Title: Acute Effects of Centrally- And Unilaterally-Applied Posterior–Anterior Mobilizations of the

Lumbar Spine on Lumbar Range of Motion, Hamstring Extensibility and Muscle Activation

Paul Chesterton 1 *, Stephen Payton 1, Shaun McLaren 1

Corresponding author *

Affiliations:

1 Department of Psychology, Sport and Exercise

Teesside University, Middlesbrough, TS1 3BA, United Kingdom

Corresponding author *

Paul Chesterton,

Department of Psychology, Sport and Exercise

Teesside University, Middlesbrough, TS1 3BA, United Kingdom

e-mail: p.chesterton@tees.ac.uk

Tel.: +44 (0) 1642 738246

Fax: Not Applicable

1

ABSTRACT

BACKGROUND: Lumbar mobilizations are used to clinically treat the lumbar and hamstring region.

Evidence is limited regarding the effectiveness of specific mobilization methods, however.

OBJECTIVE: To compare central and unilateral posterior–anterior mobilizations (CPA, UPA) of the lumbar

spine on lumbar and hamstring range of motion (ROM), and muscle activity (sEMG).

METHODS: Twenty participants received CPA, UPA, or no mobilization (CON) on separate occasions

(crossover design). Post-treatment outcome measures were ROM during active lumbar flexion (ALF) and

active knee extension (AKE), as well as sEMG of the Erector Spinae (ES) and Biceps Femoris (BF) during

these movements.

RESULTS: sEMG was possibly to very likely lower following CPA (mean difference range = -5% to -21%)

and UPA (-7% to -36%), while ROM was most likely greater (-12% to 25% & -17% to 24%, respectively).

Most sEMG measures were possibly to likely lower following UPA versus CPA (-18% to -11%), while AKE

ROM was possibly greater (-5.5%). Differences in ES sEMG (-2.5%) and ROM (-1.4%) during ALF were

unclear and most likely trivial, respectively.

CONCLUSIONS: CPA and UPA mobilizations increase lumbar and hamstring ROM whilst reducing local

muscle activity. These effects appear to be greater for UPA mobilizations when compared with CPA.

KEY WORDS: Manipulation, Spinal; Lumbar Vertebrae; Hamstring Muscles.

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INTRODUCTION

Low back pain causes more disability worldwide than any other condition and the cost to the National

Health Service in the UK exceeds 1000 million pounds per year [1,2]. Lumbar mobilizations have been

used to decrease spinal pain and stiffness whilst increasing range of motion [3]. Recent National

Institute of Clinical Excellence [2] guidelines suggested this type of manual therapy can be used to treat

patients with lower back pain as part of an overall treatment plan. In Northern Ireland, of 157

physiotherapists surveyed, approximately 42% chose to treat patients with lumbar pathology with

mobilizations [4].

The lumbar spine is widely considered to have an indirect impact on the hamstring complex due to its

anatomical and functional relationship [5,6,7]. The origin of the neural supply and neurodynamics of the

hamstring complex implicates the lumbar spine as a potential source of pain referral and impacts on the

biomechanical function of the muscle group [8]. Restricted hamstring extensibility has been

demonstrated to directly decrease lumbar flexion range [9]. Furthermore, back pain is associated with

changes in the mechanical characteristics of the hamstring, lowering muscle activity within the complex,

whilst increasing its stiffness [10,11,12].

Hamstring strains continue to be one of the most common musculoskeletal injuries in athletes of all age

ranges, genders, sports, and levels of competition [13]. Reduced extensibility of the hamstring remains

an associated risk factor for injury as well as impinging on lumbar mobility [9,14,15,16]. Recent evidence

suggests that lumbar mobilizations can increase the hamstring tissue extensibility, as measured by the

active knee extension test, and reduce muscle electromyography activity of the hamstring and Erector

Spinae (ES) during active movements in the immediate term [17,18]. Given excessive ES activity has

been reported in patients with low back pain [19], assessing muscle activity may provide valuable

3

mechanistic information related to spinal mobilizations. The Biceps Femoris (BF), as the most commonly

injured hamstring muscle [20], and the ES with its role to compensate the net moment caused by

external load and body weight are key muscles to quantify EMG activity [21] in response to spinal

mobilizations.

Mobilizations have been reported to provide both biomechanical benefits and neurophysiological

effects on symptom modulation; although the mechanisms behind this are relatively poorly understood

[22,23]. Mobilizations are reported to decrease pain by activating the central pain modulating areas of

the brain including the descending periaqueductal grey (dPAG). The side specific changes reported by

Perry and Green [24] might suggest activation of the dPAG together with stimulation of the descending

pain inhibitory systems, though further investigation to establish this theory is required. Authors have

proposed that the activation of dPAG and descending pain inhibitory systems results in hypoalgesic and

sympathoexcitatory responses extending beyond the spinal segment mobilized [22,25]. Specifically,

centrally applied posterior–anterior (PA) mobilizations at L4 have been shown to produce a

sympathoexcitatory increase, measured via skin conduction, which initiates the sympathetic nervous

system cascade of neurophysiological reaction associated with mobilization related hypoalgesia [26].

Furthermore, side-specific peripheral sympathetic nervous system changes assessed by skin

conductance and measured via electrodes, have been reported following unilateral lumbar mobilizations

[24]. Mobilizations can also increase the neurodynamics of the posterior lower limb, evaluated by the

straight leg raise test, both immediately and at a 24-hour follow-up [27,28]. Recently, Mendiguchia et al

[29] have included lumbar facet mobilizations as part of a multi-factorial approach to hamstring

rehabilitation and a return to play algorithm.

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Despite the ability of mobilizations to decrease spinal pain and improve hamstring extensibility, a lack of

understanding regarding the effects of specific technique selection remains. Numerous variables are

included with technique selection, with an evidence base existing to support clinician choice for

mobilization force, duration and amplitude [30,31]. Patient position, spinal level, force direction, grade,

rate, rhythm and duration are also key considerations. Importantly, no research exists supporting which

specific technique to apply either a central posterior–anterior (CPA) mobilization on the spinous process

or a unilateral posterior–anterior (UPA) technique on the transverse process or facet joint [32].

Decisions generated by clinicians regarding the type of mobilization to be applied must be based on

theoretical concepts and empirical evidence. The lack of research into mobilization techniques and the

comparison of their effects prevents clinician’s from making evidence based decisions [30]. Traditionally,

mobilization choice has been dependent on biomechanical limitations identified at a specific spinal level

or the primary spinal level associated with symptom presentation [23]. Central mobilizations are applied

for central pain presentation whilst side specific unilateral mobilizations are used for pain which radiates

laterally [32]. However, to the authors’ knowledge, the magnitude of the effects of CPA versus UPA

selection on distal anatomical structures including the hamstring complex has yet to be elucidated.

Comparing the effectiveness of specific locations on outcome measures related to lumbar spine range,

hamstring extensibility and muscle electrical activity will enable clinicians to make informed decisions on

appropriate technique selection.

Therefore, we aimed to quantify the effect of CPA versus UPA on lumbar spine range, hamstring

extensibility and muscle electrical activity of the ES and BF. Through this study it is aimed to provide

clinicians with evidence on which to generate evidence based reasoning.

METHODOLOGY

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Experimental Design and Protocol

This report is conducted with recommendations from CONSORT for publishing non-pharmacologic

intervention studies [33]. We utilized a counterbalanced, post-only crossover design to compare the

acute effects of CPA and UPA lumbar mobilizations on measures of lumbar and hamstring range of

motion and muscle activity. Participants visited a biomedical sciences laboratory on three separate

occasions, each separated by one week, and received either a) CPA lumbar mobilization, b) UPA lumbar

mobilization, or c) no mobilization (i.e. control condition, CON). To improve test validity participants

were instructed to refrain from caffeine at least 4 hours prior to testing, and avoid strenuous exercise at

least 24 hours prior [34]. Mobilization treatment order was counterbalanced using the Latin square

method to mitigate any potential order effects. On recruitment, participants (n = 24, details below) were

randomized to one of six possible subsets of treatment sequences to ensure every treatment followed

every other treatment the same number of times (n = 4). All testing sessions were performed at the

same time of day for each participant to reduce the influence of diurnal effects and laboratory

temperature (21.5 degs) and humidity conditions (29% humidity; 1002 barametric pressure) were

maintained constant throughout and between assessment visits. Following each treatment (CPA, UPA or

CON), participants immediately performed a test of active knee extension (AKE) and active lumbar

flexion (ALF), during which measures of range of motion and muscle electrical activity of the ES group

and BF were taken. Tests of AKE and ALF, along with the collection of outcome measures, were

performed and recorded by a practitioner who was blinded to the mobilization allocation. Outcome

measures were recorded immediately after each other, approximately one minute apart, to allow for

the participant to reach the correct position. We also counterbalanced the order of ALF and AKE

assessments within each treatment sequence subgroup to mitigate assessment order having adverse

influences on outcome measures. As per previous studies [17,18] four ALF and AKE were conducted

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prior to final assessment of the outcome measures to counteract against variations in tissue

extensibility.

Participants

Twenty-four participants (proportion of males: 55%, age [mean ± SD]: 26 ± 4 y, body weight: 75 ± 12 kg,

stature: 173 ± 10 cm) were recruited from a population of students at Teesside University, United

Kingdom, between April 2015 and December 2015. Participants were included if they were aged over

eighteen and without current spinal or lower limb pathology. Those with current symptomatic low back

pain, neurological symptoms, hamstring or hip pathology were excluded. A history of lumbar surgery or

any contraindication to spinal mobilization also prevented participation [32]. Four participants were

excluded from the study based on current lumbar or hip pain. Written informed consent was obtained

from all participants prior to testing and the study received ethical approval via Teesside University’s

ethics committee (Ethics Number: SSSBLREC250415), in accordance with the Declaration of Helsinki.

Lumbar Mobilizations

Participant’s laid prone on a plinth placed upon force plates, which measured the mobilization force.

The CPA group received central posterior–anterior lumbar mobilizations to the L5 vertebrae segment.

We selected this segmental level due to the relationships between L5 and both hamstring pain and

flexibility [35]. UPA lumbar mobilizations were administered to the unilateral zygapophyseal L4/5 joint

to the ipsilateral side as the dominant limb, determined by preferred kicking foot. Grade three

mobilizations, defined as large amplitude oscillations into resistance [32], were applied to both groups

by a physiotherapist with ten years’ clinical experience and postgraduate qualifications in spinal

mobilization. Mobilizations for both test conditions were applied as a large-amplitude oscillatory

movement for two minutes, three times at the relevant spinal level [32,36]. Spinal level was determined

7

by passive physiological intervertebral movement and spinal palpation by two independent

physiotherapists blinded to group allocation. CPA mobilizations were applied via the ulnar border of the

hand, with the area between the pisiform and hook of hamate in contact with the spinous process. The

same hand position was maintained for UPA mobilizations, with the contact area immediately adjacent

to the spinous process, on the identified transverse process [32]. Both CPA and UPA mobilizations were

applied at a frequency of 1Hz maintained by a metronome. Force plate data was recorded at 500Hz

above the frequency of the mobilizations preventing sampling errors.

The control group following initial baseline outcome measures lay prone on a plinth for a ten-minute

period, the time it took for the clinician to explain, identity and perform the lumbar mobilizations.

Following this ten-minute period, the relevant outcome measures were re-tested.

Outcome Measures

Active lumbar flexion range was measured by the modified Schober (mSchober) test [37,38]. Each

participant stood on a wooden box, 60 cm in height, with their feet positioned 8 cm apart as indicated

by tape (Figure 1). A blinded assessor identified, via a skin marker, 5 cm below and 10 cm above the

lumbosacral junction, determined by a passive physiological intervertebral movement and lumbar

palpation [32,38]. Each participant was instructed to actively flex forward as far as possible, with the

knees extended, until instructed to return to neutral. Test performance (range of motion) was recorded

as the change in distance between the two skin markers, measured by a tape measure (seca Germany)

in centimeters. The test-retest correlation coefficient (r) for lumbar range of motion measured via the

mSchober is reported to be 0.88 [39}; making this a highly reliable assessment.

Figure 1: The Active Lumber Flexion test position

8

***INSERT FIGURE 1 ABOUT HERE***

The active hamstring extensibility of the dominant leg was measured by the AKE. During the test,

participants laid supine on a plinth with one mobilization belt placed across the anterior superior iliac

spine preventing pelvic and lumbar movement. Another belt was placed 20 cm above the tibial

tuberosity of the non dominant/non-testing leg to prevent motion [40]. The belt positions were marked‐

for re-measurement purposes. The hip was held at a 90° flexed angle by a wooden wedge (Figure 2).

Participants were instructed to extend the knee of the testing leg till the end of maximal range perceived

as discomfort, determined by the participant [41]. An inclinometer (Dr Rippstein, Zurich, Switzerland),

positioned on the anterior tibial border halfway between the inferior pole of the patella and the line

between the malleoli measured positional change [42]. Throughout testing the ankle was maintained in

plantigrade by a medical brace. Test performance (range of motion) was measured as the degrees from

full active knee extension, where full active knee extension would equal 0°. The test-retest intraclass

correlation coefficient (ICC) for hamstring extensibility measured via AKE is reported to be 0.86 [41];

making this a highly reliable assessment.

Figure 2: The Active Knee Extension Test position

***INSERT FIGURE 2 ABOUT HERE***

Muscle electrical activity of the ES and BF was measured via surface electromyography (sEMG) during

both ALF and AKE assessments. Prior to the electrode application, the participants skin was prepared to

minimize any interference in the signal, by shaving and cleaning the area with a 70% isopropyl alcohol

wipe. Noraxon self-adhesive Ag/AgCl snap electrodes (Noraxon USA) were used throughout the

investigation. These electrodes have an inter-electrode placement of 20 mm and were placed on the

9

relevant muscle in accordance to the Surface Electromyography for the Non-Invasive Assessment of

Muscles (SENIAM) recommendations [43,44]. The inter-electrode method of data collection

substantially removes far-field potentials such as crosstalk signals [45]. Electrodes remained in position

throughout the testing procedure, including mobilizations, to eliminate placement error and allow

immediate reassessment of the outcome measures. No recording of sEMG activity occurred during

mobilization. Superficial muscles were chosen to provide a clearer sEMG signal and reduce cross talk

[46].

To assess Biceps Femoris (BF) muscle activity, an electrode was placed half way between the ischial

tuberosity and the lateral epicondyle of the tibia, on the participant’s dominant side. The electrode for

the Erector Spinae (longissimus) was placed two finger widths lateral to L1, on the muscle belly, to the

participants dominant side [44,47,48]. We recorded muscle electrical activity for 10 seconds at rest

(lying prone) and at end ranges of the ALF and AKE assessments, with the mean values for the 10

seconds used for analysis. Since ALF and AKE inherently involve low-level sEMG, normalizing values

against a maximum voluntary contraction was not deemed appropriate or necessary [49,50]. Data were

collected using a wireless sEMG system (Cometa) sampling at 2000 Hz. The sEMG signal was then

processed and filtered (Cometa v1.6 software) using a high pass Butterworth filter, with a cut off

frequency of 20 Hz [44,48,51]. Data were then rectified and smoothed using a root-mean-square filter

with a floating window of 20 ms [52,53,54]. While there are limitations of sEMG to isolate muscles, and

avoid cross-talk [44], sEMG has been shown to accurately assess myoelectrical activity of the Erector

Spinae [55] and Biceps Femoris muscles [56].

Statistical Analysis

10

Raw data showed no evidence of non-normal distribution, and are therefore presented as the mean ±

SD. Before analysis, data were log transformed and then back-transformed to obtain the difference in

outcome measures between each condition (CPA, UPA and CON) as accurate percentages [57]. Percent

differences are presented with 90% confidence intervals (CI) as markers of uncertainty in the estimates

[58]. In sports medicine research, null hypothesis significance testing fails to provide information about

the effect size or the range of feasible values in relation to clinically important threshold values [57,59].

The use of P values therefore provides inadequate information to the practitioner who is concerned

with real-world effects and their likelihood of substantiality. Accordingly, we used magnitude-based

inferences to examine the acute effects of CPA and UPA mobilizations of the lumbar spine on hamstring

lumbar range of motion, hamstring extensibility and muscle activation. In the absence of well-

established minimum clinically significant differences for our outcome measures, we used standardized

threshold values of 0.2, 0.6, and 1.2 multiplied by the pooled between-participant SD to represent small,

moderate and large effects, respectively [57]. Subsequently, inference was based on the disposition of

the CI for the mean difference in relation to these thresholds and the probability (percent chances) that

the true population effect was the observed magnitude that was estimated per the magnitude-based

inference approach [58]. Percent chances were qualified via probabilistic terms assigned using the

following scale: 25–75%, possibly; 75–95%, likely or probably; 95–99.5%, very likely; and .99.5%, most

likely [58]. Since there is no clear and straightforward link between measures of range of motion and

muscle electrical activity during AKE and important outcomes (e.g. health, performance), inferences

were evaluated mechanistically and deemed clear if the CI did not overlap both substantially positive

and negative thresholds by ≥5% [58].

RESULTS

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The mean (± SD) force applied during CPA and UPA mobilizations was 99.5 ± 4.6 N and 74.5 ± 5.0.

Descriptive (mean ± SD) post-mobilization data for each outcome measure are presented in Table 1. The

acute effects of CPA and UPA mobilizations of the lumbar spine on measures of lumbar and hamstring

range of motion and muscle activity during AKE and ALF are presented in Table 2. When compared with

no mobilization, CPA and UPA mobilizations incurred small to moderate reductions in muscle electrical

activity (BF and ES) during AKE; with these reductions being lower for UPA. Both mobilizations caused

small to moderate improvements to AKE range of motion, respectively; with the improvement in range

of motion being greater following UPA. During ALF, CPA and UPA mobilizations incurred small to

moderate reductions in BF muscle electrical activity, respectively, and these reductions were lower for

UPA when compared with CPA. There was a possibly small reduction in ES electrical activity for both

mobilizations compared with no mobilization and the difference between mobilizations was unclear.

There was a moderate increase in ALF range of motion following both CPA and UPA mobilizations and

the difference between mobilizations was trivial.

***INSERT TABLE 1 ABOUT HERE***

***INSERT TABLE 2 ABOUT HERE***

DISCUSSION

Lumbar mobilizations continue to form an integral part of therapeutic management of the lumbar

region. Furthermore, the ability to utilise lumbar mobilizations to alter the extensibility and muscle

activity of the hamstring complex has recently been reported [17,18,24,27]. Despite this, the

effectiveness of several variables associated with lumbar mobilizations have yet to be investigated

including the role of specific locations. We therefore aimed to investigate the acute effects of CPA and

UPA of the lumbar spine in relation to lumbar and hamstring outcome measures. The main findings from

12

our investigation were that both CPA and UPA increase lumbar range of motion and hamstring

extensibility whilst also reducing local muscle activity, yet UPA mobilizations provide greater effects on

hamstring extensibility and muscle activity when compared with CPA.

Previously, the effectiveness of the two most clinically popular spinal mobilizations, central and

unilateral posterior–anterior mobilizations, on range of motion and muscle electrical activity of the

lumbar and hamstring were unknown. Our data show that both CPA and UPA mobilizations elicit at least

a possibly small effect on the measures we assessed. These results are also comparable to other

investigations which found improvements in lumbar range post mobilization [60,61]. Against the control

CPA range increased by 25.4% and UPA 23.6%. This is consistent with results from previous studies

demonstrating an average increase of 18.6% [17], 17.8% [62] and 7.1% [63] respectively. Chesterton et

al [17] also reported an increase of 22.8% in AKE range. However, Petty [64], Chiradejnant et al [65,66],

and Stamos-Papastamos et al, [36] all found no significant effect of lumbar mobilizations on range of

motion. Although, this study did not investigate the mechanism by which these increases in range

occurred, it is conceivable that the mechanical and neurophysiological mechanisms described to

improve mobility were present. Passive motion has been reported to selectively stretch contracted

tissues [67]. Additionally, mobilizations have been found to activate the periaqueductal gray and inhibit

temporal summation which decreases the excitability of dorsal horn cells [25,66]. Following

mobilization, the Hoffman reflex has demonstrated a transient attenuation of alpha motor neuron

excitability decreasing protective muscle guarding, which may result in gains in joint range [69].

In our investigation, UPA reduced the muscle electrical activity of the BF during both ALF and AKE. A

proposed benefit of mobilization is the reduction of muscle activation which has been reported at the

lumbar spine [31,54]. Against the control CPA mobilizations also had a likely small (AKE) and very likely

13

small (ALF) effect on reducing BF activity. These results support previous work suggesting that distal

structures, including the hamstring, could be treated more proximally [17,70]. This is likely due to the

direct relationship between sympathetic excitation and pain modulation [71,72,73]. Several specific

mechanisms for this decrease in sEMG activity have been proposed. Joint afferent activity itself can

cause reduction in muscle excitability [74,75} as can the hypoalgesic effect of mobilizations [25,76,77].

Mobilizations can increase muscle spindle activity [69,78,79,80], stimulate golgi tendon organ activity

[77], which leads to a reflex inhibition of muscle. The exact neurophysiological mechanisms of both CPA

and UPA mobilizations is beyond the scope of this study. UPA mobilizations may stimulate overlying

musculature and cutaneous tissues in a different manner when compared to CPA mobilization

techniques and therefore the proposed mechanisms may be different [22,72]. An investigation of

cervical spinal mobilizations reported that UPA applied mediolateral forces are less compared to CPA

mediated forces [81]. Changing the angle of applied force will affect the magnitude of vertical force

potentially impacting on the physiological responses recorded. Future research investigating this effect

at the lumbar spine may be warranted.

As this is the first study to investigate the effects of technique selection on measures of both the lumbar

and hamstring region, evidence is presented to support specific mobilization selection. This study

suggests clinicians who wish to target unilateral tissue from the spinal column could utilise UPA

techniques over CPA mobilizations, due to the ability to influence both range of motion and muscle

activity of unilateral tissues. However, both mobilizations improved ALF and reduced sEMG activity of

ES. The trivial effects found for ALF between both mobilizations suggest that either technique can

increase range and clinicians should consider this in their clinician reasoning when selecting appropriate

lumbar mobilizations techniques.

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Limitations and Future Research

We acknowledge several limitations in our present investigation that are worthy of discussion. First, only

the acute effects of the mobilizations were investigated in our crossover trial, which may limit the

application of our data to medium- and long-term effects. A second limitation of our current work is the

recruitment of asymptomatic individuals and therefore the effect of assessing CPA versus UPA in a

symptomatic population remains unclear. Future research should investigate how variables are

influenced within a symptomatic population over the short-, medium- and long-term. We based our four

pre-measures of AKE and ALF on recommendations from pilot tests in the methodology of previous

research [17], yet no formal reliability trial has been conducted to determine the appropriateness of this

arbitrary cut-off value (e.g. a pairwise analysis of consecutive trials, Hurst et al [82]. We acknowledge

that without this, changes in ROM may have been influenced by a decrease in passive stiffness of the

soft tissue. Our treatment order was counterbalanced using the Latin Square method, yet we lost four

participants to follow-up. This ultimately resulted in treatment sequences being disproportionate—a

clear limitation of the Latin Square method.

The application of sEMG has limitations with signal influenced by external noise, electrical activity of

adjacent muscle, the depth of adipose tissue the signal is required to travel and the number of active

motor units at the time of recording [83]. Despite the reliability of sEMG in both the ES [55] and BF [56]

being previously reported this has not been established within our laboratory for these outcome

measures, therefore the precision of the measurement is currently unknown. Lastly, our data were

restricted to a traditional group-level comparison, which is unlikely to reflect the true responses on an

individual level. The individual responses to CPA or UPA mobilizations remains unknown and warrants

further investigation.

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CONCLUSIONS

The evidence base for mobilizations to form part of treatment programmes for the lumbar spine is

established whilst its ability to influence the hamstring region is still in its infancy. As part of a wider

multifactorial approach to lumbar and hamstring management, clinicians can incorporate mobilizations

which have the potential to produce positive effects on local range of motion and muscular activity. Our

results demonstrated that UPA and CPA mobilizations can be applied to increase lumbar range of

motion and reduce local Erector Spinae muscle activity. UPA mobilizations have a greater ability to

increase hamstring extensibility whilst reducing Biceps Femoris muscle activity compared with CPA

mobilizations. This data adds to the current literature aiding clinical reasoning of the management of the

lumbar and hamstring region using lumbar mobilizations.

16

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Table1. Descriptive (mean ± SD) post-mobilization data for each condition.

Outcome MeasureCondition

CON CPA UPA

Active Knee Extension

BF electric activity (μV) 12.4 ± 8.1 9.4 ± 6.0 8.3 ± 5.5

ES electric activity (μV) 8.8 ± 6.4 6.5 ± 3.5 5.0 ± 1.8

Range of motion (°)* 54 ± 14 47 ± 12 46 ± 14

Active Lumbar Flexion

BF electric activity (μV) 7.3 ± 5.4 6.3 ± 5.5 5.6 ± 4.4

ES electric activity (μV) 6.0 ± 1.3 5.7 ± 1.4 5.6 ± 1.3

Range of motion (cm)** 5.6 ± 1.4 6.9 ± 1.5 6.9 ± 1.5

*degrees from full active knee extension, where full active knee extension = 0°**change in lumbar surface length.

Abbreviations: BF = biceps femoris; CON = no mobilization; CPA = centrally applied posterior anterior mobilizations; ES = erector spinae (longissimus); UPA = unilaterally applied posterior anterior mobilizations

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Table 2. Acute effects of centrally- and unilaterally-applied posterior–anterior mobilizations of the lumbar spine on hamstring lumbar range of motion, hamstring extensibility and muscle activation.

Outcome MeasureCPA compared with CON UPA compared with CON Mobilization comparison (UPA compared with CPA)

%; ±90% CL Inference %; ±90% CL Inference %; ±90% CL Inference***

Active Knee Extension

BF muscle activity -21; ±11 Likely small ↓ -30; ±12 Very likely small ↓ -11.2; ±8.0 Possibly lower following UPA

ES muscle activity -21; ±10 Likely small ↓ -36; ±16 Possibly moderate (very likely small) ↓ -18; ±15 Likely lower following UPA

Range of motion* -12.1; ±1.8 Most likely small ↑ -17.0; ±3.4 Possibly moderate (most likely small) ↑ -5.5; ±3.8 Possibly greater following UPA

Active Lumbar Flexion

BF muscle activity -16.0; ±5.1 Very likely small ↓ -24.8; ±6.6 Possibly moderate (most likely small) ↓ -10.5; ±5.9 Possibly lower following UPA

ES muscle activity -4.7; ±2.8 Possibly small ↓ -7.1; ±7.5 Possibly small ↓ -2.5; ±7.8 Unclear

Range of motion** 25.4; ±7.8 Likely moderate ↑ 23.6; ±8.2 Likely moderate ↑ -1.4; ±2.5 Most likely trivial

*degrees from full active knee extension, where full active knee extension = 0°. A reduction therefore implies greater range of motion.**change in lumbar surface length. An increase therefore implies greater range of motion.***the magnitude of all substantial differences were small.

Abbreviations: ↓ = reduction; ↑ = increase; BF = biceps femoris; CL = confidence limits; CON = no mobilization; CPA = centrally applied posterior anterior mobilizations; ES = erector spinae (longissimus); UPA = unilaterally applied posterior anterior mobilizations

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Figure 1: The Active Lumber Flexion test position

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Figure 2: The Active Knee Extension Test position

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