Many times, for example, the case will be made for the individual who can use a leg press for 700 lb. for 12 reps or more, but cannot squat with even half that for as many reps. Somehow this is proof that the leg press doesn’t build functional strength. Yet this is an indication that the leg press actually overloads the quads, hips, and hamstrings with far more weight than could be supported when hinged upon the “weak link” of low back and abdominals. While exercising these “weak links” is paramount, providing the highest intensity to the legs can be more easily provided by a leg press than a squat. Furthermore, a person squatting regularly and well will always do better at squatting then a person who works legs in another manner, and doesn’t squat.
Functional strength is usually best defined by the manner in which the strength must be applied outside of training. And this is typically learned and developed in this arena. So “functional strength” for a football player is applying the available power and strength in a manner that makes for better football. Since there is no arena inside the weight room that is applicable to the football field, there is no style of lifting that closely mimics football performance. The only sports that truly mimic gym exercises are powerlifting and Olympic lifting. Otherwise the gym is a place to develop a base level of strength and conditioning to be honed on the practice field. For those not involved in competitive sports, functional strength is more in tune with what you do on a day-to-day basis that requires strength. For example, I occasionally like to utilize the Farmers Walk in my routine. Starting this move is similar to a Trap Bar deadlift, but not exactly the same. Nor is it exactly like a dumbbell deadlift, as the handles are quite high off the ground compared to dumbbells. And walking 120 or more feet with 300 - 400 lb. or more in the hands is nothing like either. To gain functional strength, as it were, for Framers Walking you need to have a base level of strength in hips, thighs, shoulders, back, etc. This can come from any source. But to “get good” at Farmers Walks, you have to do the move. It provides its own groove and performance envelope that cannot be developed any other way. Being a good squatter or deadlifter will not make you a better Farmers Walker outside of the base level of strength provided. This same strength can be easily provided on a range of quality Hammer, Nautilus, or Southern Exercise machines.
Re-read and realize that I do not condemn the use of free weights, or call them secondary or inferior to the use of machines. Free weights are useful, and I utilize them in my exercise programs. But development of strength via barbells is only specific to demonstrations of strength via barbells. So if one plans to competitively lift, one should spend lots of time practicing those lifts he or she will be using in competition (squat, bench press, deadlift, other competitive lifts). If one is seeking a general level of strength, power, and conditioning for martial arts, football, soccer, or general fitness one should spend a more balanced time utilizing the barbells and machines to their best advantages. You may find that you gravitate towards more use of free weights or you may fall in love with a quality line of machines. Or like most lifters you will find a core set of free weight compound moves (squat, stiff leg deadlift, overhead press) and a core group of good machines (Nautilus Pullover and Compound Row being two of my favorites) that will become the foundation for many productive routines for years to come. But whatever you do, don’t let worrisome arguments about functional and stabilizer strength concern you much. Do a quality, progressive, intense, abbreviated routine with a priority on big moves for the legs, hips, low back, upper back, and shoulders and you will have done much more than 90% of the lifters out there. Add the regular performance of Farmers Walks, Whelan Walks (sandbag carries), tire flips, and other oddities at the END of most workouts and you will be doing more than 99% of lifters, and will be doing about all that can be done to create, improve, or develop functional strength.