I've been training my 72-year-old for 6 years — the Nike Metcon sneaker he swears by just dropped below $90 for Prime Day

I've been training my dad for just over six years, and over that time, I've encouraged smart investments for his home gym set-up, whether that's a new set of dumbbells, a grippy yoga mat, or what he wears on his feet.

If you're lifting weights regularly, your training shoes matter, and a pair of the best cross-training shoes or weightlifting kicks is a great investment for protecting your body and form.

During Prime Day, his favorite pair of Nike Metcon 5s just dropped to $89 at Amazon. Are they the newest iteration of the Nike Metcon shoe? Nope, not even close; there are 10.

But I've tested many of the brand's shoes over the years, including the 8, 9 and hugely popular Nike Metcon 10, and I can tell you hands-down that the earlier models in the range are still some of my favorites today.

Here's what you need to do to snap up this deal while stocks last.

Save 34% ($46)

Nike Metcon 5: was $135 now $89 at Amazon

The Nike Metcon 5 is still widely celebrated because, unlike later versions of the shoe, it feels stable, wide and flat enough for heavy weightlifting but pliable enough for agility and HIIT. If you need versatility, I'd skip both the 8 and 9 and either make a decent saving by going for the 5, or scale up to the latest Nike Metcon 10, which I include in a deal below.

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Save 30% ($46)

Nike Metcon 10: was $155 now $109 at Amazon

I'm a huge fan of the latest in the Metcon line, but I do prefer the wide, solid heel of the 5, and my dad absolutely loves training in them. However, the 10 does return some of the pliability lost in the 8 and 9 models, with a rope guard for CrossFit lovers and plenty of grip and stability for running or lifting.

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Nike Metcon 5 vs Nike Metcon 10

You can immediately see some key differences between the 5 and 10 in design, with the former rocking a wide, flat base and solid, chunky heel. I prefer to wear the Nike Metcon 5 for heavy weightlifting, particularly squats and deadlifts, where foot play is crucial and I feel like I have more space.

Both shoes are cushioned and pliable with a soft forefoot to absorb impact if you enjoy plyometrics. Both models also use Nike's Hyperlift inserts so that you can adjust your heel-to-toe drop, which matters if you are really into your squats, wallballs, or general weightlifting but don't want a weightlifting shoe (read: cross-training shoes vs weightlifting shoes).

I'm also a big fan of the grip, so you won't have any problem with sweat-slicked floors regardless of the model you choose. The 10 gets the edge for advanced exercises like rope climbs thanks to its rope guard (paired back from the 9) and, as Nike's product team puts it: "We really streamlined the build and focused on going back to the foundation of what makes Metcon great, listening to the voices of athletes.”

In other words, back to the roots: still durable, but more lightweight, agile and flexible. If you want true cross-training shoes, both do the job very well. I'd argue the 10 is slightly more versatile, but the 5 will get you a decent saving and is brilliant for blending weightlifting with a general gym shoe.