so ive been swimming for several years now...the running i do is limited to during baseball practice and conditioning so i cant attest to being any sort of habitual runner...i will say that all of the researh ive done into running vs. swimming as brought up that there are two basic different ways to compare the two sports calories burned and time per mile...in the time per mile area i will be the first to admit that swimming a mile takes a significantly longer time then running a mile which for some people means that you can get more work done running as you can go further in a set period of time running then you can go in the same time period swimming...the other way of looking at it in calories i am yet to find any sort of conistancy in the amount of calories swimming takes, the only numbers ive found calories spend in swimming a certain distance but nothing that considers the time period the swimming takes...this all being said ive never really enjoyed running becuase of injuries if gotten over the years on my knees keeps me from running for too long at a time...this being said to talk to the runners who have stated that swimming is easier as you get time to rest in between (1), that floating in the water makes it easier as gravity is not effecting you(2), that a lower heart rate keeps you from burning as many calories(3), and that the technique advantages that come from swimming keep you from burning calories(4)...(1)while swimming the only breaks you shoudl be taking are changing from set to set as slip turns and open turns create a physical workout for abs and legs within themselves and cant be called "resting" so the only rest swimmers experience comes between sets if you feel like resting which is mostly done in the midst of sprints so how is resting then any different then catchign your breathe after running a 100m sprint?, (2) firstly the idea that water frees you from the issue of gravity im suprised that people can believe that some how water can free you from the attractive power of gravity if that is so then call nasa and rewrite the text books (sorry had to be a jerk there) but honestly jsut because swimming doesnt use gravity as a resistant force as running does that in no way negates that swimmers face a much larger resistant force coming from water resistance then friction or air resistance can effect a runner, (3)so the idea of a calorie is a unit of energy that is equal to the amount of energy required to raise one pound of water by 1 degree C...so what does this mean? so just like joules, calories are simply a measurement of energy...for exercise this pertains to the energy that we use to move through the water or across the ground respectively..so to measure the amount of work done in each the differences are skewed as personal variations drastically change the numbers...these differences come in the facts that everyone in different in weight and technique, so to say that swimming or running a certain distnce will burn so many calories as a fundemental constant for all people neglects any personalization that such a problem needs...ultimately calories burned proves itself to be a poor way to compare these two sports...(4)ill try to be shorter on this one sorry for the length of this post, ok, so to say that since technique makes swimming easier it is less of a workout is true in some cases, say im aiming to swim 100 m in 90 seconds as a untrained swimmer to meet this goal i will have to exspend far more effort to overcome my inneffecieny in the water then a trained swimmer would, so yes in that sense experience cuts out work right?...well an experienced swimmer that can easily swim 100m in 90 sec wont be doign that as a work out but rather will aim for 60 sec intervals which will require more force to achieve as water resistance, like air resistance, increase exponentially as velocity increases....so now that i only have 3 people if any left reading i will wrap p by saying that swimming and running both offer terrific workouts...personally i prefer swimming for less impact and the shoulder workout that helps me with baseball, but i will admit that its hard to find a place to swim year round....honestly i have no place to say one is harder then the other but my experience says that as a baseball player swimming helps more as a total workout then just running