REVIEW

Progressive resistance strength training and the related injuriesin older adults: the susceptibility of the shoulder

Nelson Sousa • Romeu Mendes •

Graca Monteiro • Catarina Abrantes

Received: 24 May 2013 / Accepted: 3 October 2013

� Springer International Publishing Switzerland 2013

Abstract The benefits of progressive resistance training

(PRT) among the older adults are evident, especially in the

prevention of sarcopenia and improving muscle strength,

which reverse the age-related loss of functional ability.

However, PRT carries some risk, particularly when par-

ticipants are older adults with a certain degree of muscle

weakness. The purpose of this article is to discuss the PRT-

related injuries, and present an overview of documented

shoulder injuries among the elderly, discerning possible

mechanisms of injury and risk factors. A literature search

was conducted in the PUBMED database to identify the

relevant literature using combinations of keywords:

strength-training injuries, resistance-training injuries,

sports injuries in the elderly, shoulder complex, shoulder

injury, and shoulder disorder. Acute and chronic injuries

attributed to PRT have been cited in the epidemiological

literature. The shoulder complex, has been alluded to as

one of the most prevalent regions of injury, particularly in

exercises that place the arm extended above the head and

posterior to the trunk. However, the risk for injuries

appears to be higher for testing than for training itself. One-

repetition maximum strength testing may result in a greater

injury risk. This technique, though acceptable, needs

additional precautions in inexperience older adults to pre-

vent injury. Thus, the best treatment for PRT age-related

injuries is prevention. Appropriate and individualized

training programs, the use of safe equipment, careful

warming up and cooling down, correct range of motion,

progressive intensity training, cardiovascular and muscu-

loskeletal fitness are essential aspects of injury prevention

among the elderly.

Keywords Aging � Older adults � Resistance

training � Shoulder pain � Shoulder disorders � Sport

injuries

Introduction

It is increasingly common in older population the partici-

pation in progressive resistance training (PRT) programs,

either as main mode exercise, either as a complement to

aerobic exercise. The PRT has been described as the best

way to develop muscle strength [1, 2], since participants

work against an external force that is increased as strength

increases [3], and with various benefits related to health

and quality of life [4]. There are several studies that

associate PRT with significant improvements in biomarkers

of cardiovascular diseases risk factors in elderly population

[5, 6]. Moreover, it showed great benefits related with

functional fitness, and favorable changes in body compo-

sition, including increased fat-free mass and decreased fat

mass [7, 8, 9, 10]. In addition, high intensity PRT seems to

improve, or preserve, bone mineral density in older adults

[7, 11]. Recently, in a systematic review, PRT was

described successfully as a therapeutic modality in several

musculoskeletal conditions [12].

However, despite the evidence of benefits, some cases of

injuries associated with PRT have been reported in the

literature, special in non-PRT experienced participants.

The older adults may be more vulnerable to exercise-

related injuries, particularly during high intensity PRT

programs. The combination of repetitive and heavy

N. Sousa (&) � R. Mendes � G. Monteiro � C. Abrantes

Research Center in Sport Sciences, Health Sciences and Human

Development, Parque Desportivo da UTAD, University of

Tras-os-Montes e Alto Douro, Apartado 1013, 5001-801 Vila

Real, Portugal

e-mail: nelsons@utad.pt

123

Aging Clin Exp Res

DOI 10.1007/s40520-013-0157-z

loading, unfavorable positioning, and exercise selection

represents the main injury risk factors related to PRT [13].

The shoulder complex, in particular, represents one of

the most prevalent regions of injury attributed to PRT [14,

15]. Being a spheroid joint, the shoulder is the most mobile

joint in the body, it has little bony constraint to allow all

motion, and is controlled and stabilized primarily by

muscles and soft tissues. Therefore, shoulder injuries can

damage a large number of different structures in and

around the shoulder. The greater susceptibility of the

shoulder joint is due to several factors, such as the high

stress that PRT submit this joint, and the large number of

exercises that directly or indirectly recruits this joint and

are frequent in common PRT programs. Additionally,

common PRT exercises often place the shoulder in unfa-

vorable positions such as end-range external rotation, while

under heavy loads, predisposing the shoulder to both acute

and chronic injuries [16]. On the other hand, to activate the

major muscle groups of the trunk (i.e., pectoralis major and

latıssimus dorsi muscles) it is necessary to stimulate the

shoulder complex range of motion, neglecting, mostly the

muscles responsible for scapula stabilization (i.e., trapezius

and middle and lower serratus anterior muscles) during arm

movements [17, 18]).

In order to establish loads for training, as well as control

maximum strength gains, it is essential to assess the

maximum strength of the participants. The one-repetition

maximum (1-RM) is considered the gold standard for

assessing muscle strength in non-laboratory situations [19,

20]. The 1-RM is defined as the maximal weight that can

be lifted once with correct lifting technique and is gener-

ally considered to have good to excellent (ICC [ 0.98)

reliability in healthy adults [20]. It has been suggested that

the injury risk appears to be higher for strength testing than

for training itself, in particular through the 1-RM test,

because of the high intensity associated [19, 21].

The purpose of this article is to discuss the PRT-related

injuries, and present an overview of documented shoulder

injuries among older adults, presenting a brief review of its

anatomy, and to discern the possible mechanisms of injury

and risk factors.

The shoulder complex

Shoulder motion results from a combination of five joints:

[22] the glenohumeral joint, [23] the subacromial joint,

[24] the scapulothoracic joint, [25] the sternoclavicular

joint, and [7] the acromioclavicular joint. The glenohu-

meral joint is a synovial ball-and-socket joint and

accommodates the large range of motion of the shoulder

because of the size difference between the humeral head

and the small glenoid fossa on the scapula [26, 27]. The

subacromial joint is a bursa, a synovial, lubricated

potential space lying between the rotator cuff, supraspi-

natus inferiorly and the acromion process superiorly [26].

The scapulothoracic joint is a physiological joint con-

taining neurovascular, muscular, and bursal structures that

allow for a smooth motion of the scapula on the thorax

[27]. At sternoclavicular joint, the clavicle is joined to the

manubrium of the sternum. The clavicle serves as a site

of muscular attachment, providing a barrier to protect

underlying structures, stabilizing the shoulder and pre-

venting medial displacement when the muscles contract

[27]. The clavicle is connected to the scapula at its distal

end via the acromioclavicular joint, a small and gliding

synovial joint [27]. The deltoid is the prime mover of the

arm into humeral elevation, assisted by the supraspinatus

as an accessory elevator [28]. The rotator cuff also plays

a critical role in stabilizing the glenohumeral joint against

excessive humeral head translations through the medially

directed compression of the humeral head into the glenoid

and glenoid labrum [29]. The subscapularis, infraspinatus

and teres minor have an inferior directed line of action,

which allows activation of these muscles to offset the

superior translation component of deltoid muscle action

[28]. The infraspinatus and teres minor also produce the

humeral external rotation that occurs during normal arm

elevation. The scapula is capable of being moved upward

and downward, forward and backward, or, by a combi-

nation of these movements. The middle and lower serra-

tus anterior is the prime mover of the scapula on the

thorax, producing scapular upward rotation, posterior

tilting, and external rotation [18]. Upper trapezius pro-

duces clavicular elevation and retraction, the middle tra-

pezius is primarily a medial stabilizer of the scapula, and

the lower trapezius assists in medial stabilization and

upward rotation of the scapula [18, 30]. The pectoralis

minor is aligned to resist normal rotations of the scapula

during arm elevation [22].

Shoulder injuries and risk factors

Numerous studies have documented PRT and the related

shoulder injuries [13, 15–17, 31]. Soft tissue injuries rela-

ted to PRT primarily include the rotator cuff, biceps, and

pectoralis major musculature [15, 31]. The region of pain,

most often identified in all cases, included the long head of

the bicep and supraspinatus musculature [31]. To avoid

pain, motion patterns are often changed, in fact it has been

shown that pain causes significant changes in muscular

coordination by inhibiting muscular activity, and weaken-

ing the scapula stabilizing muscles [24, 31].

The acromioclavicular joint is submitted to increased stress

during the course of upper extremity PRT, predisposing this

Aging Clin Exp Res

123

joint to a condition referred as osteolysis of the distal clavicle

[31, 32]. This condition has been specifically associated with

the bench press exercise as a result of repeated microtrauma at

the acromioclavicular joint during the lowering phase of the

exercise (Fig. 1), when the arm is extended posterior to the

trunk [32].

Anterior shoulder instability at the glenohumeral joint

has also been related to PRT [13, 32]. Unfavorable posi-

tions assumed during common exercises such as bench

press, behind the neck pull-downs, military presses, and

chest flies, may predispose to anterior shoulder instability

and impingement [13, 18] particularly in older population.

These exercises traditionally require the humerus to be

extended posterior to the trunk (Fig. 2), stressing the

anterior shoulder tissues. Thus, it may excessively increase

mobility and over time lead to decreased stability, even

when the position is adapted for the older adults (e.g.,

humerus extended anterior to the trunk). During the most

common PRT exercises, end-range external rotation is

often required, rather than the relative infrequency of end-

range internal rotation, resulting in a loss of internal rota-

tion and posterior shoulder tightness [13]. A loss of

shoulder internal rotation and posterior capsule tightness

has been implicated as etiological risk factors for shoulder

dysfunction [33].

Overuse injuries can result of an increase in training

intensity, new technique introduction, or new equipment,

particularly in older adults. The load on soft tissue struc-

tures exceeds tissue capacity, leading to inflammation and

pain. This condition is easily reversible, if the load is

adjusted to the capacity. In PRT, the load applies enormous

force through the acromioclavicular joint, this mechanisms

results in inflammation and gradually degenerative disease

in the acromioclavicular joint [17, 32].

Laxity of the glenohumeral joint is compensated by

activation of the rotator cuff muscles, if these muscles are

not strong enough for this work, then either the muscles are

overused, resulting in tendonitis and tendinosis of the

tendons and muscle pain, or the humeral head is not cor-

rectly positioned during the technic, resulting in painful

stretching of the glenohumeral ligaments and the capsule

[17].

Injuries can also be caused by pre-existing less optimal

conditions associated with aging, or by dyscoordination/

lack of dynamic stability in the shoulder and in the scap-

ulothoracic joint [23]. The shoulder represents the ana-

tomical region with most lost of mobility resulting from

age-related disuse, leading to greater atrophy of the mus-

cles that surround it, compared with the lower limb mus-

cles [2].

The insufficient stability of the scapulothoracic joint is

caused by imbalance of trapezius and serratus anterior

muscles, resulting in shoulder impingement [18]. Studies

reported a significant increased activity in upper trapezius

during arm elevation and lowering, and a significant

decreased activity in serratus anterior at some humeral

elevation angles in subjects with shoulder pain and

pathology [34, 35].

Although the incidence of peripheral nerve injuries is

rare, accounting for less than 8 % of PRT injuries [36],

specific nerves are more vulnerable to stretch or com-

pression neuropathy as a result of their location.

Age-related anatomical changes are one of the main

injury risk factors. Above 60 years, the natural decrease in

bone mineral content causes a predisposition to fractures

and avulsions. Changes that occur in the connective tissue

with aging include a decrease in elastin and a thickening of

the basement membrane. The collagen cross-links increase,

which makes the collagen stiffer. Since ligaments, tendons

and joint capsules are composed primarily of collagen, this

means that both become stiffer and therefore weaker [25].

Fig. 1 Lowering phase of the bench press exercise

Fig. 2 Military press exercise with humerus posterior to the trunk

Aging Clin Exp Res

123

There appears to be a general decline in joint range of

motion with age that may be related, at least in part, to

changes in tendons and ligaments [37]. In addition to

effects on joint motion, aging-related changes in tendons

and ligaments may contribute to the development of inju-

ries in these structures, resulting in conditions ranging from

tendonitis to tendon and ligament tears or rupture.

Finally, methods of assessing maximum strength, in

particular the 1-RM test, may stress the joints, particularly

the shoulder. However, this assessment technique is the

most reliable translator of maximum strength. There is a

concern among some observers that 1-RM testing may be

inappropriate or potentially injurious to older adults [38].

Although several authors have reported 1-RM as a safe test

[2, 9, 20].

Discussion

Progressive resistance training is an effective instrument

in the prevention of sarcopenia among older adults with

significant effects on its functionality and cardiovascular

health. Despite the few references in the literature, there

is a greater risk of injury during participation in these

programs, especially in older population. Improper atten-

tion to exercise technique, exercise selection, unfavorable

shoulder positioning required on the more common

exercises, along with the repetitive nature of lifting heavy

weight until failure, increases the likelihood of injury.

PRT routines that focus on large muscle groups while

neglecting muscles responsible for shoulder stabilization

such as the rotator cuff and scapular musculature may

predispose participants to shoulder strength imbalances

[13, 18].

The most common anatomical structures of soft tissue

injury include the biceps brachii, rotator cuff and pectoralis

major musculature. Of those cases with a known etiology,

the bench press, military press and latıssimus pull-downs

was often implicated as a causal factor along with exercises

that required participants to assume injury risk position.

Biomechanically, performing exercise up and behind the

neck position (Fig. 3) may lead to over-stretching of the

anterior shoulder tissue leading to excessive anterior

translation and instability, resulting in potential injuries of

the glenohumeral joint. Therefore, moving the arm pos-

terior to the shoulder joint should always be avoided, as

this is unnecessary to achieve the full effect of PRT.

Despite the risk of injury during the 1-RM test, pre-

disposing particularly the elderly, it does not seem that

this technique is inappropriate. Some studies reported

cases of injuries associated with the 1-RM, but few. In a

study of Pollock et al. [38] with elderly (70- to 79-year-

old men and women), 1-RM testing resulted in 11 injuries

in a total of 57 subjects (19.3 %). While in the study of

Shaw et al. [21] only two subjects sustained an injury in

total of 32 untrained older adults (8 %). On the other

hand, the other groups with PRT experience (\6 months:

n = 24; [6 months training: n = 27) safely completed

the 1-RM test without injury (97.6 % of total). Thus, it

seems that 1-RM test is a reliable and safe method for

dosing and assessing the muscle strength in older adults,

as reported in previous studies [2, 19, 20]. However,

1-RM test for military press, or any lateral dumbbell

raise, should be avoided, since it may induce pain in older

adults. Alternatively, for these two exercises, 10-RM test

can be used instead.

Final considerations

In sum, it seems that the frequency of acute injuries is

higher among older population, than of overuse injuries,

which represents by far the most common injury related to

PRT [39]. Thus, the best treatment for PRT-related injuries

in older adults is prevention.

Appropriate PRT programs design is essential to prevent

injuries among older adults. Therefore, some important

strategies should be respected such as: (a) incorporating

exercises to strengthen the lower trapezius, and external

rotators may serve to mitigate common strength imbal-

ances; (b) include exercises to increase the strength or

relative activation of the middle and lower serratus anterior

are important to consider in the rehabilitation of shoulder

impingement; and (c) flexibility exercises designed to

increase internal rotation and improve posterior shoulder

flexibility are recommended to avoid shoulder disorders

and provide balanced joint mobility.

During the PRT program, it is necessary to respect some

additional precautions. Thus, when older adults initiate a

Fig. 3 Military press exercise with humerus extended above the head

Aging Clin Exp Res

123

PRT program for the first time, it is advisable to explain the

correct movements of each exercise during the first ses-

sions. To use cable-loaded resistance machines, especially

in the begining, and let the free weights for experienced

participants. Always perform a specific warm-up for each

exercise, starting a full set without load. It is also advisable

to increase the intensity progressively, over time.

Regarding the posture during the performance, older

adult participants should not completely extend the mem-

bers in the concentric phase, to prevent joint lock position,

and should never cross the line of the shoulders with the

elbows in the eccentric phase (Figs. 4 and 5). Always avoid

performing exercises behind the head, as in latıssimus and

military press, in alternative, the elderly can pull the bar

towards the chest without touch, at latıssimus (Fig. 6), and

raising the arms slightly in front of the head without

extending completely, in the military press (Fig. 7).

Finally, in the assessment of the maximum strength, the

1-RM test is one of the best methods, but to be performed

safely it is necessary to follow some rules: (1) perform the

1-RM test in one training session, exclusively; (2) assess

1-RM between two to three attempts with an interval of

3 min between each, if not, leave for another session; and

(3) in the presence of older participants with shoulder pain

or pathology, 10-RM test should be used for deltoid max-

imum strength assessment.

Conflict of interest On behalf of all authors, the corresponding

author states that there is no conflict of interest.

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