'm just getting 70-100au - simply just by walking 7-10k steps. Also there is some training days with spikes like 200-600au which mean my training days. This measure is not perfect, because its hard to precisely count all physical activity, but it seems to be a good proxy.
Also i can easily check my training load distribution by month
Here we can start analysis and compare daily sRPE with sleep, mood and other factors. I'll present detailed analysis in future posts.
This question doesnt have an easy answer and depends on individual and environmental factors. Professional sport research field doing hard job in predicting overtraining. There are few approaches, one of them is a Strain and Monotomy of sRPE train load, described here. Other methods utilize several domains of HRV (rMSSD, HF, LF etc). Complementing objective measures with validated questionnaires also helps . I already did some investigations in beetween TL, HRV and questionnaires and will describe results in future posts.