The poor man's version of this type of testing is monitoring morning heart rate, which correlates with peripheral nervous system activity. All you need is a stopwatch. In the morning, before you've gotten out of bed, simply find your pulse and count your heart rate for 60 seconds. Take a couple weeks to establish a baseline, and after that, a high reading means you need a break, and a low reading means you're recovering well.
Although I did find this article on t-nation, a site not known for its interest in aerobic training:QuoteThe poor man's version of this type of testing is monitoring morning heart rate, which correlates with peripheral nervous system activity. All you need is a stopwatch. In the morning, before you've gotten out of bed, simply find your pulse and count your heart rate for 60 seconds. Take a couple weeks to establish a baseline, and after that, a high reading means you need a break, and a low reading means you're recovering well.