The Influence of Exercise Load and Blood Flow Restriction on the

Recovery of Neuromuscular Strength following Resistance Exercise

Charlie Davids

1,5

, Truls Raastad

, Glen Lichtwark

, Jeff Coombes

, Jonathan Peake

4,5

and Llion Roberts

2,5

School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, Australia

Griffith Sports Physiology and Performance, School of Allied Health Sciences, Griffith University, Southport, Australia

Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway

School of Biomedical Sciences, Queensland University of Technology, Brisbane, Australia

Queensland Academy of Sport, Nathan, Queensland, Australia

1 OBJECTIVES

Due to the diverse demands in many sports, athletes

are required to simultaneously develop multiple

facets of physical fitness. This often requires multiple

training sessions within short timeframes, meaning

recovery between sessions is of fundamental

importance to promote optimal performance during

training. Such effects are only exacerbated in the

competitive season when performance during games

becomes the key priority. However, traditional high

load resistance exercise (HL-RE), which is the

current gold standard for enhancing skeletal muscle

adaptations, is accompanied by high levels of

mechanical stress (Schoenfeld, 2010). Mechanical

stress can impair muscular performance in the hours

and days following training, impacting subsequent

training sessions, and competitive performance

(Doma, 2017). Consequently, many coaches reduce

volume and intensity during the season to mitigate

these mechanical stresses, but this approach may lead

to suboptimal stimuli for skeletal muscle adaptation.

A solution to this issue is the combination of

blood flow restriction with low load resistance

exercise (LL-BFR), which has been demonstrated to

produce significant increases in skeletal muscle

hypertrophy, strength and endurance (Clark, 2011;

Kacin and Strazar, 2011). This is achieved with

reduced mechanical stress, as often loads ranging

from 20-30% of one-repetition maximum (1RM) are

used. Restriction of blood, and ultimately oxygen, to

the exercising muscle results in greater metabolic

stress, which appears to compensate for the lack of

mechanical stress. Despite this change in stimulus

from mechanical to predominantly metabolic, it

appears that LL-BFR is still capable of producing

robust hypertrophic and strength gains that are

comparable to HL-RE, even in athletic populations

(Luebbers et al., 2017). Importantly, these

adaptations seem to occur with much less training

volume load (load x sets x reps), enhancing training

efficiency and minimising stress to connective

tissues. However, less is known of the acute recovery

from LL-BFR, and whether the shift in stimulus (from

mechanical to metabolic) observed with this type of

exercise leads to a hastened recovery of muscle

performance. This possibility is supported by the

absence of muscle damage that has been reported

with LL-BFR (Loenneke, 2014). Knowledge of the

timeline of recovery from LL-BFR is necessary to

understand the exercise-adaptation cycle of this

innovative mode of exercise, so an optimal balance of

maximising adaptations while still allowing sufficient

recovery periods, can be achieved.

The majority of previous studies have assessed

neuromuscular performance immediately following

LL-BFR, which appears to be impaired to a similar

extent as HL-RE (Cook, 2013; Loenneke, 2015).

However, neuromuscular performance needs to be

evaluated further into the post-exercise period to

establish an acute timeline of fatigue and recovery.

Husmann (2017) demonstrated that neuromuscular

performance is significantly impaired immediately

following LL-BFR. However, performance improves

drastically within 8 minutes upon reperfusion of the

exercising muscles, perhaps indicating that acute

strength impairment is a result of peripheral fatigue

caused by metabolite accumulation, as opposed to

central factors. It is important to acknowledge that

strength did not completely recover to pre-exercise

levels. Indeed, Loenneke (2013) reported these levels

were still not regained with LL-BFR at 60 minutes

post-exercise. However, it is not clear how these

effects compare to the use of HL-RE, and whether

there is a difference in the origin of fatigue (be it

Davids, C., Raastad, T., Lichtwark, G., Coombes, J., Peake, J. and Roberts, L.

The Inﬂuence of Exercise Load and Blood Flow Restriction on the Recovery of Neuromuscular Strength following Resistance Exercise.

In Extended Abstracts (icSPORTS 2018), pages 19-23

central or peripheral) observed after both exercise

protocols.

Therefore, the aim of the present study was to

compare how low body neuromuscular performance

was influenced 60 minutes after lower body

resistance exercise is influenced by blood flow

restriction (BFR) protocol type, and exercise load. It

was hypothesised that although the addition of BFR

to low load exercise would enhance strength

decrements following exercise, such effects would

still be reduced in comparison to high load exercise.

2 METHODS

Participants.

Twelve healthy resistance-trained males (mean 

standard deviation; age: 22.3  3.2 years; height:

182.1  6.3cm; body mass: 84.1  9.0kg) volunteered

to participate in the study. All participants had been

resistance training continuously for a minimum of

two years leading up to the trials as an attempt to

translate the findings to athletic cohorts. This study

has been approved by the Human Research Ethics

Committee at The University of Queensland.

Experimental Design.

A randomised within-participants repeated measures

experimental design was used to assess the

neuromuscular responses to different BFR protocols

and exercise intensities. After baseline and

familiarisation visits, participants attended the

laboratory on four occasions, separated by a

minimum of 5 days to complete four experimental

trials in a randomised manner. The conditions were:

(a) low load resistance exercise (LL, 30%1RM); (b)

LL with continuous blood flow restriction (LL-

CBFR); (c) LL with intermittent blood flow

restriction (LL-IBFR); (d) high load resistance

exercise (HL, 70%1RM).

Baseline Visits.

Participants first had their arterial occlusion pressure

(AOP) determined via Doppler ultrasound

(uSmart3300, Terason, USA) of the posterior tibial

artery, as previously advocated by Loenneke et al.,

(2015). Participants then completed the baseline

strength testing on the isokinetic dynamometer as

described below. On a separate visit, participants

performed their 1RM squat, and completed a

familiarisation of the LL-CBFR condition, as this has

been demonstrated to be the most challenging

(Brandner and Warmington, 2017).

Experimental Trials.

Each experimental visit began with a lower body

exercise session. The session consisted of 4 sets of

barbell squat exercise, with 2 minutes of seated inter-

set rest in between. For all LL conditions, the first set

consisted of 30 repetitions, following by three sets of

15 repetitions. For the HL condition, 4 sets of 10

repetitions were completed. Following the final set of

exercise, participants remained seated for 60 minutes.

Blood Flow Restriction Protocol.

For both CBFR and IBFR trials, participants had a

pair of 8cm-wide nylon pneumatic cuffs placed

around the proximal thigh. The cuffs were inflated to

60% of the ultrasound determined AOP immediately

prior to the first set of exercise using a rapid cuff

inflator (E20, Hokanson, Bellevue, WA). In the

CBFR trial, the cuffs remained inflated until the final

set of exercise was completed, whereas during the

IBFR trial, the cuffs were deflated following each set,

and re-inflated immediately prior to beginning the

next set.

Neuromuscular Strength Assessment.

During the baseline visit, and 60 minutes following

exercise during each of the experimental trials,

participants completed a series of maximal isometric

contractions on an isokinetic dynamometer (Biodex

3, Biodex Medical Systems, USA). Prior to being

seated in the dynamometer, participants had reusable

stimulation electrodes (50mm x 90mm; Metron,

Patterson, UK) placed over the femoral nerve. The

cathode electrode was placed just below the inguinal

fold on the anterior groin, with the anode electrode

placed underneath the gluteal fold on the posterior

thigh. Participants were then seated with a 55-degree

hip angle, with their dominant leg strapped to the

lever arm of the machine. The lever arm was fixed at

an angle corresponding to 70 degrees of knee flexion

(full knee extension defined as 0 degrees of flexion).

Following three warm-up submaximal voluntary

contractions of the knee extensors, participants

performed three 5 second maximal voluntary

contractions, each separated by 120 seconds.

Participants were instructed to apply force as rapid

and as hard as possible for the entire 5 seconds. The

peak torque value generated during the best

contraction was recorded as the maximal voluntary

torque (MVT). The rate of torque development was

also calculated by determining the time taken to reach

50% (TPT50) and 90% (TPT90) this peak torque

value.

Following these voluntary contractions,

involuntary activation of the knee extensors was

icSPORTS 2018 - 6th International Congress on Sport Sciences Research and Technology Support

achieved via supramaximal stimulation of the femoral

nerve through the stimulation electrodes, connected

to a Digitimer DS7AH (Digitimer Ltd, Welwyn

Garden City, Hertfordshire, UK). Participants

performed an additional three maximal voluntary

contractions, during which the knee extensors were

maximally stimulated, with another maximal

stimulation to the resting muscle following

approximately 3 seconds after the contraction.

Utilising the interpolated twitch technique, voluntary

activation of the quadriceps was determined, as well

as evoked twitch torque from the resting stimulation.

Statistical Analysis.

Data were initially checked for normality using a

Shapiro-Wilk test. Repeated measures two-way

ANOVAs were then used to compare differences

between trials and time points (baseline vs 1-hour

post-exercise). Significant main effects of time,

condition, or interaction were followed by post-hoc

repeated measures t-tests, with Bonferroni’s multiple

comparisons correction. Effect sizes (Cohen’s d)

were also calculated to provide magnitude-based

inferences. Effect sizes were assessed as 0.2 = small

effect, 0.5 = moderate effect, and ≥0.8 = large effect.

Statistical significance levels were accepted at

p<0.05.

3 RESULTS

There was a significant time x trial interaction for

MVT (p=0.03). Post hoc analyses revealed significant

time interactions for HL (p<0.01; -8.77%; ES=0.56)

and CBFR conditions (p<0.01; -5.90%; ES=0.36),

while both LL and IBFR showed no significant

change from baseline (Figure 1). Significant

condition interactions were also found between HL

and LL (p<0.01; ES=0.40), and HL and IBFR

conditions (p=0.02; ES=0.23) with no other

interactions between conditions reported (Figure 1A).

There was a significant time x trial interaction for

evoked twitch torque (p<0.01). Post hoc analyses

revealed significant time interactions for HL (p<0.01;

-18.75%; ES=1.51), CBFR (p=0.01; -5.96%;

ES=0.47) and LL (p<0.01; -6.79%; ES=0.53)

conditions, while no change from baseline was

reported for IBFR. Significant trial interactions were

also found between HL and each of the other

conditions (p<0.01 for all, Figure 1B).

No significant change in voluntary activation of

the knee extensors was observed in any of the

conditions (p=0.40; Table 1). There were significant

time interactions for TPT50 with LL, CBFR and

IBFR conditions being higher than baseline, but no

between condition interactions were found (Table 1).

For TPT90, there were significant time interactions

for HL and CBFR, and a significant condition

interaction, with CBFR being significantly different

from LL and IBFR conditions (Table 1).

Figure 1: (A) maximal voluntary torque and (B) evoked

twitch torque of the knee extensors. Black bars represent

baseline values. *indicates a significant difference from

baseline (p<0.05). #indicates a significant difference from

the low load (LL) and intermittent BFR (IBFR) condition

(p<0.05). &indicates significant different all other

conditions (p<0.05).

Baseli

Load

Hig

BFR

erm

tte

BFR

200

300

400

Condition

Peak Torque (Nm)

Maximal Voluntary Torque

lin

Load

Loa

ont

inu

ous

nter

tte

100

Condition

Twitch Torque (Nm)

Evoked Twitch Torque

The Inﬂuence of Exercise Load and Blood Flow Restriction on the Recovery of Neuromuscular Strength following Resistance Exercise

Table 1: Voluntary activation, time to 50% peak torque (TPT50), and time to 90% peak torque (TPT90). *indicates a

significant difference from baseline (p<0.05). **indicates a significant difference between LL and IBFR conditions.

BAS LL HL CBFR IBFR

Voluntary

Activation (%)

94.425.7 96.633.7 97.942.2 95.844.5 97.213.1

TPT50 (ms) 0.090.01 0.130.06* 0.120.03 0.140.07* 0.150.09*

TPT90 (ms) 0.710.35 0.850.31 0.960.32* 1.100.36** 0.860.27

4 DISCUSSION

The present study compared the decrements in

neuromuscular performance between different lower

body exercise protocols, varying in exercise intensity,

and blood flow restriction application. The primary

findings of the present study indicated that at 60

minutes post-exercise: (i) compared to baseline

levels, MVT was significantly impaired following

only HL and CBFR conditions, whereas there were

no differences from baseline following LL or IBFR

conditions; (ii) compared to baseline levels, evoked

twitch torque was significantly impaired following

HL, CBFR and LL conditions, with no change after

IBFR; and (iii) there were no changes in central

activation of the knee extensors in any of the

conditions compared to baseline levels. These

findings partially supported the hypothesis. Although

both CBFR and HL exercise resulted in significant

neuromuscular performance impairment at 60

minutes post-exercise, there were no significant

differences between conditions.

Previous studies examining the influence of blood

flow restricted exercise on neuromuscular

performance have often assessed this effect

immediately post-exercise. It remains unclear how

performance is recovered acutely in the hours

following exercise. Immediately post-exercise, it

appears that the combination of BFR with low-load

exercise tends to exacerbate the magnitude of fatigue,

and that this effect occurs due to contractile

perturbations caused my metabolite accumulation

(Husmann, 2017). This effect tends to remain at 1

hour following exercise, with strength performance

recovering to baseline levels in the unrestricted

condition (Loenneke, 2015). This outcome aligns

with the results of the present study. Maximal

voluntary torque remained significantly reduced at 60

minutes post-exercise following CBFR, whereas

strength recovered to baseline levels in both LL and

IBFR conditions. It is likely that the larger degree of

metabolic stress experienced in the CBFR condition

caused greater perturbations within the skeletal

muscle, impairing the contractile function.

Interestingly, despite the additional exercise volume

completed in the HL condition (volume-load = load x

sets x reps; HL: 3941.6  485kg; LL, IBFR, CBFR:

3171.9  370kg), MVT remained impaired at 60

minutes post-exercise in both HL and CBFR

conditions, with no differences between them. This

finding suggests that the restriction of oxygen to the

working muscles during exercise and rest periods that

occurs with CBFR, leads to metabolic perturbations

within the skeletal muscle that match those of higher

loads and higher volumes of exercise.

This explanation is further supported by the

reduction in evoked twitch torque, and increase is

TPT90 that was observed in the present study for HL

and CBFR conditions. Evoked twitches consisted of

supramaximal stimulations being delivered to the

knee extensors, meaning the reduction in torque after

exercise is due to factors distal to the neuromuscular

junction. This observation adds weight to the claim

that the fatigue observed in the present study is of

peripheral origin and is related to metabolite

accumulation. Further support for this idea was

provided by Suga (2012), who observed metabolic

stress (indicated by inorganic phosphate

accumulation and pH decline) to increase over the

course of four sets of exercise to match levels seen

with HL exercise. While acute impairments in

neuromuscular performance are not a valid indicator

of chronic hypertrophy, they do tend to align with the

results of chronic studies which report similar

hypertrophy between CBFR and HL conditions, with

inferior hypertrophy in load-matched unrestricted

conditions. This possibility could suggest that CBFR

may be used as a tool to achieve similar hypertrophy

as HL training, despite a marked reduction in training

volume, although chronic training studies are

required for confirmation.

The lack of change in voluntary activation of the

knee extensors found in the present study aligns with

previous findings. While Husmann (2017) found

central activation to be reduced immediately after the

icSPORTS 2018 - 6th International Congress on Sport Sciences Research and Technology Support

fourth set of LL-BFR, this effect rapidly recovered

upon reperfusion at 2 minutes post-exercise. Further,

Cook (2013) found no change in central activation

post-exercise between HL, LL-BFR or LL conditions.

This outcome would explain the lack of change seen

at 60 minutes post-exercise in the present study.

Together, with the results mentioned previously,

evidence suggests that the decrement in

neuromuscular performance observed in the present

study is due to peripheral fatigue, as opposed to

central factors.

In conclusion, HL and CBFR squat exercise

appears to impair neuromuscular performance to a

similar extent at 1-hour post-exercise despite the

reduced mechanical stress and total training volume

completed in the CBFR condition. The impairment in

performance was due to peripheral factors as

voluntary activation of the knee extensors remained

unchanged following exercise. Further research

should seek to extend the timeline of neuromuscular

performance recovery past 60 minutes to determine if

differences exist between HL and CBFR.

Furthermore, whether the equivalent acute

neuromuscular responses between HL and CBFR

exercise translate to similar chronic hypertrophic

changes should be evaluated, as LL-BFR training

may serve as a strategy to manage total training stress

and chronic fatigue during busy periods of training

and competition.

ACKNOWLEDGEMENTS

This work is supported by the Queensland Academy

of Sport’s Sport Performance Innovation and

Knowledge Excellence unit.

REFERENCES

Brandner, C. R., & Warmington, S. A. (2017). Delayed

onset muscle soreness and perceived exertion following

blood flow restriction exercise. J Strength Cond Res.

doi:10.1519/jsc.0000000000001779.

Clark, B. C., Manini, T. M., Hoffman, R. L., Williams, P.

S., Guiler, M. K., Knutson, M. J., Kushnick, M. R.

(2011). Relative safety of 4 weeks of blood flow-

restricted resistance exercise in young, healthy adults.

Scand J Med Sci Sports, 21(5), 653-662.

doi:10.1111/j.1600-0838.2010.01100.x.

Cook, S. B., Murphy, B. G., & Labarbera, K. E. (2013).

Neuromuscular function after a bout of low-load blood

flow-restricted exercise. Med Sci Sports Exerc, 45(1),

67-74. doi:10.1249/MSS.0b013e31826c6fa8.

Doma, K., Deakin, G. B., & Bentley, D. J. (2017).

Implications of Impaired Endurance Performance

following Single Bouts of Resistance Training: An

Alternate Concurrent Training Perspective. Sports Med,

47(11), 2187-2200. doi:10.1007/s40279-017-0758-3.

Husmann, F., Mittlmeier, T., Bruhn, S., Zschorlich, V., &

Behrens, M. (2017). Impact of Blood Flow Restriction

Exercise on Muscle Fatigue Development and

Recovery. Med Sci Sports Exerc.

doi:10.1249/mss.0000000000001475.

Kacin, A., & Strazar, K. (2011). Frequent low-load

ischemic resistance exercise to failure enhances muscle

oxygen delivery and endurance capacity. Scand J Med

Sci Sports, 21(6), e231-241. doi:10.1111/j.1600-

0838.2010.01260.x.

Loenneke, J. P., Allen, K. M., Mouser, J. G., Thiebaud, R.

S., Kim, D., Abe, T., & Bemben, M. G. (2015). Blood

flow restriction in the upper and lower limbs is

predicted by limb circumference and systolic blood

pressure. Eur J Appl Physiol, 115(2), 397-405.

doi:10.1007/s00421-014-3030.

Loenneke, J. P., Thiebaud, R. S., & Abe, T. (2014). Does

blood flow restriction result in skeletal muscle damage?

A critical review of available evidence. Scand J Med

Sci Sports, 24(6), e415-422. doi:10.1111/sms.12210.

Loenneke, J. P., Thiebaud, R. S., Fahs, C. A., Rossow, L.

M., Abe, T., & Bemben, M. G. (2013). Blood flow

restriction does not result in prolonged decrements in

torque. Eur J Appl Physiol, 113(4), 923-931.

doi:10.1007/s00421-012-2502.

Luebbers, P. E., Witte, E. V., & Oshel, J. Q. (2017). The

Effects Of Practical Blood Flow Restriction Training

On Adolescent Lower Body Strength. J Strength Cond

Res. doi:10.1519/jsc.0000000000002302.

Schoenfeld, B. J. (2010). The mechanisms of muscle

hypertrophy and their application to resistance training.

J Strength Cond Res, 24(10), 2857-2872.

doi:10.1519/JSC.0b013e3181e840f3.

Suga, T., Okita, K., Takada, S., Omokawa, M., Kadoguchi,

T., Yokota, T., Tsutsui, H. (2012). Effect of multiple set

on intramuscular metabolic stress during low-intensity

resistance exercise with blood flow restriction. Eur J

Appl Physiol, 112(11), 3915-3920.

doi:10.1007/s00421-012-2377-x.

The Inﬂuence of Exercise Load and Blood Flow Restriction on the Recovery of Neuromuscular Strength following Resistance Exercise