A recently published study has concluded that in a fitness club setting, members with directed training achieve significantly greater improvements than those who self train. You can read the abstract here (or skip to the bottom for a creative analogy):
Conventional wisdom suggests that exercise training with a personal trainer (PTr) is more beneficial for improving health-related fitness than training alone. However, there are no published data that confirm whether fitness club members who exercise with a PTr in the fitness club setting obtain superior results compared with self-directed training. We hypothesized that club members randomized to receive an evidence based training program would accrue greater improvements in lean body mass (LBM) and other fitness measures than members randomized to self-training. Men, aged 30-44 years, who were members of a single Southern California fitness club were randomized to exercise with a PTr administering a non-linear periodized training program (TRAINED, N=17) or to self-directed training (SELF, N-17); both groups trained 3 d/wk for 12 weeks. LBM was determined by dual-energy x-ray absorptiometry, (DXA). Secondary outcomes included muscle strength (1-RM), leg power (vertical jump), and aerobic capacity (VO2max). TRAINED individuals increased LBM by 1.3 (0.4) kg, mean (SEM) versus no change in SELF, P=0.029. Similarly, significantly greater improvements were seen for TRAINED versus SELF in chest press strength (42% versus 19%, P=0.003), peak leg power (6% versus 0.6%; P<0.0001), and VO2max (7% versus -0.3%; P-0.01). Leg press strength improved 38% and 25% in TRAINED and SELF, respectively (P=0.14). We have demonstrated for the first time in a fitness club setting that members whose training is directed by well-qualified personal trainers administering evidence-based training regimens achieve significantly greater improvements in LBM and other dimensions of fitness than members who direct their own training.
~ Storer, T.W., B.A. Dolezal, M. Berenc, J.E. Timmins, and C.B. Cooper. "Effect of Supervised, Periodized Exercise Training versus Self-Directed Training on Lean Body Mass and other Fitness Variables in Health Club Members." PubMed January 3, 2014
This abstract describes the study in detail, including what was measured (lean body mass, VO2max, leg power, and other measurements), who was measured, and how each of the measured improvements varied between the two groups. In each case, the group that trained with a coach showed measurable improvement that was higher than the improvement of those who trained on their own.
So, imagine that Fleet Feet Sports Stamford is the 'fitness club.' The members who exercise with a personal trainer "PTr" are the Fleet Feet training program participants. Over 12 weeks (coincidentally, the length of a Fleet Feet training program!), the members of the training programs will display greater improvements than other runners who train individually. So, if your goal is to improve your distance, pace, stamina, or just to have a little extra motivation, consider joining a training program and maximizing the effect of your workouts!