Weighted vests in CrossFit increase physiological stress during walking and running without changes in spatiotemporal gait parameters

Figures & data

Table 1. Subject characteristics of male and female participants.

Variable	Males	Females
Age (years)	20.9 ± 0.2	20.4 ± 0.2
Height (m)	1.79 ± 0.07	1.70 ± 0.05**
Body mass (kg)	76.7 ± 0.9	63.9 ± 0.6**
Body mass index (BMI) (kg/m^2)	24.1 ± 0.4	22.0 ± 0.2
Lean mass (kg)	61.8 ± 0.6	46.6 ± 0.3***
Body fat (%)	14.5 ± 0.5	22.6 ± 0.5**
VO2max (ml min kg^–1)	47.7 ± 0.5	41.2 ± 0.2**

Males vs. females: **p < 0.01; ***p < 0.001.

Data are expressed as mean ± SEM.

Figure 1. Schematic of the study design.

Read the detailed description of this figure

A top timeline shows the overall study order where VO2max and screening take place before two randomised experimental visits with or without a weighted vest. Visits are separated by 48h. A bottom timeline shows the protocol during an experimental visit. A control meal is taken 2 hours before the visit. A blood sample is taken before 20 min walking at 4.9km/h and the end, a second blood sample is taken. After a 15 mins break, a blood sample is taken before 30 mins running at 55% VO2max. A blood sample is taken halfway and at the end of the run. There is then a 10 mins cool down at 4.9km/h then a final blood sample is taken. Gas analysis is taken continuously throughout, and gait analysis is completed at 5 min intervals throughout the walk and run.

Table 2. Comparison of physiological variables across the walking condition.

	Weighted vest			No weighted vest
Variable	Males	Females	Sig	Males	Females	Sig
0% incline
VO2 (L/min)	1.24 ± 0.04*	0.88 ± 0.03	^^^	1.18 ± 0.05	0.84 ± 0.03	^^^
VO2/kg (ml/min/kg)	16.3 ± 0.5	13.8 ± 0.4	^^^	15.4 ± 0.5	13.2 ± 0.4	^^
Heart rate (bpm)	102 ± 4	106 ± 3	ns	98 ± 4	103 ± 3	ns
RER	0.83 ± 0.01	0.84 ± 0.01	ns	0.82 ± 0.01	0.82 ± 0.01	ns
VE (L/min)	32.3 ± 1.4	24.4 ± 0.8	^^^	30.7 ± 1.7	23.2 ± 0.8	^^^
Breathing frequency (breaths/min)	27 ± 1	25 ± 1	ns	26 ± 1	24 ± 1	ns
Blood glucose (mmol/L)	4.0 ± 0.2	4.4 ± 0.1	ns	4.2 ± 0.2	4.3 ± 0.2	ns
Blood lactate (mmol/L)	1.2 ± 0.2	1.2 ± 0.1	ns	1.0 ± 0.1	1.5 ± 0.1	ns
CHO oxidation (g/min)	0.63 ± 0.06	0.49 ± 0.04	ns	0.54 ± 0.05	0.42 ± 0.04	ns
Fat oxidation (g/min)	0.36 ± 0.03	0.24 ± 0.02	^	0.37 ± 0.04	0.25 ± 0.02	^
Energy expenditure (kJ/min)	25.0 ± 0.8*	17.8 ± 0.6	^^^	23.6 ± 1.0	16.9 ± 0.6	^^^
5% incline
VO2 (L/min)	1.58 ± 0.06	1.18 ± 0.03	^^^	1.53 ± 0.08	1.12 ± 0.04	^^^
VO2/kg (ml/min/kg)	20.6 ± 0.5	18.5 ± 0.4	^	20.0 ± 0.6	17.6 ± 0.5	^^
Heart rate (bpm)	113 ± 4*	120 ± 4	ns	107 ± 4	116 ± 4	ns
RER	0.84 ± 0.01	0.86 ± 0.02	ns	0.83 ± 0.01	0.84 ± 0.01	ns
VE (L/min)	39.9 ± 2.1	30.9 ± 1.1	^^^	38.6 ± 2.1	28.9 ± 1.1	^^^
Breathing frequency (breaths/min)	29 ± 1	28 ± 2*	ns	28 ± 1	25 ± 1	ns
Blood glucose (mmol/L)	4.3 ± 0.1	4.4 ± 0.1	ns	4.1 ± 0.1	4.3 ± 0.2	ns
Blood lactate (mmol/L)	1.2 ± 0.2	1.0 ± 0.1	ns	1.3 ± 0.1	1.3 ± 0.2	ns
CHO oxidation (g/min)	0.92 ± 0.06	0.75 ± 0.08	ns	0.78 ± 0.07	0.64 ± 0.05	ns
Fat oxidation (g/min)	0.41 ± 0.05	0.29 ± 0.04	ns	0.45 ± 0.05	0.30 ± 0.02	^
Energy expenditure (kJ/min)	31.8 ± 1.2	23.9 ± 0.6	^^^	30.8 ± 1.5	22.6 ± 0.9	^^^
10% incline
VO2 (L/min)	2.08 ± 0.08*	1.64 ± 0.04**	^^^	1.98 ± 0.10	1.51 ± 0.05	^^^
VO2/kg (ml/min/kg)	27.1 ± 0.4*	25.5 ± 0.4**	^	25.5 ± 0.5	23.5 ± 0.3	^^
Heart rate (bpm)	131 ± 4**	144 ± 4**	ns	121 ± 4	135 ± 4	^
RER	0.90 ± 0.01*	0.91 ± 0.01*	ns	0.87 ± 0.01	0.89 ± 0.01	ns
VE (L/min)	52.8 ± 3.1**	43.8 ± 1.9**	^	48.9 ± 2.6	38.9 ± 1.5	^^
Breathing frequency (breaths/min)	30 ± 2	32 ± 1*	ns	29 ± 1	29 ± 1	ns
Blood glucose (mmol/L)	3.9 ± 0.2	4.4 ± 0.1	ns	4.0 ± 0.2	4.2 ± 0.1	ns
Blood lactate (mmol/L)	2.2 ± 0.4	1.7 ± 0.3	ns	1.8 ± 0.2	1.6 ± 0.2	ns
CHO oxidation (g/min)	1.67 ± 0.06***	1.43 ± 0.10**	ns	1.36 ± 0.07	1.17 ± 0.08	ns
Fat oxidation (g/min)	0.36 ± 0.04	0.24 ± 0.04	ns	0.44 ± 0.06	0.28 ± 0.03	^
Energy expenditure (kJ/min)	42.6 ± 1.6**	33.6 ± 0.9**	^^^	40.2 ± 1.9	30.9 ± 1.1	^^^

Significance of within sex weighted vest vs. no weighted vest denoted by *p < 0.05; **p < 0.01; ***p < 0.001. Significance of between-sex differences within condition ^p < 0.05; ^^p < 0.01; ^^^p < 0.001.

Abbreviations: VO₂: oxygen consumption; RER: respiratory exchange ratio; VE: Pulmonary ventilation; CHO: carbohydrate.

Data are expressed as mean ± SEM.

Figure 2. Cardiorespiratory responses to weighted vest running. There was an increase in VO₂ in the weighted vest condition in males (A, p < 0.001), and females (B, p < 0.01). This was associated with an increase in ventilation in males (C, p < 0.001) and females (D, p < 0.05) and an elevation in heart rate in males (E, p < 0.001) and females (F, p < 0.001). *p < 0.05; **p < 0.01 WV vs. NWV.

A six-panel line graph showing VO2, VE, and heart rate in males and females in the weighted vest and no weighted vest trials. All measures are higher in the weighted vest trial in both sexes.

Table 3. Comparison of physiological variables across the 30-minute run.

	Weighted vest			No weighted vest
Variable	Males	Females	Sig	Males	Females	Sig
VO2/kg (ml/min/kg)	37.5 ± 0.5**	31.4 ± 0.7*	^^^	34.6 ± 0.5	30.1 ± 0.6	^^
VO2/Heart rate (ml)	17.4 ± 0.4	11.6 ± 0.3	^^^	17.1 ± 0.4	12.1 ± 0.3	^^^
VE/VO2	28.1 ± 0.5**	27.7 ± 0.8*	ns	26.2 ± 0.3	26.2 ± 0.6	ns
VE/VCO2	29.2 ± 0.4*	29.1 ± 0.8	ns	28.3 ± 0.3	28.2 ± 0.6	ns
VT (L)	1.89 ± 2.2	1.38 ± 0.03	^^^	1.86 ± 0.04	1.40 ± 0.03	^^
Breathing frequency (breaths/min)	47 ± 1**	44 ± 1**	ns	41 ± 1	40 ± 1	ns
Blood glucose (mmol/L)	4.3 ± 0.1	4.5 ± 0.1	ns	4.2 ± 0.1	4.4 ± 0.1	ns
Fat oxidation (g/min)	0.18 ± 0.08***	0.21 ± 0.05*	ns	0.36 ± 0.07	0.27 ± 0.06	^^^
RPE	12.6 ± 0.9**	13.3 ± 0.6***	ns	9.5 ± 0.4	11.1 ± 0.6	^^^

Significance of within sex weighted vest vs. no weighted vest denoted by *p < 0.05; **p < 0.01; ***p < 0.001. Significance of between-sex differences within condition ^^p < 0.01; ^^^p < 0.001.

Abbreviations: VO₂: oxygen consumption; VE: pulmonary ventilation; VCO₂: carbon dioxide production; VT: tidal volume; RPE: rating of perceived exertion.

Data are expressed as mean ± SEM.

Figure 3. Energy expenditure and substrate utilisation in males and females during weighted vest running. The addition of a weighted vest promoted a significant increase in RER in males (A, p < 0.001) but not females (B, p > 0.05). This was associated with a shift towards greater CHO oxidation in males (C, p < 0.001) and females (D, p < 0.01) and an increase in energy expenditure in males (E, p < 0.001) and females (F, p < 0.05). *p < 0.05; **p < 0.01; ***p < 0.001 WV vs. NWV.

A six-panel line graph showing RER, CHO oxidation, and energy expenditure in males and females in the weighted vest and no weighted vest trials. CHO oxidation and energy expenditure are greater in the weighted vest condition in both sexes but RER is only greater in the weighted vest trial in males.

Figure 4. Increased blood lactate levels in the weighted vest condition in males (p < 0.05) but not females (p > 0.05). **p < 0.01 WV vs. NWV.

A two-panel line graph showing blood lactate over time in males and females in the weighted vest and no weighted vest trials. Blood lactate is higher in the weighted vest trial only in males.

Table 4. Comparison of biomechanical variables across the walking and running conditions.

	Weighted vest			No weighted vest
Variable	Males	Females	Sig	Males	Females	Sig
Walking
Stride length (cm)	149.0 ± 1.9	149.7 ± 2.8	ns	150.1 ± 3.9	153.1 ± 3.3	ns
Stride frequency (steps/min)	110.2 ± 1.5	110.5 ± 2.2	ns	111.0 ± 3.0	108.4 ± 2.6	ns
Running
Stride length (cm)	186.2 ± 5.3	179.0 ± 5.3	ns	186.4 ± 6.0	178.8 ± 5.1	ns
Stride frequency (steps/min)	157.7 ± 2.5	162.6 ± 1.8	ns	159.4 ± 3.1	162.9 ± 2.0	ns

Non significance of between-sex differences within condition (ns).

Data are expressed as mean ± SEM.