Gaining size for rugby: how to bulk up without getting slower

“Get bigger” is the most common goal we hear from amateur players, particularly young forwards and centres. Size helps in contact: momentum is mass times speed, and a heavier player who is just as fast hits harder and is harder to stop. But size gained badly makes you slower, less fit and no better at rugby. This guide shows you how to add useful muscle and keep the speed that makes it count.

Is size the right goal for you?

Size helps most in the tight five and for players who are light for their position. For back-three players and scrum-halves, relative strength (strength per kilogram) matters more than mass. Wingers and full backs usually do better building strength without much size, from short, heavy, low-volume sets. See our guide to training for backs.

A simple rule: bigger is only better if speed holds. Track a 10 m sprint or a countermovement jump alongside your bodyweight. If the jump or sprint drops as weight goes up, slow the gain and shift emphasis back to strength and speed.

How to train for size

Muscle growth is driven mainly by doing enough hard sets: more weekly volume brings more growth, within reason Schoenfeld et al. 2017. A practical prescription for amateurs with a size goal:

• Volume: about 40–60 reps per muscle group per session, in 4–6 sets of 6–12.
• Effort: sets taken close to failure, leaving 1–2 reps in reserve. A wide range of loads works when sets are hard; 60–85% of max is a sensible default.
• Frequency: each muscle twice a week.
• Rest: 2–3 minutes on main lifts, 60–120 seconds on accessories. Very short rests (30–40 seconds) blunt muscle growth as well as strength Schoenfeld et al. 2016.
• Tempo: controlled lowering, then lift with full intent.

In trained lifters, moderate loads (3 × 10) built as much muscle as heavy sets (7 × 3) with equal volume, in about a quarter of the time and with fewer joint complaints. Heavy sets still built more strength, so keep heavy work on your main lifts even in a size block.

A sample off-season size week (4 days, upper/lower)

A four-day upper/lower split suits the off-season for players with a size goal and the time. Most amateurs should keep three sessions or fewer the rest of the year. Keep power work at the start of sessions, before fatigue: power always comes before high-rep work.

Drop sets and extra high-rep work are fine for upper-back pulling and arms. Keep them off squats, deadlifts and other lower-body lifts, where the soreness costs speed and skill at training.

How to eat for size

Calories

Muscle gain needs a modest energy surplus: about 300–500 kcal a day above maintenance, roughly 10–20% Iraki et al. 2019. In practice that’s one extra substantial snack or a bigger portion at two meals, mostly from carbohydrate. Bigger surpluses mostly add fat, which costs speed. There’s no need for bulk-and-cut cycles.

Protein

Aim for about 1.6–2.2 g of protein per kg of bodyweight a day, spread across 4–5 servings of 20–40 g, including one before bed. In a large meta-analysis, protein’s added benefit for muscle gains levelled off at around 1.6 g per kg a day Morton et al. 2018; going a bit higher costs little and suits players with a size goal. More than about 2.5 g per kg isn’t needed.

Carbohydrate and timing

Match carbohydrate to training: lighter days around 3–5 g per kg, heavier days 5–7 g per kg Close. Eat a small carbohydrate and protein snack 30–60 minutes before hard sessions and protein soon after. Eat every 3–4 hours and never start training hungry. Spreading meals helps fuelling; it barely changes body composition on its own.

Supplements

Food first. For adults, creatine monohydrate at 3–5 g a day is one of the best-supported supplements for strength and muscle gains Kreider et al. 2017. Expect 1–2 kg of extra bodyweight in the first week, mostly water. If you can be drug-tested, follow UK Anti-Doping’s advice: assess the need, the risk and the consequences, and use only batch-tested products, which reduce but don’t remove the risk UK Anti-Doping.

How fast should you gain?

Bodyweight swings by ±1 kg from day to day, so judge it on a weekly average. A gain of roughly 0.25–0.5% of bodyweight a week is a reasonable target for most amateurs Iraki et al. 2019. Faster usually means more fat. Check your jump or 10 m sprint every few weeks; if it’s falling while weight climbs, slow down. A size block only counts as working if your relative strength (strength per kilogram) holds or rises.

Don’t use BMI to judge it: it wrongly classes muscular players as overweight. If you track body composition, do it the same way each time (same time of day, similar hydration), 2–4 times a year, and look at the change rather than the raw number.

When to gain size

• Off-season: the main window. More gym volume, less running, easy aerobic sessions on recovery days.
• Early pre-season: the work capacity and size phase (8–12+ reps) before strength and power take over. Players trying to gain can delay extra conditioning a little. See the pre-season plan.
• In-season: maintain. Two short, heavy sessions a week and enough food to fuel training and games. See the in-season programme.

Common mistakes

• Dirty bulking. Large surpluses add fat, not useful mass, and slow you down.
• Size work without strength work. Keep heavy sets on the main lifts.
• Dropping speed work. Sprinting and jumping should never disappear for more than 3–4 weeks, even in a size block.
• Crash cutting before the season. Never lose weight by dehydration, saunas, sweat suits or fasting. If weight loss is needed, use a small deficit and keep eating regularly.
• Ignoring the rest of life. Sleep at least 7 hours Walsh et al. 2021; alcohol impairs refuelling and muscle repair.

If you notice signs of under-eating, such as frequent illness, repeated bone injuries, low mood or, for women, missed or irregular periods, speak to your GP or a sports doctor. Relative energy deficiency affects men too Mountjoy et al. 2023.

What an extra 300–500 kcal looks like

You don’t need to count calories to gain well. Add one of these to a normal day of eating, shown as foods rather than numbers:

• A mid-morning snack of a bagel with peanut butter and a pint of milk.
• A bigger portion of rice, pasta or potatoes at two meals.
• A pre-bed bowl of Greek yoghurt with oats, honey and fruit (which also adds a protein serving before sleep).
• A homemade smoothie of milk, banana, oats and peanut butter after training.

Weigh yourself a few mornings a week and watch the weekly average. Not moving after three weeks? Add another snack. Gaining fast and your jump is dropping? Pull one back.

Realistic expectations

Gains shrink with training age. A player new to lifting can add muscle and strength quickly in the first months, much of it from learning the movements. After a few years, expect slower progress over blocks and seasons, not weeks. Over-30s can still gain muscle, but should aim for steady improvement rather than dramatic transformations. That’s another reason to gain slowly and keep tracking speed: the size you add should make you a better player, not just a heavier one.