Table 3.

Description of interventions for RCTs investigating combined protein and exercise interventions compared to (a) exercise alone and (b) protein alone on bone health in middle-aged and older adults

Author, year	Duration (wk)	Protein intervention(s)	Control	(a) Exercise co-intervention	Adherence to the intervention
Amasene (2019)	12	Whey supplement: - B-lactoglobulin (20 g/bottle) - L-Leucine (3 g/bottle) - 150 ml - 2 × /wk after training	Placebo supplement: - Maltodextrin (23 g/bottle) - Hydroxyethylcellulose (0.200 g/bottle) - 150 ml - 2 × /wk after training	Resistance training: - 1 h/session, 2 × /wk - Supervised - Progressive (50–70% of 1-RM) - 2 sets per exercise Content: - Warm up - Strengthening of upper and lower limbs (arm-curl, knee extension, standing knee flexion, side hip raise, standing hip extension and chair stand) - Dynamic balance - Cool down	1 Participant refused to take the supplement, no further information
Daly (2014)	16	Lean red meat: - 220 g (raw weight) of veal, lamb or beef cuts) prepared by participants - Distributed over 2 meals/day at 6 days/wk - Individual counselling	High carbohydrates: - Usual diet +  ≥ 1 serving of rice/pasta - 1 × daily - Individual counselling	Resistance and balance-agility training: - 45–60 min/session, 2 × /wk - Supervised - Progressive - First 2 wks: 3 sets of 12 repetitions; thereafter 3 sets of 8–12 repetitions Content: - Warm up (rhythmic exercise) - Resistance training (included squats, lunges, box step-ups, leg extensions, standing leg curls, hip abductions, calf raises, shoulder press, upright row, bicep curls, wall pushups and triceps kickback) - Balance-agility exercises - Cool down	Assessment: RT: attendance to exercise classes (daily exercise cards completed and checked after each session) Meat consumption: compliance calendar to record daily consumption (collected 1/month) Carbohydrates: self-report calendar Degree: RT: 74% no difference between groups Meat consumption: 81% Carbohydrates: 100%
De Azevedo Bach (2022)	12	Whey supplement: - 20 g whey protein isolate - Diluted in 100 ml water - 2 × /day (after breakfast and dinner)	Placebo supplement: - 20 g of maltodextrin - Diluted in 100 ml water - 2 × /day (after breakfast and dinner	Resistance training: - 2 × /wk - Supervised, group based (6–8 persons) - Progressive (3 wks: 2 sets of 12–15 RM, 3 wks: 3 sets of 10–12 RM, 3 wks: 4 sets 8–10 RM, 3 wks: 4 sets of 6–8 RM) - Training load increased from 2.5 to 5.0 kg whenever participants were able to perform more repetitions than prescribed Content: - Chest press, bilateral knee extension, lat pull-down, bilateral elbow extension, hip abduction, bilateral elbow flexion and hip adduction	Assessment: RT: NR Supplement: collection of empty packages, recording of consumption, 3d dietary records Degree: RT: A1: 100%, A2: 99% Supplement: A1: 97.23%; A2: 97.1% Protein intake (g/kg BW/d, pre, post) A1: 1.1 ± 0.3; 1.5 ± 0.4 A2: 1.3 ± 0.4; 1.3 ± 0.5
Fernandes (2018)	12	Whey supplement: - 35 g of hydrolysed whey protein - Diluted in 200 ml water - 3 × /wk	Placebo supplement: - 35 g of maltodextrin - Diluted in 200 ml water - 3 × /wk	Resistance training: - 3 × /wk - Supervised - Progressive (training weight was adjusted on a weekly basis using the weight test for repetition maximum) - 3 sets of 8–12 RM Content: - Whole body training (chest press, horizontal leg press, seated row, knee extension, preacher curl, leg curl, triceps pushdown and seated calf raises)	Assessment: RT + Supplement intake: Supervision Degree: Protein intake (g/kg BW/day, pre, post): A1: 0.85 ± 0.1; 1.4 ± 0.1 A2: 0.81 ± 0.1; 0.87 ± 0.1
Leenders (2013)	24	Protein supplement: - 15 g of protein (milk protein concentrate); 80% of casein and 20% of whey protein - 0.5 g of fat, 7.13 g of lactose and 0.42 g of calcium - 250 ml - 1 × daily	Placebo supplement: - No protein or fat, 7.13 g lactose and 0.42 g calcium - 250 ml - 1 × daily	Resistance training: - 3 × /wk - Supervised - Progressive (1 RM was increased in the first 4 wks of training from 60% (10–15 repetitions/set) to 75% (8–10 repetitions/set), from week 5 onwards: 8 repetitions at 75–80%) Content: - Warm-up -Leg press, leg extension, chest press, horizontal row in every session; vertical lat pull, abdominals, biceps curl and triceps extension were alternated between subsequent sessions - Cool down	Assessment: RT: Supervision Protein: 3-day dietary record Degree: RT: 90% ± 1% (no difference between groups) Protein: Increase of protein intake by 0.24 (w) and 0.18 g/kg BW/day (m) in the supplement group
Roschel (2021)	16	Whey supplement: - 15 g of whey mixed in 150 ml of water - 2 × daily OR Soy supplement: - 15 g of soy mixed in 150 ml of water - 2 × daily	Placebo supplement: - 15 g of corn starch mixed in 150 ml of water - 2 × daily	Resistance training: - 2 × /wk - Supervised - Progressive (ranged from 2 sets at 50% 1 RM (first 4 wks of training) to 4 sets at 70% 1-RM (last 4 wks of training) for each exercise) Content: - Exercises for the main muscle groups (inclined leg press, leg extension, horizontal bench press, shoulder press and lat pull down)	Assessment: RT: training log of each exercise session Supplement: Record of supplement intake (time and day); return of supplement containers each month and weighing the remaining supplement in each container Degree: Protein intake (g/kg KG/day, pre, post): A1: 0.88 (0.75, 1.00); 1.19 (1.05, 1.33) A2: 0.91 (0.78, 1.04); 1.26 (1.2, 1.4) A3: 0.81 (0.68, 0.95); 0.89 (0.75, 1.03)
Verdijk (2009)	12	Protein supplement: - 10 g protein as casein hydrolysate - As 250 ml beverage - 2 × per session (during warm up and cooling down)	Placebo supplement: - Water (250 ml) - 2 × per session (during warm up and cooling down)	Resistance training: - 3 × /wk - Supervised - Progressive (from 60% of 1 RM (10–15 repetitions in each set) to 75–80% of 1 RM (8–10 repetitions) within the first 4 wks; from wk 5: 8 repetitions at 75–80%) - 4 sets per exercise Content: - Warm up - Leg press, leg-extension - Cool down	Assessment: RT: attendance in sessions Protein: supplement given before/after exercise session Degree: 35 ± 1 of the 36 sessions (no difference between groups)
Zdzieblik (2015)	12	Collagen supplement: - 15 g/day (molecular weight of approximately 3 kDa, included 2.7% leucine) - In 250 ml water - 1 × daily	Placebo supplement: - Silicon dioxide - In 250 ml water - 1 × daily	Resistance training: - 3 × /wk, 60 min - Supervised - Progressive (wks 1–4: 15 repetitions, wks 5–9: 10 repetitions, wks 10–12: 8 repetitions; 4 s/repetition) Content: - All larger muscle groups (pull down, leg press, bench press, back press, etc.)	Assessment: Supplement: collection of unused supplement; daily records about the timing of ingestion Exercise: exclusion if missing > 10% of the training sessions Degree: 7 dropouts due to incompliance with training protocol Supplement: NR
Author, Year	Duration (wk)	Exercise Intervention	Control	(b) Protein Co-Intervention	Adherence to the intervention
Evans (2007)	39	Endurance exercise: - 3 × /wk (increased until 45 min/session) - Supervised - Progressive (intensity of 55 to 60% of peak aerobic capacity (VO2 peak) and progressed gradually to 75 to 80% of VO2 peak within 4 to 6 weeks) Content: - Different exercise modes were used (e.g. a four-lane 17-lap per mile indoor track, treadmills, rowing ergometers, and stair-climbing ergo-meters)  − Individualized on the basis of participant preferences	No exercise - Maintain usual physical activities	Soy (2 groups): - 25.6 g of protein and 91.2 mg aglycone units of isoflavones - Daily Or Milk protein isolate (2 groups): - 25.6 g of protein and 0 mg aglycone units of isoflavones - Daily	Assessment: Protein: food records Degree: Significant increase of protein intake in all groups (+ 15 to  + 23 g/day) Adherence to the supplement: “ ~ 90%”
Shenoy (2014)	12	Resistance training: - 4 × /wk (40–50 min/session) - Supervised - Progressive (1 set of 15 repetitions at 40–50% of 1 RM until 3 sets of 8–12 repetitions at 60–80% of 1 RM) Content: Step up and down, prone leg curl, wrist leg curl, biceps curl, seated and supine triceps extension, standing calf/heel raise, wall push-up and knee flexion/extension shoulder press	No exercise	Soy isolate protein: - 40 g of soy protein powder/day mixed in 200 ml –250 ml milk twice a day	Assessment: Exercise: NR Protein: 24-h-recall method twice (before beginning and at the end of three months) Degree: No information regarding soy protein intake

A arm, BW body weight, d day, wk week, min minutes, RM repetition maximum, RT resistance training, NR not reported