Use of exercise training to reverse age-related changes in neuronal function and skeletal muscle morphology

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1 5th Congress of the Hellenic Society of Biochemistry and Physiology of Exercise Athens November 6-7th, 215 Use of exercise training to reverse age-related changes in neuronal function and skeletal muscle morphology Brain motor cortex cerebellum Spinal cord Muscle Per Aagaard Muscle Physiology and Biomechanics Research Unit, Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark / paagaard@health.sdu.dk Age-induced changes in neuromuscular function: Loss of motor neurons, MU reorganization 1

2 Number of Motor Units Neural factors - neuromuscular function Ageing and neuromuscular function spinal motor neurons, nerve axons, motor units Brain motor cortex cerebellum Spinal cord spinal motor neurons Muscle Spinal motor neurons reduced number of motor neurons in the spinal cord 25% average loss of spinal motor neurons (lumbospinal segments L1-S3) from 2 yrs to 9 yrs of age Tomlinson & Irving 1977 several subjects > 6 yrs showing ~ 5% less MN's compared to 2-4 yrs old Tomlinson & Irving 1977 Ageing and neuromuscular function > mean value < 6 yrs lower limit < 6 yrs Age (yrs) Motor Units reduced number of excitable (i.e. functioning) MU's observed at 6-7 yrs of age Brown et al. 1988, Doherty et al. 1993, Campbell, McComas et al Number of excitable MU's in aged subject (6-95 yrs) ~ 1/3 of that observed in younger subjects (1-6 yrs) Campbell, McComas et al Extensor digitorum brevis (n=27, age=3-96 yrs) AJ McComas: Skeletal muscle - form and function,

3 Neural factors - neuromuscular function spinal Ageing motor and neurons, neuromuscular nerve axons, function motor units # motor neurons = # motor units at increasing age ongoing process of denervation and reinnervation of skeletal muscle fibers late in life Vandervoort 22, McComas 1996 AJ McComas: Skeletal muscle - form and function, 1996 Neural factors - neuromuscular function spinal Ageing motor and neurons, neuromuscular nerve axons, function motor units # motor neurons = # motor units at increasing age ongoing process of denervation and reinnervation of skeletal muscle fibers late in life Vandervoort 22, McComas 1996 AJ McComas: Skeletal muscle - form and function,

4 Neural factors - neuromuscular function spinal Ageing motor and neurons, neuromuscular nerve axons, function motor units # motor neurons = # motor units at increasing age ongoing process of denervation and reinnervation of skeletal muscle fibers late in life evidenced by - histological findings of fiber type grouping - elevated coexpression of MHC isoforms - preferential atrophy of type II muscle fibers - very large MUAPs, indicating innervation ratio AJ McComas: Skeletal muscle - form and function, 1996 Vandervoort 22, McComas 1996 Age-induced changes in neuromuscular function: Loss of muscle mass with aging: sarcopenia Picture courtsey Paolo Caserotti Institute of Sports Science and Clinical Biomechanics University of Southern Denmark 4

5 Loss of muscle mass with aging: sarcopenia Reduced muscle muscle cross-sectional area area ( ( 4% between the age of 2 and 8 8 yrs) yrs) The decline seems to start to start in early in adulthood early adulthood and accelerate and accelerate after the age after of 5 the years age of 5 years content content of of non-contractile non-contractile tissue tissue such as intramuscular such as intramuscular fat and connective fat and tissue connective Vandervoort, tissue Muscle & Nerve 25, 22 Vandervoort, Muscle & Nerve 25, 22 McNeil et al, J Appl Physiol 12, 27 Parise & Yarasheski, Curr Opin Parise Clin Nutr & Yarasheski, Metab Care, 2 Curr Opin Clin Nutr Metab Care, 2 31 yr (m) 31 yr (m) 66 yr (m) 66 yr (m) 73 yr (f) 73 yr (f) 85 yr (f) 85 yr (f) 5

6 Jesper L. Andersen Reduced muscle mass with ageing Loss of skeletal muscle fibers Elderly male subjects (7-75 yrs) show ~4% fewer muscle fibers than young subjects (19-3 yrs) VL muscle, Lexell et al Very old male subjects (>8 yrs) ~6% fewer fibers compared to young subjects VL muscle, Lexell et al Reduction in muscle fiber size with aging Young subject (31 yrs) Old subject (79 yrs) courtsey C Suetta VL muscle Jesper L. Andersen, CMRC 6

7 Age-related reductions in skeletal muscle fiber size Study Gender Age (years) Larsson et al., Acta Physiol. Scand. 13, 1978 Vandervoort, Muscle & Nerve 25, 22 Percent reduction Type I Type II M << 25 Essen-Gustavsson and Borges, Acta Physiol. Scand. 126, 1986 Lexell et al. J. Neurol. Sci. 84, 1988 Hakkinen et al. J. Gerontol. 53B, 1998 Fiatarone Singh et al. Am. J. Physiol. 277, 1999 Hikida et al. J. Gerontol. 55, 2 M F << 45 M << 29 M << 1 M, F << 6 M << 4 VL muscle Neuronal and Muscular changes induced by Ageing Motor Unit remodeling Motor unit number # Spinal motor neurons Motor unit size innervation ratio (# fibers/neuron) Muscle strength / power Reduced muscle mass cross sectional area ('sarcopenia') Total muscle fiber number Muscle fiber size (pref. type II) 7

8 Age-induced changes in neuromuscular function: Impairments in mechanical muscle function Decreased Muscular Strength With Aging CROSS-SECTIONAL DATA Isometric muscle strength Is preserved to ~5-6 yrs of age (cross sectional data) Decreases at a rate of 1-1.5% per year from 6-65th year Substantial individual differences! Spirduso, Physical dimensions of aging, 1995 Vandervoort & McComas 1986 Spirdoso

9 Muscle function in elite master weightlifters trained untrained Peak Peak Power Power Trained (closed circles) and untrained (open circles) individuals demonstrated similar age-related decline rate in peak power (1.3% vs 1.2% per year, respectively) Mean Mean Power Power Pearson, Harridge et al; Med Sci Sports Exerc 22 9

10 Muscle function in elite master weightlifters trained untrained Peak Peak Power Power 2 years Trained (closed circles) and untrained (open circles) individuals demonstrated similar age-related decline rate in peak power (1.3% vs 1.2% per year, respectively) Mean Power Mean Power Pearson, Harridge et al; Med Sci Sports Exerc 22 Is maximal muscle power important in elderly individuals? YES! 1

11 Stair-climbing speed (m/s) Walking speed (m/s) Chair rising speed (s -1 ) Functional performance in the elderly is influenced by maximal mechanical muscle power r=.83 r=.45 Women Men P<.5 P<.1 r=.86 r=.91 r=.93 r=.58 Leg extensor power (W/kg) Leg extensor power (W/kg) Bassey et al, 1992 Nursing Home residents Aging loss of motorneurones loss of muscle fibers muscle fiber atrophy reduced muscle strength, RFD and Power Aging & strength training Impaired function in tasks of daily living (stair muscle walking, fiber rising hypertrophy from chair, etc) improved neuromuscular function 11

12 Aging loss of motorneurones loss of muscle fibers muscle fiber atrophy reduced muscle strength, RFD and Power Aging & strength training Impaired function in tasks of daily living (stair muscle walking, fiber rising hypertrophy from chair, etc) improved neuromuscular function loss of motorneurones Aging loss of muscle fibers loss of motorneurones muscle fiber atrophy loss of muscle fibers muscle fiber atrophy reduced muscle strength, RFD and Power reduced muscle strength, RFD and Power Aging & strength training Aging & strength training muscle fiber hypertrophy muscle fiber hypertrophy improved neuromuscular function improved neuromuscular function Marked gains in muscle strength, RFD, Power improved function in everyday activities Marked gains in muscle strength, RFD, Power improved function in everyday activities 12

13 loss of motorneurones Aging loss of muscle fibers loss of motorneurones muscle fiber atrophy loss of muscle fibers muscle fiber atrophy reduced muscle strength, RFD and Power reduced muscle strength, RFD and Power Aging & strength training Aging & strength training muscle fiber hypertrophy muscle fiber hypertrophy improved neuromuscular function improved neuromuscular function Marked gains in muscle strength, RFD, Power improved function in everyday activities Marked gains in muscle strength, RFD, Power improved function in everyday activities Age-induced changes in neuromuscular function: Adaptive alterations in neuromuscular function with strength/power training 13

14 Percentage increases in Muscle Size (CSA) and Maximal Muscle Strength (MVC) with Strength Training in old vs young adults Häkkinen 1985 Jones & Rutherford 1987 Narici 1996 Aagaard et al, J Physiol 21 Narici et al, J Musculoskel Neron Interact 24 Percentage increases in Muscle Size (CSA) and Maximal Muscle Strength (MVC) with Strength Training in old vs young adults Häkkinen 1985 Jones & Rutherford 1987 Narici 1996 Ferri 23 Frontera 1988 Häkkinen 1998 Harridge 1999 Narici et al, J Musculoskel Neron Interact 24 14

15 Heavy-resistance strength training also induces muscle fiber hypertrophy in the very old (85-98 yrs, mean age 89 3 yrs) um 2 Loading 8% 1RM, 3/week, 12 weeks Muscle fibre CSA Kryger & Andersen, Scand J Med Sci Sports 27 Heavy-resistance strength training also induces muscle fiber hypertrophy in the very old (85-98 yrs, mean age 89 3 yrs) 85+ year old discharged geriatric patients 12 weeks of resistance exercise knee ext. 3 x weekly, 3 x 8 rep, >7% 1 RM Results Type IIa fibre CSA 22% Quadriceps muscle CSA 1% Quadriceps strength 4-45% Chair rising time (5 reps) 3% faster Maximal walking speed 25% faster Kryger & Andersen, Scand J Med Sci Sports 27 p<.5 15

16 Increases in muscle fibre size in older individuals following high-intensity dynamic leg strength training. Based on biopsy samples obtained from vastus lateralis Vandervoort, Muscle & Nerve 25, 22 Muscle fiber size increase (%) Study Type I Type II Frontera et al., J. Appl. Physiol. 64, 1988 Charette et al., J. Appl. Physiol. 7, 1991 Grimby et al., J. Appl. Physiol. 73, 1992 Häkkinen et al. J. Gerontol. 53B, 1998 Fiatarone-Singh et al. Am. J. Physiol. 277, < > -12 Hunter et al., J. Appl. Physiol. 86, 1999 Hikida et al. J. Gerontol. 55, 2 14 < Changes in explosive muscle strength (rate of force development, RFD) induced by strength training in the elderly 16

17 Force Force Force RFD Rapid force capacity [ 'explosive muscle strength' ] Maximal rate of force Maximal development Explosive (RFD) Muscle in elderly Strength vs young individuals Force (N) Force (N) Rate of Force Development (RFD) Maximal Explosive Muscle Strength Rate of Force Development (RFD) RFD = Force RFD = / Time Force / Time max Force max Force Time Time Time (seconds) Time (seconds) Aagaard et al, J Appl Physiol 22 RFD RFD Rapid Contractile force Rate capacity of Force Development ['explosive muscle strength' ] Maximal explosive rate of force muscle development strength in elderly (RFD) vs in young elderly individuals vs young individuals Force (N) RFD = Force / Time 2 15 Time Time (seconds) Contractile RFD is substantially reduced in healthy aging individuals compared to young individuals RFD (Nm/s/kg) max Force m. quadriceps femoris -3 ms 5 ms -3 ms 5 ms -3-3 ms ms 5 5 ms ms Clarckson et al 1981, Häkkinen et al 1995, Clarckson et al. 1981, Häkkinen et al. 1995, Izquierdo et al 1999, Barry et al. 25, Izquierdo et al. 1999, Korhonen et al. 26, Klass et al 28, Suetta, Hvid Korhonen et al 28 et al 26, Klass et al 28, Suetta, Kjær, Hvid et al 21 Young (67 yr, n=9) Old (24 yr, n=11) Quadriceps muscle - maximal isometric MVC efforts Young (24 yr, n=9) Old (67 yr, n=11) Y < O (p<.5) Suetta, Kjær, Aagaard et al, J Appl Physiol 29 17

18 Force RFD Rapid force capacity Effects of resistance training on RFD in the elderly? 5 max Force Force (N) RFD = Force / Time Time Time (seconds) 18

19 Explosive-type strength/power training in the old (6 yrs) and the very old (8 yrs) Subjects Mean age 62.7 (SD 2.2) and 81.8 (SD 2.7) yrs n = con n = con Caserotti, Aagaard et al, 28 Explosive-type strength/power training in the old (6 yrs) and the very old (8 yrs) Subjects Mean age 62.7 (SD 2.2) and 81.8 (SD 2.7) yrs Duration, frequency of training 12 weeks, twice a week Familiarisation period 2 wks with lower training loads (5% 1RM), and reduced movement velocity Progressive load adjustment: Every two weeks with a new estimated 1RM (5-RM test) Exercises (bilateral) Horizontal leg press, knee extension, calf rise, incline leg press, leg curl - slow ECC, rapid (max acc) CON actions Exercise intensity and reps 75-8% 1RM loads, 8-1 reps, 4 sets each exercise Caserotti, Aagaard et al, 28 19

20 Newton Explosive-type strength/power training in the old and the very old Static leg extensor MVC and RFD Unilateral isometric leg press test device Paolo Caserotti Explosive-type strength/power training in the old and the very old F peak 12 F5 1 8 F F1 F5 Start of contraction Force Time (msec) 6 Paolo Caserotti 2

21 Explosive-type strength/power training in the old and the very old marked increases in rapid force capacity (RFD) Contractile Rate of Force Development Leg Press MVC; -2 ms 6 yrs old Diff = 43% p <.1 8 yrs old week (pre) 12 weeks (post) TG6 TG6 CG6 CG6 TG8 TG8 TG6 CG8 CG8 CG6 TG8 CG8 P<.5 within-group changes (n=2) (n=2) (n=12) (n=13) Caserotti, Aagaard et al, Scand J Med Sci Sports Exerc 28 Explosive-type strength/power training in the old and the very old marked increases in rapid force capacity (RFD) Contractile Rate of Force Development Leg Press MVC; -2 ms 6 yrs old Diff = 43% p <.1 8 yrs old week (pre) 12 weeks (post) Diff = 15% n.s. 12 wks of explosive-type HRST in 8 yr old TG6 (n=2) 2 years younger! TG6 CG6 (n=2) CG6 TG8 TG8 TG6 CG8 CG8 CG6 TG8 (n=12) CG8 (n=13) P<.5 within-group changes Caserotti, Aagaard et al, Scand J Med Sci Sports Exerc 28 21

22 Force Moment (Nm) Explosive-type strength/power training in the old and the very old marked increases in MVC, RFD and power TG 6 TG8 MVC (maximal strength) +22% +28% RFD (rapid force capacity) +18% +51% SSC muscle power +5% +6% (CMJ force plate) 1-leg muscle power +12% +28% (Power rig) pre vs post (p<.5) Caserotti, Aagaard et al, Scand J Med Sci Sports Exerc 28 RFD Contractile Rate of Force Development Elderly subjects (6-86 years) - hip replacement patients (n=11) Pre and Post 12 wks unilateral resistance training - Affected Limb % Post training % Pre training % RFD = Force Moment / Time Time (ms) Suetta, Aagaard, Kjær et al. J Appl Physiol 24 22

23 Training induced changes in explosive muscle strength (RFD) Adaptive responses in aged individuals Heavy-resistance strength training 1 Nm 4 uvolt -4 3 uvolt uvolt -25 slow concentric contraction pre training Concurrent increases in maximal RFD and neuromuscular activity (iemg) in elderly individuals Neural drive m. quadriceps position Moment EMG VL EMG VM EMG RF slow eccentric contraction pre training Häkkinen & Häkkinen 1995 (age 5, 7 yrs, gender F, M) Häkkinen et al (age 4, 6 yrs, gender F, M) Häkkinen et al. 21 (age 63 yrs, gender F) Suetta et al. 24 (post hip replacement surgery, 6-86 yrs) Barry et al. 25 (age 6-79 yrs, gender F, M) Time (msec) Time (msec) Training induced changes in explosive muscle strength (RFD) Adaptive responses in aged individuals Heavy-resistance strength training Concurrent increases in maximal RFD and neuromuscular activity (iemg) in elderly individuals Functional consequences - enhanced acceleration - elevated maximal movement velocity - elevated muscle force & power during rapid movements - reduced risk of falls 23

24 Influence of neuromuscular activity on RFD Rapid force capacity (RFD) is strongly influenced by the magnitude of neuromuscular activity at onset of contraction 3 2 Nm 1 15 uvolts uvolts 4 uvolts rectified EMG signal VM VM EMG Rectified EMG signal (grey) lowpass filtered lowpass filtered EMG signal 1 1 uvolts uvolts RF RF EMG raw raw EMG EMG signal signal 4 highpass highpass filtered filtered Time Time (milliseconds) Time Time (milliseconds) ( miliseconds ( miliseconds ) ) VM muscle -8 uvolt uvolt RFD 3 = Moment/time subj subj LN LN 2 Nm Force Force Force Force Moment 1 Moment Isometric Quadriceps knee extensor moment signal 15 uvolts VL VL EMG -15 Aagaard et et al. al Time (miliseconds) Fig.1A art14f1a.jnb Very high firing rates of spinal motorneurons increases the maximal Rate of Force Development Muscle Force Stim rate 4 Hz 2 Hz 12 Hz 8 Hz De Haan, Exp Physiol 1998 (rat GM, in situ) 24

25 Elevated motorneuron firing rates leads to increases in the maximal Rate of Force Development Muscle Force Not affecting maximal force generation Stim rate 4 Hz 2 Hz 12 Hz 8 Hz De Haan, Exp Physiol 1998 (rat GM, in situ) Elevated motorneuron firing rates leads to increases in the maximal Rate of Force Development Muscle Force However, greatly affecting max Rate of Force Development Stim rate 4 Hz 2 Hz 12 Hz 8 Hz Force / time De Haan, Exp Physiol 1998 (rat GM, in situ) 25

26 Ageing and neuromuscular function Motorneuron firing frequency What is the effect of strength/power training on maximal MN firing frequency in old adults? Ageing and neuromuscular function Motorneuron firing frequency What is the effect of strength/power training on maximal MN firing frequency in old adults? UNTRAINED STATE: Maximal motorneuron firing frequency recorded during MVC is reduced in elderly vs young subjects Patten et al. 1999, 21, Connelly et al. 1999, Kamen & Knight 24, Klass Duchateau et al. 28, Christie & Kamen 21 26

27 Ageing and neuromuscular function Motorneuron firing frequency Effects of strength/power training on maximal MN firing rate... A MVC Force Young Old B ( ) ( ) Young Old MN firing rate MVC, greater than pre training (p<.1-.1) greater than pre training (p<.5) Kamen & Knight, J Gerontol 24 Graph modified from Duchateau, Semmler, Enoka, J Appl Physiol 26 Ageing and neuromuscular function Motorneuron firing frequency Effects of strength/power training on maximal MN firing rate... A MVC Force Young Old B ( ) ( ) Young Old MN firing rate n.s. MVC, greater than pre training (p<.1-.1) greater than pre training (p<.5) Kamen & Knight, J Gerontol 24 Graph modified from Duchateau, Semmler, Enoka, J Appl Physiol 26 27

28 Ageing and neuromuscular function Motorneuron firing frequency Effects of strength/power training on maximal MN firing rate... A MVC Force Young Old B ( ) ( ) Young Old MN firing rate n.s. MVC, greater than pre training (p<.1-.1) greater than pre training (p<.5) Kamen & Knight, J Gerontol 24 Graph modified from Duchateau, Semmler, Enoka, J Appl Physiol 26 Strength training induce changes in maximal motorneuron firing frequency in young and old individuals Strength/power training motorneuron firing rate (at 1% MVC) in both young and old subjects Patten et al (old, young), 21 (young) Van Cutsem et al (young), Kamen & Knight 24 (old, young) Christie & Kamen 21 (old, young) Furthermore, after strength training maximal motorneuron firing rate did not differ between old and young subjects Patten et al. 1999, Kamen & Knight 24, Christie & Kamen 21 28

29 Effects of strength training in frail elderly patients Well, does the need exist? Effects of strength training in frail elderly patients Well, does the need exist? YES! Often, severe muscle atrophy is observed in elderly patients... Strength training is the only exercise modality known to effectively increase muscle mass 29

30 Effects of strength training in frail elderly patients Does it lead to improved functional capacity? pre post training? Effects of strength training in frail elderly patients Does it lead to improved functional capacity? YES! pre post training 3

31 Rehabilitation from elective Hip replacement Surgery by use of Strength Training Strength Training protocol Strength exercises - heavy loads unilateral heavy-resistance strength training - Affected Limb Kneeextension Legpress wks 1: 3 sets x 1 reps (5% 1RM ~2RM load), wks 2-4: 3 x 12 (65% 1RM ~15RM), wks 5-6: 4 x 1 (7% 1RM ~12RM), wks 7-8: 5 x 8 (8% 1RM ~8RM), wks 9-1: 4 x 8 (8% 1RM ~8RM), wks 11-12: 3 x 8 (8% 1RM ~8RM) Suetta, Aagaard et al, JAGS 24, J Appl Physiol 24 Rehabilitation from elective Hip replacement Surgery by use of Strength Training Changes in anatomical Muscle Cross Sectional Area (CT-scanning) PRE training POST training Suetta, Aagaard et al, J Appl Physiol 24 31

32 CSA (mm²) Rehabilitation from elective Hip replacement Surgery by use of Strength Training Changes in anatomical Muscle Cross Sectional Area (CT-scanning) Standard Rehab SR Electro Stimulation ES Strength Training ST # CSA (%) S ST - CSA % E ES - CSA % K SR - CSA % ES ST SR 3 Pre 5wk 12wk Pre 5wk 12wk Pre 5wk 12wk 92 9 # Pre 5w 12w Suetta, Aagaard et al, J Appl Physiol 24 Rehabilitation from elective Hip replacement Surgery by use of Strength Training Changes in maximal muscle strength (isometric MVC) Isometric strength RT ES SR resistance electrical standard training stimulation rehabilitation +24% strength-op elstim-op kontrol-op Torque (Nm) # -22% 4 2 Pre 5w 12w Pre 5w 12w Pre 5w 12w Suetta et al, J Appl Physiol wk > pre (p<.5); # 5 wk < pre,12 wk (p<.5) 32

33 Rehabilitation from elective Hip replacement Surgery by use of Strength Training Changes in Functional Capacity Max 1m walk speed Speed of Chair-rising x 5 Procent (%) S - % E - % SR - % ST ES SR Procent (%) S - % d i f f E - % d i f f SR - % d i f f ST ES SR $ Pre 5w 12w Pre 5w 12w Suetta, Aagaard, Kjaer et al, JAGS 24 Rehabilitation from elective Hip replacement Surgery by use of Strength Training Does training-induced gains in rapid force capacity RFD result in improved functional performance?? 33

34 Rehabilitation from elective Hip replacement Surgery by use of Strength Training Does training-induced gains in rapid force capacity RFD result in improved functional performance? YES! Suetta, Aagaard, Kjaer et al, J Appl Physiol 24 Impaired fine motor control with aging Effects of resistance training Neural factors - neuromuscular function Force steadiness Greater force error, less steady muscle forces (SD) during submaximal constant-force motor tasks in A measurement elderly of compared the fluctuations to young in force subjects during isometric or dynamic muscle contraction Tracy & Enoka 22, Hortobagyi et al. 21 old SD(force) young tracking of 25-N target force during 5-sec slow-speed eccentric quadriceps contraction (15 o /s) post 1 familarization trials Hortobagyi et al

35 Impaired fine motor control with aging Effects of resistance training Neural factors - neuromuscular function Force steadiness Greater force error, less steady muscle forces (SD) Greater force error, less steady muscle forces (SD) during submaximal constant-force motor tasks in elderly during submaximal constant-force motor tasks in compared to young subjects elderly compared to young subjects Tracy & Enoka 22, Hortobagyi et al. 21 Tracy & Enoka 22, Hortobagyi et al. 21 old old young tracking of 25-N target force during 5-sec slow-speed eccentric tracking of quadriceps 25-N target contraction force during (15 o /s) 5-sec slow-speed eccentric quadriceps contraction (15 post 1 familarization trials o /s) Hortobagyi et al. 21 post 1 familarization trials Hortobagyi et al. 21 Impaired fine motor control with aging Effects of resistance training Neural factors - neuromuscular function Force steadiness Potential mechanisms: age related changes in Greater force error, less steady muscle forces (SD) during - MU submaximal size and firing constant-force rate variability Tracy & Enoka 22, Barry & Enoka 27 motor tasks in elderly - MU synchronization compared to young Patten subjects & Kamen Antagonist coactivation Tracy & Enoka Enoka 22, 1997 Hortobagyi et al. 21 old old young tracking of 25-N target force during 5-sec slow-speed eccentric tracking of quadriceps 25-N target contraction force during (15 o /s) 5-sec slow-speed eccentric quadriceps contraction (15 post 1 familarization trials o /s) Hortobagyi et al. 21 post 1 familarization trials Hortobagyi et al

36 Impaired fine motor control with aging Effects of resistance training old individual pre post Hortobagyi et al. 21 Impaired fine motor control with aging Effects of resistance training old individual pre post Hortobagyi et al

37 Impaired fine motor control with aging Effects of resistance training Effects of resistance training in elderly Improved force steadiness reduced SD(force) Improved force accuracy = Improved fine motor control pre Hortobagyi et al, J Gerontol 56A 21 Tracy, Enoka et al, JAP 96, 24 Tracy & Enoka, MSSE 38, 26 post SUMMARY Effects of strength/power training on neuromuscular function and muscle size in the elderly 37

38 SUMMARY Effects of strength/power training on neuromuscular function and muscle size in the elderly Strength and Power properties Neural factors dynamic muscle strength, isometric muscle strength Frontera 1988, Fiatarone 199, Häkkinen 1998, Harridge 1999, Suetta 24, Beyer 27 muscle power Beyer 27, De Vos 25, Caserotti 28 rapid force capacity (rate of force development: RFD) Häkkinen , Hortobagyi 21, Suetta 24, Barry 25, Caserotti 28 EMG amplitude and rate of EMG rise Häkkinen , Suetta 24, Barry 25 maximal motor neuron firing frequency Patten 1999, Kamen & Knight 24, Christie & Kamen 21 improved force steadiness, enhanced fine motor control Hortobagyi 21, Tracy 24, Tracy & Enoka 26 Muscular factors single muscle fiber CSA, whole muscle CSA Frontera 1988, Häkkinen 1998, Harridge 1999, Esmarck 23, Kryger & Andersen 27, Suetta myogenic satellite cell activation MacKey 27, Petrella 28 muscle fiber pennation angle, tendon stiffness Reeves 23, Reeves 26, Suetta 28 Effects of aging on muscle and neural function - influence of training OVERALL CONLUSION The age-related loss in muscle mass and the concurrent decrease in maximal muscle strength, rapid force capacity (RFD) and power can be slowed or reversed by training (strength training!) Likewise, the age-related impairment in neural function can be effectively compensated by training (strength training)!! ALSO the case in frail elderly patients!! 38

39 OVERALL EFFECT OF STRENGTH/POWER TRAINING IN THE ELDERLY? Strength/Power TRAINING Resistance Training Adaptive changes in muscle size and neuromuscular function improved function in ADL (activities of daily living) Aagaard, Suetta,Caserotti, et al, Scand J Med Sci Sports 21 Acknowledgements Charlotte Suetta Paolo caserotti Jesper L. Andersen Steve Harridge Lars Hvid Ulrik Frandsen Niels Ørtenblad Michael Kjær Peter Magnusson Anders Holsgaard Larsen Anders Jørgensen Jakob L. Nielsen Peter Krustrup Lis Puggaard Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark; Institute of Sports Medicine Copenhagen, University of Copenhagen 39