You'd have far more success training your dog not to pull than hoping these leads would stop it for you. They might take the initial impact off the pulling but I'd imagine a real puller would just stretch them to their maximum length and keep pulling, and you've only had about 2 seconds of relief from the pulling
If you're struggling to walk a dog because it pulls so much, then maybe look at a headcollar or a harness with a front attachment as well as one on the back - these help give more control over the direction of the dog. Something like the Mekuti harness, though more and more companies are making similar harnesses so there's a bit more choice now.
Also, I would look into the 300 peck method - if you google it you can find various descriptions. The general gist is that you do short training sessions (don't try to train it on your regular walk to the park unless you have hours of spare time to get there
but on a serious note - a short 10 minute training walk will be more likely to end on a good note with neither you or the dog being frustrated or bored) and you train your dog to walk with a loose lead, one step at a time.
You can use a clicker, or condition your dog to a 'clicker' word (much like a clicker but you just say a word, e.g. "good", instead of the click) and then get yourself somewhere with the least amount of distractions possible. Position your dog to your side and take a step forward - did they manage this with a loose lead? If so, click and treat, and carry on walking, counting from one again. One, two, C&T, one, two, three, C&T. Once, two, three - then the dog pulls? Stop, don't acknowledge anything but wait for them to fall back to your side (you can lure them with a treat if necessary) and start over, back at one, C&T, one, two, C&T, one, two, three, C&T, etc.
I actually did it wrong the first time I did it, but it worked for me. It was similar, just more baby steps. One, C&T, two, C&T, three, C&T, four - whoops, she's pulled. Back to one, C&T, two, C&T, three, C&T. Once I was getting to around 20, I'd skip a few, so 18, C&T, 19, C&T, 20, C&T, 21, 22, 23, C&T, 24, 25, 26, C&T, 27, 28, 29, 30, C&T, 31, 32, 33, 34, 35, C&T, 36, 37, 38, 39, 40, C&T, etc.
Once you're getting good, solid loose lead walking with no distractions, you want to gradually up the distractions. Repeat the exercise in a quiet sideroad. Then an empty park. Then a busier road, a busier park, etc. - don't go too fast, if the dog is consistanty pulling, drop down a few distractions, but you'll get there.
The idea was from the amount of times they could train pigeons to peck on a bar for a reward, they found out they could increase it to 300 pecks before they reinforced it with a treat. By going in such small steps, your dog is pretty much guaranteed to succeed - unlike expecting a perfect loose lead on a half hour walk to the park. The goals are so easily achievable, basically you walk one step with a loose lead and it's a success! The next stage, two steps, another success! Three steps, you're on a roll. Easily achievable goals means you and the dog experience more successes than failures, and you eliminate the frustration and boredom of trying to achieve a goal that you can't quite reach.
One important thing to do is make sure your dog can differentiate between when it HAS to walk well, e.g. these training sessions, and when pulling can be excused. So do these 10 minute training sessions several times a day, with the dog wearing a comfortable harness for example, and when you really do have to do that 30 minute walk to the park where you know the dog will pull, pop a headcollar on to save your arms a bit. The dog will learn the difference, and once they've got the hang of a loose lead, you should eventually be able to lose the headcollar and just walk them everywhere on their comfy harness, with a well-learnt loose lead.