Alfie wrote:
90 mins is not particularly "long" from a fatigue point of view, compared to 2 -2.5 hours. Is there benefit to doing more than one "long run" per week? Many of my easy runs are 75 mins (ish). Should I increase them to 90 mins?
From a capillary development/aerobic point of view there is not a reason to go past 90 minutes.
From a musculoskeletal point of view, there is not a reason to go past 2 hours.
From a psychological point of view, it doesn't really matter.
After 120 minutes of impact we can see structural damages start to occur and injury risk starts going up exponentially so we really try and limit 2 hour + efforts unless someone is training for an ultra and at that point, we've used a progressive overload plan to get their tendons and ligaments strong enough to take the beating.
The biggest thing with going longer than 90 minutes is nutrition - glycogen replacement and electrolytes in heat. The goal during a race is to NOT bonk, so what do you do to replace your glycogen stores to keep up your aerobic output is personal choice, most people find isotonic gels the easiest on the stomach and a way to get 90g cho/hr which will stave off bonking for most training runs and races. For electrolytes, again personal choice. Cramping is usually a result of sodium potassium imbalance and needs to be kept in check.
Elite marathon programs do not call for more than 10 hours/week at their top end for 100 mile weeks. Rather than looking at your milage, look at your time. You may be spending too much time on your legs. There is a sweet spot for everyone it's not always more is better. Most elites in their base phase have long runs at 15 - 18 miles. Why? this is right at 90 minutes for them.