Contrary to popular belief, you don’t NEED an overlocker (aka serger) to sew exercise gear, but it does make it considerably quicker. If you’ve only got a sewing machine, experiment both with different needles for your chosen fabric (stretch or ballpoint in varying sizes), different zigzag stitch settings, and also presser feet (roller, teflon, or a walking foot might work better than the standard one). Once you’ve sewn some scraps, be brutal with your seams – stretch them as far as they can go in all directions, and test whether you can pop the stitching at all before starting on your main fabric.
If you’ve got an overlocker, you’ll also want to experiment with different stitches before you start. I personally know I’m brutal on my seams, so I tend to go for a four-thread overlock stitch rather than three, so if the first stitching pops I know I’ve got a backup line of defence. If you are particularly prone to chafing, you might want to consider using woolly nylon thread in the loopers, or playing with your tension to get a “mock flatlock” stitch on your seams. Some people also find that the crotch seams on leggings and shorts irritate them, or they need a fuller range of movement for sports like gymnastics, so you could also consider modifying your pattern to use a crotch gusset instead.
When it comes to finishing the edges of fabrics, you’ve got a few options depending on whether the edge needs to be tight against the body or not. If you just need a hem, like on the bottom of a top or the ankles on leggings, then you just need to fold the hem allowance under and topstitch using a twin needle on a regular sewing machine (be sure to loosen your bobbin tension to avoid “tunnelling”!) or a coverstitch machine if you’ve got one. For elastic waistbands, I prefer a method where you stretch the elastic to match the fabric, turn inside, and topstitch, which means the elastic doesn’t twist or bunch up like in the traditional casing method.
If you’re finishing the edges of a close-fitting top, you’ll want the fabric to stay snug against the body rather than shift around as you move. One option is to use foldover elastic (aka FOE) to encase the seam edge and then zigzag stitch overtop. The advantage here is that FOE comes in a million colours and can provide a great contrast to your edges, but remember to trim away any seam allowances from the edges first! Or if you’ve got a coverstitch machine with a binder attachment, you can use lengths of contrasting fabric to bind the edges with stretchy stitching, but in my experience this can be very tricky to sew neatly!
If you don’t want to interrupt your fabric, however, another method is to attach 1cm (3/8″) braided elastic to the inside along the edge, then fold it inside again and topstitch with a twin needle or coverstitch (like a mini version of the waistband elastic application). I was initially skeptical about the comfort of this method, but as the elastic is totally encased in the fabric and you’ve only got two lines of stitching against the body (one from the first pass zigzag, and the second from the twin needle or coverstitch), it’s actually become my preferred method for finishing necklines and armholes.
Testing your sewn workout gear might seem like an afterthought because “Yay! I’m done!” but it’s actually one of the most important steps! Every single person prefers their exercise clothing to fit a certain way, and different activities have different demands on your clothing. Do you prefer your tops to be tight around the bust but loose around the waist and hips? Have you discovered that your legs are shorter or longer where you wern’t expecting it? Are the pockets too loose and the contents bounce around as you move?
Overwhelmingly I hear again and again from my pattern customers that the first version they sew isn’t quite 100% where they want it to be, but the second version comes out pretty much perfect after making a few tweaks to suit how they like their workout wear to be. Don’t rush this testing step, and make sure you workout in your first versions a few times before getting excited and making more!
The wonderful thing about sewing your own workout clothes is that you really can get a bespoke fit in the exact style you want, and often for less than the price you’ll spend in the shops. When you feel comfortable and confident in what you’re wearing, it can really help you focus on the workout at hand.